QUOTING myself after the discussion: My stroke is 4.00". My intakevalves will close at 36 degrees after.I needsome help figuring outwhat compression ratio Iwillbe at?I'veused some calculators at some of the major builder websites and I come up with different answers.I want to make sure that I'm in the ball park of 10:1 compression.
Thanks
Just to help myself and to squelch myfriendsnagging meand anyone else thathas questions of their own; I CC'd my heads with a syringe and water. They are dead on 78 CC's. I checked them twice because I know how I am.

 

I used the calculator at rbracing-rsr.com and come up with 9.65 compression...I'm assuming zero deck height...with 36* intake close at sea level that's 185# compression

 

zero deck; that's correct. Thanks.That is a corrected value?

 

go to bigboyzcycles.com
then go to their calculator section - there is a place to fill in your engine specs and the cam you are using - gives you the hot and cold compression and even the corrected compression based on the specific cam you have.
nice.

 

You will be around 9.7 to 9.8 to one. my cam closes and 40 deg. after and I have 200 lbs of cranking cylinder presure.

you will need a 4 cc pop-up piston to make a mechanical 10 to 1.

This is how my motor is setup.

 

I've been to big boyz. I'mcalculated at 9.63:1. Head quarters puts me at 10.43:1, butHQ use the simple formula of (cyl volume + chamber volume) divided by chamber volume. What is correct?

 

Did you use the HQ formula?

 

Big Boyz calculators are correct, go with those and skip the others.

I had 82cc chambers, S/E flattops, .030 head gasket, 0 DH.........and I was at 9.63-1 CR.

Now I have 78cc chambers, S/E flattops, .030 head gasket, 0 DH..........and I'm at 10.04-1 CR.

Steve

 

maineultraclassic is correct...9.65 static is what you'll have...what cam are you using?...10 to 1 is high compression for a 36* intake close

 

I'm using the HQ-0039-G cams. I asked my Head work guy to mill my heads to put me at 10:1 compression. They put my "CC" number on my sales reciept at 82 CC.

I know that my cams will work at this compression ratio, but I would rather be at 10:1 compression. I'm going to contact my Head work guy and see if this was written incorrectly, before I jump to conclusions. I'll get back with you guys later. Thanks for the input.