Kris Mangrum

I have a ls1 that I'm using in a kit car. I bought some 243 heads to replace the stock 241's. So I know that will jump the compression by half a point. I'm thinking of trying to bump the compression closer to 11:1 without milling. I have found a .40 gasket but how do I calculate what compression ratio that will give me? If I can reuse stock 241 pushrods that would be awesoome.

I will be buying a cam also, somewhere around 228/228.

1SLwLS1

iTrader: (6)

With 64.45cc heads, 3.910" bore and 0.040" thick gaskets, stock 3.898" bore, stock 3.622" stroke, flat top pistons, 0.010" out of the hole yields you 11.07:1 compression ratio.

http://www.kb-silvolite.com/calc.php?action=comp

1SLwLS1

iTrader: (6)

Also, you may get by with the same pushrod length, but I would go with hardened over stock. With the thinner gasket, and smaller base circle, those differences may come out equal. Either way, CHECK

Kris Mangrum

Thanks for the link, why two different bore sizes? Are you saying one is the size of the bore of the block and the other is the bore of the gasket? Thanks

Kris Mangrum

Also, what do I put in the field for "Piston Head Volume"?

1SLwLS1

iTrader: (6)

Yes, the bore of the gasket.

0 if it is a flat top

The_Rizzle

iTrader: (4)

If its stock bottom end parts, the piston isn't out of the hole .010. Depending on the block, it can range from .003 to .007. I use .007 just in case.

1SLwLS1

iTrader: (6)

Hmm I guess we have different sources. Not to proclaim one is better than the other, but mine is only read. I will verify later this evening, just out of curiosity.

Kris Mangrum

Ok, so I entered

64.45 for Cylinder Head Volume
0 for Piston Head Volume
.40 Gasket Thickness
3.910 Gasket Bore
3.898 Cylinder Bore
Don't know for Deck Clearance
3.622 for Stroke

Rod length blank
Intake Closing point blank

Static Compression Ratio says 3.529
What am I missing. Sorry

I know for cylinder volume I do bore x bore x stroke gets cubic inchs then x .7854 for cubic centimeters.

1SLwLS1

iTrader: (6)

Stock rod length is 6.098" or 6.125, cannot remember exactly right now and intake closing point is what's so critical for dynamic compression calculation. Once the valve closes is when the cylinder starts building pressure/compression.

69LT1Bird

iTrader: (1)

Cylinder Head Volume (cc) 64.45 Cylinder Head Vol (cubic in.) 3.931
Piston Head Volume (cc) 0 Piston Head Vol (cubic in.) 0.000
Gasket Thickness (in.) .040 Swept Volume (cubic in.) 43.224
Gasket Bore (in.) 3.910 T.D.C. Volume (cubic in.) 4.351
Cylinder Bore Diameter (in.) 3.898 Gasket Volume (cubic in.) 0.480
Deck Clearance (in.)Note: Neg. nubmer above deck, Pos. number below deck -.005 Deck Volume (cubic in.) -0.060
Stroke (in.) 3.622
STATIC COMPRESSION RATIO

10.934

Kris Mangrum

Thanks for the help 69tbird.

How did you come up with .005 , just trying to understand thats all.

Kris Mangrum

Nevermind, thats how far the piston is above the top of block. Gotcha

Kris Mangrum

Holy freakin crap. .040 head gaskets.....$77 dollars a piece! I was so far off on what I thought they would cost. I figured I could pick up both for that price.