2 Head Gaskets???

[art leong]

Dave the calculator I used ( http://www.slowgt.com/Calc.htm ) gave me a slightly different reading (about a full point lower). Now I'm not sure which one is right?
I was under the thought that my compression was 13.58 to 1 with the 0.40 head gasket,
and about 12.16 to 1 with the 0.80 gasket.
Can anyone take a look at which calculator is correct?

There are only a few cams for the motor I'm using I don't want to go way up on the compression to start off plus the larger cams might have piston to valve issues. The overhead cam is probably more forgiving than a pushrod motor Due to very little weight. But I want to shoot for at least 0.060 The larger cam is .492 at the valve. The smaller one I'm using is .453

[Tom Goldman]

Art, I use the calculator Dave uses. ...I also use Challenger engine software. ... Both programs came out with similar numbers,altho higher than yours, using the specs you posted. . .....You didn't spec the gasket bore, but assuming it is 3.520"i.d., both programs indicate 14.25 to 1 compression with the .040" gasket,and 12.75to1 with an .080" gasket, if the 7.5cc dome volume is the net volume,including the valve reliefs ......Tom

[art leong]

The 7.5 cc number is the total dome displacement counting valve releifs and the piston flat area being 0.10 out of the hole. I poured the cylinder with the piston .500 down the bore. Got the volume of the bore and stroke times .500 then subtracted the volume from what I had measured. That was my dome volume.
The head gasket is 3.490.
I guess I'll have to run the thick gasket. 14+ comp ratio will be way to much for the cams I'm running but I can play with overlap due to 2 cams.

[Dave Goob Cook]

I think the Weiss calculators are pretty good, within a couple of tenths on the ratio.

You should be able to come up with a good number for the gasket, I didn't have the bore size on it, but catalog gaskets have the cc's calculated.

Don't forget to plug in the "-.010" for the piston out of the hole.

[art leong]

I added piston out of the hole to the dome cc's. I brought the piston down 0.500 then poured the cylinder. And figured the volume of the dome and the 0.10 out of the hole.
I hope I did it right?
I think the calculator I was using seems faulty 3 others had figured higher in comp ratio. Than the one I used.
Oh well I guess I'll be running a little over 13 to 1. With the 0.074 gasket. That will have to do for now.

[Dave Goob Cook]

I added piston out of the hole to the dome cc's. I brought the piston down 0.500 then poured the cylinder. And figured the volume of the dome and the 0.10 out of the hole.
I hope I did it right?

Shouldn't have needed to do that on the Weiss calculator.....it will register the "out of the hole" for you by putting the "-" in the deck clearance position.