Advanced Engineering Tech - Vizard's LSA - CI/Inch Valve Diameter chart

"LSA - Vizard's LSA to CI/Inch of valve diameter chart puts my 21.4 at 108. This chart is supposed to be for accurate for 9.0 to 11.0 compression."

I pulled this statement from a recent post. Regarding Vizard's chart, do you think it is applicable to Gen III SBC heads? I read the article and am a bit weary to apply his principles to Gen III, when it seems he is referring to Gen I heads.

I read the article and thought the same thing. I rarely see LS1s anywhere near 108LSA. I just assumed he meant Gen I heads and that it wasn't applicable to LS1s.

Could someone explain why it is/isn't applicable?

I was wondering if the chart leaned more to carb applications versus EFI. It's my understanding that the narrower the LSA the harder it is to tune the ECM.

Well one things for sure... Our intakes are totally different from single and double plane intakes of gen 1's. Therefore, I assume reversion characteristics relative to LCA and overlap would not be highly correlated b/w gen 1 and gen 3.

I was wondering if the chart leaned more to carb applications versus EFI. It's my understanding that the narrower the LSA the harder it is to tune the ECM.

I'm not a tuner, and I have heard statements like that before; however, I am under "assumption" that anything a carb can do, a computer can do better. It just depends on the quality of the individual who is doing the tune.

I was wondering if the chart leaned more to carb applications versus EFI. It's my understanding that the narrower the LSA the harder it is to tune the ECM.
Thats exactly it.

I think that chart is the biggest bunch of bullshit I have ever seen. Overlap amount is going to change with port efficnecy, cubic inchs rpm manifolding headers etc etc etc. Valve size doesn;t have shit to do with overlap.

I'm not a tuner, and I have heard statements like that before; however, I am under "assumption" that anything a carb can do, a computer can do better. It just depends on the quality of the individual who is doing the tune.
Try gettin the surge out of a cam like that in an EFI car. You wont have near the problems with a carb.

That was me that used his chart and refered to it in another thread.

I got the info from reading this article:

http://www.compcams.com/Community/Articles/Details.asp?ID=-2026144213

I learned a lot from it too.. it's a great read.

And efi car will tame a wild cam far far easier than a carb ever will.....


And the same rules probably dont apply. Tight LSA cams tend do be favoured on engines with crap heads, as they have to resort to such measures to try and make some power.

LSx heads flow very well...so these tight LSA's arent needed, or wanted.

And efi car will tame a wild cam far far easier than a carb ever will.....

SAY WHAT? Who's buildin your carbs? I run/build carbs for cams I would never even think about running in an efi car. 250/260+ duration on a 108. Silky smooth with a carb.
There are some very specific carb mods that need to be done to make them work right.

SAY WHAT? Who's buildin your carbs? I run/build carbs for cams I would never even think about running in an efi car. 250/260+ duration on a 108. Silky smooth with a carb.
There are some very specific carb mods that need to be done to make them work right.

I havent used a carb in about 5 years....I have moved on with technology.

All thats required with efi...is a laptop and suitable software/computer.

Fuel and ignition control at your fingertips. No very specific mods at all. Just simple tuning.

its great.

I havent used a carb in about 5 years....I have moved on with technology.

All thats required with efi...is a laptop and suitable software/computer.

Fuel and ignition control at your fingertips. No very specific mods at all. Just simple tuning.

its great.

Yeah. Preachin to the choir. I do a bunch of LT, LS stuff, not to mention the stand alones.
But fact is a carb doesnt have the same issues as a computer with high overlap cams. I'm talkin cams that are pretty much race car shit. Over .700 lift, over 260 degrees duration, 108, 106 LSAs.
A properly tuned carb will make just as much HP as an EFI system. And just as good of driveability. The only trade off, is cold start, because most perf carbs dont use a choke.

Yeah. Preachin to the choir. I do a bunch of LT, LS stuff, not to mention the stand alones.
But fact is a carb doesnt have the same issues as a computer with high overlap cams. I'm talkin cams that are pretty much race car shit. Over .700 lift, over 260 degrees duration, 108, 106 LSAs.
A properly tuned carb will make just as much HP as an EFI system. And just as good of driveability. The only trade off, is cold start, because most perf carbs dont use a choke.

I agree and have found the same, Carbs as archaic as they are, do allow you to get away with stuff EFI will not in general. But you have to get dirty tuning them :)

Dave

I think that chart is the biggest bunch of bullshit I have ever seen. Overlap amount is going to change with port efficnecy, cubic inchs rpm manifolding headers etc etc etc. Valve size doesn;t have shit to do with overlap.


I don't think overlap has anything to do w/ port efficiency, ci, or headers. You are correct however, that valve size doesn't have anything to do w/ it either. I'm willing to bet that all those variables do affect reversion-including valve size.

I don't think overlap has anything to do w/ port efficiency, ci, or headers. You are correct however, that valve size doesn't have anything to do w/ it either. I'm willing to bet that all those variables do affect reversion-including valve size.
Overlap, or the amount of it, affects scavenging. Scavenging aids in cylinder filling. This can either help or hurt the output. Depending on the flow characteristics of the entire motor.
So, how does it not have anything to do with any of those parts? They all have an effect on the engines ability to breathe. Well flowing intake runners combined with well flowing heads and headers would seem to not require as much overlap. So, running a bunch of overlap would tend to hurt the power in the way of wasted energy right thru the motor.

