ToxicWS6

so i got an LQ4 out of an 06 sierra 2500 for doing a turbo build for my trans am, wanted a newer block for the better rods and piston design, when i picked it up it was all priemer gray and i found out it was a jasper rebuild engine, which didnt bother me but when a friend and i where disassembling it and cleaning it the pistons have "050" stamped on them, im assuming this means its bored .050 over, which is cool but some one brought ul wall thickness being an issue, so my concerns where
how weak is it now its bored .050?
what kinda of pistons would jasper use?
is this block equal to an oem lq4 for strength?

KCS

iTrader: (20)

.050" isn't a common bore size. Try to measure the bore to see what it is. A cheapo digital caliper from the auto parts store would do the job.

If it is really .050" over, I would take it to someone with a UT Wall Thickness gauge and see how much meat is left and if it's enough for the power you have in mind. I'd say it would be okay for moderate power levels, but I probably wouldn't try for 1000whp with it.

ToxicWS6

ill try to get a set today or borrow some from work, heres some pics i took, it has a weird notch in them too i cant get identified

KCS

iTrader: (20)

That notch is basically a reference for pistons with offset pins. When you install the pistons, that notch should be facing the front of the engine.

A.R. Shale Targa

iTrader: (2)

These engines are metric...
050 most likely means a half mm overbore or .020" in.

ToxicWS6

that makes a lot more sense as it looks like 0.50 and i was like BS its bored .50 an inch lol, awesome info, thanks!!

KCS

iTrader: (20)

Good point, didn't even think of that. Probably Speed Pro pistons then.

ToxicWS6

how are speed pro piston quality?

A.R. Shale Targa

iTrader: (2)

They were terrific for decades until they up and moved manufacturing to India. Then for a good while weights and sizes were all over the place. I've heard better quality control as of late however I've not personally used a set in a few years.

A.R. Shale Targa

iTrader: (2)

Another very noticeable detail for an experienced engine guy like yourself is the remaining GM bore chamfer. Removing only .010" material (.020" overbore) will still leave enough of a chamfer to not crash the rings whereas .015" or .020" (30 or 40 over) most always requires an extra machining step or at least the sanding cone on a drill fixer. This is why .020" is such a popular choice for Jasper and Cloverland rebuilds. In fact I'd be willing to bet that they power hone that size in order to skip boring. Saving money is what they are all about....