Advanced Engineering Tech - Cam shaft selection with N20 use in mind (CamKing , racer7088 etc...)

I REALLY wanted to drop this bomb in the "advs/disadv of rod length" thread , but I figured it might ruffle a few feathers by disrupting the present topic of conversation (although its changed about 4 or 5 times already :jest: ). Its hard to get really good information about this from true experts.

Moving on , I have a 358 inch LSX engine in my race car. It was originally assembled for use in the LS1tech series extreem mod class which was an all motor class. We kept it under 360 inches to get the wieght break. We soon found out that to get this little engine to 60ft , it needed so much converter that it was no longer efficient on the big end of the track. Faced with having to put a jerico(sp?) in the car or do something else with the engine, I gave up and put a plate system on the car and decided to have some fun. The camshaft was sourced from LSM , and ground specificly for NA use. Is there a possibility I will see a gains from a cam change if I get one targeted towards N20 use? If so, why? and what are the differences between an NA specific and a N20 specific cam.

I know N20 is a dirty word for "real engine builders". I also realize that this thread is kind of "self serving" , but there is not a whole lot of really good info out there on this topic. I think all of us N20 addicts would benifit greatly from a truely intellegent conversation on this subject.

It's probably also going to change the header requirement and possibly the head gasket thickness.

How much N2O are you looking at here? If it's not a huge shot then there is not much the cam itself is going to make huge changes in.

FWIW the guys on here don't know nearly as much about cams as the guys at LSM. Them and a few other guys out there are some of the best in the bussiness.

Bret

It's probably also going to change the header requirement and possibly the head gasket thickness.

How much N2O are you looking at here? If it's not a huge shot then there is not much the cam itself is going to make huge changes in.

FWIW the guys on here don't know nearly as much about cams as the guys at LSM. Them and a few other guys out there are some of the best in the bussiness.

Bret

I already have the largest Header available without going to a custom set (1 7/8" stepped to 2" with 3.5 inch collector) . I have a 300 pill in the plate and use a progressive controller. I have already backed off the timing in an appropriate manner , installed the correct plug etc.. I have been told that with a 15:1 compression ratio, I need to have a really tight LSA to help bleed off cylinder pressure to keep it alive.I have also been told if I go with a wider LSA it will make more power. I just want some info to try and make an informed choice , and understand how changes in the camshaft design affect a nitrous engine (if it is any different than an NA app).

I've never understood how LSA bleeds off any cylinder pressure.... the IVC point does that and if you go tighter with the same LSA it increases the cylinder pressure.

With a 300 shot, yes you will need more camshaft, mostly more LSA and more exhaust duration.

Al from LSM is on here sometimes, pretty smart dude. Maybe he will say something...

BTW what's the rest of this combo? If you want to keep it private PM me.

Bret

I've never understood how LSA bleeds off any cylinder pressure.... the IVC point does that and if you go tighter with the same LSA it increases the cylinder pressure.

With a 300 shot, yes you will need more camshaft, mostly more LSA and more exhaust duration.

Al from LSM is on here sometimes, pretty smart dude. Maybe he will say something...

BTW what's the rest of this combo? If you want to keep it private PM me.

Bret

No need to keep it private everybody has seen the car run.

Here is a component list for the long block (Long block assembled by LME)

6.0 litre block with custom oiling system.(ext oil press reg and remote mount oil filter)

GRP aluminum rods

Wiesco custom pistons,with hellfire ring set (15.5 to 1 comp ratio)

LSM solid roller cam (264/268 .705 .705 110lsa)

Lunati solid roller lifters

CV dual taper 3/8 pushrods

Cylinder heads are 6.0l castings that have been extensivley worked by Trevor Johnson. They feature 1.590 PSI springs , Xeldyne 2.100 ti intake valves and 1.67 ti exhaust valves. The rockers are shaft mount .50 offset jesel j2k's. Combustion chambers were welded to create a custom shape, and increase compression. Obviously a 2.100 valve wont clear 4.00 bore , so the heads are offset on the deck 50 thou to correct this issue.

GM perf parts carb style intake also worked by Trevor johnson , with fabricated alum elbow and 90mm throttle body.

I've had problems with head gaskets on this engine from day 1 and I am in the process of swaping over to a new set of heads , and stepping the head studs up to 1/2". I figured why not get the cam program squared away while Im at it. I just don't want to go the wrong direction with it and not see the gains I am looking for. I would like to pick up 100rwhp. I am hoping the right cylinder heads , a new cam , and a direct port system will get me there.

I'd go with a longer exhaust duration to keep the temp down.

At what RPM will you be using the NO2?

I'd go with a longer exhaust duration to keep the temp down.

At what RPM will you be using the NO2?

I usually activate the system right off of the trans brake @ 5K and shift around 8.4K I have hit the limiter at 9200 and it never seems to quit pulling. This is one of the things that got me so interested in the discussion going on in the other thread. I am afraid of going to a larger cam and more cylinder head because I don't want to have to spin this engine 10k to see the increase in power. I am starting to wonder if maybe I am at the very edge of what an engine this small is capable of making in a useable rpm range.

