[Mike00804]

Hey Eric,
It sounds to me like piston slap from what your telling me, but I'd have to hear it. When I did my first rebuild on the 2 bolt, I micrometered the old pistons to determine if the cylinders were bored, because there was no stamp on the pistons indicating .010, .020, etc. After getting the factory specs, I concluded that it was a standard bore piston. I them procceded to order a set of standard bore pistons from Ross, which they didn't have designed yet. (only .010, .020, etc.) It took me about 8 months to get them, and I threw it all back together.
My car ran good, but almost sounded like a deisel...kind of like the school bus sound when idiling. I couldn't for the life of me figure out what it was. I took the entire engine back apart to plastigauge the mains and the rods......everything came out ok. Again I was stumped, so I did the same to my heads. With nothing out of spec, I retorqued the whole motor, ans started it up again.......Same noise, but ran terrific ..especially under boost conditions.
This sound started getting better, and was vertually gone after 2000 rpm. I chalked it up to piston slap, which was right, but thought it was caused by the aftermarket pistons maybe being slightly undersized to compensate for swelling under extreme heat, or something under those lines (as it seemed to pretty much disappear after beating the shit out of it on the highway). This is what the problem was.........
#1, I was using total seal gapless rings. The machine shop that did the 4 bolt work told me while those rings make a great seal, it is usually too great to have a long lasting motor..."race only" application. If your not getting some blowby, the piston doesn't hydroplain on the bypassing gasses, and tends to go down "cock eyed". works great for more power, but not the best choice for a street car. You need a little blowby to help the piston skirts from hitting the walls, hence why all stock stuff is gapless and cars have PCV.
#2, my cylinders were slightly egg shaped from wear, and should have been bored/honed before putting it together, hence why ross didn't design standard sized pistons. Your not really ever supposed to put a motor together without checking this stuff precisly, as most people know. Also it is really important to torque plate hone your cylinders for this same reason, you want the bores done with the same torque that it will experience with the heads strapped on. Heat will also cause your engine to slightly warp, after it does "tempered" your bores, main line, etc. will be slightly off. not enough to be the end of the world though. If your engine is used, it most likly has been tempered simply from continuous running conditions.
#3, I used TONS of motor oil to lube my cylinders and pistons before putting them in the engine. This caused my rings to retian from seating properly until I crossed about the 1000 mile mark. Running it for so long with the rings unseated also contributed to the slap. After reading the "fine print" I later noticed that it specificly says..."DO NOT lubricate the rings with motor oil, this will prevent your new rings from seating properly. A light household oil such as WD-40 is prefered". I always did this with motor oil when rebuilding dirt bikes, and didn't think anything of it at the time.
Now, I don't know how much of my first fuck ups might be related to your motor, but it should definatly be some "food for thought" You should give me a call later and describe the noise your hearing in detail. I might be able to help, or at least point you in the right direction.
I did spend big money at the machine shop for all brand new parts, but there is logical explainations for why everything is done the way it was. The guy that did my block does 2000+hp nitro motors for several race teams, and has tons of knowledge of blown applications. (that is the main reason it took him 9 months just to get around to my job) I'll admit, he doesn't know everything about the import stuff, such as the software "tuning" end of it, but as far as the hardware end, he is pretty amazing with his equipment and knowledge. He's an older guy that loves old V8 stuff, hahaha. Anyway, give me a call.
Talk to you soon buddy,
-Mike