compression ratio

give me your methods of figuring comp ratio an a hemi engine. Please
Kevin Newburgh

 

comp. ratio

Kevin I found this one in the back of a 2005 rulebook.

Add all the CC's of the combustion chamber, head gasket, deck hieght together. Then add the total of the displacement of the engine times 2.0483.
(To get this number it is bore x bore x stroke x .7854 x number of cylinders x 2.0483 =)
Then you divide this total by the combined CC's of the combustion chamber, deck hieght, head gasket.

Example:
Combined CC's of the combustion chamber, deck hieght, head gasket. = 101
Then add bore (4.310) x bore (4.310) x stroke (4.5) x .7854 x number of cylinders (8) x 2.0483 = 1075.82
Add 1075.82 + 101 = 1176.82
then divide 1176.82 by 101 = 11.65

I hope this helps

 

Remove Push Rods From #1 Cyl.

If Your Engine Is Asembled Just Put It On Tdc And Pour Liquid Thru Spark Plug Hole With The Engine Head Level Until It Reaches The Bottom Thread Of The Spark Plug Hole. Record The Cc's.

Now Rotate The Crank To Bdc And Pour Liquid Thru Spark Plug Hole Until It Again Comes Up To The Bottom Thread Of The Spark Plug Hole And Record The Cc's.

Add The Two Figures Together And Divide By The Combustion Chamber Cc's In First Step.

This Takes About 15 Minutes And Is Accurate.

 

I put an O-ring in the top ring groove of the piston (so no fluid leaks out), and bring the piston up to TDC. Level the deck of the block. Use a buret (graduated cc chamber) to pour fluid through the spark plug hole, you might have to stop at 100 cc's, reload the buret and finish pouring until the fluid gets to the bottom of the spark plug hole. Don't spill any, as it is easy to affect the compression numbers. Read the final cc's, enter the bore, stroke, and cc pour volume into your handy dandy GORR calculator (I've had mine for 20 years, hopefully you can find something similar), and it spits out the exact compression ratio.

 

I use the same method as Ken Sitko does but I have a Moroso power speed calculator # 8965 that gives the same reading . It cost less than 10 bucks when I bought it years ago .