Rebuilt engine burning oil ??
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From: stockport Cheshire
Rebuilt engine burning oil ??
I have just fitted a rebuilt 350ci 1969 engne in my vette to replace the tired 307ci someone had fitted. The engine was built by a reputable shop, The problem I have is once the engine is warm it is belting out blue smoke at idle, if I rev up to 1500rpm the smoke goes but comes back at idle. The car runs great apart from this, I got a friend to follow me driving down the road and he said it only puffs smoke when I step hard on gas pedal, when I back off the gas after accelerating and on gear change. I have spoke to guy who did the engine and he admitted it should not smoke but suggested that since the block had been stood for six months for rebuild to fitting that it probably just wanted a good run, I have since done a 100 miles with no improvement so I plan to get back onto him. So has anyone got any thoughts on possible cause so I can at least look like I have some idea in case he tries to blind me with tech talk.
Any help would be great !
Mark.......
Any help would be great !
Mark.......
Drifting
Joined: Jul 2002
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From: Edinburgh
Re: Rebuilt engine burning oil ?? (British Mark)
If it wasnt for the belting out blue smoke at idle when warmed up I would have said valve stem oil seals, but lots of blue smoke at idle especially when warm suggests a bit more. If they are a reputable dealer they should fix it, if they did not install it, better check all ancilleries are working properly before you take it back and be sure and check your oil level after 100 miles+ with that much smoke it should be down at least a pint. Also take the plugs out and check them in case one is more heavily oiled up than the others, then you can point to that cylinder(s). :cheers:
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From: San Diego - Deep Within The State of CONFUSION!
Re: Rebuilt engine burning oil ?? (British Mark)
Was the engine bored and fitted with new pistons/rings? If so then YES take it back to the builder. OTOH, if the bore was re-used then new rings will need to be broken in, to work with the old bore. Give it 500 miles to 1,000 miles depending on the age and miles on the old block.
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From: stockport Cheshire
Re: Rebuilt engine burning oil ?? (SanDiegoPaul)
Not sure about the bores I think they were just honed but he did fit new crank, pistons and cam. If it is that the rings still have not seated souldent it somke even under acceleration ?
Thanks Mark.
Thanks Mark.
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From: Plano TX
Re: Rebuilt engine burning oil ?? (British Mark)
Back when I bought mine I had the same symptoms (got a good deal on the car partly because of that). The engine was a fresh rebuild, yet smoked at idle as well as when letting off the gas.
Turned out to be torn valve seals. They had used double valve springs where the inner spring was of such small diameter that it grabbed the umbrella seal and shredded it. I had to remove the heads and install PC-seals and no more smoke.
Turned out to be torn valve seals. They had used double valve springs where the inner spring was of such small diameter that it grabbed the umbrella seal and shredded it. I had to remove the heads and install PC-seals and no more smoke.
Drifting
Joined: Jul 2002
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From: Edinburgh
Re: Rebuilt engine burning oil ?? (zwede)
:yesnod: Thats the way I was thinking Zwede, but hadn't come accross the smoky idle before. They must be really torn up for that to happen :eek:
Mark I would be interested to hear who built it for you, (offline) maybe you could drop me an email?
:cheers: :cheers:
Mark I would be interested to hear who built it for you, (offline) maybe you could drop me an email?
:cheers: :cheers:
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Thread Starter
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From: stockport Cheshire
Re: Rebuilt engine burning oil ?? (Graemeinvette)
I bought the block as a 1969 short block and the engine guy supplied the heads (1970 camle hump) which He said he has fitted new springs, would he have to have fitted new seals as well ?
Mark...
Mark...
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From: Plano TX
Re: Rebuilt engine burning oil ?? (Graemeinvette)
:yesnod: Thats the way I was thinking Zwede, but hadn't come accross the smoky idle before. They must be really torn up for that to happen :eek:
After the new seals the consumption dropped to about a quart every 1000 miles, and no smoke. I think it sucked oil through the intake gasket. Later I switched to Edelbrock aluminum heads and EFI and now it uses just about no oil. Never touched the short-block so the cylinder walls and pistons/rings were fine all along.
