Advanced Engineering Tech - Cam Design...

Hi All,

I have been testing various cams (off-the-shelf cams and home-built) with Engine Analyzer Pro for my future "427" L-92 build and getting mixed results. Supposedly, altering the LSA should be making much more difference than what the program shows, I'm not seeing but maybe 2-3% change from 102 to 114. And it seems like whatever grind numbers I use always make max power at 6000 and max torque at 5000 (that's about where I want it, however), just not understanding why it doesn't move up the RPM range when plugging in larger numbers.

My main question is this, do I want to be looking for the best "average" HP & torque numbers regardless of the peaks? So far, I've been looking strictly at the AVG numbers.

Is there anything else I should be considering besides what the different specs do to my dynamic CR & knock index since changing the specs are not affecting the RPM range?

I have an adjustable valvetrain, would it be worth the gains by going to a solid roller even with a 6500 RPM max?

You want to look at power under the curve. Peak means nothing. Also, I wouldn't worry about going solid roller for that low of an RPM, but I think you will want to go higher. What is the build for? What cam specs are you looking at? A higher displacement engine will naturally want a higher duration cam.

Just to throes some numbers at you to think about top (not sure what duration you are talking) in my 408 I'm running 12.5:1 scr, with a 255/263 .624/.624 115lsa cam which drops my dcr down to a very pump gas friendly 8.22:1 dcr....so don't get stuck on static compression, the larger your duration )later intake valve closing point) the higher you can safely, and want to raise your overall compression.

Have you use this VE calculator?
http://ls1tech.com/forums/6299673-post34.html

If you're going through this much analysis, then I'd suggest consulting one of the custom cam grinders IF you're using this to determine best cam selection, because you'll need the cam, lifters, retainers and springs to work as a system to capitalize on the gains.

The thing about solid rollers is they're more responsive on the street. You can increase @0.050 duration 8-10º and get the same idle quality with more rpm capability and less chance of valvetrain hysterisis at higher rpm.

I haven't run a hydraulic in a max effort street build in a long time. The new 'street' solids are just too much fun and with the right parts, they'll last a long time with very little/no maintenance.

;16295149']You want to look at power under the curve. Peak means nothing. Also, I wouldn't worry about going solid roller for that low of an RPM, but I think you will want to go higher. What is the build for? What cam specs are you looking at? A higher displacement engine will naturally want a higher duration cam.

Strictly street, I've had a turbo Buick for years and am used to low-revving high torque engines. So far, I get the best AVG numbers using a SR with Xtreme Energy Street lobes: 236/236 & .639/.639 on a 108 +4. It makes over 480+ ft-lbs from 2300 - 6500 peaking at 602. I have some HR's that's aren't too far off, including a "free-bee" I inherited from a used engine.

Just to throes some numbers at you to think about top (not sure what duration you are talking) in my 408 I'm running 12.5:1 scr, with a 255/263 .624/.624 115lsa cam which drops my dcr down to a very pump gas friendly 8.22:1 dcr....so don't get stuck on static compression, the larger your duration )later intake valve closing point) the higher you can safely, and want to raise your overall compression.

Much smaller than that (see above), my CR will be 11.5 and the dynamic ends up around 9.1. After pulling some timing, it shows acceptable knock index numbers.

Have you use this VE calculator?
http://ls1tech.com/forums/6299673-post34.html

No, I will take a look...

If you're going through this much analysis, then I'd suggest consulting one of the custom cam grinders IF you're using this to determine best cam selection, because you'll need the cam, lifters, retainers and springs to work as a system to capitalize on the gains.

The thing about solid rollers is they're more responsive on the street. You can increase @0.050 duration 8-10º and get the same idle quality with more rpm capability and less chance of valvetrain hysterisis at higher rpm.

I haven't run a hydraulic in a max effort street build in a long time. The new 'street' solids are just too much fun and with the right parts, they'll last a long time with very little/no maintenance.

So far, I have a N-I-B set of Patriot 2.08 valve, 59cc heads with a sightly used set of T&D adjustable rockers that were priced right, so those are in the mix, along with the "mystery cam" mentioned above. It had all the numbers ground off it, but degreeing it shows 234/244 & .598/.612 on a 110 LSA (looks like XE-R lobes). It averages 427HP/513TQ from 2000 - 6500.

