Quote:
Originally Posted by johnta1
I don't know when they first came out, but the TRW SD pistons were specifically made for the SD, narrower opening for the rod.
They wouldn't work with the stock rods.
I had a set in 77, and they worked great, using the HO setup like Lloyd said.
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The L2423F TRW flat-top replacement pistons for the SD455 were exactly the same piston as the OEM pistons. The only difference being the part number. (TRW was the supplier for GM)
The SD455 pistons had a single "trough" valve relief and were made to fit only the SD forged rods which had a narrower small end than the non-SD cast rods. These stock pistons would need to be machined in order to be used with the wider cast rods.
The L2394F domed "racing pistons" are machined wider to fit non-SD cast rods. If the L2394F pistons are used with forged SD rods, there is excess gap or "play" between the piston pin boss and the rod. This is not a problem with stock wrist pins. But, if thin wall "light weight" wrist pins are used, wrist pin failure could occur.
The L2394F domed pistons were made for, and marketed for, use in both 455HO and SD455 engines.
TRW made a number of "racing pistons" with domes for use in many different types and brands of engines. Many of these were low production engines.