I am considering two cams, and was wondering what would be better, less duration and more lift, or vise versa. Here are the specs on the two cams:
230/236 duration, .544"/.555", 112lsa
227/233 duration, .560"/.569", 112lsa
I was also considering doing the 230/236 custom ground with more lift. I will have decnt heads flowing 27x at .600, and 19x exhaust. Just wondering what would make more horsepower on the stock bottom end, and also what would effect emissions more. Thanks for the help,
Brandon

 

I belive you want the one with more lift. More lift is always better. Durration and overlap is what affects drivablity and emmisions the most.

 

Duration has way more effect on emissions than lift. Who makes that 227/233 cam? Haven't seen that grind before...

 

The 227/233 is one of the new combination motorsports grinds, they also have a 233/239, and a 239/245 grind.
Brandon

 

Duration will always make more power when compared like that. Not an expert, I read it in a HP book called camshafts and valvetrains. The higher lift cam will always lead to premature valve guide wear and worn out springs.

Jeff D.

 

So in theory would a 230/236 with a little more lift, such as 255/266 make more power than an off the shelf 230/236 with a good flowing set of heads??

 

go with the 227/233 you said your car was stock bottom ended. so you probably havent upped the compression so the smaller one wouldn't bleed off so much cylinder pressure. it will also have a smoother idle from less overlap. along with an earlier intake closing point which would bump your dcr up over the 230/236 cam. the added lift is nice too. if you dont plan on it already i'd suggest using impy head gaskets when you put it all back together which would put your compression at 10.8 which would also up dcr and improve throttle response. as for the high lift version of the 230/236 which is .605/.622" i think. i dont feel its worth the added abuse to the valve train but if you like changing vavle springs "frequently" (relative term) and shelling out wads of cash for lightwieght vavle parts to maintain control, go right ahead. yes the added lift and added duration @ .200" lift will make more power, is it worth the extra hassle/cost for the power, thats up to you. imho its not worth it, i'd take reliability and years of trouble free use over maybe 15 more hp. which is a generous estimate given that its a good ported set of stock heads.

just my humble $.02

 

not true at all, and the reasoning is more complex than I care to discuss here.

 

Not true. Old "musclecar" cams from the 60's had huge duration numbers but small lift. Those cams get their asses kicked by modern cams with way less duration, but improved lift and ramp profiles.

 

yea, but the old muscle cars were by no means compressing mixture at 10.5:1.

 

Get some decent lobes if its a custom grind and more lift.

 

yea, I'm a fan of lift as well. But it is more strain on the valvetrain. Be careful though. Too much lift and duration equals engine rebuild.

 

True, get some good springs, lifters, pushrods, retainers etc, etc. May cost alot now but youll end up using everything again in the future outside of the springs and possibly the pushrods. Plus its a lot cheaper than a rebuild.

 

Actually, most of the "hot" motors were higher! They had big compression numbers, but the larger cam durations bled off cylinder pressures and reduced the dynamic compression.

 

I think those two grinds are so close that the power difference won't be that much at all. Maybe 10 hp and tq. Unless your that finicky on max power, I'd go with the smaller one for driveability and emissions. That's your choice though. Just my .02 cents.