I'm putting together a 355 with RHS 12402 heads and an HSR. I want to go with the comp xe-268, its 224/230, 477"/480" on a 114 lsa, which I think is a little wide, I was thinking of having them custom grind it on a 113 or prefferable 112 lsa. Any advice? Its going to be a street/more strip car, 700r4 with 2400rpm stall, 3.42 posi rear, gutted, all a/c emissions gone, and a bunch of other odds and ends. Just curious as to how much the different lsa's are going change things, as I know its a critical part of cam choice.

James

 

There is already a Comp grind available pretty similar to what you are describing - but with a bit more lift. I know Thunder Racing sells the Xtreme Energy line with the wider LSAs.

I'm not familiar with the RHS heads. Where do you think the engine will be peaking? Can the bottom end handle some rpms? Also, is this going to be an EFI engine? If so, the 110 spread may present some tuning challenges. And forced induction or N2O will compound any issues with the increased overlap...regardless of whether you have a carb or EFI.

 

I would go with the 112. Unless you are going to spray, then the 113-114 would be better.

Idle will be noticibley smoother with the 114.

 

I plan on it peaking around 5500 with useable power up until 6000. 112 is what I ran in both my TPI's, I like the 268 XFI but the ramp rates are ridiculous and I already have springs so theres where I'm at. The car isnt going to see to much street like it used to, a little choppy idle is no concern. Plus I dont plan on spraying it. I just think 114 is a little to much of a spread. Any other advice on how the spread will affect the power range?

 

If you dont want to change head springs, then dont get the XFI lobes. Even the XE lobes may be a challenge to control after 5500 rpm. What are the specs on the springs you have now?

 

Comp 972-16, 1.46" OD, 1.06" ID, coild bind height is 1.195" with a 308lbs/in spring rate. I deffinatly have ruled out the XFI, my mind is pretty much made up on the XE-268 but I dont like the 114LSA, still trying to get some good input on if I should have them grind it on a 113 or 112 and how much that will affect things.

 

Alot has to do with the heads, engine size, and the intended RPM use. I typically like to go with as tight as I can with the duration needed to get me the needed RPM range and the overlap required for a decent idle - whether that's a 106 or 112 spread. I typically stay away from anything over a 112 spread for a naturally aspired engine unless the duration is large and that's what I need to get the idle right. No bigger than the cam is you're asking about and with your heads I'd go with a 112.

 

Thanks for the input guys, I've never run a cam with anything over 112 despite them both being considerably smaller. Even the XE-268 on a 112 should still be easy to tune on my 165'. Its getting close to that time to get everything back in the car and I just cant wait to see what she does.

 

My build is close to yours. I just put in that cam and broke it in yesterday. I also reused my 1.6rr's so my lift is .508 / .512. I definetly notice a cam in there now. Right now I'm untuned so the idle is a bit choppy but not to terribly bad. I've driven about 10 miles so far and am really liking the set up I have. But again I need to get my tuning done.

 

I just got the cam in today , I hope the extra cost for the custom grind justify's the 112 lsa. I'm planning on putting my motor back together tommorow hopefully.

 

So I've been wondering alot how much a 114lsa vs 112lsa on the XE268 is going to affect performace in my motor, so I played around with DD2003 and with a 114 peak hp was 367 @5000 with 366 @5500, with a 112 it was 385 @5000 and 386 @5500, same story with torque numbers. I've always been told not to take the peak numbers to seriously but more so how changes in heads, cam, etc affect things, but is that really the case? Thats 20 more pony's at 5500rpms with a 112lsa. Any input?