Overlap, or the amount of it, affects scavenging. Scavenging aids in cylinder filling. This can either help or hurt the output. Depending on the flow characteristics of the entire motor.
So, how does it not have anything to do with any of those parts? They all have an effect on the engines ability to breathe. Well flowing intake runners combined with well flowing heads and headers would seem to not require as much overlap. So, running a bunch of overlap would tend to hurt the power in the way of wasted energy right thru the motor.

The point is... Overlap isn't a funcion of port efficiency. Engine's ability to breathe is a function of port efficiency. My statement is only true if overlap is defined as degrees of rotation over which both valves(assuming 2 valve engine) are open.

To the point of the original post: I'm not so sure that Vizard's handy graph applies particularly well to most LSx applications. In particular, LSx motors seem to like later intake valve open and close points (and hence, a larger LSA) than older generation small and big blocks of similar displacement.

I suspect that this difference is due primarily to the very different characteristics of the plastic "candy cane" style intakes, which tend to have runners that are longer and less tapered than those of performance 4-barrel style intakes. I would bet that a 4-barrel single plane LSx intake would require very similar cam timing as a first gen SBC with similar intake.

The point is... Overlap isn't a funcion of port efficiency.
.
Well, duh. Never said it was. Overlap is nothing more than how long both valves are off their repective seats.
Engine's ability to breathe is a function of port efficiency..
Yeah. And the ability to breathe can be influenced, both positively, and negatively by valve events/overlap.

My statement is only true if overlap is defined as degrees of rotation over which both valves(assuming 2 valve engine) are open.
Not really sure what you mean there. Overlap is ONLY defined as degrees of rotation over which both valves are open. So, thats another DUH statement.
Virtually all of the components and specs you've regarded as meaningless, all have an effect on what cam specs will work best.

Ed,

Thanks for the clarification. So going back to your original post... I assume your answer to the original question is that since an EFI application is harder to tune on a narrow LSA when compared to a carb application, then Vizard's Cubic inch:valve diameter ratio chart is useless... Now it's clear.

I think it is directed more at Gen 1 engines with so-so cylinder heads and primarily carb'ed applications....and at that I feel the Vizard info is a guideline at best. There are too many factors and variables that play into the picture to say A + B always equals C (weight of car, application, trans and gear choice, idle quality, etc. etc.....all the typical stuff that applies).

In our Gen III applications, different manifold design to promote more TQ (longer runners) doesnt need as tight an LSA (to crutch and enhance midrange TQ) and in fact benefits from a wider LSA to carry that TQ (and the added upstairs power numbers that always brings). No need for tha additional overlap for better carb signal in the Gen III engine....and better airflow traits and combustion chamber design in general warrant wider LSA's (the low lift flow is better so you dont need as much overlap to generate the same amount of intake charge pull from the high speed exhaust gases exiting during the overlap period).

I have never been a huge fan of wide LSA's but I must say the Gen III engines just seem to love them. All of my combinations have made great power from the bottom of the curve till redline and most of them have been built around a 113 or a 114 LSA camshaft.....unheard of numbers in the older Gen engines (you would kill the midrange TQ with that wide a stick).

Gen III stuff kicks butt....except a Gen I/II engine built with our new Eliminator heads of course (shameless plug I know....LOL)

:usa:

And efi car will tame a wild cam far far easier than a carb ever will.....


And the same rules probably dont apply. Tight LSA cams tend do be favoured on engines with crap heads, as they have to resort to such measures to try and make some power.

LSx heads flow very well...so these tight LSA's arent needed, or wanted.Not true at all..

Tight LSAs bring hp and torque curves closer together and will generate more power and torque sooner. If the right lobes are chosen can even run to 7500 without falling on its face or EGRing (ie reversion.)

Not true at all..

Tight LSAs bring hp and torque curves closer together and will generate more power and torque sooner. If the right lobes are chosen can even run to 7500 without falling on its face or EGRing (ie reversion.)

So if this is the case....why arent the LSx community using them ? why are wider LSA's more prevalent ?

So if this is the case....why arent the LSx community using them ? why are wider LSA's more prevalent ?
Because LSx motors, and heads dont NEED tight LSA cams. Plus all the driveability bullshit that goes along with running high overlap cams with EFI.
That being said, there are guys out there running high 240s/250s on a 108/110 in LSx motors. They're just not the norm.

What driveability BS ??


Exactly what problems do you encounter when tuning big cams with efi ?

I run a 239/251, 106 LSA in my 346/LS6 - stock bottom end except for valve notches. It's a GM LSx cam for road racing.

No surge hot or cold. Self tuned. Low end torque sucks < 2500 rpm.

But, nice broad tq curve from 3000 -7000 rpm (350-400 lb-ft. rwtq).

fwiw.

I run a 239/251, 106 LSA in my 346/LS6 - stock bottom end except for valve notches. It's a GM LSx cam for road racing.

No surge hot or cold. Self tuned. Low end torque sucks < 2500 rpm.

