I have misplaced my spec info on the internals of my 383. I am doing research to ad possibly a power adder, super/turbo charger. I have KB D dish pistons stock heads no porting yet. with a .030 bore, stock head gasket, how can I determine my compression ratio?

I do not know the cc of the Pistons, I assume they are 5cc.

any Ideas?

 

Assuming these numbers here's your compression ratios. KB has two dcup pistons one 18 cc and one 28cc and I have it calculated for both for ya there.

Bore = 4.030
Stroke = 3.75
Rod Length = 5.7
Deck height = 9.008
Comp. Height = 1.433
Dcup = 18 or 28
Combustion Chamber (cc) = 54cc
Thickness = .043
Bore Diameter = 4.060
Compression ratio = 10.7 or 9.5

 

wow now that is service....you are a gentlemen and a scholar.

 

Stock head gasket size is .049 not .043, also stock bore is 4" with a .030 overbore as he stated results in 4.030 not 4.060...

And 93z383 I can't calculate your static c/r without knowing what your deck height is after the block was machined.

 

Ok, That too is going to be hard to come by. My block was in very good condition when the machine shop worked on it. I hate to assume anything but for argument sake what is a minimal to average amout of milling done to a block for this type of situation, I am sure the pistons are the smaller of the two options from KB, 18cc. with that I'm probably in the 10.1 to 10.8 range I assume. I'd like to get a close ballpark so once I do something, I can calculate my best option for chamber size etc for a blown application, this is a daily driver but I don't mind puting in the preimium, I do it already.

thanks for the help.

 

I assumed the gasket diameter was 4.060 not the block diameter, I also guessed on the gasket thickness, but your not going to see that much of a change in cr with the difference in either dimension.

play with this to get static and dynamic compression
http://www.et-motorsports.cc/tech/93z383.xls (right click and save)