OK , now you guys have another dummy to pound on, but here we go. I have been reading up on compression and camshafts and now I am more confused than ever. I purchaced a comp cam 274 xtreme cam with adv 274/286 and 230/236 @.050, it has 110 lobe sep. Now my question is How high can I go with the compression and still run 92 gas? I am installing this engine in a 55 Chevy Pickup that I will mostly be driving on the streets but I do want to have the power to maybe run it on he strip at the vintage nats and not get laughed at to much. I want to stay with the speed pro pistons but really have only two choices, a -5 cc flat top or a 5cc domed. By the way I have a set of 62cc/ 2.02 cast heads. OK now I did it so have fun. John.
I would recommend that you don't go over 10.0/1 for compression ratio. I'm presently running a 406 with 10.2/1 and it runs good on 93 octane. If you end up running a piston with a dome, make sure that all the sharp edges on the dome are rounded off.
We might also point out the recent thread about building a pump gas motor and the great info in that thread, anybody save it? P.S. Think "quench!"
The cam will work ok if there's some stall speed in the torque converter in the transmission, 2200-2500 would be about right.
You could, but since the truck will mostly be street driven, I would rather run a bit less compression to make sure it won't ping on pump gas. The small potential gain from having a bit more compression isn't worth it to me.
I have a 327 with that cam and about 10:1 compression. I had the 2.02 camel humps when I switched to that cam and didn't have any problems running 90 octane gas.
Might get away with the domed pistons...and they have the advantages of being real pistons. Tough choice.
A buddy punched in my # into his puter and came up with 300 hp at the engine and about 400 lbs of torque with the flatops..... just seems low to me
Back then I was running stock flattops. Now I have hyper flat tops. But I also have 6" rods, and Iron Eagle heads, so the comparisons aren't really the same anymore. Have you run the math with different gaskets? From shims to huge gaskets, you can make enough compression difference to consider. If you could use the domes, and use big gaskets to stay in the low 10's, I'd probably do that. That way you can put thinner gaskets later if you feel you need more performance. By then, you'll be looking for 10ths of a second, not a big seat of the pants difference.
With all of the parts I mentioned before, I figure I'm somewhere in the 375-399 hp range. That may even be optimistic. I'd think that around 300 seems about right. It's just a baby 327, after all.
well thanks you guys for your input, probably stay with the flattops and just settle for just cruisin
who's specs? the piston manufactures? at what deck height are they useing for their specs? some use a zero deck height as a reference , most 327's that havent been cut on are in the .020 to .025 area......so your piston is already in the hole this much before a head gasket.if someoone has decked the block before , then your " spec" is off check the compreession height of the piston also......some of the hypers come in a ways off which heads do you have exactly? I am going to ***ume a camel hump, if they are the "461" castig , they dont work worth a **** with a domed piston due to their spark plug location. are you getting the 62 chamber from a reference book or has someone CC'd them for you , and you knowthat they are indeed a true 62. all these things are gonna play into your compression number if you are trying to stay inside certain parameters.......put it together by using"spec" sheets, and not verifying and you could be off from whare you think you are edit...sorry buzzard beat me to it while I was typing......he has been down this road before and speaks from expierence.
I think(maybe someone can verify) that the advertised compression ratios are figured at Zero deck height. My 327 was .022 down the hole and my 461 heads after worked over were about 68 cc's Edit racefab beat me to it also
The Jalopy Journal
