What do i need to tell my mechanic if he wants to know the compression ratio. I know the pistons are keith black hypereutectic and the crank and rods are typical 383 parts. The heads and deck were plained and the bowls are stock on the heads. Do you need more specifics to find the CR? Thanks, Brian

If you can help me find this info then i can plug it into my compression ratio calculator.

Engine bore that has been 30 thousenths over

Engine stroke with the 383 rods

Deck height with 5 thousandths removed

Regular gasket thickness

stock cly. head (cc)

and its got flat top pistons

 

Making the following assumptions:

Bore 4.03 (inches)
Stroke 3.75 (inches)
Rod Length 5.7 (inches)
Cyl. Head Vol. 54 (cc)
Deck Height 0.020 (inches)
Head Gasket Bore 4.166 (inches)
Head Gasket Thickness 0.039 (inches)
Piston to Cyl. Wall Clearance 0.003 (inches)
Top Ring Land Height 0.25 (inches)
Piston Dome Vol. -6.2 (cc)

The compression ratio = 11.716:1

Rich

 

Was that the compression of my motor? I figured it to be at 9.75:1.

 

Show your work.

Maybe we can show you where you made your mistake. With a 383, the LT1's smallish chambers and flat-top pistons, the static comp is usually pretty high. Really need to know the specifics of your combination, like the actual piston volume, etc..

-Mindgame

 

I have no idea, my calculation was based on the little info you provided (stroke = 3.75", presumptive bore = 4.030", and the rest assumptions based on typical LT1 numbers. If you provide the actual values I can point you to a calculator.

Rich

 

http://cgi.ebay.com/ebaymotors/ws/eB...category=33620

Those are the pistons in the car. The gaskets are fel-pro. The shop said the heads were plained and the block decked. The heads otherwise are stock with mild port work. The other stats should just be general, If not i will find them out to help me get an accurate CR reading.