Oil Burner
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Joined: Jan 2005
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From: Aylesbury Buckinghamshire. UK
Oil Burner
My 1980 has been using some oil since its purchase in 2004. Not loads, but finally got bored of cleaning the plugs. Car has covered a well documented 47K so hopefully bore/ring wear wasn't the major problem.
A recent compression check showed all readings in the 140's. ( 141 - 146 ) nothing wrong there !. Removed the intake today to find that there was no sealant used on the intake gaskets and the inlet bores were caked in oil..... a bit of a clue.
So I think I've found the major problem. Question from a novice Corvette head remover !. What is the function of the centre inlet on both sides of the intake. This was contaminated with oil the worst. Looks like some sort of exhaust connection ?.
Thanks
Bob ( UK )
A recent compression check showed all readings in the 140's. ( 141 - 146 ) nothing wrong there !. Removed the intake today to find that there was no sealant used on the intake gaskets and the inlet bores were caked in oil..... a bit of a clue.
So I think I've found the major problem. Question from a novice Corvette head remover !. What is the function of the centre inlet on both sides of the intake. This was contaminated with oil the worst. Looks like some sort of exhaust connection ?.
Thanks
Bob ( UK )
Le Mans Master
Joined: Oct 2005
Posts: 9,429
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From: Macon, GA
If you have smoke on inital start-up, your problem may lie in the valve guide seals which is allowing oil to drip in the cylinders while the car sits. Not a big deal to replace those.
Good luck.
Good luck.
Racer
Joined: Apr 2001
Posts: 391
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From: Bend, Oregon
The center passages are a crossover to heat the area under the carb . It sounds like you may have had an intake gasket leaking. This can cause oil consumption. While you are in there I would go ahead and replace the valve seals. I would leave the heads on for now and address the valve seals and sealing the intake. Do you have any pics?
Garson
Garson
Drifting
Joined: Nov 2003
Posts: 1,634
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From: Northern NJ
St. Jude Donor '04 & '05
Originally Posted by sperkins
If you have smoke on inital start-up, your problem may lie in the valve guide seals which is allowing oil to drip in the cylinders while the car sits. Not a big deal to replace those.
Good luck.
Good luck.
Did the valve seals on my 75 last fall and it made all the difference in this area. No more puffs (clouds?) of smoke at startup and upon deaccelleration. Was well worth the effort and the few dollars in parts.
Now I gotta go back and do them on the 84 too. Same issues just not quite so bad. I guess they are 9 years newer.
Good Luck!
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Joined: Jan 2005
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From: Aylesbury Buckinghamshire. UK
Originally Posted by Garson
The center passages are a crossover to heat the area under the carb . It sounds like you may have had an intake gasket leaking. This can cause oil consumption. While you are in there I would go ahead and replace the valve seals. I would leave the heads on for now and address the valve seals and sealing the intake. Do you have any pics?
I have been collecting bits for a winter power increase so I can fit the new Edelbrock 2101 intake to cure the problem until winter.
Thanks for the feedback.
Bob ( UK )Attachment 47594478Attachment 47594477
Melting Slicks
Joined: Feb 2006
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From: Japan
Bob, when I rebuilt the (numbers-matching) 350 in my vette some years ago my machinist angle-milled my heads without asking me about it first. Their mill was set up for angle-milling and when he went to take a .003" swipe off the decks about .030" wound up coming off the outside edge. Not knowing the exact nature of the problem, I put the motor back together, put it in, and ran it. It used a quart of oil every 100 miles, so to answer your question- YES, your Chebby can suck colossal amounts of oil through the head-to-manifold joint if there's a leak there. My guess is that if you just clean everything up and replace those gaskets with some good new ones and seal up the intake ports (I like grey hi-temp permatex RTV) the problem should disappear, assuming your heads weren't butchered like mine. As far as the exhaust crossover ports, I seal around those with copper hi-temp RTV, and they should be useful in Jolly England where it's cold.....
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Safety Car
Joined: Oct 2000
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From: Carbondale Pa.
Is the intake manifold cracked on the # 8 cylinder runner, or is it just a casting flaw ? A crack would allow oil to be sucked in that cyl. & how does # 8 plug look ? Peace,,,,Moosie
Also looks cracked at the dist. hole .
Also looks cracked at the dist. hole .
Last edited by moosie982; Jun 21, 2006 at 09:56 AM.
Le Mans Master
Joined: Oct 2004
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From: Orlando Florida
St. Jude Donor '05
Originally Posted by moosie982
Is the intake manifold cracked on the # 8 cylinder runner, or is it just a casting flaw ? A crack would allow oil to be sucked in that cyl. & how does # 8 plug look ? Peace,,,,Moosie
Also looks cracked at the dist. hole .
Also looks cracked at the dist. hole .
looks like two cracks...
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From: Aylesbury Buckinghamshire. UK
The most contaminated inlets were 6,7 & 8. and the crossover. I thought this was the reason why my compression levels were good at first, but then I checked the " dry " cylinders and they were low 140's as well.
Having checked the old intake there dosnt appear to be any cracks that have passed oil looking from underneath. The inlet ports are so caked with oil it has to be the main cause of my oil consumption.
I have fitted up the new Edelbrock 2101 with all the fittings, thermostat housing ,water inlets etc and now just awaiting the new gaskets in the post tomorrow.
Incidentally the previous owner or garage persons unknown who fitted the new holley 600 mounted the adapter plate upsidedown
!!. The air/fuel mixture entering the inlet was met with a flat wall of aluminium rather than the chamfered smooth curves that were machined on the other side. What a **** ! Must be a few horses lost there !.
Bob ( UK )
Having checked the old intake there dosnt appear to be any cracks that have passed oil looking from underneath. The inlet ports are so caked with oil it has to be the main cause of my oil consumption.
I have fitted up the new Edelbrock 2101 with all the fittings, thermostat housing ,water inlets etc and now just awaiting the new gaskets in the post tomorrow.
Incidentally the previous owner or garage persons unknown who fitted the new holley 600 mounted the adapter plate upsidedown
!!. The air/fuel mixture entering the inlet was met with a flat wall of aluminium rather than the chamfered smooth curves that were machined on the other side. What a **** ! Must be a few horses lost there !.Bob ( UK )
Melting Slicks
Joined: Feb 2006
Posts: 3,428
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From: Japan
mvftw, about the copper RTV on the exhaust crossovers- it's meant for use in super high-heat places like headers, etc.- all the other silicone sealants just turn to dust when you subject them to lots of heat so I figgered it'd be a good bet in that one spot-the copper in it stays there after the base material burns away. I've experimented with all kinds of sealers (haven't we all?) and Permatex grey hi-temp seems to work best in my experience- it's a little more 'pasty' than the others and seems to resist oil intrusion best. As far as that baffle goes, what you suggested is exactly what is mentioned in the ubiquitous "How to Rebuild Your Small-Block Chevy" book. You have to be careful to put the smallest possible sheetmetal screws back in there though or the heads will rub against the lower corners of your heads.
Last edited by birdsmith; Jun 21, 2006 at 07:06 PM.
