Thread: need more compression

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I am building a 454 with the 781 heads, after milling heads and putting in larger valves my CC is 115. I am trying to get my compression to 9 or 9.5 . with a .250 dome piston I am still at less than 8.5 I will be running a 69 corvette tri-power setup, and will be installed in my 68 chevy c10. what can I do to increase the compression.

check your fiqures---you have make some mistake somewhere------

I have you at 10.2:1 Static Compression Ratio with that piston at +0.030. Too much for iron heads and pump gas, piston dome is about 23cc's.
Overbored 0.030", 0.020" piston deck height, shim gasket, 11cc piston dome, I get 9.3:1 static compression ratio. Same setup, but with 9cc dome, I get 9.16:1 SCR, so replace your present pistons with 9cc, 10cc or 11cc domes to get low 9's. Here's the piston I might use.....
http://www.summitracing.com/parts/sl...make/chevrolet

With that piston, 115cc chambers, 0.020" shim gasket, 0.020" piston deck height and bored +0.030", I get 9.25:1 SCR.
Here's the calculator I used.....
http://www.csgnetwork.com/compcalc.html

With a Keith Black KB203-030, I get 9.37:1 SCR.

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Tech, you are da' man! I clicked on the CompCalc and promptly saved it for future reference - a very cool tool!

thanks for your reply's I did something wrong. Now how can I calculate HP

if the deck been cut on block and bigger valves put in heads you need to check that intake valves are not past deck of heads and your 250 dome pistons clear the head chamber as some can hit on the EX side of head chamber and you will have no pistons to valve clearance /room with even a small lift cam . you can build it any way you want but tin gaskets are for dead flat parts with a good finish if you do not have that i would not run tin gaskets on very many things use a fel1037 that a 9.7 cc gasket like said if the dome is 250 you will have more then 9to1 can use the icon 9919 200 dome get you close to what your looking for and built many iron head engines at 10to 1 you will need good fuel mild grade or better there is some block and head prep work to run past 10to1 but its a bit of work that i do not know if its been done in your case