Check the squish,no less than .029 if you want reliability.With 210,you best be running race fuel,at least 108

 

i run c12 and have 190psi cold.ran it very hard 5 times now.atleast 50 gallons of c12 thru it now.

 

I invested in some super thick gasket material. The material is three times as thick as the gasket vitos sent me. I hope it will drop the compression some.

 

ya that might lower it too much tho.

 

I got it lowered to 160. Can I run 91 octane?

 

no.. your supose to run 93 in a stock shee...

 

i ran 93 in my sons 90 at 40 to 1 and we grenaded a piston(detonation) thanks to the high comp head. We now run cam 2 (115) or Sunoco(113)from the local dragstrip still at 40 to 1 and we have had no problems in a year. If you think 115 is too much than mix it with some 93 octane to bring the rating down to around 100+ hope this helps you,from the gang at teambooger AMA Dist. 6 #3 mini-quad Atco MX 3rd place points finish 03

 

150 is safe to run 93 octane in. 155 is marginal. Your squish must have been about .020 to have compression like that. Changing a piston doesn't change compression (given they are not different bore sizes). The angle on the top of a banshee piston is 12 degrees and must stay at 12 degrees to run right (for information a blaster is 9 degrees so you must change your head to run blaster pistons). .028" squish is the minimum and anywhere from 28-35 is optimum. That thick gasket will actually add about 2.5-3 degrees of exhaust duration to it, which will add power.

I just put my new race motor together and checked all clearances except for compression. 17cc domes is what the builder suggested I run for about 190psi. Imagine my surprise when I finally checked my compression after the first race and it was at 290! It was too late and detonation had already occured and messed up my pistons. Now with 20cc domes, it is still at 200.

 

Raise your exhuast ports and you'll kill two birds with one stone: lower compression and more top end!

 

I agree with Hiram.
Maybe you were in neeed of a rebuild and thats why the comp jumped up real high.