Strange TRW chevy piston ???

So I bought a set of new (old) TRW 283 pistons p/n L2248a.

At least I'm pretty sure that they are 283 pistons. They have stamped on the top STD, but the pistons all measure 3.935 which would be .060 over????

Otherwise everything seems right for a 283, .927 pin, 1.775 compression height. They are big solid dome pistons (which is why I bought them. The ring sizes are 1/16, 1/16, 1/8 not that it really matters for the purpose of this discussion.

Do I have an old TRW screw-up? Does anyone have an old TRW catalog handy? Has anyone ever seen this before?

 

olds 330 is 3.938 bore

hopefully Glenn will see this thread and straighten us out

 

I have seen the 283 punched as far as 0.100 with CR of 13:1. Your leaning toward the alcohol type of CR there with these pistons. I had a set of 13:1 Jahns slugs ina 0.060 327. Put on a set of 882's and dropped to around 10.25:1. It ran great till I missed a gear and spun 8,500 and stretched a rod. The end of fun with that motor

 

Blair, The TRW L2248A piston is a 12.5 to-1 compression, with a 64cc head. The .060 will make 292 inches out of a 283. The TRW part number for the rings for your pistons, is T9036MM.

Ed

 

My 1972 TRW performance catalog makes no mention of the part number you've listed. The shortest compression height I see listed for a 283 piston is 1.800.

 

Thanks! So I don't have some oddball piston here. I guess they just screwed up on the marking??? Seems strange.

As for the compression height if you look at sealed power's 283 forgings that summit offers they have a compression height less than 1.8". Also, I just used a dial caliper to measure and subtract so I might be a little off.

Thanks for the help, it doesn't seem like there is much info online about old TRW #'s.

 

Oh, I should have clarified that the piston doesn't actually measure 3.935, but more like 3.931, and I tacked on the 4 thou for skirt clearance, so they are for a 3.935 bore.

 

Blair,
I've got a set of those pistons too marked L2248A Std.,when I got them with the 57 283 block I checked the bore of the block and saw it was 60 over and thought well these are useless,but after reading your post I checked the pistons and they are 60 over also even though they are marked standard,so I'm guessing they must be for some other application,even though they work for the 292.Anybody have any ideas what it might be?

 

Could be TRW had a few to many std 302 pistons and machined them down to fit the 283? The 1/16 ring for those are spendy$$$. It would make a cool little engine to try the E85 with though.
Jeff