Bit the bullet and decided to pull my old 5.2. I have it torn down and the block is already at the machine shop. Its going to be bored to .020 over and i don't plan to stroke it so i can relatively save my mpgs. My goal for this motor if possible is to have a reliable 350 ft/lbs around 3.5k. The shop recommended upping the compression ratio to about 9.7:1. Here are my questions:

• The pistons I'm looking at claim to have +5 cc on summit racing but from everything I can tell these are volume reducing Pistons which would get me to 9.7:1 leaving everything else equal. I've attached the link. Am I interpreting this correctly? https://www.summitracing.com/parts/uem-kb167ktm-020
• If I'm able to reuse my stock heads, would 9.7:1 be safe enough to use 87 octane or 85 at elevation? The truck lives most of its life in Colorado.

Thanks for any input.

Too far to turn back now.

 

The higher the compression the more octane you need is the rule of thumb. Lower octane fuels may knock. You are under 10:1 so you should be ok. Not sure if there is still an issue with the Keith Black pistons but there have been some instances where they crack the tops of the pistons. Ring gaps are important with them so make sure your builder(or you) go by their guidelines. Stock heads have been known to crack so if you plan on reusing them have them checked out. Don't know how much you were planing on spending but some aftermarkets heads with bigger valves may be appealing.

 

Gotta agree with this sentiment. Replace the heads. Should be able to get a pair of NEW heads, that are better designs, for under 1000......

 

Thanks for the feedback. Got the heads torn down today and didn't see any evidence of cracking. Machine shop is going to clean and mill them if they don't find anything. Looked at Clearwater heads but going to try and save money for other parts. I've read alot that even if these heads crack its usually not an issue. Hopefully that doesn't come back to bite me.