I usually activate the system right off of the trans brake @ 5K and shift around 8.4K I have hit the limiter at 9200 and it never seems to quit pulling. This is one of the things that got me so interested in the discussion going on in the other thread. I am afraid of going to a larger cam and more cylinder head because I don't want to have to spin this engine 10k to see the increase in power. I am starting to wonder if maybe I am at the very edge of what an engine this small is capable of making in a useable rpm range.
I'd look at running a smaller intake lobe, or at least tightening the intake centerline to make the cam more efficient at the lower RPM's.
The NO2 has the top end handled.

If you haven't yet, give Steve Sr. a call. We may even be able to regrind that cam to the new specs if it isn't too large of a change.

Al

I'd look at running a smaller intake lobe, or at least tightening the intake centerline to make the cam more efficient at the lower RPM's.
The NO2 has the top end handled.

Very cool , thanks for the advice!

anybody have anything to add?

With that setup there is a lot of things you can do. The intake and cam combination is interesting, but the intake can use a TON more work to get it where I would want it for that application.

I'd throw more converter at it with that cam, you have too much in there on average and the RPM band is too wide.

As for a N2O cam that's another story.... but the motor looks good to me pretty similar to one I have in the shop except we have a LS2 block, a little lower compression and a much different cam. Oh yeah and some Darts that are heavily worked over from AirFlowDevelopment.

I'd also look at the Wilson elbow it's going to work a bunch better than a fabbed one with some work on the inside of it.

How much power are you making now and what's that puppy run?

Bret

If you haven't yet, give Steve Sr. a call. We may even be able to regrind that cam to the new specs if it isn't too large of a change.

Al

Thanks Al , I will do so. I just thought I should have all of the other specs inline before I called. I wanted to make sure I could answer any questions he might have for me about the set up (hardware), and what I was trying to accomplish.

Do you guys keep detailed record of cams that you grind for your customers? I don't know the details of the valve timing events , lobe profile , etc... I only know what Brian at LME gave me for specs verbally. It would be neat to document the changes made to see what effects they have in this real world application.

With that setup there is a lot of things you can do. The intake and cam combination is interesting, but the intake can use a TON more work to get it where I would want it for that application.

I'd throw more converter at it with that cam, you have too much in there on average and the RPM band is too wide.

As for a N2O cam that's another story.... but the motor looks good to me pretty similar to one I have in the shop except we have a LS2 block, a little lower compression and a much different cam. Oh yeah and some Darts that are heavily worked over from AirFlowDevelopment.

I'd also look at the Wilson elbow it's going to work a bunch better than a fabbed one with some work on the inside of it.

How much power are you making now and what's that puppy run?

Bret

Bret , thanks for the advice. I think when I get ready to do something with the cylinder heads I will give you a call if you don't mind. The intake has been heavily modified it looks very similar to a vic jr internally, and the elbow is fabricated from 4" od aluminum. I was told the heads and bore size were the limiting factors at this point. I would tend to agree more with Erik K and say that RPM seems to be a huge issue , IMO The valve train is just not gonna live for very long above 8500.

The car has made as much as 540 at the rear wheels when I had it tuned for NA use. This is through a Rossler TH400 (lightwieght billet rotating assembly) , and a Strange 9" with 40 spline axles. Now, with about 16 degrees of timing it makes in the mid 490's on the motor and just a touch over 820 with the 300 pills in the NOS bigshot plate.

I have only run the car a few times in the 1/4 , the first pass off of the trailer at southern shoot out in san antonio it went 8.73 156mph , and backed it up second pass with an 8.76 @ 154. If I could keep the heads on the damn thing I would stop all of this talk about selling it. I'm gonna give it one more try , and see how she goes without the weight in the car.

Thanks Al , I will do so. I just thought I should have all of the other specs inline before I called. I wanted to make sure I could answer any questions he might have for me about the set up (hardware), and what I was trying to accomplish.

Do you guys keep detailed record of cams that you grind for your customers? I don't know the details of the valve timing events , lobe profile , etc... I only know what Brian at LME gave me for specs verbally. It would be neat to document the changes made to see what effects they have in this real world application.

Yes we do, it's based on the cam identification number(CIN) stamped on the end of your cam. Any changes made to a cam gets supplemented to that CIN in our database. We spend the extra money to case harden our cams as deep as our heat treater can go for events such as these. Now, if the profiles need to be changed slightly, we can regrind the cam without breaking through the case hardening. It's all assuming that the change isn't too great of course.

Sr. has been doing this for most of his lifetime, and can rattle off cam specs off the top of his head that would take me a while to calculate. I have an idea of which way you should go, but I would rather not give my opinion, but let you talk to him instead.

Al

Bret , thanks for the advice. I think when I get ready to do something with the cylinder heads I will give you a call if you don't mind. The intake has been heavily modified it looks very similar to a vic jr internally, and the elbow is fabricated from 4" od aluminum. I was told the heads and bore size were the limiting factors at this point. I would tend to agree more with Erik K and say that RPM seems to be a huge issue , IMO The valve train is just not gonna live for very long above 8500.