But, nice broad tq curve from 3000 -7000 rpm (350-400 lb-ft. rwtq).

fwiw.
I'm sure you can lugg thru a school zone, in second gear, at 25 mph, and 1200 rpms, right?

I'm sure you can lugg thru a school zone, in second gear, at 25 mph, and 1200 rpms, right?
I think so. Not sure....so I'll try it. :D

what is with this presumption that Overlap has anything to do with Mid ragne power ? It doesn't. It's all about focusing the power curve through helmholtz tunning. If you get the correct runner lengths on the input and output side the right cam timming IVC IVO EVO EVC and the correct cube's and you find the FQ, tunning in a bit of overlap can "Ehance Power In a Very Narrow RPM Band" not make it.Typically what I find is that very efficiently headed Engines, high Revving 4cylinders dohc 4v engines come to mind Do Not need or benefit from lots of overlap.

Usually Overlap is a very vain attempt to procude more power through a limited and highly restricted induction system. go to far with it on a system that has a fairly low restriction level and you'll start killig power.

And thats All I have to say about that.


I think it is directed more at Gen 1 engines with so-so cylinder heads and primarily carb'ed applications....and at that I feel the Vizard info is a guideline at best. There are too many factors and variables that play into the picture to say A + B always equals C (weight of car, application, trans and gear choice, idle quality, etc. etc.....all the typical stuff that applies).

In our Gen III applications, different manifold design to promote more TQ (longer runners) doesnt need as tight an LSA (to crutch and enhance midrange TQ) and in fact benefits from a wider LSA to carry that TQ (and the added upstairs power numbers that always brings). No need for tha additional overlap for better carb signal in the Gen III engine....and better airflow traits and combustion chamber design in general warrant wider LSA's (the low lift flow is better so you dont need as much overlap to generate the same amount of intake charge pull from the high speed exhaust gases exiting during the overlap period).

I have never been a huge fan of wide LSA's but I must say the Gen III engines just seem to love them. All of my combinations have made great power from the bottom of the curve till redline and most of them have been built around a 113 or a 114 LSA camshaft.....unheard of numbers in the older Gen engines (you would kill the midrange TQ with that wide a stick).

Gen III stuff kicks butt....except a Gen I/II engine built with our new Eliminator heads of course (shameless plug I know....LOL)

:usa:

what is with this presumption that Overlap has anything to do with Mid ragne power ? It doesn't. It's all about focusing the power curve through helmholtz tunning. If you get the correct runner lengths on the input and output side the right cam timming IVC IVO EVO EVC and the correct cube's and you find the FQ, tunning in a bit of overlap can "Ehance Power In a Very Narrow RPM Band" not make it.Typically what I find is that very efficiently headed Engines, high Revving 4cylinders dohc 4v engines come to mind Do Not need or benefit from lots of overlap.

Usually Overlap is a very vain attempt to procude more power through a limited and highly restricted induction system. go to far with it on a system that has a fairly low restriction level and you'll start killig power.

And thats All I have to say about that.

Thank you!

Mamma Always said Life was like a box of chocolates.



Thank you!

So if this is the case....why arent the LSx community using them ? why are wider LSA's more prevalent ?Depends on who you ask....And it depends on application. I have a 110 cam in my car straight up. I know of a few others about to get one similar. They tend to get peakier per say but do start to make power sooner and dependant on other things do carry it out as well.

What driveability BS ??


Exactly what problems do you encounter when tuning big cams with efi ?

You shouldnt have any to be honest. Overlap=torque. Tightening up LSA's moves the hp and torque graphs closer together and therefore are more friendly. If things are setup right and are effiecient together a tight LSA cam will still pull 7200-7500 in hydraulic applications and not run out of steam like some tend to think they do. The 236/242 110 cam in my car will go 7200+ no issues but the stock A4 wont. So we put the rev limiter at 6800. Its actually flat and not climbing hard but its not nose diving either. RPM=HP with this cam. :secret2:

I think it is directed more at Gen 1 engines with so-so cylinder heads and primarily carb'ed applications....and at that I feel the Vizard info is a guideline at best. There are too many factors and variables that play into the picture to say A + B always equals C (weight of car, application, trans and gear choice, idle quality, etc. etc.....all the typical stuff that applies).

In our Gen III applications, different manifold design to promote more TQ (longer runners) doesnt need as tight an LSA (to crutch and enhance midrange TQ) and in fact benefits from a wider LSA to carry that TQ (and the added upstairs power numbers that always brings). No need for tha additional overlap for better carb signal in the Gen III engine....and better airflow traits and combustion chamber design in general warrant wider LSA's (the low lift flow is better so you dont need as much overlap to generate the same amount of intake charge pull from the high speed exhaust gases exiting during the overlap period).

I have never been a huge fan of wide LSA's but I must say the Gen III engines just seem to love them. All of my combinations have made great power from the bottom of the curve till redline and most of them have been built around a 113 or a 114 LSA camshaft.....unheard of numbers in the older Gen engines (you would kill the midrange TQ with that wide a stick).

Gen III stuff kicks butt....except a Gen I/II engine built with our new Eliminator heads of course (shameless plug I know....LOL)

:usa:

This guy hit the nail on the head. Read the part about better carb signal with tight LSA. Now go take the blue pill.

