V-12 problem

T

Tom Overfield

Junior Member
Hi Folks,

I finally finished my 41 Lincoln with a v-12 which I rebuilt many years ago. I had about 6 hours of break in time on a test stand, then I put it in the car and started driving it locally to shake down any problems. 534 miles on it, ran it down an interstate at 60 for 8 miles, got off, four blocks later at 35mph, a big BANG, then engine ratteling and our white smoke from tail pipe. I thought ok, blown head gasket no big deal. Wrong, gasket was perfect BUT somehow a piece of something just slightly metallic broke off somewhere, ended up in the combustion chamber and beat the piston top up a little, then it put a nice size hole in the polished aluminum head. Pulled one intake valve on the damaged cylinder looking at maybe a broken seat, that one was fine, will pull the other today, Any one out there have a clue where this piece of metal may have come from? This motor ran like a Swiss watch up until this.
Thanks
Tom

Ok are two photos, one on the right it better, that is two pices that fit together and were driven into the head. Feels like still, but very little reaction to a magnet.
 

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I feel your pain, wish I could help. I'm just wondering if the foreign object stuck in the head or is in the water jacket of the head?
 
Arghh! If it was not a valve seat, check the carb for a missing throttle plate screw. Or it could have been something inadvertently dropped into the intake during the build; just took a while to dislodge.
 
Tom Overfield said:
Hi Folks,

I finally finished my 41 Lincoln with a v-12 which I rebuilt many years ago. I had about 6 hours of break in time on a test stand, then I put it in the car and started driving it locally to shake down any problems. 534 miles on it, ran it down an interstate at 60 for 8 miles, got off, four blocks later at 35mph, a big BANG, then engine ratteling and our white smoke from tail pipe. I thought ok, blown head gasket no big deal. Wrong, gasket was perfect BUT somehow a piece of something just slightly metallic broke off somewhere, ended up in the combustion chamber and beat the piston top up a little, then it put a nice size hole in the polished aluminum head. Pulled one intake valve on the damaged cylinder looking at maybe a broken seat, that one was fine, will pull the other today, Any one out there have a clue where this piece of metal may have come from? This motor ran like a Swiss watch up until this.
Thanks
Tom
Click to expand...

oh NO,,sorry to hear..hang in there..you like me love our cars and want them running and happy.
with these antique machines we never really know what tomorrow will bring.
Every time I drive my 1933 I feel like Charles Lindbergh heading out over the Atlantic Ocean praying that it won't have a major breakdown.
 
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The white smoke was water/coolant dumping into your cylinder. (you prob also now have some in your oil pan.)

I wonder if this is an edge of your piston maybe? Could also be some part of your carburetor, or something that was in your air cleaner sucked in.

That could possibly have been a screw that was pounded flat.... just an idea.
 
Well, after checking everything possible, the only thing that makes sense at this point was there must have been something that was lodged in the intake manifold and finally shook its way loose and went into that cylinder. All valves are good, seats are good. 120#s compression on the other bank. I have a right side polished head ready to go back on and I will have the damaged head repaired. Thanks for all your help.
Tom
 
Have you visually checked and positively verified that every valve seat in every cylinder is intact? A broken piece in one cylinder can (and does) somehow find its way into any other cylinder, even on the opposite bank!
 
I've also heard of valves seats being loose, popping up and then back into their pocket. It could have been the bottom edge of the valve seat broken off, and then the valve seat is back in it's correct position. Lift the valves and try pulling on the seats to ensure that one isn't loose, but visually sitting correctly in the block.
 
Visually inspected each and every valve, seat, under extremely bright led and a magnifying glass. Took both valves out of the damaged cylinder and replaced one as it had a slight mark in it. Seats on all seem perfect. I'll find out soon. Compression test next once the head is on.
 
It is off right now and I will shake the crap out of it and check it as much as I can inside with a bore scope. Great minds think alike.

Tom
 
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