[racerboy]

The pistons have some carbon on top. Do I have to get rid of that (and how)? Also I don’t think it is at zero-deck. It looks like when it is at TDC the piston is still a little below the deck.


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[Formulajones]

Originally Posted by racerboy

The pistons have some carbon on top. Do I have to get rid of that (and how)? Also I don’t think it is at zero-deck. It looks like when it is at TDC the piston is still a little below the deck.


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Just an FYI, those are the exact same pistons I used in a 428 build I did about 25 years ago. The L2257 is an old TRW forged flat top piston for a 428 with 4 valve reliefs. Obsolete part number now I believe.

So that dish is machined in there. Here is a picture of mine after I machined a 16cc dish in that same piston. When I ran these pistons in a .030 over 428 and .004" down in the hole with a 76cc head, my compression was right around 9.7:1

Your dish is much smaller than mine, so you'll have to measure it.

[Formulajones]

Here's a better picture of it so you can see the L2257 part number.

[racerboy]

Originally Posted by Formulajones

Here's a better picture of it so you can see the L2257 part number.

Thanks FJ
Would machining a dish be less expensive than buying new pistons?


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[Formulajones]

Originally Posted by racerboy

Thanks FJ
Would machining a dish be less expensive than buying new pistons?


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Yes absolutely it would be cheaper to machine what you have further, if needed. As long as the pistons themselves are in usable shape.

Back when I did it, there wasn't an aftermarket forged dish piston available off the shelf for a 428 Pontiac. Just the 4 valve relief TRW flat top. They have plenty of meat, and are always accused of being heavy pistons anyway. So I just machined them to what I wanted, while removing some weight at the same time