So what's the preferred method to increase comp? Head milling, different pistons, rods? What's cam lift limit if milling the head for 9.5-10:1 comp? I guess it depends on the piston deck clearance and dish. And what's the deal with 2.2L pistons? Thanks

My "preferred" method to increase compression on a RG (tall block) SL6 is to use the 7 inch long 198 SL6 connecting rods (or K1 aftermarket rods) along with the Mopar 2.2 pistons. (or aftermarket Wiseco pistons)

This combo gives you a lighter piston, thinner, low friction rings, a better rod ratio and between 9.5 and 11 to 1 compression... with-out head or block milling.

Historically, the con rods have been hard to find but they are out there, see
ebay or ask around.
To be honest, the K1 aftermarket 7 inch rod is a great value for what you get.
DD

Doc makes great suggestions there. I agree that the K1/Wiseco deal is hard to beat all around, but does add some coin to your build.

For best bang for the buck and least work on an already running engine, milling the head should cost about $60-200 for 0.100 - 0.120" cut (yes, you read that right) and will take you to between 9 - 10:1 depending on other volumes as you know. You can do combinations of head and deck cuts to get any comp you want with stock rods/pistons.

Lou

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Home of Slant6-powered fun machines since 1988

How much compression and lift can stock pistons take? I'm pretty sure my 225 has under 70K original miles. It's a '69 Dart Custom.