educated guess at my stroker compression ratio???

[Islander90]

So I bought an already built stroker engine from a local guy who was selling his Jeep before he could put it in. I got to thinking today that I didn't ask him the compression ratio, and none of the papers include enough information for it. So I'm hoping that someone on here might have a similar experience with similar parts and might be able to take an educated guess at what it might be.

Parts used:
Crane Cam 753901 (http://store.summitracing.com/partdetail.asp?part=CRN%2D753901&N=115&autoview=sku)
Speed Pro pistons (http://store.summitracing.com/partdetail.asp?part=STL%2DH802CP30&N=0&autoview=sku)
Stock 4.2L crank and rods (obviously)

Work done (to my knowledge from the receipt):
clean block
press rods
valve job head
resurface head
blanace pistons and rods
bore block (0.030)
install cam bearings and freeze plugs
assemble motor


So what do you guys think? Any guesses?
Thanks
-Steven

[Chato]

If you bought a stroker engine with a stock crank somebody sold you a bill of goods. By definition a stroker engine has an increased displacement by using a crank which increases your stroke length, or in other words an unstock crank. Seems to me that if you start it and it runs okay without detonation you'll be okay even if you don't know the compression ratio.

[Islander90]

reread that... stock 4.2L crank... the crank that increases the 4.0L to 4.6L

[B3nMJ]

prolly 9 or 9.5 to 1, like the man said, if it runs good, then your good to go.

[bowtied_micky]

I would start with half a tank of race fuel (100 octane) and see how it runs. that stuff is expensive. Run the motor and make sure everything is fine. After about quarter of a tank, top off with premium and run that tank out. next straight premium then mid grade and finally the "cheap" stuff. if you get detonation anywhere along the way upgrade 1 level in fuel and run that.


micky

[Chato]

I knew what you meant but since you said it sdrawkcab I though I'd rub it in.

[xjbeerwagon]

Your compression ratio will be exactly 9.72:1 lol

[xjbeerwagon]

Your compression ratio will be exactly 9.72:1 lol :D

[rockcrawler304]

Without knowing the cc size after the head was milled you will never know. But like said before you are probably around 9:1 to 9.5:1 and at most 10:1 if it will run on pump gas.