The car has made as much as 540 at the rear wheels when I had it tuned for NA use. This is through a Rossler TH400 (lightwieght billet rotating assembly) , and a Strange 9" with 40 spline axles. Now, with about 16 degrees of timing it makes in the mid 490's on the motor and just a touch over 820 with the 300 pills in the NOS bigshot plate.

I have only run the car a few times in the 1/4 , the first pass off of the trailer at southern shoot out in san antonio it went 8.73 156mph , and backed it up second pass with an 8.76 @ 154. If I could keep the heads on the damn thing I would stop all of this talk about selling it. I'm gonna give it one more try , and see how she goes without the weight in the car.

With the N2O, you probably have a issue with the deck thickness of the heads and a issue with the quench that's giving you the head lifting.

I agree that the bore is really a limit. A 4.0" bore is better than a 3.900" bore though! Trevor does good work, I don't think it has any issues with him but I do think the issues are the castings themselves.

As for the intake when I say HEAVILY modified it's got about 3lbs of weld in it and doesn't look as much like it did. We have talked about a few different things to try but I think that were we are starting from will be fine. We have talked about sheetmetal intakes and L92 heads as well, but I don't think a OEM casting will have enough deck thickness for ya.

I was telling these guys in another thread about how much pulling timing hurts power, and I'm guessing you pulled 6-10degs out of yours. I can believe that 50hp loss though. How much were you running just for reference for the other guys.

I have some ideas of what you would want to do with the cam as well to get everything to work with the intake and the N2O.

Bret

Friendly Freddie,

I would back way off of the compression and run a lot wider LSA right off the bat if you are going for more power with the nitrous. Tightening your LSA BUILDS compression and certainly does NOT bleed any away! Anyone telling you that you need to tighten LSA as you add compression is just plain wrong or doesn't understand camshafts very well. Tightening LSA is for classes where you can't make good compression and/or where you have tons of exhaust flow and low backpressure compared to your intake capability.

Tightening LSA opens the exhaust later which hurts power on NOS and it also closes the intake earlier which increases cylinder pressure down lower in the rpm band but may even reduce power overall depending on the engine. With the compression you have I can't imagine needing too tighten LSA or advance the cam much at all! Tightening LSA also increases overlap which is also NOT where you want to go on a nitrous engine unless you have huge exhaust and even then 110 is too tight. It is just increasing reversion.

I would have a cam probably much wider in LSA with a fairly large split to the exhaust side in duration. You need to size your exhaust lobe such that it can handle along with your headers and exhaust system the power you are aiming to make on NOS. The cam you have is not one that is going to make big power on NOS probably. Your intake lobe is big enough but certainly not huge and you shouldn't really make power as high as you are turning it anyway.

Also If you could leave on a little less NOS and phase in the extra NOS at even higher rpm your gaskets will live longer. Most people spray too much too soon and the cylinder heads simply lift and /or detonate. The LS1 just isn't the greatest on the head gasket situation that's for sure! Spraying 300 at 2500 rpm is 600 ft pounds more tq and spraying 300 at 5000 rpm is 300 foot pounds more tq and spraying 300 at 7500 rpm is only 200 foot pounds more tq.

How much N2O are you looking at here? If it's not a huge shot then there is not much the cam itself is going to make huge changes in.

FWIW the guys on here don't know nearly as much about cams as the guys at LSM. Them and a few other guys out there are some of the best in the bussiness.

Bret

Bret,

NO one at a cam company light years away knows as much as the people really running these engines and really using those cams. NO offense to either of the places you mentioned as they know their products totally from top to bottom and are absolutely top notch but until you've seen several cams all from dedicated race cam shops and you see them against each other and then you see the next batch of cams and then you see the next batch of cams you will know that no one knows exactly the best cam for any situation other than the engine builders testing it all for real.

I've seen some big cam guys tell us that they knew we were on the wrong track and we used their cam and lost power and went slower and then went further the direction we were going and picked up and went faster. Now when you have guys sitting down and running engines on dynos and on the track for twenty years like they do in Pro Stock or NASCAR and running the valvetrain on spintrons for thousands of hours with every conceivable rocker and pushrod and valve spring combination then you'll find someone that can tell you a whole lot about that exact combo but they still might not be able to pick as good a cam as you could for your car.

I can't tell you the hundreds of situations where a cam company promised people I know to pick them up and did not. I'm not saying that the problem was just the cam but I've seen one too many "cam gurus" in my lifetime already and most don't know a damn thing and I am NOT talking about anyone in particular because I actually like most of the "cam gurus" I know but I think you know what I mean! The guys from LSM and Camking are experts in their field of camshaft design and manufacturer and are NOT what I am talking about in general as well so I am not talking about them. http://ls1tech.com/forums/images/smilies/LS1Tech/gr_stretch.gif

LS1Tech is quite simply the most cam obsessed and cam driven web site on the planet! People on this site have routinely told me how they could tell the "difference" between cams that were actually the same! I just don't say anything anymore. http://ls1tech.com/forums/images/smilies/LS1Tech/gr_stretch.gif

LS1Tech is quite simply the most cam obsessed and cam driven web site on the planet! People on this site have routinely told me how they could tell the "difference" between cams that were actually the same! I just don't say anything anymore. http://ls1tech.com/forums/images/smilies/LS1Tech/gr_stretch.gif

I would have to agree with this! That's a good laugh as well.

