Technical 64 Cad engine seized after 15min, cooled down ok

Hi,
I came across and was asked help with a weird 1964 Cadillac DeVille engine problem.
Haven't seen the car yet.

According to the car owner, the engine runs good for about 15-20 mins and then dies completely. The starter would not turn the engine (replaced battery and starter already). Hot and dead, you can't hardly manually turn the engine Engine temp is normal and double checked with an external new gauge. After complete cool down you can start the engine and run until hot again.

Engine was rebuilt on a machine shop. And opened there again to fix the seize problem. The owner says the shop ground piston rings for more gap. I don't know if/how they measured piston to wall clearance etc, but the shop should be reputable and been long time in the business. guess they should know.

I can't figure out anything else than too tight piston/wall... main/rod bearings likely not - they would be ruined by now ... as far as understand in tranny there is nothing to jam....

what do you think, what is going on? thanks.

 

Wouldn't rule out the transmission... And would have that checked out first.

 

I had a 64, rebuilt the 429 and it ran like a clock. I know those motors from the factory ran real close tolerances. They called for 20w oil in the summer and 0w in the winter. I guess it could be possible the ring gap is tight enough to cause a problem but not sure it would seize the motor like that. I would lean more to piston clearances being too tight causing the problem. I would have to see it apart.

Sent from my Moto G Play using The H.A.M.B. mobile app

 

OPENED THE RING GAP......
This shop HAS NO CLUE..!
You set the ring gap and go. If you THINK that opening the gap from a "properly" set original gap, all you did was waste the rings.
Many more things to look at.
A "single" tight wrist pin WILL will bring a running engine to a halt..! I know, I watched a friend go thru this with his fresh big Chevy.
I would not let this shop touch anything of mine from the info posted.

Good luck

Mike

 

Maybe the engine was rebuilt with forged pistons trying to run with cast piston clearances?

 

I would send off a sample of the oil to be analyzed, first thing. I suspect metal in the oil will show a bearing failure somewhere. flatspotting the cam is a common failure nowadays. I had one lock up, but then seemed to run fine. Of course it blew up before long. Everything inside looked like it had been run without any oil at all. I'm not sure why they suspected the rings, but I say they should have torn every piece apart, inspected and reassembled all.

 

Had a new circle track engine that would lock up/shut off after a few laps. We took it apart and found a broken cam drive dowel (351W Ford). Put it back together with a new pin and the next week it locked up in hot laps. I was pissed. Started ripping the hot engine apart in the pits. When I got the timing cover off the cam pin was broken again. Went to move the cam and I couldn't turn the cam in the block. Went out in the next morning and when I tried to turn the cam it turned just fine. Tracked the whole thing to a tight cam bearing. It can be the little things.
SPark

 

The distributors in the 390/429 engines were known for locking up. I had a 62 that the distributor would seize in when hot.

Denny

 

Cracked piston skirt?

 

I've had an alternator seize up and keep an engine from turning over. You'd think the belt would slip, but in my case it didn't.

 

Got a set of pistons several years ago, same thing engine seized up, happened several times, pulled oil pan and had goobers hanging from the pistons, shop admitted they had cammed the pistons incorrectly, so this let them swell up at the wrong point and seize, they built new pistons and crooected the problem.

 

I installed a BEST GASKET rope rear main seal wrong in a 455 Pontiac and it would lock up after 15-20 of run time. I should say, would not start back up, it might have kept running, I shut it down after the first break-in run. Tried to restart and it was locked solid. Next day it fired right back and ran fine. I had used an infrared heat gun and you could watch the rear of the crank heating way up as it ran.
I packed a little to much seal into each groove, then failed to oil the surface. I follow the direction when I replaced it!

 

Vimtage Iron, what is this "cammed the pistons" you speak of? Thanks!

 

At 90 degrees from the wrist pin the piston is slightly bigger, in my case it wasen't at 90 degrees it was some what less, this is what the piston manufacture told me, this allowed the piston to swell up in an wrong spot.

 

Is this Cad motor in a Cad?
My Dad had a Cad that did the same thing, seems there were GM's back in the day that had double wall exhaust manifold pipe. You couldn't see it from the outside pipe but the inside liner would collapse restricting the exhaust flow, heating up the engine. The first sign was loss of power, than the engine finally quit only to start again when cooled down. New exhaust system later and it ran just fine............................................

 

Vintage Iron, I have installed pistons on many small block Chevy dirt track race motors backwards on purpose to lessen the side load on the bores, not tighten them up. The only residual effect was the motor rattled when cold and quieted down when warmed up. Ran thousands of laps with motors built like that . With several track championships.