I thought that those nice forged pistons that Tom has will take a stock 250 to abot 9.5:1 without any decking. The pistons go up just a little higher than the 307 flat tops. But maybe these are different pistons. How does one drop the compression? Special thick head gasket?
I do not recommend 6:1, too low. :-)
I agree 6:1 is waayyy to low. I was orginally planning on 8:1 but I'm pretty set on 9:1 now. The flat top ones on 12bolt.com do get you into the mid-high 9's but he has a different set now with dished tops. If you custom order he can have Ross Racing make whatever size dish you want. I originally ordered flat tops but the machine shop owner was adamant a lower compression would be safer on my .070 overbored cylinders and allow me to pump 87 octane.
The dished pistons could be made as big (deep) as you need to allow for a lower compression. After reviewing the Inline 6 power manual further, and a bunch of online resources I'm confident my block will be fine with 9:1 while allowing me to meet my performance goals. Plus, if (when?) I decide to up the power, I'll be in a better position to increase boost.
Most of you guys are pros but if anyone wants a refresher I found this page on www.xcceleration.com was very well written and gave me a basic understanding of the low vs high compression topic.
