TTopJohn

Using the assumtion that you have a restrictive exhaust system to work with (like factory manifolds, cats, and y-pipe)
is a split pattern cam with more duration on the exhaust side going to make more power than a single pattern cam that is identical save for brining the exhaust duration down to match the intake duration?

In theory? In practice with an LS1?

I ask because somewhere back in the day I read that more exhaust duration was better for a restrictive exhaust system.

CHRISPY

Yes definitely...
The more exhaust duration you have the smaller the optimal primary tube size and header length/collector size.
Cheers,
Chris
ps- LS1's seem to need a little more help on the intake side more so than the exhaust side. Due to the intake restriction.
Cheers,
Chris

RPM WS6

iTrader: (3)

So say your running stock ’00 cast manifolds, 2 1/2” off road Y-pipe with a good collector and a very free flowing catback. Is a single pattern going to hurt you any? I ask because this is my current exhaust setup and I’ve got a B1 that’s going in the car as soon as the weather improves...

TTopJohn

Thanks Chris, that's the sort of answer I was looking for.

So, are there any ill effects from a split pattern cam? I know there is a sizable group of people that prefer single pattern cams for the LS1.

CHRISPY

Single patterns are generally easier setting up with the stock program for idle and emissions concerns. Especially on a 114LSA. IMO a good cam choice is one with about 226 degrees intake duration and depending on your exhaust mods the same exhaust duration or a little more.
Lift ranges in the .560 range are great with a double spring and LSA in the 112-114 range. (Remember with higher duration your peaks rise. A 112LSA will help lower your peak HP and boost your midrange torque slightly. However emissions are impacted)
I think a great cam for power in the 4500-6500rpm range with a 6500-6700rpm shift point would be a 226/230 .566 lift 112LSA cam.
With 1 3/4 headers, good catback and a 1000cfm race muffler you would make great power.
When the exhaust is opened up the intake becomes the main source of restriction. That is why I feel a 226-228 intake duration cam would make GREAT power on a 112LSA. with a 114LSA 224-226intake duration would work very well too.
Good luck,
Chris

98SS#2018

iTrader: (-1)

Chris- You raise an interesting point that I haven't considered. You can see my mods below, I think I'm breathing pretty well on the exhaust side, but on the intake side I'm lacking, no LS6 IM. Now are you saying our cars even w/ the LS6 IM still exhale better than inhale? If so, then my question is what about a 226/222 duration cam. Make the intake longer than the exhale. How does this sound? Also, if you'd rather not publish your ideas, I will be getting a cam soon and would be happy to be a guiena pig.

Jason

AKA-TALCUL1

...not trying to step on your thread, but...

Do you guys have an opinion on a 224/230, .538/.538, 114lsa. in an A4 w/hollow-log stock manifolds, gutted cats, SLP cat-back and stock heads?

CHRISPY

You could certainly try it to see what happens <img src="gr_stretch.gif" border="0">
It is definitely true that the LS1 intake is a restriction with good exhaust mods.
I think a good experiment would be a 226/224 112LSA cam with .566 lift and double springs.
Give it a shot I think it would work pretty well and be different <img src="gr_stretch.gif" border="0">
Chris

224/230, .538/.538, 114lsa
I think you would definitely want more lift with this cam. Probably in the 560 range. Are emissions a concern? If not go with a 226/230 on 112LSA.
Cheers,
Chris

[ March 01, 2002: Message edited by: Chris ARE 360 ]</p>

WMSuperSport

iTrader: (23)

My heads that are being machined right now have doubles. <img src="gr_stretch.gif" border="0">

98SS#2018

iTrader: (-1)

Chris- you have mail

Jason

LS1derfull

My experience with extra exhaust duration is it will somewhat help when exhaust system is restrictive, but this help is only really at peak power and above, extra exh. duration causes torque loss from backpressure at lower speeds contaminating intake stroke charge.It suffers at idle for the same reason.

Carlitos

[quote]Originally posted by Chris ARE 360:
<strong>Single patterns are generally easier setting up with the stock program for idle and emissions concerns. Especially on a 114LSA. IMO a good cam choice is one with about 226 degrees intake duration and depending on your exhaust mods the same exhaust duration or a little more.
Lift ranges in the .560 range are great with a double spring and LSA in the 112-114 range. (Remember with higher duration your peaks rise. A 112LSA will help lower your peak HP and boost your midrange torque slightly. However emissions are impacted)
I think a great cam for power in the 4500-6500rpm range with a 6500-6700rpm shift point would be a 226/230 .566 lift 112LSA cam.
With 1 3/4 headers, good catback and a 1000cfm race muffler you would make great power.
When the exhaust is opened up the intake becomes the main source of restriction. That is why I feel a 226-228 intake duration cam would make GREAT power on a 112LSA. with a 114LSA 224-226intake duration would work very well too.
Good luck,
Chris</strong><hr></blockquote>

This is very similar to the cam I had custom ground through Internet Racer's Supply. It's a 224/228, .581/.588, 114. I love it! Awesome power mid to high. The power kick in around 2600 and keeps pulling right up to 6600. I think this is a perfect street cam. Since I know I will never put slicks on my car (trannys and rearends are too expensive), having the power come on progressively makes launching with minimal wheel spin pretty easy, and then all the upshifts put me right back in the middle of my powerband. When I get my 3.73s it will be just that much better. <img src="gr_grin.gif" border="0">