excessive oil usage 65 stock 389 - Pontiac GTO Forum
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post #1 of 4 (permalink) Old 05-26-2018, 07:47 PM Thread Starter
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excessive oil usage 65 stock 389

Will use 1 quart of oil after only 300 miles. Rebuilt now has 8000 miles
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post #2 of 4 (permalink) Old 05-28-2018, 12:00 PM
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Originally Posted by kodowdy View Post
Will use 1 quart of oil after only 300 miles. Rebuilt now has 8000 miles
Could be a number of things. You don't give us very much details and need a whole lot more.

Broken rings.
Burned a hole in a piston.
Glazed cylinder walls so rings did not seat.
Valve guides worn.
No valve seals.
Blown head gasket.
Warped head.
Bad intake gasket.
Hole in the pan.
Leaking gaskets.
Rear main seal.
Timing cover seal at crank bad.
Bad PCV valve or sucking oil from valley pan.
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post #3 of 4 (permalink) Old 06-21-2018, 06:48 PM
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Is it leaking oil externally or is it using it? If it's using it, I would do a cylinder leakdown test. My bet is that the rings didn't seat or could be broken if you have been detonating.
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post #4 of 4 (permalink) Old 06-23-2018, 07:18 AM
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Hope this might help. I had my '62 409 engine rebuilt at the machine shop and it was started and dynode for a break in and adjustment purposes. Sounded great. Previously, advised the machinist to do what it takes to make the engine correct. Never limited the money invested. No budget. Just wanted it right. Short story, brought it home and installed it. Sounded and ran great, but noticed it was using about 1 quart of oil every 300 miles or so. Not leaking it. Talked to the machinist and tried many different remedies. Nothing worked. Two thousand miles later, still using oil. Checked both tail pipes and there was a dark black substance, quite heavy, in both pipes. This certainly was motor oil. Tried to figure this out on my own and thought that the oil was coming from the top down, not the bottom up. Then decided it had to be the valve guides and/or seals. Asked the machinist if he changed them and he said no. They looked good. Wrong. Took the heads off and had him install new valve guides and seals. Put the motor back together and problem was solved. No more oil usage. Can't begin to tell you how disappointed and disgusted I with this issue, especially since I didn't limit him to a dollar amount on the rebuild. Valve guides are cheap in the scheme of things. So, that's my story.
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