Flat Top or dish? Looking to boost compression!!

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Old Jun 10, 2010 | 01:37 PM
  #1  
nuttkaze's Avatar
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From: Laplace, Louisiana
Flat Top or dish? Looking to boost compression!!

To make a long story short I called summit to see what they had to boost my compression up in my original 4 barrel 71' cutlass witha 350.

I told him I'm going with:

Clean up heads and go with 2.00 intake valves
Headman Headers
Eaton Posi w/3.36 gears
Rebuild my Quad Jet Carb
Edelbrock 7111 Intake
442 Air cleaner
MSD Ignition
I will choose cam after I know my compression, but I'm shooting for 9.5

He recommend TRW Speedpro Forged Dish Pistons then my phone disconnected and when I called back they were close...that was last night.

I wondering why he didn't recommend the TRW Speedpro Forged Flat Top
http://www.summitracing.com/parts/TRW-WL2320F/

What will be my compression if I went with the dish pistons vs. the flat top pistons?
Old Jun 10, 2010 | 06:29 PM
  #2  
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From: Central Fl
Can't really answer that, need to know head cc, deck height etc. but typically the flat top will give you about a half point or better over the regular dish.
Old Jun 10, 2010 | 07:14 PM
  #3  
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X2, it depends on actual measurements, but as a ballpark assessment, the 68-70 W-30 motors with steel shim head gaskets and 64-ish CC chambers were factory rated at 10.5:1. Of course, production tolerances can change that, and using the thicker FelPro blue head gaskets will lower it.
Old Jun 10, 2010 | 07:40 PM
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Joe did you mean W31?
Old Jun 11, 2010 | 07:31 AM
  #5  
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Originally Posted by svnt442
Joe did you mean W31?
Yeah, sorry. I'm kinda big-block-centric...
Old Jun 12, 2010 | 03:12 PM
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From: Phx, AZ
Originally Posted by joe_padavano
X2, it depends on actual measurements, but as a ballpark assessment, the 68-70 W-30 motors with steel shim head gaskets and 64-ish CC chambers were factory rated at 10.5:1. Of course, production tolerances can change that, and using the thicker FelPro blue head gaskets will lower it.
Too bad these heads came with a 68-70cc chamber from the factory.
Factory rating, and production pieces, are sometimes two different monsters.
It will take at least a .030" cut to get to the 64-65cc chambers. Then cut another .020" to account for the gaskets.
Then you might be at the 10.5:1.
If you skip the milling, you will be much closer to your target, IMHO.
Jim

Last edited by Warhead; Jun 12, 2010 at 03:23 PM.
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