GMJim

I have a 68 C10 with a Gen 3 LS engine in it and am trying to identify it. I used a bore scope to see It has dished pistons so I assumed it was a 5.3 but I recently dropped the pan and found a three digit casting number on one of the counter weights (482).




Is it typical to see this type of ID using 3 digits? 12553482 is a 4.8 crank. I was expecting to find a 7 or 8 digit casting number somewhere but this looks almost like a stamp. It would seem based on the info I have that my engine has a 4.8 crank with 5.3 dished pistons in it? Talk about low compression? Has anyone seen this type of ID and can confirm that this is a 4.8 crank.
Thanks

1FastBrick

iTrader: (16)

That is a 4.8L crank. It will have a full set of raised digits on one of the weights.

GMJim

Kinda thought so. I didn't spin the crank over much after seeing this. Now I have to figure out why someone would use a 4.8 crank with 5.3 dished pistons? Turbo charging? Any idea what rods would be in there?
Thanks

1FastBrick

iTrader: (16)

Those are the early rods with the press pins.

I have no Idea why people do strange stuff like that.
I picked up an engine like that which someone mickey moussed back together and figured out that they weren't able to make it run because it had the wrong cam gear in it.

GMJim

Strange that this engine was rebuilt at a reputable shop (according to the previous owner) . All I can figure is the owner told the rebuilder that it was a 5.3 and he built it as such without checking the crank. You would think that when the flat top pistons were pulled out it would have been obvious to the rebuilder. The only mystery is the rods would have to have been changed or the pistons are low in the hole? Anyway I have a 4.8 with low compression that I want to fix. I guess new crank and rods?

dixiebandit69

Hell, if you're going to do all that, just throw in the flat-top pistons as well.

GMJim

Not a bad idea! Any idea what the compression ratio would be? Would a stock tune work?

GMJim

Has anybody used flat top pistons in a 5.3? My engine is comming out soon to change the crank (4.8 to 5.3) and rods. The flat top pistons would increase comp ratio but to what? Any assistance appreciated.
Jim

1FastBrick

iTrader: (16)

GM did it in the L33 5.3L And the LS4 as well.

But to be more direct. Yes I have done it on mine as well as a few freinds.

GMJim

Thanks for the reply. Will it run properly on the stock LM7 tune?

LS299S10

GM did it with the LS4, LY5, LMG, LH6, LC9, LH8.
With 706 or 862 heads it should make around 10.5:1 compression with flat top pistons.