Camshafts, idle quality, driveability and LSA-REAL WORLD EXP and OPINION

I didn't want to muddy up the other 340 thread with more camshaft discussion and really felt the need to share some of my experiences in this matter. Why? Maybe its the season or maybe its the Ceasars (Bloody Mary's for my US brethren)?

In my personal observations over the years I have observed the exact opposite concerning Lobe Separation Angle and duration. Warning: Blanket statement imminent.

LSA has a much greater impact on idle quality than duration does--Here's where it gets really good: CID Engine displacement means absolutely nothing! I bought into the whole "displacement eats up duration" BS for years until I kept running into the same scenario over and over and over. I've used the same tight LSA cams in every thing from a 318 to a 416 and guess what? The 416 didn't idle much better than a similar build 318 with the same cam. It really hit home when I had a chance to re-do a couple of 705 cube SuperMerlin Chevs in a Fountain boat. They had 250 @ .050" Comp solid rollers on a 106 and guess what? They idled like total garbage--very low manifold vacuum. I just want to get that out of the way. How come you can compression test a 318 with stock heads and observe 120 psi and then bolt on a set of 300+cfm race heads with the same size chamber and PSI doesn;t read any different? I'd think the mega heads would fill the cylinders better and show more cranking compression. Shouldn't they? They don't and I think I know why. I believe piston speed below about 3000 rpm just doesn't mean much.

A respected Mopar mag editor and I had this discussion a few years ago and I was the first to say---"I believe LSA has MORE to do with idle quality than duration does" He was in complete agreement and still is as far as I know.

Bottom line--tight LSA equals lumpy idle, wide LSA equals smoother idle. given same family of cam lobes.

J.Rob