Bret

With the N2O, you probably have a issue with the deck thickness of the heads and a issue with the quench that's giving you the head lifting.

I agree that the bore is really a limit. A 4.0" bore is better than a 3.900" bore though! Trevor does good work, I don't think it has any issues with him but I do think the issues are the castings themselves.

As for the intake when I say HEAVILY modified it's got about 3lbs of weld in it and doesn't look as much like it did. We have talked about a few different things to try but I think that were we are starting from will be fine. We have talked about sheetmetal intakes and L92 heads as well, but I don't think a OEM casting will have enough deck thickness for ya.

I was telling these guys in another thread about how much pulling timing hurts power, and I'm guessing you pulled 6-10degs out of yours. I can believe that 50hp loss though. How much were you running just for reference for the other guys.

I have some ideas of what you would want to do with the cam as well to get everything to work with the intake and the N2O.

Bret

Brett, Trevor seems to think that part of the problem with head gasket retension in this particular application is due to the fact that the cylinder heads have been welded (pretty extensivly). This has compromised the casting by giving different expansion characteristics to the welded and untouched portions of the deck. Add in the thin factory deck, and head gaskets become a problem.

I have a set of AFR castings that started life as "porters castings" Trevor started on them for another project but never finished them. What is your opinon on these casting as far as deck thickness and longevity in this application? Or maybe I should just get a set of big chamber 4 inch bore ETP LS7's ?

I think a lot of the things that you guys are bringing up, each play a minor role in the issue that I'm seeing with the head gaskets. I know a different set of cylinder heads are a must , as well as a camshaft revision. Now I just need to make the decisions as to which cylinder heads , and get the guys at LSM to fix me up on the cam change.

P.S. the timing was around 24 or 26 to begin with. When I Speed density tuned the car and added the plate I dropped 10 degrees of timing.

Yeah, the welding definately doesn't work to help the integrity of the heads due to it's change of the heat treatment. Welded chambers and N2O don't go together.

As for the other stuff, I'd have him finish the AFR's for you. They are going to require the least amount of change to the motor and most likely solve your problems.

Bret

Friendly Freddie,

I would back way off of the compression and run a lot wider LSA right off the bat if you are going for more power with the nitrous. Tightening your LSA BUILDS compression and certainly does NOT bleed any away! Anyone telling you that you need to tighten LSA as you add compression is just plain wrong or doesn't understand camshafts very well. Tightening LSA is for classes where you can't make good compression and/or where you have tons of exhaust flow and low backpressure compared to your intake capability.

Tightening LSA opens the exhaust later which hurts power on NOS and it also closes the intake earlier which increases cylinder pressure down lower in the rpm band but may even reduce power overall depending on the engine. With the compression you have I can't imagine needing too tighten LSA or advance the cam much at all! Tightening LSA also increases overlap which is also NOT where you want to go on a nitrous engine unless you have huge exhaust and even then 110 is too tight. It is just increasing reversion.

I would have a cam probably much wider in LSA with a fairly large split to the exhaust side in duration. You need to size your exhaust lobe such that it can handle along with your headers and exhaust system the power you are aiming to make on NOS. The cam you have is not one that is going to make big power on NOS probably. Your intake lobe is big enough but certainly not huge and you shouldn't really make power as high as you are turning it anyway.

Also If you could leave on a little less NOS and phase in the extra NOS at even higher rpm your gaskets will live longer. Most people spray too much too soon and the cylinder heads simply lift and /or detonate. The LS1 just isn't the greatest on the head gasket situation that's for sure! Spraying 300 at 2500 rpm is 600 ft pounds more tq and spraying 300 at 5000 rpm is 300 foot pounds more tq and spraying 300 at 7500 rpm is only 200 foot pounds more tq.

Erik , I will keep all of this in mind. Thanks for all of the usefull info. I hope we all learn somthing from this little experience of mine.

BTW, I have a progressive controler on the car. I leave on 10% of total power and ramp it to 100% over about 1.5 seconds. The car 60 fts 1.21's and 22's pretty consistantly on a good track. I have never had spark plug issues and A/F ratio is very conservative. I think fuel and N20 is divided pretty evenly because of the Carb style intake. I say this, because I don't think the tune is the issue here. I would'nt want to back it down any because the 60 ft is what makes the car a quick as it is (it has never run out the back door like it really should).

Here's my very academic opinion on your cam setup. Basically, it sounds like your cam is spec'd very well for naturally aspirated performance. When running a 300 shot, it's not going to be necessary to deviate from the intake valve closing point that you're using now. Basically, you can keep the same intake duration and ICL as before.

