[Jay S]

John is the YS engine a 69? Looked at your profile, guessing that it 350 hp with 62 heads? (Nice car collection btw). I have calculated around 9.6 when trying to use ours 62s. The 62 heads we have measure 75 cc untouched. Seen some folks say they run 77-78 sometimes. I had a set of 13s years ago off a 70 gto 350 hp, seemed like they ran closer to 77cc. Thought they were all 72cc for years, until some others said some castings ran more cc’s and I checked what I had. Two sets of 16s have run 72. Have single nice 48 laying around I will never use to if some needs one. I think it was 72cc.

I think I posted a few weeks ago my 70 455 Olds has 10:1 with factory pistons with a 214/224 cam. Got to looking the other day at some engine specs I had down, it is 9.6. Pontiac was not the only one over rating stuff.

FWIW, My 452 with the roller cam is a pump gas F.A.S.T. type build. So I have different reason for going on the high side of compression. If I was running a big intake, carb and headers it would been fine some place in the 9s. Factory appearing is a little different deal for big hp.

[John Milner]

Originally Posted by Jay S

John is the YS engine a 69? Looked at your profile, guessing that it 350 hp with 62 heads? (Nice car collection btw). I have calculated around 9.6 when trying to use ours 62s. The 62 heads we have measure 75 cc untouched. Seen some folks say they run 77-78 sometimes. I had a set of 13s years ago off a 70 gto 350 hp, seemed like they ran closer to 77cc. Thought they were all 72cc for years, until some others said some castings ran more cc’s and I checked what I had. Two sets of 16s have run 72. Have single nice 48 laying around I will never use to if some needs one. I think it was 72cc.

I think I posted a few weeks ago my 70 455 Olds has 10:1 with factory pistons with a 214/224 cam. Got to looking the other day at some engine specs I had down, it is 9.6. Pontiac was not the only one over rating stuff.

FWIW, My 452 with the roller cam is a pump gas F.A.S.T. type build. So I have different reason for going on the high side of compression. If I was running a big intake, carb and headers it would been fine some place in the 9s. Factory appearing is a little different deal for big hp.

Thank you, I have a car addiction I guess you could say. Yes, it is a '69 model. You are probably right in that it is closer to 9.5:1. It does still have the stock un touched 62 heads. I am running 216 heads on the ram air 4 cammed 400. They might have deeper chambers than advertised too.

[HWYSTR455]

My last iron head engine was a .030 over 400, scr was 9.98. I swapped multiple cams thru it, and it just wasn't worth the effort of tuning to keep it out of det. Bad tank of gas, dial the timing back. Weather gets above 90 degrees, dial the timing back. 3-4 people in the car, dial the timing back. It was insane, would literally carry a timing light with me and dial it back on the side of the road. I had marks on the dizzy base and a mark on the block, could do it that way, but preferred to use the light, was more accurate.

I'm at about 300' elevation though.

455s, different story, they needed a half a point less everywhere to keep it out of det than the 400s.

So along the same lines, you can see why folks with 289s, 302s, 350s, and 351s can get it to live at 10:1. You might be able to do it with a 400P, but still think it's not worth it, the minor power you might gain will be lost having to dial the timing back, so, again, pointless.

.

[chiphead]

Originally Posted by HWYSTR455

My last iron head engine was a .030 over 400, scr was 9.98. I swapped multiple cams thru it, and it just wasn't worth the effort of tuning to keep it out of det. Bad tank of gas, dial the timing back. Weather gets above 90 degrees, dial the timing back. 3-4 people in the car, dial the timing back. It was insane, would literally carry a timing light with me and dial it back on the side of the road. I had marks on the dizzy base and a mark on the block, could do it that way, but preferred to use the light, was more accurate.

I'm at about 300' elevation though.



.

Do you know the deck height on that combo? Just trying to account for all the variables.