Cam spec info..

gaetz1985

Registered User
Okay I have a 218/226 .500 .500 108lsa cam I bought and installed in my SC build engine.. Im told that it may not be the best match w my ported heads and m90... Ive even gotten comments from people saying it may "work against" my blower.. What do they mean? What specs does your cam have? And what should mine?
 
Whats a large cam spec'd at? Who around here does regrinds? I know a regrind guy that ive successfully gotten a cam from but he's more recently been called out on taking peoples money and banned.. Frankly i'm scared to get taken like those people have..
 
gaetz,

There are a couple folks that sell cam shafts for these cars but there is only one that really specializes in it. The prices are nearly identification between them. Give XR7 Dave a shout. His e-mail address is in his signature.
 
thats a small ~~~ cam with really low lobe separation angle.

It's a bigger cam than stock in both lift and duration. There is a little more overlap than stock, considering that the duration is longer than stock. So I think it sounds like a decent cam, a moderate upgrade from stock.
 
It's the LSA that may be an issue. With a short LSA you actually run more valve overlap. In an NA motor this makes for good performance at higher RPM's as leaving the exhaust and intake valves open together for a longer period of time will allow the exhaust to help pull in the intake charge (assuming you have a high efficiency exhaust system that isn't restricitve, in which case the exhaust pressure would actually fight the intake charge entering the cylinder). Typically in cams with low LSA's you build more cylinder pressure at higher RPM.

In our engines because they work under pressure running a lot of valve overlap isn't as necessary. The SC actually forces the intake charge in and doesn't necessarily need the help of the exhaust to pull the charge in. In fact running a lot of valve overlap only allows much of the boost/intake-charge to go right out the exhaust as waste. A higher LSA will actually build more cylinder pressure down low as their is less waste exiting the exhaust.

There is plus and minus to large and small LSA's. Their is much give and take. Turbo guys typically like LSA's around 114 degrees. But the fact is that our SC's build so much low end cylinder pressure that we can probably get away with running a shorter LSA and pick up more power at higher RPM. We simply do not need to wait for a Turbo to spool up.

a large LSA will also allow for more vacuum at idle. The more valve overlap you run the less vacuum at idle. For me personally I run a 114 degree LSA as I prefer to have real good low end performance at the sacrifice of some top end performance as well as good drivability and good vacuum at low RPM.

It really depends on the application and it's intended use. A 108 degree LSA seems a little on the low side to me as 110 - 112 degrees is probably the sweet spot for optimum performance but again it all depends on what you are trying to achieve.

As a side note. Valve size in relation to cylinder volume is really the largest determining factor of the ideal LSA.
 
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I agree completely, but I think that in this case, the duration is a much bigger deviation from stock than the LSA. So focusing on the LSA is a little off target, because the majority of the increase in overlap is coming from the increased duration anyway.

I could be wrong, but I am guessing that it wasn't possible to modify the LSA on this cam because it was a regrind and began with a stock core.

The stock cam specs by year are here:
http://www.sccoa.com/forums/showthread.php?p=672394#post672394
 
It's the LSA that may be an issue. With a short LSA you actually run more valve overlap. In an NA motor this makes for good performance at higher RPM's as leaving the exhaust and intake valves open together for a longer period of time will allow the exhaust to help pull in the intake charge (assuming you have a high efficiency exhaust system that isn't restricitve, in which case the exhaust pressure would actually fight the intake charge entering the cylinder). Typically in cams with low LSA's you build more cylinder pressure at higher RPM.

In our engines because they work under pressure running a lot of valve overlap isn't as necessary. The SC actually forces the intake charge in and doesn't necessarily need the help of the exhaust to pull the charge in. In fact running a lot of valve overlap only allows much of the boost/intake-charge to go right out the exhaust as waste. A higher LSA will actually build more cylinder pressure down low as their is less waste exiting the exhaust.

There is plus and minus to large and small LSA's. Their is much give and take. Turbo guys typically like LSA's around 114 degrees. But the fact is that our SC's build so much low end cylinder pressure that we can probably get away with running a shorter LSA and pick up more power at higher RPM. We simply do not need to wait for a Turbo to spool up.

a large LSA will also allow for more vacuum at idle. The more valve overlap you run the less vacuum at idle. For me personally I run a 114 degree LSA as I prefer to have real good low end performance at the sacrifice of some top end performance as well as good drivability and good vacuum at low RPM.

It really depends on the application and it's intended use. A 108 degree LSA seems a little on the low side to me as 110 - 112 degrees is probably the sweet spot for optimum performance but again it all depends on what you are trying to achieve.

As a side note. Valve size in relation to cylinder volume is really the determining factor of the ideal LSA.