D.J.

too much overlap will hurt intake vacuum...so how would that improve a carb signal ???

With modern EFI....you can map it, and you dont even need to see a intake manifold signal. Just use TPS vs RPM.

too much overlap will hurt intake vacuum...so how would that improve a carb signal ???

With modern EFI....you can map it, and you dont even need to see a intake manifold signal. Just use TPS vs RPM.Vacuum is a good thing.

Interesting nut on overlpa discussion here. 244 244 on a 116 is the same amount of overlap as a 28 218 on a 110. Well it might not really be the same but you get the jist of what I am saying here. LSA is a stupid number. Overlap degrees is useful.

I would say overlap additively from what I have seen shortens the power band. the more you ad the shorter it gets. Its all bout focusing the powerband with overlap. If you have a 15 speed transmission and a slipper clutch you could creat the most insane 500rpm powerband possiable and the car would be fast.

Depends on who you ask....And it depends on application. I have a 110 cam in my car straight up. I know of a few others about to get one similar. They tend to get peakier per say but do start to make power sooner and dependant on other things do carry it out as well.

Except for the fact that overlap lowers vacum and therby lowering carb signaling.

This guy hit the nail on the head. Read the part about better carb signal with tight LSA. Now go take the blue pill.

D.J.

this would be why so many Carberated engines run like dogshit.

too much overlap will hurt intake vacuum...so how would that improve a carb signal ???

With modern EFI....you can map it, and you dont even need to see a intake manifold signal. Just use TPS vs RPM.

this would be why so many Carberated engines run like dogshit.
No, that is usually operator error. Nobody really knows how to work on them anymore, b/c everything has went to some form of injection over the last 19 yrs.

Obviously you are not familar with all the drilling modifing jetting pump adjusting etc.


No, that is usually operator error. Nobody really knows how to work on them anymore, b/c everything has went to some form of injection over the last 19 yrs.

Obviously you are not familar with all the drilling modifing jetting pump adjusting etc.

I have no problems with my carbed motors and tuning them properly. I was stating that most people can't tune their combo's properly anymore, b/c of the popularity of fuel injection and the lack of people useing carb's today. That is where your statement about the carb's comes into play.......or is it you that can't get a carb to run right? :engarde:

I dunno I work on a blow through carbed 468 going mid 8's so maybe I know what I am talking about.

I have no problems with my carbed motors and tuning them properly. I was stating that most people can't tune their combo's properly anymore, b/c of the popularity of fuel injection and the lack of people useing carb's today. That is where your statement about the carb's comes into play.......or is it you that can't get a carb to run right? :engarde:

Obviously you are not familar with all the drilling modifing jetting pump adjusting etc.
Oh, but I am. And none of my carbed engines run like dog shit.

How much oil do they consume on average ? There would be my idea of running like shit. You can make them drive nice but you will always have a spot in the curve where its to rich and it will wash the rings down and create oil consumption.

This would be why the Big 3 and all the foriegn manufacturers went to EFI in the first place. Reducded ring wear due to fuel wash secondly fuel control for emissions reasons.
.

You can make make a carbed car drive nice but it'll never be anywhere as good as an efi car at fuel control.

And the carbs go marching on.

:engarde:
Oh, but I am. And none of my carbed engines run like dog shit.

How much oil do they consume on average ? There would be my idea of running like shit. You can make them drive nice but you will always have a spot in the curve where its to rich and it will wash the rings down and create oil consumption.

This would be why the Big 3 and all the foriegn manufacturers went to EFI in the first place. Reducded ring wear due to fuel wash secondly fuel control for emissions reasons.
.

You can make make a carbed car drive nice but it'll never be anywhere as good as an efi car at fuel control.

And the carbs go marching on.

:engarde:
If you're washing, rings you're carb is not right, point blank. To wash out rings, it would have to off considerably.
The only time it would be that rich would be either an accelerator pump shot, or the PV opening. Both of which (esp pump shot) are mechanical 'cover ups' for 2nd or 3rd circuits that arent working right.
The more 'sensitive' the main circuits are, the less of a pump shot you need.
Most people up the pump shot with bigger squirters, or bigger CC pumps, or both. I increase the sensitivity of the main circuit, or booster. How? Well, I could tell you, but I'd have to kill you! :nod:
So, back to the original topic. Carbs, set up right, are more forgiving than EFI.
The BIG 3 never intended EFI to control engines with 8 in of manifold vacuum, driving around at 1400 rpms.

[QUOTE=LS1curious]How much oil do they consume on average ? There would be my idea of running like shit. [QUOTE]

I don't know about that, I have tuned circle track "Modified's" that are on methanol and run at 7k+ most all of the time on the track. My combo's are running for a full season without blowby on the valve cover breather's. I have several motors that have two full season's on them without having to tear them down at all. They will be refreashed at the end of this season, as the blowby is starting to get progressively worse. These cars that I am talking about are in the top 6 this year for the points lead on their 46+ race engine's. I may not be the smartest guy in the automotive industry, but I am smart enough to know that you don't make blanket statements about all carb'd motors run like dogshit. If that was the case I guess all of the NHRA race team's have crappy running carb motors too.

the fact is that you'll never get a carb 100% right ever. If you could they would still come on new cars. there is no point in continuing the discussion becuase the case was closed on this long ago.

