I rebuilt a 4 bolt 350 for my 67 Camaro 7 years ago and there has been a "rattle" in it ever since.
The engine was bored .030 ove, new Hyper utectic pistons, rods, crank, bearings, cam, lifters, timing chain to a double roller.......the works.
At start up there was a rattle noise. Tried re-adjusting lifters, removed front belts, even took off the fuel pump to eliminate that. Alas, no difference.
It runs strong so I was hoping it either goes away or blows up. Neither has happened.
Opened up the engine this winter and replaced the cam, lifters and rockers. At start up, same old rattle. Crap...
Jacked up the engine and pulled the oil pump. Couldn't find anything wrong there and the oil pan was clean.
Distributor is the same as before rebuild when it had no noise. Same water pump, alternator, fuel pump and valve covers.
Gonna pull it out of the car this winter. Can't take it anymore.

Any suggestions.

Define "rattle"... You say "hyper eutectic" pistons. Are they Kieth Black or Speed Pro? The KBs are notorious for ring and ring land issues. A pin could be galled or loose, causing it. Are the rods "floated" or press-fit? Need more detail.

Jim

I don't think the pistons are KB. I can't remember, I'll have to look it up the pile of paper I have for the engine.
As for pressed pin, I think so. When I got the pile of parts back from the machine shop, the rods and pistons were assembled.
The noise is a rattle or a clatter. Not a knock I would associate with a cylinder or a bearing knock.
I thought it may be the oil pump. I definately have good oil pressure as the gauge is rarely below 3/4. When cold or under higher RPM's the gauge is at full.
Someone else also suggested distributor gear, but it is the same distributor before and after the rebuild. No noise before.