With that many cubic inches I'd bet the T-Rex would be right at home.
I think it's like 242/248

With that many cubic inches I'd bet the T-Rex would be right at home.
I think it's like 242/248

Cams in that range give higher peaks, but consistently lower average numbers. If I'm thinking correctly, the average numbers are more power "under the curve"...

Cams in that range give higher peaks, but consistently lower average numbers. If I'm thinking correctly, the average numbers are more power "under the curve"...
Are you talking lower average #s based on computer simulations ??? I'm not
trying 2b sarcastic....just asking. For off idle torque and drivability then yes
average #s are where it's at but a 427 will have so much torque everywhere
and the 3600 stall gets past most any potential power band issues. Is this
for your blue car or another project ????

I have an engine dyno program too. Dyno Sim 5. I actually tried two different cams and modified cam timing and compared my track time changes to the dyno programs predicted power changes. It wasn't very accurate.

It also predicted that my car would make more average power if a retarded my cam a degree or two. My car slowed down 2 tenths.

Also, it always predicts that every possible combo is optimum with 8 degree duration spread regardless of head flow, intake, headers etc.

I don't know about your program, but I have determined that this program is more of a toy than a tool.

I think we're losing sight of the original question. I'm trying to understand why changing the LSA on various cams has relatively no effect on my "simulator" engine. Is it because of the displacement? Or maybe being oversquare?

Are you talking lower average #s based on computer simulations ??? I'm not
trying 2b sarcastic....just asking. For off idle torque and drivability then yes
average #s are where it's at but a 427 will have so much torque everywhere
and the 3600 stall gets past most any potential power band issues. Is this
for your blue car or another project ????

Everything's a "SIM" for now, it'll prolly end up in the Mav... I may end up going to a 5 speed though. If I keep the 200R4, I'll definitely be dropping the stall down a grand or so.

So far, my "mystery cam" produces the 3rd best "under the curve" powerband. If it saves me $400+ (but only costs me a couple HP or ft-lbs), how can I not justify using it?

I have an engine dyno program too. Dyno Sim 5. I actually tried two different cams and modified cam timing and compared my track time changes to the dyno programs predicted power changes. It wasn't very accurate.

It also predicted that my car would make more average power if a retarded my cam a degree or two. My car slowed down 2 tenths.

Also, it always predicts that every possible combo is optimum with 8 degree duration spread regardless of head flow, intake, headers etc.

I don't know about your program, but I have determined that this program is more of a toy than a tool.

Engine Analyzer Pro... I realize nothing is etched in stone, but where else can one "try" parts w/o spending $$$? Not looking to "beat the world" here, just building an engine using parts I already have on hand. I like the planning and building stages more than anything else. If I was Greg Anderson or Allen Johnson, I'd prolly have a different approach.

Hi All,

I have been testing various cams (off-the-shelf cams and home-built) with Engine Analyzer Pro for my future "427" L-92 build and getting mixed results. Supposedly, altering the LSA should be making much more difference than what the program shows, I'm not seeing but maybe 2-3% change from 102 to 114. And it seems like whatever grind numbers I use always make max power at 6000 and max torque at 5000 (that's about where I want it, however), just not understanding why it doesn't move up the RPM range when plugging in larger numbers.

My main question is this, do I want to be looking for the best "average" HP & torque numbers regardless of the peaks? So far, I've been looking strictly at the AVG numbers.

Is there anything else I should be considering besides what the different specs do to my dynamic CR & knock index since changing the specs are not affecting the RPM range?

I have an adjustable valvetrain, would it be worth the gains by going to a solid roller even with a 6500 RPM max?

Valve timing is not the main thing that determines torque and hp curve shapes and peaks. You are seeing that in Pro. Think intake manifold.

Especially for a street car (and road race cars) average torque and hp in the rpm range you use is what gets 'er done.

Done correctly stock LS lifters and rocker arms are good for 7500+. There are also more good hydraulic lobes than solid lobes for the rpm range you are running.

The corrrect valvetrain need not be expensive. If it were my engine, I'd chose the correct valvetrain guy and sell the T&Ds to help pay for the valvetrain.

Would you do your own surgery? Neither would I. Even automotive engineers hire out their valvetrain design and their cataract surgeries.
BTDT on both counts.

My $.02

Jon

Valve timing is not the main thing that determines torque and hp curve shapes and peaks. You are seeing that in Pro. Think intake manifold.

