I want a custom grind to replace the LT4 hotcam I have now. I was pointed in the direction of 230/236 .544/.555 113LSA by Comp, or if I wanted to go bigger 236/242 .560/.580 112LSA. Car is not a dd, btw. I don't want to spin the engine past 6200 though, so I was thinking custom grind. Something around 232 duration and .560-.570s in lift on a 110-113 LSA. Any suggestions? Bret Bauer suggested not going past 232 in duration if I don't want high rpms. Car is only driven on weekends, no track time. I don't really have the $$ to be constantly replacing engine bearings and such, so that's why I'd like to avoid a top ended cam. Thanks!

 

6200rpm max RPM means you want something smaller than what you are looking at. As I said before when we talked a big cam is not what you need for that RPM range.

Bret

 

there's a lot more than just duration... lower rpm means you want ot make a lot of power down low, and there's a lot of ways to do that.
I think it would be worth your while to have a good port job done on your exhaust ports, at least a 30-degee back-cut onthe valves, a good matching cam with steep lobes and an 8 degree split with the exhaust being on the higher end. The best thing you can possibly do is get the heads done, get them flow-bench tested, and then match the cam to that.

 

aifilaw....

What happens if the 30° backcut makes the port turbulent?
Why would you want a 8° split if you are trying to make more TQ at a lower RPM?

Bret

 

When you do your porting with the plan ahead of time to back-cut the exhaust valves for better flow, then turbulence shouldn't be a problem at that point.
having a split at all goes contrary to the idea of a "small" cam that makes lots of low-end torque. But dependant on the entire combination it shows a world of gains when you are trying to make an engine with a large bandwidth (aka, torque curve peaks and stays as flat and tall as possible as early as possible, while still maintaining a decent HP curve up top (see 5500-6000rpm).
While leaving no split, or worse does give you much more torque generally speaking, you end up with a recipe for an engine that does fantastic at 2-4000 RPM, but has no guts up top, it will make great gas mileage. But if you have your foot in the throttle, your going to go past that mark and not have the power there you wanted in the first place unless you gear it way down, what you have is something fun for doing burnouts and getting off the line, and getting good gas mileage...but you'll get walked away from by every LSx engine after the 60-ft.

flame on, I suppose if I was really interested in backing my statements I could start doing dyno sheet searches on this site and post them in the thread.

Morale of the story for the original poster is to not waste your time reading this crap, if you don't know about cam mechanics, aren't doing your own porting, and have no clue about fluids, or statics...go find yourself a known reputable cam manufacturer and spend half an hour on the phone going over exactly what you want with them after you go to a known good machine shop, tell them what you want out of the heads, and then get the flow-bench results from them.

 

aifilaw,

You might want to dig into camshafts a little bit more.... some motors will want LOTS more duration on the exhaust. I just had an example where the E/I% was well over 75%, changed cams and gained a ton more at the top end with LOTS more exhaust duration, that was the part of the curve that needed it. In other situations where the E/I% ratio was @ 70%, taking exhaust duration out of the cam made for a faster car down the track and more TQ where the motor needed it. This is with 4000+ stalls and well over 6000rpm shift points. These aren't searches on the site but real world results that I run into daily. Every situation is different and there are no stead fast rules where "good matching cam with steep lobes and an 8 degree split with the exhaust being on the higher end" generally apply. It just doesn't happen.

Bret