Which pistons for supercharged 306? Compression ratio questions

[Mike92GT]

I'm planning on buying a new shortblock in the near future. My previous DSS 308 had flat top pistons. I'm wondering if I should stick with flat tops this time around, or if I should go with a dished piston? I'm going to be using my S-trim, but I only plan on running 10-12 psi. Heads are Edelbrock Performers with about a 60cc combustion chamber. I'm wondering what the difference in compression would be between the two pistons? I want to keep it around 9:1 I think

 

[Mike92GT]

Hmmm, I was just looking at CHP's site. They list compression ratio with flat top and 61 cc chamber as 9.3:1. Dish piston with 61cc chamber is only 8:1. I'm thinking I should stay with the flat top...

 

[Rick 91GT]

Is you motor a "o" deck??????? I assume you are using the same block.

If it is not and it is 8.2" (pistons are .010" in the hole) with a 4cc flat top here are your numbers.

Compression Ratio Calculator v2.d
Sunday, June 25, 2006 8:57 am

Bore Size: 4.040
Gasket Bore: 4.100
Piston Top Land Dia: 4.005
Stroke: 3.000
Connecting Rod Length 5.090
Compression Height: 1.600
Deck Height: 8.200
Ring to Top of Piston 0.250
Gasket Thickness: 0.040
Valve Notches Volume: 4.00
Dome Volume: 0.00
Volume Head: 61.00
-------------------------------------
:COMPRESSION RATIO: 9.221
-------------------------------------

calculation variables:

Piston to Deck: 0.010
Crank Throw: 1.500
Vol. Above Top Ring: 0.91 cc
Piston to Dec Vol.: 2.10 cc
Gasket Volume: 8.65 cc
Volume Clearance: 76.66 cc
Cylinder Volume: 630.19 cc
CID: 307.534

If you do have a "0" deck motor you'll be

Bore Size: 4.040
Gasket Bore: 4.100
Piston Top Land Dia: 4.005
Stroke: 3.000
Connecting Rod Length 5.090
Compression Height: 1.600
Deck Height: 8.190
Ring to Top of Piston 0.250
Gasket Thickness: 0.040
Valve Notches Volume: 4.00
Dome Volume: 0.00
Volume Head: 61.00
-------------------------------------
:COMPRESSION RATIO: 9.452
-------------------------------------

calculation variables:

Piston to Deck: 0.000
Crank Throw: 1.500
Vol. Above Top Ring: 0.91 cc
Piston to Dec Vol.: 0.00 cc
Gasket Volume: 8.65 cc
Volume Clearance: 74.56 cc
Cylinder Volume: 630.19 cc
CID: 307.534

(notes/messages)

× Piston Flush with Deck

 

[Mike92GT]

Cool, thanks Rick. I'll be OK with 9.3-9.5:1 compression and 10 or so psi right? I'm thinking a 13cc dish piston would drop my compression too much, plus I want this thing to still run OK if I take the blower off