Help calculate my compression
10-01-2006, 10:08 PM
#3
You'll need the chamber volume of your heads after milling, the deck height of the piston (should be above the deck a few thousandths), the thickness of the head gasket used, any dome/dish volume on the piston if it is not a flattop. Those should be enough to get the static compression.
Since you have listed the cam, I'm guessing you've looking for dynamic compression also. I've never found the durations and ICL listed for the G5X3 cam, so I don't know how you could calculate it.
Since you have listed the cam, I'm guessing you've looking for dynamic compression also. I've never found the durations and ICL listed for the G5X3 cam, so I don't know how you could calculate it.
10-01-2006, 10:15 PM
#4
I see. Help me if you don't care. I absolutely meant DCR. SCR is easy.
I think that 243's milled .030 brings them to 59cc. Is that right?
Using GM MLS gaskets, which are .060".
Stock bottom end, so piston is -.008" (sticks out of the hole .008").
G5X3 is a 234/242 duration.
112LSA but they are +4. So I don't know if that means they're on a 108 ICL or how that works out. Maybe someone like Patrick G can chime in on that.
Piston will be flycut .060. Any estimates on the volume of that?
I think that 243's milled .030 brings them to 59cc. Is that right?
Using GM MLS gaskets, which are .060".
Stock bottom end, so piston is -.008" (sticks out of the hole .008").
G5X3 is a 234/242 duration.
112LSA but they are +4. So I don't know if that means they're on a 108 ICL or how that works out. Maybe someone like Patrick G can chime in on that.
Piston will be flycut .060. Any estimates on the volume of that?
10-01-2006, 10:38 PM
#6
Ahh see I had also read that it was every .007" is 1cc. That's why I'm confused.
Also, do you think I should be using a thinner gasket? I mean, will the difference be noticeable on anything other than a dyno (and my wallet)? I think there's another brand that's cheaper than the hit or miss Cometic, but not sure what brand that is. I've already got my GM MLS on the way, but considering changing if it's THAT necessary.
Also, do you think I should be using a thinner gasket? I mean, will the difference be noticeable on anything other than a dyno (and my wallet)? I think there's another brand that's cheaper than the hit or miss Cometic, but not sure what brand that is. I've already got my GM MLS on the way, but considering changing if it's THAT necessary.
10-01-2006, 10:47 PM
#7
I think I recall every .005 being worth 1cc, so 59cc should be close - we'll use that.
I use the DCR spreadsheet available here.
I plugged the specs for the 3727 and 3731 XER lobes in on 112 LSA, 108 ICL. Assuming the rest of my calcs are right, I come up with 11.24:1 SCR (no clearance volume added for valve notches) and a DCR of 8.81:1.
Right where you want to be! Good Selection & thanks for the G5X3 specs.
EDIT - I recalculated on the same sheet I referred to above (instead of the one I had saved) and came up with the same SCR, but a DCR of 8.6:1...
I use the DCR spreadsheet available here.
I plugged the specs for the 3727 and 3731 XER lobes in on 112 LSA, 108 ICL. Assuming the rest of my calcs are right, I come up with 11.24:1 SCR (no clearance volume added for valve notches) and a DCR of 8.81:1.
Right where you want to be! Good Selection & thanks for the G5X3 specs.
EDIT - I recalculated on the same sheet I referred to above (instead of the one I had saved) and came up with the same SCR, but a DCR of 8.6:1...
Last edited by hammertime; 10-01-2006 at 11:26 PM.