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From: Living in the Hartland
Re: Rebuilt engine burning oil ?? (British Mark)
Have you given the eng a good flogging to seat the rings? You have to rev it to 5000 rpm's under load to get them to seat properly. GM recomends waiting till about 500 miles but others say to do it right away. Either way you have to get some pressure built up in the cylinders to get the rings to seat properly.
[Modified by Fevre, 1:17 PM 6/18/2003]
[Modified by Fevre, 1:17 PM 6/18/2003]
Drifting
Joined: Sep 2000
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From: Germantown Maryland
Re: Rebuilt engine burning oil ?? (British Mark)
My symptoms after build were similar. I figured it out since the builder couldn't. :confused: Turned out the intake wasn't torqued down. After I did that it went from QT every 200 miles to QT every 2000 miles. This is a cheap easy fix 5 minutes...
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From: Tilehurst Reading
Re: Rebuilt engine burning oil ?? (British Mark)
As others have said.. could be faulty / missing / worn oil seals
Also could be worn valve guides. If you have both these things, then smoke would be worse. More noticable at idle because of stong inlet vacuum pulling oil down the valve stems. Vacuum reduced as you throttle up.
Also could be worn valve guides. If you have both these things, then smoke would be worse. More noticable at idle because of stong inlet vacuum pulling oil down the valve stems. Vacuum reduced as you throttle up.
Le Mans Master
Joined: Dec 2000
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From: Blue Ridge Georgia
Re: Rebuilt engine burning oil ?? (Col-UK)
I don't see anyone talking about what oil you are using. Don't use synthetic oil to break in a motor. I suggest using Castrol Oil for break in. The synthetic won't let the rings seal. As for valve seals. I believe you should replace them every time you pull the heads. In your case you should have replaced them if the heads had been used before you installed them.
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From: wi
Re: Rebuilt engine burning oil ?? (Paul 75 L82)
I had a problem similar to this in an old continental flathead engine a friend built for me. It turned out that he had installed the rings wrong.. It ran but would not quit smoking. They were sealed power rings btw.
Good Luck
Good Luck
Melting Slicks
Joined: Mar 2003
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From: Franklin IN
Re: Rebuilt engine burning oil ?? (British Mark)
If you are using a synthetic like Mobil 1 it may not allow the rings to seat in. My motor rebuilder told me not to use it untill I had several thousand miles on the rebuild.
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From: Plano TX
Re: Rebuilt engine burning oil ?? (87bob)
If you are using a synthetic like Mobil 1 it may not allow the rings to seat in. My motor rebuilder told me not to use it untill I had several thousand miles on the rebuild.
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Joined: Oct 2001
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From: Pampa Tx
Re: Rebuilt engine burning oil ?? (zwede)
Couple of other thoughts:
Check the compression on each cylinder.
1. If it is good then check seals and intake.
2. If compression is bad, check the difference between cylinders. If you see more than 3-5 lbs, then suspect broken ring or improper orientation of the ring gaps
Are you sure it is not fuel rich carburation? Smoke can look blue and be mistaken for oil.
Hope it helps :seeya
Phlash 72 BB Roadster
Check the compression on each cylinder.
1. If it is good then check seals and intake.
2. If compression is bad, check the difference between cylinders. If you see more than 3-5 lbs, then suspect broken ring or improper orientation of the ring gaps
Are you sure it is not fuel rich carburation? Smoke can look blue and be mistaken for oil.
Hope it helps :seeya
Phlash 72 BB Roadster
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From: stockport Cheshire
Re: Rebuilt engine burning oil ?? (Phlash)
Thaks for the info,
I have given it a good blast to help seat the rings, I have 14/40 oil and plan to change it this weekend to 20/50. I will take the car back to the engine builder and seewhat he thinks, I hope it is as simple as valve seals. I will let you know the outcome.
Mark.......
I have given it a good blast to help seat the rings, I have 14/40 oil and plan to change it this weekend to 20/50. I will take the car back to the engine builder and seewhat he thinks, I hope it is as simple as valve seals. I will let you know the outcome.
Mark.......
