Quote:
Originally Posted by X72GPX
The block was 0 decked and currently has flat top pistons. I don’t have access to E85 here in NJ.
Not sure which way to go now……
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You still have to account for any valve reliefs in the piston face. It may not be a "dished" piston, but I can almost guarantee it has valve reliefs. Check on that based on your ordering info for the rotating assembly.
At any rate, if the deck height is already at zero, that 72 cc head is going to create a lot of compression. Going to a thick headgasket will lower the compression marginally while making the quench distance pretty terrible, likely causing more propensity to detonate.
If you don't have E85 available, your options become, rebuild your current heads which should be fine if you were using them prior, replace the pistons with something that has enough dish to get you down to around 10.5:1, or sell your speedmaster heads and buy a KRE/Edelbrock head.
Outside of that, you'll need really great cam selection, really great tuning and really great heat management. It can be done, people like Cliff have proven it, but it won't happen with a "throw it together" deal.
I've been through this game trying to get my 455 with #62's to perform and behave on pump gas. You end up hating the car, and it becomes expensive to drive as you hobble it with low timing and expensive octane boosters or high octane fuel. Then, because the tune is so neutered to keep it from pinging, it becomes a dog and it'll likely run hot.
You'll end up rebuilding the heads you have, or buying the KRE/Edelbrock D ports anyway. Save yourself the time, aggravation and added expense, just bite the bullet now.