I knew it... I'm told w my ported heads that reversion could occur w a cam w that much overlap.. Im not going to be stretching the rpms in the engine much.. I want all of my power out of the hole really...
 
As far as the cam goes it is a regrind from ESG-642T from over at MM and its the same spec as the SSMS "lumpy" cam.. is this cam not going to be good for anything but n/a?
 
Not reversion, that has more to do with high backpressure and pulling "dirty air" back into the combustion chamber. Someone run a similar cam and lost power with a procharger. Pullied the crap out of it and could not get boost up. Figured out he was loosing intake air through the exhaust. I have always been told with fi to run at minimum 112* for this very reason.

If it were me I'd sell it to one of the na mustang guys and hit up Dave Dalke for a real blower cam. He will not run off with your money like esg aka "Thug Scammer" lol.
 
Not reversion, that has more to do with high backpressure and pulling "dirty air" back into the combustion chamber. Someone run a similar cam and lost power with a procharger. Pullied the crap out of it and could not get boost up. Figured out he was loosing intake air through the exhaust. I have always been told with fi to run at minimum 112* for this very reason.

If it were me I'd sell it to one of the na mustang guys and hit up Dave Dalke for a real blower cam. He will not run off with your money like esg aka "Thug Scammer" lol.

A little off topic, but what cam do you have in your mustang? 92bird and I are in the process of mocking up a turbo kit for my 94 sc. I have stage 3 heads from SSM, the block has been checked out at the machine shop, decked so I can run MLS head gaskets, stock sc bottom end.
Looking to run the 6262 cea turbo, 80lbs injectors, 344 LPH steath fuel pump
 
I agree completely, but I think that in this case, the duration is a much bigger deviation from stock than the LSA. So focusing on the LSA is a little off target, because the majority of the increase in overlap is coming from the increased duration anyway.

I could be wrong, but I am guessing that it wasn't possible to modify the LSA on this cam because it was a regrind and began with a stock core.

The stock cam specs by year are here:
http://www.sccoa.com/forums/showthread.php?p=672394#post672394

I know when the cams get reground that most of the machining takes place on the base circle. I have never seen it done so I can't comment too much. I do know that my stock 92 cam I was using had a stock lsa of about 110.5 degrees and when the regrinding was complete it is 114 degrees. So I would imagine there is some wiggle room to change this during the machining process but not certain of how it takes place. I can say that just a couple degree change of lsa will dramatically change the amount of overlap. There is certainly a relationship between duration, lsa and total overlap. Below are two articles I read for reference from time to time. I have felt they do a pretty good job at explaining cam shaft basics. A simple change of lsa by 2 degrees can change overlap by sometimes as much as 4 to 6 degrees. LSA IMO is the most important variable in cam selection. It will dramatically change the behavior of an engine. It affects vacuum, at what rpm you build cylinder pressure, etc. again just my opinion and I know they are like belly buttons and we all have them. LOL

http://www.hotrod.com/pitstop/hrdp_1011_cams_for_turbocharged_engines/viewall.html

http://www.popularhotrodding.com/tech/0607phr_camshaft_basics/viewall.html
 
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okay Ive got in touch with someone to regrind a core for me on the cheap cheap.. what cam profile are alot of you running? im looking for that nasty lope at idle and most of my power made in the low-mid range.. any idears?
 
okay Ive got in touch with someone to regrind a core for me on the cheap cheap.. what cam profile are alot of you running? im looking for that nasty lope at idle and most of my power made in the low-mid range.. any idears?

I would reach out to Dave Dalke and buy one of his cams. If this is going to be a street driven car I would steer clear of a cam that will be real lumpy at idle. That usually means poor vacuum at idle and that just causes drivability issues. IMO
 
If you want something that sounds nasty and has a very narrow power band, then stick with the cam you already have.
 
If you want something that sounds nasty and has a very narrow power band, then stick with the cam you already have.

Thank you dave.. I knew youd know.. I appreciate your input.. I would love to bug a cam spec'd by you but I already have spent my money elsewhere and would hate to have to put even more into it..
 
Below are two articles I read for reference from time to time. I have felt they do a pretty good job at explaining cam shaft basics. A simple change of lsa by 2 degrees can change overlap by sometimes as much as 4 to 6 degrees. LSA IMO is the most important variable in cam selection. It will dramatically change the behavior of an engine. It affects vacuum, at what rpm you build cylinder pressure, etc. again just my opinion and I know they are like belly buttons and we all have them. LOL

Thanks for the link. I read through the articles and I did like the PHR one. I agree with you in a sense - that the increase or decrease in overlap area does not have a linear relationship with the increase or decrease in degrees. The area of overlap can grow exponentially as the lobes get closer together (depending on the exact cam profile, of course).