Metering circut senstitivty isn;t your issue. Try instead on graphing up your AF across various RPM and Load ranges. You see what I am talking about.


If you're washing, rings you're carb is not right, point blank. To wash out rings, it would have to off considerably.
The only time it would be that rich would be either an accelerator pump shot, or the PV opening. Both of which (esp pump shot) are mechanical 'cover ups' for 2nd or 3rd circuits that arent working right.
The more 'sensitive' the main circuits are, the less of a pump shot you need.
Most people up the pump shot with bigger squirters, or bigger CC pumps, or both. I increase the sensitivity of the main circuit, or booster. How? Well, I could tell you, but I'd have to kill you! :nod:
So, back to the original topic. Carbs, set up right, are more forgiving than EFI.
The BIG 3 never intended EFI to control engines with 8 in of manifold vacuum, driving around at 1400 rpms.

the fact is that you'll never get a carb 100% right ever. If you could they would still come on new cars. there is no point in continuing the discussion becuase the case was closed on this long ago.

Metering circut senstitivty isn;t your issue. Try instead on graphing up your AF across various RPM and Load ranges. You see what I am talking about.
I never said you could get a carb 100% perfect. I said they were more forgiving than EFI on radical cam engines. And they are.
You stated some crap about washing rings. I stated if you were washing rings your carb is wacked.
Now you wanna make it about graphing A/F across the entire MAP/RPM table.
You're pulling shit out your ass. You're not gonna have a carb, thats damn close for the most part, rich enough in the zones where its not close, to cause any type of ring wash.
I got alot of respect for you, but sometimes you just talk shit to be argumentative.
You aint talkin to some punk kid whos got a buddy wit a dis or dat. I've tuned, wrenched, built, assisted on TS cars, alcohol funnys, etc. Upwards of 2000 hp.

I said they were more forgiving than EFI on radical cam engines.

Can you explain why ?

When a carb relies totally in intake manifold vacuum present, a radical cam can fuck this up entirely with very poor vacuum signal.

A modern efi system can be tuned, with total disregard to manifold vacuum, which means you can tune it pretty much perfectly, and easily everywhere, regardless of how big or small a cam is.

When people started switching from carbs to efi, this was one of its biggest assets. The ability to smooth and tame what were previously horrible cams to use down low.

I can get EFI to run on shit a carb wouldn't have a prayer at. I have run EFI with zero idle vacum. Alpha-N blending is a thing of beauty.

And yes you will have metering issue across load RPM ranges. No matter how sophisticated your carb is its still a beer can full of gas with a straw in it.

there are also sevral SAE papers on this discussion and the studys that they did. go read some papers on ring wash and engine life come back here and we can disucss this on the same footing.

I never said you could get a carb 100% perfect. I said they were more forgiving than EFI on radical cam engines. And they are.
You stated some crap about washing rings. I stated if you were washing rings your carb is wacked.
Now you wanna make it about graphing A/F across the entire MAP/RPM table.
You're pulling shit out your ass. You're not gonna have a carb, thats damn close for the most part, rich enough in the zones where its not close, to cause any type of ring wash.
I got alot of respect for you, but sometimes you just talk shit to be argumentative.
You aint talkin to some punk kid whos got a buddy wit a dis or dat. I've tuned, wrenched, built, assisted on TS cars, alcohol funnys, etc. Upwards of 2000 hp.

Blah, Blah, Blah.
Carbs are more forgiving. Alpha-N or not. And you aint tunin no shit with no idle vacuum.
And believe me, I've cleaned up more tunes than I can count. Idle problems, surge problems, shit others cant seem to figure out. Even 'well known' tuners.
Carbs are not near as sensitve as EFI is. Even with very low vacuum, and lots of intake reversion.
And just from a pure performance standpoint, why has Harold Martins EFI NOS Pro Mod never been able to keep up with the Carb cars? Hes got all the backing in the world.
I'm not an EFI critic. I love EFI. I'm an electronics guy for the past 15 plus years. But I know their limitations.
I've tuned some of the craziest shit out there. And I know what works and what doesnt. And what you can get away with and what not.
Your analogy of a carb being a 'can of gas with a straw in it' explains your misunderstanding of the level of technology of carburators these days.

Blah, Blah, Blah.
Carbs are more forgiving. Alpha-N or not. And you aint tunin no shit with no idle vacuum.

If there was no vacuum...I guess the engine probably wouldnt be running lol, so thats maybe an extreme example.

But defo cases where vacuum is very low. I can only think, that if you think carbs are easier...you must be trying to tune with a calculator. Because it sure isnt a modern efi system !!

hmm I think you don't understand highoutput 4cylinder ITB stuff. 90 kpa idle on its best day.

No matter what you do to a carburator it'll never be anything beyond a gas can with a straw sticking out of it period.

