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I recently bought a 78 spider (I posted some electrical issues that you guys helped me with) and have come across a odd issue. every once and a while usually after slowing down and then accelerating I have a lot of blue smoke as oil much like oil seals but most of the time there is nothing. The exhaust pipe is clean I have not driven it a lot but the oil is clean I have tried to get it to smoke by revving the engine while stopped but to no avail. The engine runs fine no smoke at all at idle. The engine has been converted to webers an is suppose to have been overhauled but there was no paperwork. I did notes that there is some oil on the exhaust manifold outside I haven’t checked the compression but there is no oil in the coolant. Usually when I have had bad rings the exhaust shows some smoke all the time and when the valve guides leak you have it puff at shifts or when cold so I am confused.
 

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As you slow down (throttle closed) the intake vacuum will be highest. This can tend to suck oil past the valve guides/seals. Then when you accelerate that oil gets burned off.

I assume it is possible to install new seals on the valve guides but you'd have to remove the cam shafts and obtain a valve spring compressor. The valves can be held shut during seal replacement using compressed air or the 'rope in the spark plug hole' trick.

As long as you don't find coolant in the oil &/or oil in the coolant, I'd consider it OK to drive as is. Just check the oil level (dip stick) often enough that you don't run low on oil.
 

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Umbrella seals, guides and valve seat/facing can all sump a little oil into the cylinder on the over-rev/engine braking when the throttles are closed and vacuum pulls through the seats.

You'll get a huff once you get back on it with any kind of vigor as it burns it off the piston crowns.

You could pull your plugs and peek down inside to look at the runner side of the valve heads to see if there's any wet on them after a slow putt around town.

A pretty over-rich A/F mixture (or accelerator pumps set way too fat) can cause smoke too, but it's not usually really blue or oil stinky, and can generally be reproduced in a number of ways, not just after an over-run.
 

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That make a lot of sense to me. I had hoped that that would be the most probable problem and one that I can live with. I had a Merc that had worn seals and until it was hot it would puff like mad at every shift but never seamed to burn much oil. I will keep an eye out for oil in the coolant. The car is new to me and I do not want to do any thing to hose it up just because I didn’t know a quirk. I have done some reading but you never know there is a lot of experience out there. Thanks
 

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I have the same symptoms with my '79. I keep an eye on the oil, but it doesn't lose much at all, so I'll keep running this way until the engine needs more serious work, and deal with the situation then.
 

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does your car knock a bit when it smokes? Mine will drive around fine for a long time with absolutely no smoke no matter how hard i get on it and then after a gentle drive usually after slowing down and the accelerating I will leave a cloud of smoke then nothing It does appear to be valve seals but mine does not smoke when i start it or at shifts. the oil is clean so I don’t think there is ring blow by I will tell you if I find a definite answer
 

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does your car knock a bit when it smokes? Mine will drive around fine for a long time with absolutely no smoke no matter how hard i get on it and then after a gentle drive usually after slowing down and the accelerating I will leave a cloud of smoke then nothing It does appear to be valve seals but mine does not smoke when i start it or at shifts. the oil is clean so I don’t think there is ring blow by I will tell you if I find a definite answer
No knocking that I've heard. I don't alway notice the smoke myself, but I'm not always looking, either. It does mainly seem to happen when I've slowed & downshifted, then get on it hard, not just when I accelerate away from a stop. I especially notice it after taking corners, but that could just be because corners often give some background for the smoke to stand out (as opposed to asphalt and sky on a straight road).

Plenty of soot gets spit out on a cold start, but no smoke. My oil's clean, too, the car runs well, and it's been well-serviced its whole life, so I'm not particularly concerned.
 

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just make sure you keep the oil level up. my old spider got hot from a broken heater hose, went to smoking on decel and my X wife ran it dry on oil. thee overheat had cooked the valve guide seals.
cliff
 

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It seems that a compression test would show ring trouble, but not leaking valve guide seals. still smoking with good compression would indicate valve guide seals. before I did the headgasket last summer with new valve guides, seals and such, my 74 would smoke after decel, and also after holding 70 or so for several miles. now it dont smoke.
cliff
 

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If the problem is only intermittent, check that the oil separator isn't filling up and throwing a slug of gunk in the intake every now and then. Clean and check the whole system, hoses and all. The oil separator can be cleaned in some clean gasoline. Be careful not to bang it around since there's charcoal nuggets inside.
 

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I especially notice it after taking corners,...
This clue, along with it smokes 'only once in a while' tells me that the brake master cylinder may be at fault. The primary piston rear seal can leak brakefluid into the booster where the fluid will get sucked into the engine and burned when;
A) the fluid level in the booster gets high enough
B) under high vacuum conditions (such as decelerating)
C) when cornering - the fluid can slosh up to the level of the vacuum hose
I'd remove the master cylinder mounting nuts, pull the master cylinder away from the booster (no need to disconnect the lines) and have a look inside the booster.
 

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This clue, along with it smokes 'only once in a while' tells me that the brake master cylinder may be at fault. The primary piston rear seal can leak brakefluid into the booster where the fluid will get sucked into the engine and burned when;
A) the fluid level in the booster gets high enough
B) under high vacuum conditions (such as decelerating)
C) when cornering - the fluid can slosh up to the level of the vacuum hose
I'd remove the master cylinder mounting nuts, pull the master cylinder away from the booster (no need to disconnect the lines) and have a look inside the booster.
Thanks. I'm not constantly looking in my mirror, and my comments only reflect what I've noticed on a random basis, so it may not reflect reality, but since it seems pretty simple, I'll check it out.

If the fluid is getting burned off after it's sucked in, what would I be looking for inside the booster? Just some sort of gunky residue, or might there be some actual fluid in there, too?

If this is the cause, is that seal bad, or is my master cylinder just overfilled?
 

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Discussion Starter #16
Yes mine does it mostly in taking a corner the first time I noted it was after making a U turn it has never happened in a strait line even after long deceleration the knocking is most likely cause by the oil burning it is not bad but you can hear it otherwise the engine runs great. Hey so far I have had all the other problems solved here my heater fan was not working and some on was telling that the fan commonly get corrosion in the bearing and gets stuck so I reached in and turn the fan with my fingers an now it works great no disassembly.
 

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This clue, along with it smokes 'only once in a while' tells me that the brake master cylinder may be at fault. The primary piston rear seal can leak brakefluid into the booster where the fluid will get sucked into the engine and burned when;
A) the fluid level in the booster gets high enough
B) under high vacuum conditions (such as decelerating)
C) when cornering - the fluid can slosh up to the level of the vacuum hose
I'd remove the master cylinder mounting nuts, pull the master cylinder away from the booster (no need to disconnect the lines) and have a look inside the booster.
Jim - Doesn't burned brake fluid come out as white smoke, not blue?
 

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In my experience;

fuel = gray to black
oil (including ATF) = light blue
brake fluid = bluish white
coolant/condensate = white

The color, tint and intensity of any smoke can vary with the amount being burned. Another factor is the experience of the observer.

My thought on the M/C as a possible cause was based very little on the color of the smoke and mostly on the conditions under which the smoking occured.
 

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Jim,
Is the light blue almost white? The smoke I see appears white to me. I did a wet compression test while trying to determine where the oil is going. When I started the engine after putting oil down the plug holes, the clouds of smoke appear white to me.
I am very confused :)
 

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Discussion Starter #20
it was the master cylinder leaking into the brake booster. I was told to clean the boosteer out with water 3 times and then alcohol
 
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