Instead of going with large duration and wide LSA to compensate, wouldnt it be a good idea to go short duration, with good lift, and tight LSA? Wouldnt this make good lowend, and street manners, while beating or matching the larger cams on the topend? Maybe something like a 214/224 .565/.605 110 or 108 on a LT1 with heads and bolts ons for example. Or is my idea flawed?

Thanks
Jeremy

 

Jeremy,

I've run that exact camshaft. It does have what you are talking about, but their is only a limit to what small duration can do. To make big power with it you need good heads, a bigger cam will make more power. Then again that cam also have a single plane intake with it, so it made good TQ, but the long runners could have used more camshaft. A LT1 has short runners, so it's closer to optimum.

I've come up with a smaller duration cam for stock head LT1's that's alot like what you are talking about. (BRE-M1) A ported head car will like a little bit more cam than a stock headed car, just because it will run better in the higher RPM range and the added flow does help the whole power curve.

More overlap is always going to help a small cam because that's the main problem with them. Sometimes short duration cams even want some retard to them on top of the small LSA to get the valve events right for a higher RPM setup. Look at the LS6 cam, 204/218 (big split) with a 117.5 LSA Retarded 2.5 degs. That thing pulls to 6400 pretty dam well, but adding 10 degs to the intake and some more to the exhaust while giving it some overlap will help it out even more.

Bret

 

A good flowing head is going to be needed to make good power with a small cam like that true. But, does it work the other way, ei: long duration and wide LSA? I was wondering bcuz I have EA Pro and it doesnt seem to support my idea. It says that a wider, 114 vs 110, would not only make more avg power, but more peak power. Though, granted it is only EA Pro.

 

A good flowing head is needed to make big power, but a small duration narrow LSA cam will still work on stock heads. The program is telling you that because it's not as sensative to overlap and it likes the later IVC to make the power.

I'm suprised that the 214/224 3190/3192 110 doesn't work well in Pro, it did for me.

Bret

 

Oh it did, infact a lot better then just about evey other shelf cam, but didnt do as well as compared to the 114 LSA one.

 

I actually have v3.0, thought I had Pro. Sounds like a web browser, "New Version 3.0."

 

I've been thinking about that concept alot myself.

I'm running an L98 Camaro but with a Stealth Ram and AFR 195 heads. I've been chatting lately with the techs at comp cams. They seem to recommend the 112* lobe sep cams for fuel injection cars. I guess they're most concerned with vacuum and idle? The tighter lobe sep. makes less vacuum/ rougher idle? All the cams they recommend for carbed cars use the 110* lobe. Is this because the tighter lobe sep. makes more midrange torque and higher average horsepower?

I just picked up the extreme 218/224 cam with 110* lobe sep and .536 lift with 1.6 rockers. I figure the cam's small enough that it will still make lots of vacuum but the moderate duration and good lift should still make decent power.

My other option was to go to the cam one size bigger- 224/230 but with the 112* lobe sep. I am concerned about the size of this one, since i do lots of summer road trips and want to retain some mileage/torque in my 2500 overdrive cruise RPM (75/80mph).

I'm currently using a tiny 210/220 comp cam with 112* lobe sep. and .513 lift. Its a tiny cam, but it was in the Tuned Port Motor. It will now pull to the 6200 rev. limiter using the Stealth Ram manifold. (one awesome peice!) I'm told that my car is now faster than stock and many bolt on LS1's, but i've never driven one, so i don't know that for a fact. It idles almost like stock.

What do you guys think? Smaller with tight lobe sep, or bigger with wider lobe sep?

 

stealthramman,

Shoot me an e-mail.

A 110 or lower can work on a street car no problem, even with EFI. The cams you are looking at are in the right duration range, which means you can be even more aggressive with the LSA than you think.

Your basically looking for a balance of mileage, TQ and HP and this type of cam is a good comprimise.

Bret

 

I was flipping through the November 2003 GM HTP magazine where they did an article on some hot street LS1 and LT1's to see what they used for camshafts.

I noticed that they seemed to be 112* or 113* with a couple of owners not wanting to give out their specs. A lot of these cars are in the low 11's, so these are fast street f-bodies IMO.

Comp cams recommends 110* lobe sep. on all their carburated cams but fast injected cars all seem to use a wider lobe? I must be missing something....

 

Most of those cars are running large cams and need the wider LSA to help out the idle quality. With short duration, like I was talking in the beginning, you can run very tight LSA and not worry about idle quality. Another thing about doing the later, you dont lose your lowend and you have great part throttle drivability while still making decent power up top. Remeber a race is about avgs and not peaks.

 

yep that's right.

 

i'm always kinda miffed that, with all the spec's the cam manufacturer's publish, none of them ever mention overlap. the overlap (in mind) is the most critical part of choosing the right cam for the application. the amount of overlap controls idle quality, emissions, fuel economy, low-torque and high rpm breathing.

lsa's and duration are good for comparing similiar-ramp cams, but kind of inadequate when dealing with cams that have different ramps. for instance:

take two cams with identical lsa's and dur. specs -

1. aggressive ramps
230° (int/exh) @ 0.050"
112° lsa

2. lazy ramps
230° (int/exh) @ 0.050"
112° lsa

with aggressive exhaust closing and intake opening ramps, cam 1 would would have a small overlap area, and therefore give a smooth idle, better low-torque, lower emissions and better fuel economy but be limited in upper-rpm breathing. with "lazy" ramps, cam 2's overlap area would increase and the results (vs the first cam) would be reversed.

i can see CC's point about carbed motors needing the tighter lsa (a carb relies to a good extent on the overlap to pull fuel in, efi doesn't) but i don't think it's a hard and fast rule. CC makes circle-track cams with 114° lsa's, but the wide separation is not enough to compensate for the 300+° (Dur @ 0.050" ) as far as using these in a daily driver.

 

The the street racers in the article i was referring to were all using cams that had less than 230* duration. 224-228 was the most common range which is aggressive for a street car, but mild for a drag car. Still as i mentioned, they were all in the 11 second 1/4 range, which is very impressive. That's technology for you!
I've read that the tighter lobe sep. makes more mid range, while the larger 112-up lobe sep gives a little more rpm.
Does this sound correct SStroker ace?

 

From what I've been told by several guys who run FI and big BIG cams, big overlap seems to give them some odd O2 readings in the lower RPMs, when using an O2 sensor. Like at idle and such.

Why? Dunno, really. I suspect that at low RPMs a lot of fresh A/F mix drifts right out the exhaust during overlap. No biggie except that the AIR part of that mix seems to scew the O2 readings to the point that they don't really like to trust them to tune the idle and near-idle mixture fuel tables.

These are anecdotal observations, not to be taken as fact. I'm sure the guys with more FI experience could comment to either confirm or dispell this.

The "right" LSA for any given combo is the one that best meets your needs for torque, HP, fuel economy and emissions with the rest of the combo of parts. Just that FI has such different intake manifold designs and control systems than a carb setup, it can affect the choice of the "right" LSA.

 

Right, but those durations are 10* more, for the intake, then what I am talking about. Cams in those duration #s, that were in the artical, dont come on until about 2500rpms, from people I have talkled to. The cam I was talking about in the beginning will pull from off idle to well into 5000+ rpms. The good thing about this is you dont have to run steep gears, so any milage you lose in overlap you could arguably gain back in having less gearing.