hi , can anyone tell me if rebuilding a engine for a truck be better off re-honing my 4" cyl. or should i re-size 1996 chevy 2500 pick up truck that has 27900 k on a vortec 5.7 350 short block engine

SORRY I MEANT TO PUT DOWN 279,000 K

Your better off freshening up the 5.7L engine. So do you have two trucks? You wouldn't want a 4 cylinder in a Chevy 2500.

It would depend on how the measurements for the 4" cylinders come out. Is there an excessive ridge at the top of the bore? Is a ridge reamer required to safely remove the pistons? If so, then a rebore to .010 or more likely .020 oversize will be necessary as well as new pistons, rings and bearings. And wile you are at it timing chain and gears, water pump, plugs and wires and possibly a camshaft, lifters, push rods and rocker arms may be needed. You can only hone a cylinder correctly if there is very little wear and the cylinder is not tapered or out of round. With 279K on it I would guess the wear is substantial.

I took the heads off already and found that the top of the cylinder has a very slight turn as if it where deburred and also as if it were another type of material in the very tip just about 1/8 to 1/4 inch all the way around evey cylinder with a thin glob lining of burnt fuel carbon ..

Here goes a picture

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The cylinders will have to be looked at by someone or measured. Your photos are not very clear and will not help.

I'll get the measurement in a bit so that I can give a correct analysis of the size .. just a bit later today as soon as I get home.. at work right now. Late shift THANKS Bob

You already got the heads off - what's keeping you from tearing it the rest of the way down and giving it a mild rebuild? At least hone those cylinders, that some carbon build up there. They do make oversized rings for resized bores. It really depends on how they measure up. Or just get the block dipped, magnafluxed, and some basic machine services like honing (or rebored) and decking. (There's a lot of scaling in the water jacket too that can be taken care of via dipping). A full rebuild kit with pistons will run you around 300. Mild machining about the same. Otherwise if on a tight budget, hone it yourself and use a basic gasket/bearing kit.

Lots of carbon makes me think it was using oil and that it may need bored out, but the measurements will tell you. You likely will need to have the bores measured and checked for taper by a machine shop.