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Discussion Starter · #1 ·
I'll start this off by saying I am aware of the proper accurate ways to measure piston dome CC. The motor is currently together though (didn't think to measure when rebuilding it - doh!) and the pistons are too old for JE to have data on.

That said, I'm looking to see if with a bigger cam and some reduced timing I could make this engine cruise on pump 93 to survive a Drag Week style event. So I'm looking for a worst-case scenario. Could these domes be 40cc? 50cc? 60cc?

At some point I will measure for sure but I'm wondering if some expert eyes can ballpark this for me. The pictures below are all I have unfortunately, and again I'm not taking this as gospel just looking for guesses. Thanks guys!

Edit: Forgot all the vital information.
Engine is a 540ci BBC, 4.5 bore 4.250 stroke 6.7 rod in a 10.2 deck block. Deck clearance is right at zero maybe a few thou under at most.

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Discussion Starter · #3 ·
In the 40 range. Those unfinished domes with all those sharp edges won't help with detonation. You could loose a couple CC's just rounding off the dome.
Yeah looking back at those pictures there's some nasty sharp edges we should have cut down a bit. Assuming 40cc dome I get around 13.5:1 SCR and 10.7:1 DCR. Car runs great on 110 at 37° total timing as-is, I had an idea to upgrade heads and valvetrain to make this work on drag week but I think I'm gonna be too far over the edge with these pistons.

Keep the guesses coming though! My machinist's only guess was "fuckin huge!" so anything is welcome haha.
 

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42.732134 cc
You could contour them a bunch and add some head gasket thickness to knock it down.Leave short alone and open chambers up or soften some.
 

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Discussion Starter · #6 ·
42.732134 cc
You could contour them a bunch and add some head gasket thickness to knock it down.Leave short alone and open chambers up or soften some.
How did you arrive at this exact number? I agree there's a lot of sharp edges to knock down and soften up overall. Gaskets are copper so can get way thick if I need to, I think current is .032 could go to .060.

I won't touch the heads though they're cheap procomp junk, hoping to have the funds to replace them sooner than later. Not worth my time to mess with for now IMO.

Measure the deck height at TDC. Lower the piston exactly 1". Grease the edge of the piston to the bore. Then CC the bore. Now calculate how many CC's your bore would be for a 1" depth. Subtract the numbers you get from this number.
Doug
I am aware of this method, the engine is still fully assembled though. I'm just trying to assess if my plan of leaving the rotator untouched is even feasible or not before I tear into this thing. Head studs make this thing a bear to disassemble in the car.
 

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Discussion Starter · #8 ·
Curious. How old are the pistons?
My guess would be very old - possibly mid 2000s. I called JE and they said the number on the pistons was just a batch number and the guy said they used to do that on old custom designs.

The history of these is also unknown, we bought the car with these in it and unfortunately that's all I know.

They all cleaned up and measured good with a caliper, I didn't mic them though or if I did I lost the numbers.

The whole rotator is old but it all mic'd fine and I'm only making around 650hp with this pile so it should be fine.
 
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