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Help with 312 old y block Thunderbird engine.

Posted: Mon Sep 14, 2020 2:10 pm
by gn69z28
This is a fresh rebuild. 60lbs of oil pressure. But almost no oil to the top of the engine. With head off and running oil pump with drill oil barely runs out of hole in top of block. Online search tells me this is a common problem with this engine. There used to be oil line kits to bypass oil pumping through the block and heads. Don't want to do that. Any ideas or suggestions on what to do or look for. The middle cam journal that the oil flows around has a very small and shallow groove. Is that the problem? Does it need a bigger groove? Are there different can bearings other than stock replacement? Anyone here dealt with this before. Thanks for any help or advice.

Re: Help with 312 old y block Thunderbird engine.

Posted: Mon Sep 14, 2020 6:56 pm
by donsboy
The head is off and there's no flow? Clogged oil galley?

Re: Help with 312 old y block Thunderbird engine.

Posted: Mon Sep 14, 2020 7:05 pm
by gn69z28
Head is off. No clogged galley. Fresh rebuild with starting to break cam in only. Oil comes out of hole very slowly after running pump with drill a minute or so. Took engine apart this afternoon and it doesn't have the grooved cam bearing on no. 3 journal. Will that make that much of a difference. From what I've found online this has been a problem since the 50s. But I need to get oil to the top of the engine for the rocker arms.

Re: Help with 312 old y block Thunderbird engine.

Posted: Mon Sep 14, 2020 7:18 pm
by bone6145
The last one I did I cut a groove in block behind cam bearing to send oil to the heads then put a restrictor in each head to cut the flow down

Re: Help with 312 old y block Thunderbird engine.

Posted: Mon Sep 14, 2020 7:23 pm
by Mummert
Its not a clogged oil galley. Its the center cam bearing that is causing your issue combined with the depth of the radial cam groove in the camshaft itself. A new hardened center cam bearing and increasing the depth of the radial groove in the camshaft by .025" will give you oil to the top end for days.

Re: Help with 312 old y block Thunderbird engine.

Posted: Mon Sep 14, 2020 8:11 pm
by pdq67
Please check the clocking of your cam bearings because if the holes in them don't lne up with the passages in the block, no oil to the top end.

My Mom had a '56 Ford 292 engine that had a copper tubing outside oil system installed on it to oil the top end. Crude, but it worked until the copper tubing broke and she lost all the oil and ruined the engine.

pdq67

Re: Help with 312 old y block Thunderbird engine.

Posted: Mon Sep 14, 2020 10:20 pm
by Krooser
The external oil line deal was needed because of sludge caused by using non detergent oil back in the day.

Ford wasn't the only one with that issue...those Stovebolt Sixes were good for that, too.

Re: Help with 312 old y block Thunderbird engine.

Posted: Tue Sep 15, 2020 4:31 pm
by piston guy
Trust Mummert. He's forgotten more than most will ever know about Y blocks.

Re: Help with 312 old y block Thunderbird engine.

Posted: Tue Sep 15, 2020 4:56 pm
by liqu
Mummert is the man