But I do think that on a purely factual basis, decreasing LSA by 2 degrees will increase overlap by 2 degrees. And increasing LSA by 2 degrees will decrease overlap by 2 degrees.

However, to tie back in to the point you made, the 2 degrees of increased overlap are moving in the direction where the cam lobe is getting taller. And the 2 degrees of decreased overlap are moving in the direction where the cam lobe is regressing to the base circle.

So it's always 2 degrees, but these 2 degrees may be "bigger" than those 2 degrees! ;)

That's how I understand it at present, anyway.
 
A little off topic, but what cam do you have in your mustang? 92bird and I are in the process of mocking up a turbo kit for my 94 sc. I have stage 3 heads from SSM, the block has been checked out at the machine shop, decked so I can run MLS head gaskets, stock sc bottom end.
Looking to run the 6262 cea turbo, 80lbs injectors, 344 LPH steath fuel pump


The cam in it currentlly is a custom .580 lift from Dave Dalke. My heads are stage 1 split port. Are you running single port heads? You will like a 6262. It really come to life at 16psi on my previous 3.8l motor. That motor had a mild comp cam 210/218 in it.
 
Thanks for the link. I read through the articles and I did like the PHR one. I agree with you in a sense - that the increase or decrease in overlap area does not have a linear relationship with the increase or decrease in degrees. The area of overlap can grow exponentially as the lobes get closer together (depending on the exact cam profile, of course).

But I do think that on a purely factual basis, decreasing LSA by 2 degrees will increase overlap by 2 degrees. And increasing LSA by 2 degrees will decrease overlap by 2 degrees.

However, to tie back in to the point you made, the 2 degrees of increased overlap are moving in the direction where the cam lobe is getting taller. And the 2 degrees of decreased overlap are moving in the direction where the cam lobe is regressing to the base circle.

So it's always 2 degrees, but these 2 degrees may be "bigger" than those 2 degrees! ;)

That's how I understand it at present, anyway.

I thought about this some more and you are right and wrong. In the example from the PHR article they made a 4 degree change to LSA only on two cams with otherwise identical specs and it results in an 8 degree change in overlap. You are right about it being a bigger percent change due to the angle of the triangle. The degrees of overlap is not 1:1 with change of degrees in Lobe seperation angle.
I pasted the excerpt from the article in PHR.


To understand where I am going, let's take a look at a typical cam-buying scenario. A hot rodder calls up and asks for a hydraulic cam of, say, 290 degrees for his 350 small-block street driver. Now this is a fairly big cam and could involve a lot of overlap, possibly even too much for the application. What usually happens is the cam tech guy, recognizing that this cam may not be as well-mannered as the customer would like, recommends the cam be ground on a wider-than-optimal LCA. Widening the LCA reduces the overlap and tightening it increases overlap. To maintain sufficient idle and vacuum qualities, the cam tech recommends the cam be ground on, say, 112-degree LCA, which gives an overlap of 66 degrees. For a typical performance-headed 350, the optimal LCA is usually 108 degrees. Grinding the 290-degree cam, our guy is calling for on a 108 LCA results in 74 degrees of overlap. At first this does not sound like too much more, but the reality is it's the area of the overlap triangle that influences the situation, and the through-flow area of the overlap triangle goes up just about as the square of the overlap angle. This makes the 74-degree overlap a 26 percent increase, not the 12 percent you might have expected.
 
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I thought about this some more and you are right and wrong. In the example from the PHR article they made a 4 degree change to LSA only on two cams with otherwise identical specs and it results in an 8 degree change in overlap. You are right about it being a bigger percent change due to the angle of the triangle. The degrees of overlap is not 1:1 with change of degrees in Lobe seperation angle.
I pasted the excerpt from the article in PHR.


To understand where I am going, let's take a look at a typical cam-buying scenario. A hot rodder calls up and asks for a hydraulic cam of, say, 290 degrees for his 350 small-block street driver. Now this is a fairly big cam and could involve a lot of overlap, possibly even too much for the application. What usually happens is the cam tech guy, recognizing that this cam may not be as well-mannered as the customer would like, recommends the cam be ground on a wider-than-optimal LCA. Widening the LCA reduces the overlap and tightening it increases overlap. To maintain sufficient idle and vacuum qualities, the cam tech recommends the cam be ground on, say, 112-degree LCA, which gives an overlap of 66 degrees. For a typical performance-headed 350, the optimal LCA is usually 108 degrees. Grinding the 290-degree cam, our guy is calling for on a 108 LCA results in 74 degrees of overlap. At first this does not sound like too much more, but the reality is it's the area of the overlap triangle that influences the situation, and the through-flow area of the overlap triangle goes up just about as the square of the overlap angle. This makes the 74-degree overlap a 26 percent increase, not the 12 percent you might have expected.
 
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