You can add a ton of air bleeding and emulsifiying orifices and circuts you can redesign the discharge orifices all day but its doesn't change that fact ever. A carberator is a pressure differential device. No pressure difference no function. Sure a carb can tolerate low idle vacum becuase the venturi it self genrates Some of the signal. but as soon as that fuel hits the plenum it falls right out of suspension.

we have a huge difference between a Electronics guy and someone who does what he talks about for a living. Honestly the EFI system is not holding the EFI pro-mod back. Something else in the system is.Could be the ratting for flow on the TB's honestly. You have one TB with a rating at 1.5 inchs of mercury and another at 28inch of water deprssion. You also have a laminar flow elemnt in the carberator which is the venturi itself the helps drive airflow through the plate.

but I am done with this topic. EFI wins if carbs are so great why is proof is in the pudding. F1 runs EFI. if a carb had an advatage I think the companies spending millions daily to find HP would be all over it.

If you want to talk fankly about fuel atomoization differences between carberators and EFI glad to have that discussion.



Blah, Blah, Blah.
Carbs are more forgiving. Alpha-N or not. And you aint tunin no shit with no idle vacuum.
And believe me, I've cleaned up more tunes than I can count. Idle problems, surge problems, shit others cant seem to figure out. Even 'well known' tuners.
Carbs are not near as sensitve as EFI is. Even with very low vacuum, and lots of intake reversion.
And just from a pure performance standpoint, why has Harold Martins EFI NOS Pro Mod never been able to keep up with the Carb cars? Hes got all the backing in the world.
I'm not an EFI critic. I love EFI. I'm an electronics guy for the past 15 plus years. But I know their limitations.
I've tuned some of the craziest shit out there. And I know what works and what doesnt. And what you can get away with and what not.
Your analogy of a carb being a 'can of gas with a straw in it' explains your misunderstanding of the level of technology of carburators these days.

If there was no vacuum...I guess the engine probably wouldnt be running lol, so thats maybe an extreme example.

But defo cases where vacuum is very low. I can only think, that if you think carbs are easier...you must be trying to tune with a calculator. Because it sure isnt a modern efi system !!

I'll bet you $1,000.00 that Ed can make more HP in a tune than you & get it to drive better on the street than you. :)

hmm I think you don't understand highoutput 4cylinder ITB stuff. 90 kpa idle on its best day.

No matter what you do to a carburator it'll never be anything beyond a gas can with a straw sticking out of it period.

You can add a ton of air bleeding and emulsifiying orifices and circuts you can redesign the discharge orifices all day but its doesn't change that fact ever. A carberator is a pressure differential device. No pressure difference no function. Sure a carb can tolerate low idle vacum becuase the venturi it self genrates Some of the signal. but as soon as that fuel hits the plenum it falls right out of suspension.

we have a huge difference between a Electronics guy and someone who does what he talks about for a living. Honestly the EFI system is not holding the EFI pro-mod back. Something else in the system is.Could be the ratting for flow on the TB's honestly. You have one TB with a rating at 1.5 inchs of mercury and another at 28inch of water deprssion. You also have a laminar flow elemnt in the carberator which is the venturi itself the helps drive airflow through the plate.

but I am done with this topic. EFI wins if carbs are so great why is proof is in the pudding. F1 runs EFI. if a carb had an advatage I think the companies spending millions daily to find HP would be all over it.

If you want to talk fankly about fuel atomoization differences between carberators and EFI glad to have that discussion.
I do do what I'm talking about for a living. I never said carbs were "better" than fuel injection. I said, and I'll repeat it again for you guys that like to twist words; Carbs are more forgiving than EFI. Listening to the two of you, you would wonder how anything every ran with less than 20 in of idle vacuum before the introduction of EFI.
F1=huge technology. No doubt.
Indy car, same thing, or close anyways.
But, you gotta give some props to the NASCAR guys (I'm not a big fan) for gettin it done on 1960s technology. Not to mention all the thousands of bracket cars, circle track cars, that run engines for sometimes several seasons without tear down, and never experience "ring wash" that would be severely detrimental to the performance, and life of the engine.
PS, I also recognize the atomization difference between the two.
We can be done here.

But defo cases where vacuum is very low. I can only think, that if you think carbs are easier...you must be trying to tune with a calculator. Because it sure isnt a modern efi system !!
I didnt say they were easier. Damn, will you guys get it right.
I tune LS1s, LT1s, aftermarket systems, yada, yada. There nothing "easy" about any of them. Not to make a cam with 8 in of idle vacuum drive nice, and idle nice, and return to idle, and not surge.

I'll bet you $1,000.00 that Ed can make more HP in a tune than you & get it to drive better on the street than you. :)

What sort of retarded comment is that ?

I'm sure you can lugg thru a school zone, in second gear, at 25 mph, and 1200 rpms, right?

Tried it.
It won't run at 25 mph and 1200 RPM in 2nd gear (3.42 rear gear) - 1200 RPM 2nd gear is about 14 mph .
It will lope along ....at 1200 rpm in 3rd gear at about 22 mph. Lope ...riding on the cam.
FWIW .

actually carb are far less forgiving then EFI. EFI systems when properly setup and designed are self compensating.

Sure you can make anything work barely with enough time. If Nascar engine builder could switch to ITB with injector above the plate setups like F! it would happen tommorow.

As for ring wash I ain't gonna waste the time pulling pictures of the many engines I have discetted over the years from the various experts at carb tunning with wasted ass rings and cylinder walls.

What looks good to you might be a totaly failure in my book.

