Stroker Math

[Diamond-x]

I posted this at another site but I'm getting very little activity there, so....

Please check my math here, any input is really apprecietd

I dropped the block and head at the shop today. The owner has never done a jeep but had a lot of questions concerning the stroker, especially about compression ratio. I of course brought up quench and then the lesson began. I am a backyard mechanic at best, I've rebuilt an import and worked on a super stock car at Irwindale for a year, so like most of you guys this is a hobby. My head hurts from the math.

We measured and calculated the deck height of my block at 9.455
We cc'ed the head at 55.75, seems to be at little less than others here.

I calculate my swept volume at 768.7 cc. This accounts for the .020" overbore. Making the total displacment 4612.2
(pi x bore x bore x stroke) / 4 = SV
(3.1416 x 3.915 x 3.915 x 3.895) / 4 = 46.88ci (768.7cc)

Gasket Vol is calculated as follows
(pi x gasket bore x gasket bore x compressed gasket thickness) / 4 = GV
(3.1416 x 4 x 4 x .043 / 4 = .54" (8.852cc)

Deck Vol is obtained
(pi x bore dia x bore dia x deck clearance) / 4 = DV
(3.1416 x 3.951 x 3.951 x .045) / 4 = .55" (9.04 cc)

Quench is .088
Deck clearance + compressed gasket thickness = Quench
.045" + .043" = .088"

Dish vol will be reached by dishing the 677CP pistons to 18cc. I've seen some discussion about the true dish volume on these.

I calculate TDC Volume at 91.64
head vol + gasket vol + deck vol + dish vol = TDCV
55.75 + 8.852 + 9.04 + 18 = 91.64

This should make my compression ratio 9.38 : 1
(Swept Vol + TDCV) / TDCV = CR
(768.7 + 91.64) / 91.64 = 9.38 : 1

[dwg86]

On your calculation you are multiplying 3.1416 x diameter twice. It should be just once. Example...3.1416x4.0x.043=0.5403552. Then you would need to convert that to cubic centimeters to find out the cc,s. I don't know the conversion right now.

[Diamond-x]

the algorithum is correct I guess it's the math I am asking about. Dividing by .061 will yeild cubic centimeters.


Thanks for the reply.

[Muad'Dib]

Did you try punching your numbers into our calculator instead of doing the math yourself?

Or are you asking something else.. because it sounds like you just wanted us to double check your math...

[Cheromaniac]

A 20 thou overbore yields a bore size of 3.895" and a displacement of 4563cc. Your quench and head gasket volume calculations are correct but I make the swept volume 760.5cc, the deck volume 8.8cc, and the compression ratio 9.32:1.
Not much difference from your numbers to be of any significance.

[fishyjeep]

pi times radius squared times height is the volume of a cylinder. Not pi times diameter squared.....