[Cliff R]

"Why so rich on the A/F ratios? You're about a full point under what we aim for."

For the record I had NOTHING to do with this engine build, or the dyno sessions. My contribution to the project came after the shop owner/dyno operator called me up and told me they "pinged" the first set-up and knocked the rod bearings out of it. Of course everyone involved was blaming the ugly Q-jet carburetor.

I had him give me all the engine specs, told him the cam was shi#, and gave him specs for a replacement cam. He followed my instructions, changed ONLY the cam, and the dyno sheets tell the rest of the story.




"Pontiacs are a little different animal and although something could have been up with Steve's spring pressure (quite possibly the case), it could have been the particular lobe too.

Again, I'd have to see the specs on each camshaft if he's willing to share. The LSA wasn't what was making the second camshaft work though.....I suspect it was the duration and lobe intensity."

Pontiac engines are going to respond poorly or at least not as well to really fast ramp stuff. Couple of reasons for this, one is the flat chamber floors in the heads and EXCELLENT low lift numbers. Why shove the valves right past all that and shorten up the duration, the factory heads flow very well to about .450" lift or so. Second reason is the port layouts, and port flow ratios, combined with very conservative cross section for the CID they are feeding. That statement is sort of an opinion on my part, backed up by quite a bit of engine building, dyno and track testing. To make things even worse for these engines are the long strokes, long rods, heavy internals and undersquare design. From what I've seen here the wider we put the LSA the more we are rewarded with smoother idle, broader power curve (torque), and stronger upper mid-range and top end power. Of course I'm describing street/strip engines, full race stuff and max-effort race car with muffler stuff you can pretty much run the monster cams on tight LSA's and make great power.

I deal mostly with "stock appearing", and we use crappy iron intakes, even the horrible EGR ones, q-jets, factory distributors, etc. Since most are in real street cars, that have to life on pump gas, dead solid reliable in any weather, and still run the numbers at the track on weekends, parts selection, specifically camshafts and compression ratios must be "spot-on" on the entire deal is doomed from the moment you fire it up.

Case in point is the Super Duty 455 we're building here, it was a pretty "high end" build, FULL of "exotic" parts, and very short lived. Even if the pistons didn't lock up in the bores it was showing signs of heavy detonation and a ticking time-bomb anyhow, not to mention the owner was having a horrible time trying to get it to run well for "normal" driving. It simply refused to idle well and behave on the street......Cliff