Check the SAE papers on ring and cylinder wear. Look at the average life of a modern engine. in 1980 average engine life was about 70K or so. By 1987 and with the standardization of efi ,engine and seal life doubled. directly attribuable to fuel control.


I do do what I'm talking about for a living. I never said carbs were "better" than fuel injection. I said, and I'll repeat it again for you guys that like to twist words; Carbs are more forgiving than EFI. Listening to the two of you, you would wonder how anything every ran with less than 20 in of idle vacuum before the introduction of EFI.
F1=huge technology. No doubt.
Indy car, same thing, or close anyways.
But, you gotta give some props to the NASCAR guys (I'm not a big fan) for gettin it done on 1960s technology. Not to mention all the thousands of bracket cars, circle track cars, that run engines for sometimes several seasons without tear down, and never experience "ring wash" that would be severely detrimental to the performance, and life of the engine.
PS, I also recognize the atomization difference between the two.
We can be done here.

hmm I think you don't understand highoutput 4cylinder ITB stuff. 90 kpa idle on its best day.

No matter what you do to a carburator it'll never be anything beyond a gas can with a straw sticking out of it period.

You can add a ton of air bleeding and emulsifiying orifices and circuts you can redesign the discharge orifices all day but its doesn't change that fact ever. A carberator is a pressure differential device. No pressure difference no function. Sure a carb can tolerate low idle vacum becuase the venturi it self genrates Some of the signal. but as soon as that fuel hits the plenum it falls right out of suspension.

we have a huge difference between a Electronics guy and someone who does what he talks about for a living. Honestly the EFI system is not holding the EFI pro-mod back. Something else in the system is.Could be the ratting for flow on the TB's honestly. You have one TB with a rating at 1.5 inchs of mercury and another at 28inch of water deprssion. You also have a laminar flow elemnt in the carberator which is the venturi itself the helps drive airflow through the plate.

but I am done with this topic. EFI wins if carbs are so great why is proof is in the pudding. F1 runs EFI. if a carb had an advatage I think the companies spending millions daily to find HP would be all over it.

If you want to talk fankly about fuel atomoization differences between carberators and EFI glad to have that discussion.

Carbs make more power then EFI because of fuel atomization properties. The droplets turn into vapor in a well ported intake and cylinder head. So fine a mist/vapor that you can make the power over EFI.

That may be true....

But peak power is only a number.

Id rather have a very wide spread of power, than a simple big number over a narrow rpm band.
If high numbers were all that mattered...maybe we would all run big 2 stroke engines, that make no low end power or torque, but very impressive numbers at the top end.

A carb can maintain good AFR's etc over a limited range of operating conditions, whereas EFI can maintain optimium AFR's under ALL conditions. So generally speaking, in most cases, it will offer better performance.

the F1 guys seem to have found a way to fix that problem by locating the injector at the top of or just above the velocity stack in the TB. In doing so they get a much better atomoization and then its all straight toss up. It takes a bit of refinament and testing to find the optimal angle and hieght but locating the injector above the Blades on a single plane would be very close. In fact I am wating to see somebody ambitous enough to try a big injector TBI 4bbl setup vs a carb. Very straightforward A-B tsting.



Carbs make more power then EFI because of fuel atomization properties. The droplets turn into vapor in a well ported intake and cylinder head. So fine a mist/vapor that you can make the power over EFI.

There are plenty of dual injector ITB setups that run a primary injector close to the valve, and a secondary injector at the mouth of the velocity stack or trumpet.

Carbs need some vacuum/KPA in order to get the fuel out of the carb. Fuel injection needs none. IMHO FI has more potential to make the most horsepower.

That may be true....

But peak power is only a number.

Id rather have a very wide spread of power, than a simple big number over a narrow rpm band.
If high numbers were all that mattered...maybe we would all run big 2 stroke engines, that make no low end power or torque, but very impressive numbers at the top end.

A carb can maintain good AFR's etc over a limited range of operating conditions, whereas EFI can maintain optimium AFR's under ALL conditions. So generally speaking, in most cases, it will offer better performance.
The power band of EFI engines, LSx in particular, have more to do with intake runner length than the fact that they are EFI. Change to an open plenum, short runner carb style intake, while maintaining the t-body and injection and the operating characteristics of the engine will change.

This has gotten pretty far off track and turned in to a Carb vs EFI post, not the intended Vizad LSA argument.


I have a few questions based more on the original topic.

Say you have 2 cams specs first one being a popular cam:

Cam 1 (108 icl / 110l lsa)

Intake
.006 - .050 - .200
294 -- 243 -- 164

Exhaust
.006 - .050 - .200
300 -- 250 -- 169

IVO .006 - .050 - .200
------ 39* - 13.5* - (-26) --- BTDC

IVC .006 - .050 - .200
------ 75 --- 49.5 ---10 ----- ABDC

EVO .006 - .050 - .200
------ 82 ----57 ----- 12 ----- BBDC

EVC .006 - .050 - .200
------ 38 ----13 -- (-32) ----- ATDC

26.5* overlap
11.03 SCR - 8.02 DCR





Cam 2 (106icl 108lsa)

Intake
.006 - .050 - .200
286 -- 236 -- 159

Exhaust
.006 - .050 - .200
286 -- 236 -- 159

IVO .006 - .050 - .200
------ 37 -- 12* - (-26.5) --- BTDC

IVC .006 - .050 - .200
------ 69 --- 44 ---5.5 ----- ABDC

EVO .006 - .050 - .200
------ 73 ----48 ----- 9.5 -- BBDC

EVC .006 - .050 - .200
----- 33 ----- 8 --- (-30.5) - ATDC

20* overlap
11.03 SCR - 8.47 DCR




Wouldn't cam #2

Have less chance of reversion?
Make more bottom end TQ?
Carry TQ/RPM just about as far as cam 1?
Be "easier" to tune?