But because nitrous burns the charge so much faster, we need open the exhaust valve quite a bit earlier to cut pumping losses and retard the spark enough to keep our peak cylinder pressure occuring around 13-15 degrees ATDC.

Assuming 110 intake centerline, the current IVC is 62 degrees ABDC and current EVO is 64 degrees BBDC (at .050"). Common nitrous practice would recommend opening the exhaust valve about 10 degrees earlier for the 300 shot and backing timing about 8-9 degrees from what was optimal NA.

That said, a nitrous dedicated cam would look more like this:
264/276 113LSA +3
Same 62 degree IVC
New 74 degree EVO (now 10 degrees earlier)
2 degrees less overlap at .050"

Again, this is a very academic approach, but will get you in the 90% range of what is ideal. I'll leave getting you the last 10% to the experts and to track testing.

Erik , I will keep all of this in mind. Thanks for all of the usefull info. I hope we all learn somthing from this little experience of mine.

BTW, I have a progressive controler on the car. I leave on 10% of total power and ramp it to 100% over about 1.5 seconds. The car 60 fts 1.21's and 22's pretty consistantly on a good track. I have never had spark plug issues and A/F ratio is very conservative. I think fuel and N20 is divided pretty evenly because of the Carb style intake. I say this, because I don't think the tune is the issue here. I would'nt want to back it down any because the 60 ft is what makes the car a quick as it is (it has never run out the back door like it really should).

If you fix the cam you will see a lot more on the back half.

If you fix the cam you will see a lot more on the back half.

That motor is probably having a problem blowing down the cylinder at rpm, and Id take 3 full points or so of compression out of it. Getting rid of cylinder pressure is your friend when lifting heads.

It doesnt take "huge" shots to justify having a "nitrous cam"

We have seen 50 hp gains playign with the cam on 200 shot setups even with pretty decently sized header primaries etc.

That motor is probably having a problem blowing down the cylinder at rpm, and Id take 3 full points or so of compression out of it. Getting rid of cylinder pressure is your friend when lifting heads.It seems to me, that if you lower cylinder pressure, you will also lower hp and tq. I don't believe this is the answer he was looking for. He may just need heads with thicker decks or a more robust gasket setup (like o-ringing).

I REALLY wanted to drop this bomb in the "advs/disadv of rod length" thread , but I figured it might ruffle a few feathers by disrupting the present topic of conversation (although its changed about 4 or 5 times already :jest: ). Its hard to get really good information about this from true experts.

Moving on , I have a 358 inch LSX engine in my race car. It was originally assembled for use in the LS1tech series extreem mod class which was an all motor class. We kept it under 360 inches to get the wieght break. We soon found out that to get this little engine to 60ft , it needed so much converter that it was no longer efficient on the big end of the track. Faced with having to put a jerico(sp?) in the car or do something else with the engine, I gave up and put a plate system on the car and decided to have some fun. The camshaft was sourced from LSM , and ground specificly for NA use. Is there a possibility I will see a gains from a cam change if I get one targeted towards N20 use? If so, why? and what are the differences between an NA specific and a N20 specific cam.

I know N20 is a dirty word for "real engine builders". I also realize that this thread is kind of "self serving" , but there is not a whole lot of really good info out there on this topic. I think all of us N20 addicts would benifit greatly from a truely intellegent conversation on this subject.
Friendly Freddie's setup sounds alot like KECHME's old car. :lurk:

What was the first clue?

What was the first clue?
The motor. Then the origin of business. Whats up Ben. hehe

Friendly Freddie's setup sounds alot like KECHME's old car. :lurk:No coincidence.
http://www.ls1tech.com/forums/showthread.php?t=514695
If the motor doesn't sell, I hope a nitrous-dedicated picks the car up enough to run lower 8s.

Friendly Freddie's setup sounds alot like KECHME's old car. :lurk:

It's the same set up I've always had. 1936FordPU (aka V6bird), I thought you knew I was over here at Friendly.

It seems to me, that if you lower cylinder pressure, you will also lower hp and tq. I don't believe this is the answer he was looking for. He may just need heads with thicker decks or a more robust gasket setup (like o-ringing).

I am of the same opinion that lowering compression (by a large margin) will slow the car down.

Here's my very academic opinion on your cam setup. Basically, it sounds like your cam is spec'd very well for naturally aspirated performance. When running a 300 shot, it's not going to be necessary to deviate from the intake valve closing point that you're using now. Basically, you can keep the same intake duration and ICL as before.

But because nitrous burns the charge so much faster, we need open the exhaust valve quite a bit earlier to cut pumping losses and retard the spark enough to keep our peak cylinder pressure occuring around 13-15 degrees ATDC.

Assuming 110 intake centerline, the current IVC is 62 degrees ABDC and current EVO is 64 degrees BBDC (at .050"). Common nitrous practice would recommend opening the exhaust valve about 10 degrees earlier for the 300 shot and backing timing about 8-9 degrees from what was optimal NA.

