Winter came a little early today. Took it for a spin, flogged it and came home and pulled the motor apart. I took the intake/carb off as well as one head so far, and was a little dissapointed in what I found. I found that I have a stock bore 454 (thought it was .030 over) and flat top pistons:sad: . Was a little upset, but it could have been worse. I have yet to pull the cam, but I know that it is nothing too radical.

So now my plans may change a little. I origonally said I had about 10-10.5:1 CR because I talked to the guy who built the motor and he said that it was ~10:1 with teh 120 cc heads. I doubt it now with the flat tops.

My compression ratio should be low right? I have yet to measure 'in the whole' or the head gasket, but I would think its not going to be anywhere near the 10:1 I hoped for. I know it has been decked (no numbers on pad) but not sure how much.

I had 120cc Chamber -236 Peanut Port heads on there, and was planning on going with the 119cc Brodix RR's. But now I am thinking I can go with the 115cc or even the 110cc set to bump my compression. How many cc's in the chamber can I take off and still be safe? I know thats a tough question without knowing the starting CR, but any educated guess would be great.

Am I going to be able to get to between 10-10.5:1 with the flat tops? Or would I be better off pulling the motor and replacing the pistons with a domed? Maybe a closed chamber head?

And lastly, the Performer 2-0 intake has one side if the plennum raised above the other by about 3". What does that do for you? I have never seen that and it look strange to me.

Thanks a lot,

Chris

Back when my 454 LS-5 was stock it had flat tops and 113 cc 820's and 8.5:1 CR.

Chris, I milled my heads down to about 102cc and decked the block to about .005 in the hole and I have about 10:1 in my 502 with the stock flat top pistons (+1cc dome). By rough calculations you would need to run a closed chamber head at about 96cc to get close to 10:1. Maybe if you run a really thin head gasket, you can get away with as much as a 100cc chamber head to get to 10:1.

Tom

And lastly, the Performer 2-0 intake has one side if the plennum raised above the other by about 3". What does that do for you? I have never seen that and it look strange to me.

Chris,
That is the typical design of a "dual plane" intake.

You'll never get any real compression with those flat tops and an aftermarket pair of cylinder heads unless you buy the 100 cc Edelbrock heads,and then you might end about 9.0 to 9.25 to 1
Forget about getting anyhere near 10 to 1 with those pistons.
IMHO,if I didn't want to tear into the shortblock,I would buy the Edelbrock 100 cc heads and get a solid flat tappet cam.

Chris (REDSS), what year motor was this? If this motor has peanuts, stock bore and flat tops, it also has a low compression ht. Guaranteed those pistons are down there a min. of .025. A lot of rebuilder Chevy 454 flat top pistons are down as much a .030 - they are also most likely a std cast piston, not a hypereutectic or forged. Personally would not run them over 5500 RPM. My suggestion, either get the heads you really want and put in some new pistons to make things right or get some closed chamber heads and cam it to make power and be done by 5500 or so.