Thread: Overhaulling a L36, pistons not marked for front of engine. Help

I am overhauling a 3800 L36 for my 01 GP. I already replaced the engine a year ago with a used engine, but it threw a rod through the side of the block so I am building one this time. I had 2 extra engines in the garage, the original one from this car, and the one out of my wrecked 97 GP. I disassembled both extra engines to decide which one to build. I marked all the rods for which cylinder they came out of, but not the tops of the pistons. I did not realize these pistons are not marked on top to identify which side is the front. Here is the top of the piston.
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I do see a couple of marks on the bottom of the piston.
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If I remember correctly from my days rebuilding small block Chevys the notches for the rod bearings went towards the outside of the block. If I do that to this motor the mark on the bottom of the left bank pistons will be towards the front of the engine, but the right bank will be towards the back of the engine. Does anyone know for sure which way these pistons go? I can pull the blown engine out of the car and tear it down to look, but I would rather have the new engine built and ready to drop in when I pull that one out.

I was wondering if you found out the orientation of pistons and rods. I have the same question about the marks. I had to buy two new pistons that have arrows on them that are on the same side as the mark on the bottom of piston has seen in your pic. but not sure if all arrows are suppose too point towards front, or odd side front,even side towards rear of engine.

I am building one because it is about the same price to build one as it is to buy a used one with 130,000 miles on it. The biggest problem with these engines is the bearings getting washed out and they start to knock. If I can start with new bearings I expect to get a lot more miles out of it. I have another vehicle to drive, so there is no reason not to build it. It is also a great opportunity to teach my 12 year old son how an engine works and how to fix it.

I pulled the other engine out of the car tonight to check which way the pistons are in that motor. All the pistons are installed with the mark on the bottom of the piston to the front of the engine. That makes all the notches for the rod bearings on the left side of the engine, but the notches on the main bearings are on the right side of the engine. I thought the marks on the bottom of the pistons would go to the front, but the notches were throwing me off. I am used to the notches being toward the outside of the engine, not all on the same side of the engine.