That said, a nitrous dedicated cam would look more like this:
264/276 113LSA +3
Same 62 degree IVC
New 74 degree EVO (now 10 degrees earlier)
2 degrees less overlap at .050"

Again, this is a very academic approach, but will get you in the 90% range of what is ideal. I'll leave getting you the last 10% to the experts and to track testing.

Patrick, thank you for the info. I am going to get the ball rolling on this pretty quickly. I just have to find the time to get the car apart.

It's the same set up I've always had. 1936FordPU (aka V6bird), I thought you knew I was over here at Friendly.im just razzing ya. Im more excited you decided to keep the setup then going SBC. Ive thought at that myself actually lately to keep away from what you are experiencing at your power level. Im following the thread to see what comes of it.

I can't tell you the hundreds of situations where a cam company promised people I know to pick them up and did not. I'm not saying that the problem was just the cam but I've seen one too many "cam gurus" in my lifetime already and most don't know a damn thing and I am NOT talking about anyone in particular because I actually like most of the "cam gurus" I know but I think you know what I mean! The guys from LSM and Camking are experts in their field of camshaft design and manufacturer and are NOT what I am talking about in general as well so I am not talking about them.

LS1Tech is quite simply the most cam obsessed and cam driven web site on the planet! People on this site have routinely told me how they could tell the "difference" between cams that were actually the same! I just don't say anything anymore.

Hey Erik...

Guess this is pretty much sums up what we were talking about the other day... Glad you said it, shit if I wrote this, I'd be banned!

Ed

It seems to me, that if you lower cylinder pressure, you will also lower hp and tq. I don't believe this is the answer he was looking for. He may just need heads with thicker decks or a more robust gasket setup (like o-ringing).

Patrick, no offense but you have to realize that NHRA Pro Stock only runs around 15.5 to one or so and they are not spraying (Well most aren't!). An engine with an only 26x at .050 cam doesn't usually run compression like that most of the time at least on gasoline and expect to spray a ton of NOS. Now if the car has crap heads or a restrictor maybe then it would work but it's just a lot of compression for a decent engine. Then you add a lot of NOS and you WILL probably detonate if God isn't your tuner. Dedicated NOS engines just don't run that kind of compression from what I've seen.

When I see the big boys running compression like that and cams anywhere near that I will let everyone know! Right now they are light years away from that and much lower compresion, at least the fast ones are.

I am of the same opinion that lowering compression (by a large margin) will slow the car down.

Well you don't need it at 8 to 1 but I would say 12-13 to 1 is more common place. I did a small block chevy for a guy on LS1tech here that went low 8s and 170+mph right off the trailer and it wasn't anywhere near as radical as 15.5 to one! I don't think he was even spraying anymore NOS either.

Hey Erik...

Guess this is pretty much sums up what we were talking about the other day... Glad you said it, shit if I wrote this, I'd be banned!

Ed

Yes it is but I am encouraged that people are at least talking about all this stuff. The problem is that there are still guys telling people like Friendly Freddie that you can increase overlap and "bleed off compression!" This is the stuff that scares me and I hear stuff like that everday. People should know better. Even with all the cam talk on these boards though I just never stop hearing the crap like that.

Yes it is but I am encouraged that people are at least talking about all this stuff. The problem is that there are still guys telling people like Friendly Freddie that you can increase overlap and "bleed off compression!" This is the stuff that scares me and I hear stuff like that everday. People should know better. Even with all the cam talk on these boards though I just never stop hearing the crap like that.

Erik, Bryan from LME just informed me that my compression is more like 14:1. I think I'll do something to back compression off just a touch.

I for one, really appreciate you guys that are "in the know" chiming in to help the rest of us out. I like to think I'm a pretty intelligent guy , but I don't know about a lot of the more complex things that are going on inside of a combustion chamber. I want to talk to people that are more versed in these areas and be able to make an informed decision. They say "jack of all trades, master of none" , I don't want to fall into that category.

Erik, Bryan from LME just informed me that my compression is more like 14:1. I think I'll do something to back compression off just a touch.

I for one, really appreciate you guys that are "in the know" chiming in to help the rest of us out. I like to think I'm a pretty intelligent guy , but I don't know about a lot of the more complex things that are going on inside of a combustion chamber. I want to talk to people that are more versed in these areas and be able to make an informed decision. They say "jack of all trades, master of none" , I don't want to fall into that category.

Well even 14 to 1 sounds a lot better and I know you were set up for NA at first. 15.5 to 1 is usually pretty damn hard to get anyway! at 14 to 1 you aren't way out of range at least. The NOS will make a little more power with high compresion as well but most experienced NOS guys get leery of super high compression and big NOS since it's starting to get unstable at those compressions to tune so usually they have to back off the tune quite a bit for safety.

Ha, love it. Sort of reminds me of a discussion I had back in the day on this
forum about Nitrous and relatively low compression on pump gas.

Nice to know someone knows better!

Ha, love it. Sort of reminds me of a discussion I had back in the day on this
forum about Nitrous and relatively low compression.

Nice to know someone knows better!

