[enkeivette]

Ring gap changed to boost specs when I replaced all the moly rings with stainless. (Compression was the same with both rings sets).

Valves are adjusted pinky tight to zero lash, quarter turn of preload. Pushrod height and valve tip wear pattern checked when I installed the 1.65 harland sharp rockers. I did NOT over-tighten them, I am very aware of that mistake. (Compression was the same before and after different rockers).

Static compression, no, absolutely not sure. The history of this motor is that I relied on the machine shops calculation to yield 10.5+:1 compression, NA cam, dynoed it, down on power. Did the math myself after measuring piston depth with a feeler guage (pistons are relieved, heads are 74cc), calculated 9.4:1. Installed a blower, kept breaking pistons. Went with a thicker HG to drop it to a then calculated 9:1, saying bye bye to proper quench, and hello to functionality. (The closest I've been since the machine shop math blunder).

The end.

[Damian]

Reading through this whole thing a couple times, I think your problem is as simple as the carb itself. You said you cleaned it, but is it possible you put it back together not quite right?

[Shaolin Crane]

Originally Posted by enkeivette

Ring gap changed to boost specs when I replaced all the moly rings with stainless. (Compression was the same with both rings sets).

Valves are adjusted pinky tight to zero lash, quarter turn of preload. Pushrod height and valve tip wear pattern checked when I installed the 1.65 harland sharp rockers. I did NOT over-tighten them, I am very aware of that mistake. (Compression was the same before and after different rockers).

Static compression, no, absolutely not sure. The history of this motor is that I relied on the machine shops calculation to yield 10.5+:1 compression, NA cam, dynoed it, down on power. Did the math myself after measuring piston depth with a feeler guage (pistons are relieved, heads are 74cc), calculated 9.4:1. Installed a blower, kept breaking pistons. Went with a thicker HG to drop it to a then calculated 9:1, saying bye bye to proper quench, and hello to functionality. (The closest I've been since the machine shop math blunder).

The end.

Which is exactly what I was getting at, advertised numbers are fun and all but they mean absolutely dick. AFR advertised my heads at 58cc and when actually measured, my first set were 65cc and the second set was 63cc. Same goes for the pistons with a 4cc relief that was actually 6cc. Piston depth is to be done with a dial indicator and degree wheel, blah blah.

So while 10.5:1, 9.4:1, 9:1 might be close, when you get precise you'll find out that it is probably closer to 8.6-8.8:1 which there is nothing wrong with, would explain why it runs better at that compression with the cam you currently have.

[enkeivette]

Guy,

8.6 would not surprise me at all. In fact it would explain the low compression gauge reading, and the tolerance of my 4032 pistons with that much boost ya? Plus, I gapped my rings on the conservative end for boost specs. What about my cam would be better off with low comp?

Damian,

Solved the problem. It was having severely oil fouled spark plugs on the left bank. Runs like a champ now.

[Shaolin Crane]

Originally Posted by enkeivette

Guy,

8.6 would not surprise me at all. In fact it would explain the low compression gauge reading, and the tolerance of my 4032 pistons with that much boost ya? Plus, I gapped my rings on the conservative end for boost specs. What about my cam would be better off with low comp?

Damian,

Solved the problem. It was having severely oil fouled spark plugs on the left bank. Runs like a champ now.

MR. Vizard will explain it a ton better than I ever can
http://www.hotrod.com/how-to/engine/...ne-angle-tech/

The dumbed down version is, your cam is meant to make good power N/A so cylinder pressures will reflect that, cycle compression will be higher, so add in boost, you either add octane, or pull timing and/or compression. Right now your compression, boost and engine is very much like a pro drag motor. They don't give much of a shit about "driveability" just "engine pressures".

[Shaolin Crane]

Here ya go, a good thread with discussion of Vizards cams
http://ls1tech.com/forums/forced-ind...reversion.html