calculating compression ratio
Thread Starter
Staging Lane
Joined: Sep 2013
Posts: 97
Likes: 8
calculating compression ratio need help calculating my compression ratio. I have a stock 6.0 ironblock with ported 243 heads. Heads have been cleaned up and surfaced at 0.006, other then that, nothing was touched on combustion side. I will also be running LS9 headgaskets that feature a 4.100" bore and a .055" thickness when compressed. This was a later model LQ4, therefore, it does have the Gen4 rod and pistons in it.
Thread Starter
Staging Lane
Joined: Sep 2013
Posts: 97
Likes: 8
Lq4 piston is aprox 6.7 dish
typical oe deck height is .006-.008 out of the hole. Call it .007
crank is 3.622
243 heads are aprox 64.45cc
mill. 006 makes for aprox 63.5
Gasket you already listed
online calculator says 10.251
typical oe deck height is .006-.008 out of the hole. Call it .007
crank is 3.622
243 heads are aprox 64.45cc
mill. 006 makes for aprox 63.5
Gasket you already listed
online calculator says 10.251
Thread Starter
Staging Lane
Joined: Sep 2013
Posts: 97
Likes: 8
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Thread Starter
Staging Lane
Joined: Sep 2013
Posts: 97
Likes: 8
I plugged in the following information:
Enter the number of cylinders of your engine --> 8
Bore
Finished bore of your engine --> 4.0
Stroke
Stroke of your engines crankshaft --> 3.622
Rod Length
Ctr. to Ctr. length of your connecting rods --> 6.098
Gasket Bore
Head Gasket bore diameter --> 4.100
Comp. Gasket
Compressed Head Gasket thickness -->.055
Block Deck Height
Center of main bearing bore to top of block --> 9.230
Top Ring Down
Top of 1st ring to top of pistons (FLAT) --> 0.350
Chamber Volume
Cylinder Head chamber volume in CC's --> 64.5
Dome/Dish Volume
DOME (-) or DISH (+) vol. (theoretical) in CC's --> 6.7
Piston to Deck
Top of BLOCK to top of piston (FLAT) @ TDC --> 0.15
and I am getting 9.52 for my compression ratio. Does everything look correct?
Enter the number of cylinders of your engine --> 8
Bore
Finished bore of your engine --> 4.0
Stroke
Stroke of your engines crankshaft --> 3.622
Rod Length
Ctr. to Ctr. length of your connecting rods --> 6.098
Gasket Bore
Head Gasket bore diameter --> 4.100
Comp. Gasket
Compressed Head Gasket thickness -->.055
Block Deck Height
Center of main bearing bore to top of block --> 9.230
Top Ring Down
Top of 1st ring to top of pistons (FLAT) --> 0.350
Chamber Volume
Cylinder Head chamber volume in CC's --> 64.5
Dome/Dish Volume
DOME (-) or DISH (+) vol. (theoretical) in CC's --> 6.7
Piston to Deck
Top of BLOCK to top of piston (FLAT) @ TDC --> 0.15
and I am getting 9.52 for my compression ratio. Does everything look correct?
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Thread Starter
Staging Lane
Joined: Sep 2013
Posts: 97
Likes: 8
I guess I dont understand what I did wrong. I changed my previous 64.5cc to 63.5cc to make up for the milling and changed the Top of BLOCK to top of piston (FLAT) @ TDC from 0.15 to 0.007 and I still ended up with a compression ratio of 9.79