I can't tell by your reply , which side of the fence are you on? Assuming fuel is not an issue and its an all out race app , where would your compression ratio be?

I'm a firm believer in letting the engine breathe and let the valve timing
fill the cylinder as opposed to raising the SCR to make up the difference.

There is more power available from more charge entering, than a smaller charge
which is compressed higher.

Fuel type is always a concern when selecting the variables, so I wouldn't
know how to answer in a general view.

Selecting your maximum SCR without knowing how well the engine breathes
and target DCR for a specific fuel is a shot in the dark. Even knowing those
variables is still a science.

I would be looking at the torque peak RPM and work from there.

Yes it is but I am encouraged that people are at least talking about all this stuff. The problem is that there are still guys telling people like Friendly Freddie that you can increase overlap and "bleed off compression!" This is the stuff that scares me and I hear stuff like that everday. People should know better. Even with all the cam talk on these boards though I just never stop hearing the crap like that.

LOL, that "Bleeding off compression" thing with too much overlap scares me as well. I still want to know if they have even thought about that sentence and what would take for a motor to do all of that.

Freedie,

I would say the 13-14 range would be much better than 15.5:1. I think you can tune the compression with a new cylinder head with a larger chamber and settle most of your issues. You might also want to try different gasket thicknesses, maybe even larger than what you are running right now, and not just to control the compression ratio.

Bret

I'm a firm believer in letting the engine breathe and let the valve timing
fill the cylinder as opposed to raising the SCR to make up the difference.

There is more power available from more charge entering, than a smaller charge
which is compressed higher.

Fuel type is always a concern when selecting the variables, so I wouldn't
know how to answer in a general view.

Selecting your maximum SCR without knowing how well the engine breathes
and target DCR for a specific fuel is a shot in the dark. Even knowing those
variables is still a science.

I would be looking at the torque peak RPM and work from there.

In this app I kinda have a problem with "breathing" so to speak. I am limited by a small bore (4.030), and the fact that the engine is only 358ci. The cylinder heads flow mid 330's at 600 lift. If I go to a cylinder head like an ETP 4.0 bore LS7 (because it flows better than my existing head) will I have to spin the engine even higher to make use of the extra intake capacity? I am already buzzing this little engine to it's limit. The gearing , and converter already work very well with the power band I have now. I have never had the engine on a dyno , so I could'nt honestly tell you where it truely makes peak torque. Chassis dyno torque #s don't mean squat with a really large converter.

With my given situation I feel like I should get these AFR castings that I already own, finished up. If I don't make any more power than I have now, at least the thicker deck and better casting quality should bring me some reliability(and bring compression down a touch). Have my cam reground (or buy a new one) , this should net me a HP gain.

I am limited by a small bore (4.030), and the fact that the engine is only 358ci. The cylinder heads flow mid 330's at 600 lift.

Talk about intimidation...posting behind Bret and Erik!

Seems to me you might have too much head for the displacement. What RPM are
you spinning to? What size are the ports?

THe cam specs that you have listed seem fairly decent. I would imagine the
overlap region is fairly high on a 110 LSA? Do you have the valve timing?

As for breathing, if you're limited with bore diameter, there's always power to
be found in the intake and exhaust lengths. What sort of exhaust setup
are you using, and what are the details?

Keep in mind, this reply is based on 69.9% theory, 20% application and, 10% dyno testing...the other .1% contains a little luck and bench racing! ha

In this app I kinda have a problem with "breathing" so to speak. I am limited by a small bore (4.030), and the fact that the engine is only 358ci. The cylinder heads flow mid 330's at 600 lift. If I go to a cylinder head like an ETP 4.0 bore LS7 (because it flows better than my existing head) will I have to spin the engine even higher to make use of the extra intake capacity? I am already buzzing this little engine to it's limit. The gearing , and converter already work very well with the power band I have now. I have never had the engine on a dyno , so I could'nt honestly tell you where it truely makes peak torque. Chassis dyno torque #s don't mean squat with a really large converter.

With my given situation I feel like I should get these AFR castings that I already own, finished up. If I don't make any more power than I have now, at least the thicker deck and better casting quality should bring me some reliability(and bring compression down a touch). Have my cam reground (or buy a new one) , this should net me a HP gain.

Ditch whatever crankshaft you have and get a bigger one.

Talk about intimidation...posting behind Bret and Erik!

Seems to me you might have too much head for the displacement. What RPM are
you spinning to? What size are the ports?

THe cam specs that you have listed seem fairly decent. I would imagine the
overlap region is fairly high on a 110 LSA? Do you have the valve timing?

As for breathing, if you're limited with bore diameter, there's always power to
be found in the intake and exhaust lengths. What sort of exhaust setup
are you using, and what are the details?

Keep in mind, this reply is based on 69.9% theory, 20% application and, 10% dyno testing...the other .1% contains a little luck and bench racing! ha

I would have to get with my head porter to get an idea of the size of the intake port (I do think they are pretty large, 235cc give or take) . I need to pull the cam out of the engine to get the cam id # so I can get complete specs on the cam from LSM.

