Ok so here is the deal. I have a fresh rebuilt 350 out of an 88 vette. Low mile engine that was honed with new rings and bearings installed. Factory heads, holley stealth ram and mild cam. I just got the motor together and it fires up instantly and runs good. After about 10 minutes of idling it just dies like its locked up. It wont turn over till it has sat for about 10 or 15 minutes. You can put a breaker bar on the crank pulley and you are unable to turn it until the engine is cool. I cut apart the oil filter and there is no metal in any of the filter. I changed the oil and there is only a slight metallic tint but i think that is to be expected in a new engine with the rings seating. Any ideas what could cause it to seize up and then start again fine after cooling?

 

The piston to wall clearance and the ring gaps are the first thing I'd check.
It seems inevitable that you'll be able to avoid disassembling the engine again.

So if you pull the sparkplugs you can't turn the engine with a breaker bar?
That's bad.

 

Wrong piston rings. Not enough ring end gap. Possible bent connecting rod, tight piston pin,, piston/bore clearance. Water jacket partially blocked in block, cylinder head or water pump/hoses.

 

No not until it cools off. We checked the piston ring end gap when it was assembled and it was within spec. Its the origional pistons in the engine. The end gap on the rings is the only thing i could think that would cas it to stall when hot.

 

What spec was that?
Original as in stock cast pistons?
I know that facing the connecting rods the wrong way can sometimes cause binding, but that's both cold and hot.
If you pull all the plugs and it still won't turn, then that eliminates hydrolock.

 

Sounds like it could be yor rings are too tight to me also...if your rod or main bearings were too tight, you'd normally see oil pressure go down to nothing before the engine quits. Either way it might be a good idea not to run it anymore to prevent any further / or cause damage. Somethng bad is wrong.

The crappy thing about it is you'll need to tear it all down again to find out. I'm assuming since you only had the block honed, you put in standard size rings? I don't understand how you checked the ring end gap after it was assembled....

I do mine by placing a ring 1/3 of the way down the cylinder without it being on the piston or anything and make sure it's square in the bore and then take your end gap measurement with flat feeler gages. The install directions that came with your ring set will tell you what the min. gap should be.

 

Sorry I should have worded it better. I did check the end gap by placing the ring in the cylinder like you said. They were standard size rings and the origional cast pistons

 

So what is the oil presure? Does it stay constant when idling all the way up until it "seizes". Are you sure it won't turn after 10 minutes of idling? Gonna be hard to turn anyway with all the plugs still in it.

-A bad starter will get heat soaked after the engine warms up and refuse to turn the engine over - doesn't mean the engine is seized.

 

Oil pressure stays constant. The starter is brand new. I wish i had the stuff to do an amp draw test on it.

 

is there a need to? If you cant turn it with a breaker bar I doubt its starter related.

 

If it were my engine, I'd make darn sure the engine is actually seizing before disassembling the entire engine by pulling the plugs and trying to turn it as 305sbc mentioned....the OP has also used two words to describe when the engine shuts down - "seized" and "stall". These are two totally different things.

 

If is truly seizing, did you check the crankshaft end play when you assembled it? I've seen a too tight thrust bearing shell surface on the rear main melt an engine down.