That may be true....

But peak power is only a number.

Id rather have a very wide spread of power, than a simple big number over a narrow rpm band.
If high numbers were all that mattered...maybe we would all run big 2 stroke engines, that make no low end power or torque, but very impressive numbers at the top end.

A carb can maintain good AFR's etc over a limited range of operating conditions, whereas EFI can maintain optimium AFR's under ALL conditions. So generally speaking, in most cases, it will offer better performance.
Why would you think I was talking about a peak number? They will make better average power period. Now who in the world has the money to purchase an F1 setup mimmicked to fit in their street duty car. Each unit has its pros and cons and the main thing to me is tuneabilty, consistency, and best economical power.

Bottom line is a person with a high knowledge base on carbs can and will outperform the EFI guy. Argue all you want, show me proof that EFI will outperform it in a series as tight as NASCAR or Pro Stock.

This has gotten pretty far off track and turned in to a Carb vs EFI post, not the intended Vizad LSA argument.


I have a few questions based more on the original topic.

Say you have 2 cams specs first one being a popular cam:

Cam 1 (108 icl / 110l lsa)

Intake
.006 - .050 - .200
294 -- 243 -- 164

Exhaust
.006 - .050 - .200
300 -- 250 -- 169

IVO .006 - .050 - .200
------ 39* - 13.5* - (-26) --- BTDC

IVC .006 - .050 - .200
------ 75 --- 49.5 ---10 ----- ABDC

EVO .006 - .050 - .200
------ 82 ----57 ----- 12 ----- BBDC

EVC .006 - .050 - .200
------ 38 ----13 -- (-32) ----- ATDC

26.5* overlap
11.03 SCR - 8.02 DCR





Cam 2 (106icl 108lsa)

Intake
.006 - .050 - .200
286 -- 236 -- 159

Exhaust
.006 - .050 - .200
286 -- 236 -- 159

IVO .006 - .050 - .200
------ 37 -- 12* - (-26.5) --- BTDC

IVC .006 - .050 - .200
------ 69 --- 44 ---5.5 ----- ABDC

EVO .006 - .050 - .200
------ 73 ----48 ----- 9.5 -- BBDC

EVC .006 - .050 - .200
----- 33 ----- 8 --- (-30.5) - ATDC

20* overlap
11.03 SCR - 8.47 DCR




Wouldn't cam #2

Have less chance of reversion?
Make more bottom end TQ?
Carry TQ/RPM just about as far as cam 1?
Be "easier" to tune?Cam # 1 will make the better low end grunt. Cam 2 would have more chance of reversion if the intake and cylinder head ports werent tuned for what that cam will want as far as runner length goes.

The only reason they are not running EFI is do to rules.

Well, duh. Never said it was. Overlap is nothing more than how long both valves are off their repective seats.

Yeah. And the ability to breathe can be influenced, both positively, and negatively by valve events/overlap.


Not really sure what you mean there. Overlap is ONLY defined as degrees of rotation over which both valves are open. So, thats another DUH statement.
Virtually all of the components and specs you've regarded as meaningless, all have an effect on what cam specs will work best.

What a prize

I'm trying to understand why. I'm happy to admit I don't know everything, but know one explains why so I try to use logic, and logic tells me that there is less over lap. I have always been under the impression overlap can aid in reversion. Is it due to where the exhaust valve opens?



Cam # 1 will make the better low end grunt. Cam 2 would have more chance of reversion if the intake and cylinder head ports werent tuned for what that cam will want as far as runner length goes.

This has gotten pretty far off track and turned in to a Carb vs EFI post, not the intended Vizad LSA argument.


Bringing this back up. It definitely has went off topic. Maybe someone should start a new thread to get it back on track?

Anway, I found David Vizard's article called Perfect Timing he wrote specifically for GMHTP in Oct-03. It's a 6 page article geared toward Gen III engines. I also found another article he wrote called Setting the Record straight: Exploding Valvetrain Myths. Both are good articles about camshafts with good images to reinforce his points.

Cam # 1 will make the better low end grunt. Cam 2 would have more chance of reversion if the intake and cylinder head ports werent tuned for what that cam will want as far as runner length goes.

I dissagree if they are both in the exact same motor. Let us say they are in cam only 346.
First of all these cams aren't even in the same league. Can't even compare them.
You are comparing a T-Rex size cam to like a TSP torquer.
Look at the IVC and EVO of both cams it is pretty obvious that cam2 will come on sooner in the rpms, peak sooner, peak trq sooner.

So basically minor bolt on, stock gears the cam2 would whoop the others ass in quarter and it wouldn't even be funny.

But if you optimize the combo of both, then you are comparing a midget Asian elephant to a mamoth.