400 burning oil
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400 burning oil
I have recently purchased a 1978 f250 4x4 4spd manual np205 (I think) with a divorced transfer case and a 400 under the hood. It leaks oil from the rear main seal but also burns plenty of oil too. When I start it it starts fairly easy so I doubt the rings are worn but when i idle it in my heater shop it smokes quite a bit and especially more on the passenger side headers. I was thinking it might be burnt valves because I have already replaced the pcv valve and that did nothing so I’m thinking it’s a valve or two that are burnt. If that is the case how do I fix it? Do I have to send the heads to get finished or something? Do I have to get new valves and seat them? If so what’s the procedure for that? What would a ballpark cost be for it? Would I be better off to buy a replacement engine? Sorry for all the questions I’m more of a diesel guy. Thanks in advance
PS if I figure out how to post a video on here I’ll show you it’s idle
PS if I figure out how to post a video on here I’ll show you it’s idle
Last edited by 1978F2504x4400; Nov 19, 2021 at 03:33 PM.
Laughing Gas
Joined: Feb 2011
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Welcome to Forum. Well if you have a divorced t-case its not a 78 drivetrain. But that's irrelevant to your question. Just because it starts easy, doesn't mean the rings aren't worn. I'd start with a basic compression test on all cylinders. Then depending on results you may want to do a leak-down test to further isolate root cause. We can speculate a lot of causes but you have to collect facts and base your conclusion from them vs guessing.
So you have blue smoke coming out the exhaust during idle? See what the compression test indicates and report back. If you aren't sure of the correct way to do one, have someone assist who does. Its not hard and a tester is inexpensive but you just need to study up on the procedure to insure you get accurate results.
So you have blue smoke coming out the exhaust during idle? See what the compression test indicates and report back. If you aren't sure of the correct way to do one, have someone assist who does. Its not hard and a tester is inexpensive but you just need to study up on the procedure to insure you get accurate results.
More Turbo
Joined: Nov 2018
Posts: 563
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From: CA
Welcome to Forum. Well if you have a divorced t-case its not a 78 drivetrain. But that's irrelevant to your question. Just because it starts easy, doesn't mean the rings aren't worn. I'd start with a basic compression test on all cylinders. Then depending on results you may want to do a leak-down test to further isolate root cause. We can speculate a lot of causes but you have to collect facts and base your conclusion from them vs guessing.
So you have blue smoke coming out the exhaust during idle? See what the compression test indicates and report back. If you aren't sure of the correct way to do one, have someone assist who does. Its not hard and a tester is inexpensive but you just need to study up on the procedure to insure you get accurate results.
So you have blue smoke coming out the exhaust during idle? See what the compression test indicates and report back. If you aren't sure of the correct way to do one, have someone assist who does. Its not hard and a tester is inexpensive but you just need to study up on the procedure to insure you get accurate results.
Hotshot
Joined: Feb 2004
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From: The Shenandoah Valley
Smoking on the headers is a sign of leaking valv cover gaskets. Might also check for oil leaking at the back of the intake manifold there on the engine block, oil sender unit. Burnt valves do not smoke on headers, they just leak compression and a vacuum gauge will fluctuate. Myine leaks at rear main seal, but also from up top and a little on the lower sides of the valve covers.
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Smoking on the headers is a sign of leaking valv cover gaskets. Might also check for oil leaking at the back of the intake manifold there on the engine block, oil sender unit. Burnt valves do not smoke on headers, they just leak compression and a vacuum gauge will fluctuate. Myine leaks at rear main seal, but also from up top and a little on the lower sides of the valve covers.
mine leaks at the valve cover gaskets so I tried tightening them up and it’s seemed to help a bit but it still smokes on the passenger side. I ordered a compression tester and hopefully it will be here soon so I can test it. I also have a 351m that I was thinking of throwing in if I need to rebuild my 400
Hotshot
Joined: Feb 2004
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From: The Shenandoah Valley
I had one start leaking so bad that oil ran down onto the exhaust manifold and I pulled over to look under the hood for smoke source, opened hood, it was on fire on the manifold so I shut the hood, drove the half mile to my home, parked near the water hose outlet, luckily the hose was there in a neat coil hooked up ... jumped out and grabbed the hose as I turned on faucet, then I opened the hood and was able to put the fire out.
It was really "BURNING OIL" you might say.
My fire was on the driver side, my fuel line to the carburetor was on the passenger side of the carb ... was mostly metal too which was a good thing .... no doubt saved my truck. Didn't even ruin my new plug wires. Investigating, I found that the lower run of cork valve cover gasket had slipped out of line resulting in a massive oil leak. I found a really good sealer for new cork gaskets at NAPA, was white type of gasket glue. That was near 30 years ago.
It was really "BURNING OIL" you might say.
My fire was on the driver side, my fuel line to the carburetor was on the passenger side of the carb ... was mostly metal too which was a good thing .... no doubt saved my truck. Didn't even ruin my new plug wires. Investigating, I found that the lower run of cork valve cover gasket had slipped out of line resulting in a massive oil leak. I found a really good sealer for new cork gaskets at NAPA, was white type of gasket glue. That was near 30 years ago.
Cargo Master
Joined: Jul 2010
Posts: 2,099
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From: York, Pa
ummm no
Maybe someone hung a divorced 205 on a 2wd.
Maybe someone hung a divorced 205 on a 2wd.
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More Turbo
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