Especially for a street car (and road race cars) average torque and hp in the rpm range you use is what gets 'er done.

Done correctly stock LS lifters and rocker arms are good for 7500+. There are also more good hydraulic lobes than solid lobes for the rpm range you are running.

The corrrect valvetrain need not be expensive. If it were my engine, I'd chose the correct valvetrain guy and sell the T&Ds to help pay for the valvetrain.

Would you do your own surgery? Neither would I. Even automotive engineers hire out their valvetrain design and their cataract surgeries.
BTDT on both counts.

My $.02

Jon

Hey Jon, long time no hear. ;) I'm planning on using the hydraulic cam I got for free (see above, #6 I think) as it makes the 3rd best curve of all the cams I've "tested" and only then by < 5 HP/ft-lbs. As I go up in duration, the peak numbers naturally go up, but the area under the curve suffers. This is pretty much the best compromise and I could easily get by with stock lifters and trunnion-upgraded rockers with my RPM limit. I've pretty much got everything except the rotating asm. Are you saying the intake is a bottleneck? Because EAP actually shows this to be true at higher RPM's...

Like Jon said, the intake....

Tony Mamo spent some time figuring this combo out.
417 11.5ish LSL lobe 243/247 114+2
better heads than yours and a ported 102
Setup for a vette w/ 6spd.
663HP @ 6600 for dyno glory.
For my heavier, better traction, awd setup, lot's of freeway driving, I went with a 239/243 114+2.
http://ls1tech.com/forums/dynamometer-results-comparisons/1324130-417-cid-new-v2-afr-230-heads-now-updated-w-chassis-dyno-s.html

236/240 .630/.610 111 lsa Ed Curtis shelf cam
http://www.ls1tech.com/forums/dynamometer-results-comparisons/648228-video-idle-plus-streetability-wot-my-511rwhp-fti.html


From a PatG post, he says the LR intake on a LS1 wants a 42 deg IVC @050. For a 427 you'd add about 10-12 degrees.
Any later and your loosing bottom power for marginal increase up top. The LS6 cam is 40 deg IIRC.


The theory for the wide lsa according to Tony is it creates less fall off past peak with the same or slightly less peak and better low rpm efficiency. -narrow lsa equals higher and narrower peak, wide equals flatter. -and better mileage due to less overlap.
Maybe Jon will say more.....

So, if the consensus "brain trust" says to stay away from a single plane high-rise, what is the recommended setup? I'd really like to keep my MSD-6010 box and use a stand alone fueling system (like an EZ-EFI or Avenger) that I can diddle with rather than a GM ECM.

Found out from the previous owner that my mystery cam is actually an LG Motorsports G5-X3. I can only discern it's specs by reverse engineering it, as the numbers are ground off the back. Here's a mock dyno sim using it with the Victor, JR & 1200 CFM throttle valve, 40# injectors and 1.75" headers...

Edelbrock XT or ported fast 102. ECM doesn't care as long as it can fire 8 injectors.

I still need to figure out how to get a 102 on an XT for my build....


make sure your chosen ignition will work with your chosen ECM.

Hey Jon, long time no hear. ;) I'm planning on using the hydraulic cam I got for free (see above, #6 I think) as it makes the 3rd best curve of all the cams I've "tested" and only then by < 5 HP/ft-lbs. As I go up in duration, the peak numbers naturally go up, but the area under the curve suffers. This is pretty much the best compromise and I could easily get by with stock lifters and trunnion-upgraded rockers with my RPM limit. I've pretty much got everything except the rotating asm. Are you saying the intake is a bottleneck? Because EAP actually shows this to be true at higher RPM's...

Not necessarily. I was suggesting that the intake runner lengths might be important.

Just curious: Why a 427? What sort of rpm, power and torque goals do you have? I've seen some mighty strong 6L or 6.2L with stock bottom ends (with upgraded rod bolts). Being basically cheap, I'd spend my money on the stuff that moves the air, and use the strong bottom the General provided.

One of the car mags just did an LS head comparo: 317 cathedral port vs. LS2(?) rectangular port, both stock, vs. a 345 cc full-on aftermarket head. However they did it on a costly 408 shortblock. Makes me wonder why they spend all that on the bottom end for 44 (or 32) cubes and perhaps 50-60 lb-ft. and hp. It wasn't really a killer in it's best configuration. (about 175-177 psi BMEP at power peak). IMO, it was not really an apples to apples to apples test either.

