should I use .030 or .040" cometics?
 

ok, about to buy my cometic gaskets. just realized they have .030 as well as the .040" I was goin to buy. I havent ordered my pushrods yet, cause I have to wait till the heads are bolted on before I can measure for custom length. anyways, any draw backs to useing the .030" cometics over the .040? I just want to make sure you dont think that will have anything to do with leading to leaks. as in the thinner they are, more prone to leaking. just never heard of anyone using the .030" before. thats all. thought Id throw this out there before I just buy them. here's how the #s look, comparing the to diff. head gaskets. the .030 puts me at the ideal 8.5#. with a custom dyno tune, should be fine for premium pump gas right?

setup #1 with .030"
ENTER YOUR DATA CALCULATED DATA
Cylinder Head Volume (cc) Cylinder Head Vol
(cubic in.) 03.782
Piston Head Volume (cc) Piston Head Vol
(cubic in.) 00.061
Gasket Thickness (in.) Swept Volume
(cubic in.) 43.200
Gasket Bore (in.) T.D.C. Volume
(cubic in.) 04.131
Cylinder Bore Diameter (in.) Gasket Volume
(cubic in.) 00.360
Deck Clearance (in.)
Note: Neg. nubmer above deck, Pos. number below deck Deck Volume
(cubic in.) -0.072
Stroke (in.) STATIC COMPRESSION RATIO 11.458

OPTIONAL DATA
Rod Length (in.) Adjusted Stroke (in.) 02.604
Intake Closing Point (degrees)
ABDC @ 0.050 lift plus 15 degrees
DYNAMIC EFFECTIVE COMPRESSION RATIO 08.523

setup #2 with .040"


Cylinder Head Volume (cc) Cylinder Head Vol
(cubic in.) 03.782
Piston Head Volume (cc) Piston Head Vol
(cubic in.) 00.061
Gasket Thickness (in.) Swept Volume
(cubic in.) 43.200
Gasket Bore (in.) T.D.C. Volume
(cubic in.) 04.251
Cylinder Bore Diameter (in.) Gasket Volume
(cubic in.) 00.480
Deck Clearance (in.)
Note: Neg. nubmer above deck, Pos. number below deck Deck Volume
(cubic in.) -0.072
Stroke (in.) STATIC COMPRESSION RATIO 11.162

OPTIONAL DATA
Rod Length (in.) Adjusted Stroke (in.) 02.604
Intake Closing Point (degrees)
ABDC @ 0.050 lift plus 15 degrees
DYNAMIC EFFECTIVE COMPRESSION RATIO 8.310

I wouldn't use the .030" or the .040" gaskets with your pistons sticking out of the block that far. How far are your pistons sticking out of the block? In your math you show them to be out of the hole .072". That is a awful lot, just checking for a typo error.

It looks like the values listed are all in cubic inches.

.072 CI would be a 3.9" bore, out of the hole .006"

:cheers:

I would run the .040" gaskets in that case to set your quench at .034" for a motor car or smaller dose of n20(150 or less).

yeah, I dont know why it copied that side. I copy/pasted my calc. from silvolite calculator. but I measered them at .006 out of the hole.

it will be a N/A car, maybe later in life we'll add a small N20 shot, maybe not. now that you mention it I think I do remember that you want quench around .030 right?
any other reason I would want the .040 and not hte .030?

Quench street .035>.045, why because of carbon build up. Race I've seen .025 but that motor gets torn down after every meet.

ok cool beans. thanks for all the info guys. .040" cometics comeing right up.