I have had the car on the limiter on a couple of occasions :emb: (9100). It pulls hard all the way there. I run a 1 7/8" stepped to 2" with 3 1/2" collector Kooks header , with a header muffler and then a short section of pipe with turn downs.

The long and short of it is this, I have to do some work to get the info everybody is asking me about. :( (I'll get to it, over the next couple of weeks).

Ditch whatever crankshaft you have and get a bigger one.

He he, shut up Mike! you know I would if could, without changing everything else. I wish I had built a big motor in the first place , but alas I had faith in the LS1tech series that is now defunct.

9100 RPM is not for the average valvetrain or cylinder head. I was under the
impression this was more a street/strip motor than a pure strip motor.

I run a 1 7/8" stepped to 2" with 3 1/2" collector Kooks header , with a header muffler and then a short section of pipe with turn downs.

I bet the placement of that muffler will pick up some power. Is the muffler
connected dirrectly to the collector? Have you tried extending the collector
before inserting the muffler? Collector design, length and secondary length is very important.

9100 RPM is not for the average valvetrain or cylinder head. I was under the
impression this was more a street/strip motor than a pure strip motor.



I bet the placement of that muffler will pick up some power. Is the muffler
connected dirrectly to the collector? Have you tried extending the collector
before inserting the muffler? Collector design, length and secondary length is very important.

I have about 4 or 5 inches of pipe between the muffler and the collector and then maybe 24" after the muffler before I put the turn downs in place. What is the proper procedure for calculating these lengths?

heres a clip of the car.

http://video.ls1tech.com/search/8.73+%40+156/0/63062FAB-1ED0-4B0B-A511-1272E1CACD51.htm

Are you using a 5.3L crankshaft to make a 358 with a 4.030" bore?

I have about 4 or 5 inches of pipe between the muffler and the collector and then maybe 24" after the muffler before I put the turn downs in place. What is the proper procedure for calculating these lengths?

heres a clip of the car.

http://video.ls1tech.com/search/8.73+%40+156/0/63062FAB-1ED0-4B0B-A511-1272E1CACD51.htm


Sean,

What ive always used for the folks that want header/muffler setups is the ole crayon trick. When the wax stops melting, i place the muffler there and then a short turndown at the end. It really depends on how well your collectors scavense as well. Poor collectors seem to lose exhaust velocity shorter and quicker compared the to the better versions. When tuning the headers on the Edelbrocks I shoot for around 32" total primary lenght before adding the collector (HVMC's at the end). Seems to be working on the cars ive used them on for making good all around power.

Mike

Are you using a 5.3L crankshaft to make a 358 with a 4.030" bore?

I thought its a 4.8 crank but could be wrong.

Are you using a 5.3L crankshaft to make a 358 with a 4.030" bore?

Ben, it's 5.7l stock replacement lunati crank, but offset ground to reduce stroke. The Guys over at LME could better explain the exact specs. I might be full of poop when it comes to bore size, but I think its 4.030.

Static compression doesnt work for much on a heavy nitrous motor. 15 hp doesnt go far when 50 is just another jet away. ;)

Weve got cars going fast on 10.8 that was originally setup for 11.5

I always would err on the lower side for compression than higher - as per Erik and a few others that know well. Big nitrous motors are like Fuel motors than anything else in my opinion

Static compression doesnt work for much on a heavy nitrous motor. 15 hp doesnt go far when 50 is just another jet away. ;)

Weve got cars going fast on 10.8 that was originally setup for 11.5

I always would err on the lower side for compression than higher - as per Erik and a few others that know well. Big nitrous motors are like Fuel motors than anything else in my opinion

I agree , BUT I am already pushing this NOS bigshot plate to the limit now and the class I want to race will not allow a direct port system.

Pm me, up the pimpness on the plate you can run more nitrous accurately through a plate system than an LS1 will keep its heads down on under any circumstances

Pm me, up the pimpness on the plate you can run more nitrous accurately through a plate system than an LS1 will keep its heads down on under any circumstances

Done , any suggestions are very much appreciated!!

The crayon/paint method is much better than guessing, but according to
several tuners, the length is not optimum.

Where the exhaust heat stops burning off the paint, or crayon does not
necessarily represent the tuned wave length for a specific RPM.

I don't know of any programs that calculate the correct length.
Does "Pipemax" have such a feature?

I have used some empirical values suggested by Vizard to tune my exhaust.

The crayon/paint method is much better than guessing, but according to
several tuners, the length is not optimum.

Where the exhaust heat stops burning off the paint, or crayon does not
necessarily represent the tuned wave length for a specific RPM.

I don't know of any programs that calculate the correct length.
Does "Pipemax" have such a feature?

I have used some empirical values suggested by Vizard to tune my exhaust.
I can calculate it.

I just need the seat duration of the exhaust lobe(not .020" duration, but the actual opening to closing points.), the RPM that you want tho length tuned for, and the exhaust temp at that RPM.

Pipemax is definitely the program to have to design headers.

Pipemax is definitely the program to have to design headers.

Yes definately the best I have found for that purpose.

Bret