Oh well. I did get a killer deal on a 2 year subscription to that mag. ;)

My $.02

Jon

I started "testing" with this displacement only for sentimental reasons, I'm not locked into displacement. Right now, I have a 6.2L bare block and will need to buy a rotator anyways.

I'm mainly looking for something fun to drive that's not temperamental at all. My current 346" combo is peaky and being carbed, is smelly and hard to start. It also has some annoying vibration around 3k that I can't seem to track down (on a different thread here last night, someone mentioned it could be due to poly motor/trans mounts but I wouldn't know how to rule that out)...

Here's a chart with more of the stats on this "paper tiger", the BMEP is quite a bit higher than what you saw in the mag, and I can't argue at all with the BSFC numbers!

No offense, but not everyone can get 200 psi BMEP at powerpeak rpm on a real engine. That's not far off what Engine Masters Street winners have done for over 10 years. That doesn't often happen with bolt-it-together engines.

190 psi BMEP @ power peak rpm is really quite good. That's -32hp @ 6000 on a 427 compared to 200 psi. Finding the last 32 hp is not always easy.

Look a little closer at your intake manifold flow coefficient and actual runner lengths and maybe the head flow numbers. Don't necesarily take claimed numbers as gospel. Look deeper into EAP. You may get more real-world numbers.

My $.02

Jon

This is a question but kind of ties into yours:

Why such wide LSA's on most LS cams?

1. Is it what works good for making power with pump gas and stock ecm's?
2. A sales and marketing type thing, ie peeps get steered that way by forums, and its hard to sell them if they are not ground wide?
3. Its the real deal and makes LS motors make big power?
4. some combo of the above?

Your program is showing you little change from 102 to 114 lsa, wow I wouldnt think that would hold true in real world. The 102 to 114 is 12 degrees different, But your actually spreading both lobes by that 12 degrees so 24 degrees total. LSA is intake CL to exhaust CL divided by 2. I do not see how you could be moving around lobes by 24 total degrees and not be effecting your results more than that on your program.

This is a question but kind of ties into yours:

Why such wide LSA's on most LS cams?

1. Is it what works good for making power with pump gas and stock ecm's?
2. A sales and marketing type thing, ie peeps get steered that way by forums, and its hard to sell them if they are not ground wide?
3. Its the real deal and makes LS motors make big power?
4. some combo of the above?

Your program is showing you little change from 102 to 114 lsa, wow I wouldnt think that would hold true in real world. The 102 to 114 is 12 degrees different, But your actually spreading both lobes by that 12 degrees so 24 degrees total. LSA is intake CL to exhaust CL divided by 2. I do not see how you could be moving around lobes by 24 total degrees and not be effecting your results more than that on your program.

And thus, the reason for this thread! It's a really good program and I cannot come to grips with this amount of change not showing up drastically in the results...

Damn I work 3rd shift and I am fading fast...

The other day I was driving home from work and thought of this. IS there any input in the program that might deal with how fast the air is flowing in the heads, not just total airflow. Like maybe they flow this many cfm and the ports have X amount of cross sectional area in inches squared? I ask because I would like to see the numbers tweaked to represent a lazier flowing intake port, like same flow but good bit bigger port. I would like to see if it still showed such a small change to moving the lobes around.

Another thing would be lower compression ratio and see if it still has a small effect.

I was just wondering if the program is estimating that really good port velocity and a good base compression ratio is making it not so sensitive to moving the valve timing events around.

sounds to me like you may have a bottle neck somewhere in your specs in the program. you should be getting change. Look at custom intake and exhaust flow numbers and calcs. I've used EAP and found it to be pretty close to real world numbers compared to some of the other programs out there that seem to be more just games. numbers are usually closer to rear wheel dyno numbers.

sounds to me like you may have a bottle neck somewhere in your specs in the program. you should be getting change. Look at custom intake and exhaust flow numbers and calcs. I've used EAP and found it to be pretty close to real world numbers compared to some of the other programs out there that seem to be more just games. numbers are usually closer to rear wheel dyno numbers.

I've got numbers for the heads (from the Patriot website) but nothing for the (Victor, JR) intake. In fact, I may need to revisit the manifold dimensions, as I did those myself...

Thanks!

well that would seem to be the likely culprit. If you can't increase airflow through the motor...all things point to air ;)