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Sudden case of burning oil

JoeliusZ28

JoeliusZ28

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Hey all,

This is my 3rd year with my 84 K10. Its a clean original 113k mile truck. The first couple years I spent a lot of time tinkering with the distributor & carb tuning and in hindsight ended up wasting a lot of time on the OEM distributor which ended up having a whacked timing curve. About a month ago I followed the advice of some old school mechanics and junked the ESC distributor in favor of a generic summit non-ESC HEI. Long story short, after 3-4 hours of dialing it in I ended up with a truck that runs WAY WAY better than it ever did with its original distributor. I was one happy camper because it went from a total dog to making a surprising amount of power for a 305, and it has near perfect driving manners. But per tradition in my garage I can't ever seem to cross one problem off the list without adding another, and now its burning oil like crazy on a cold start. I wouldn't say they are giant clouds, but definitely visible. If I let it idle in the driveway it will gradually fog out the neighborhood, and it stinks bad... hell I have a splitting headache from trying to diagnose it for 5 minutes. Revving it will make a healthy puff of smoke as it settles back down. However, if i take the truck around the block for 20 minutes until its fully heatsoaked, the problem seems to dwindle to absolutely nothing. Even revving it hard. But I can't deal with 20 minutes of horrendous fumes every time she comes out of the garage. Most of the smoke is coming from the drivers bank of cylinders.

I had 3 possible theories about this. When I was tuning the dist I changed some vacuum lines around for better performance so I thought maybe one of them might be sucking oil back through the PCV. I verified they're all dry, so I think that's out. The second is that I may have missed an O-ring or something of the sort with the distributor install. From the documentation i have that doesn't appear to be the case but still possible maybe? And third, I'm thinking its a likely possibility that the extra 40-50hp I gained from this new distributor (seriously) might have found a weak spot in this 34 year old engine... valve guides or piston rings I'm not sure. Prior to this the truck would make a mild puff of smoke on startup and clear within seconds. Wasn't really enough to bother me but this is a different animal.

Anything else to consider before I :hack:? Only other thing I have in the back of my mind is a compression test but it doesn't seem to be lacking power. Cheers!
 
Update: I think i found the problem. Turns out I overlooked a vacuum line that the PCV system connects to and there is indeed oil in it. Hopefully I just need a PCV valve.
 
I had the same issue with a 1985 305...at about 70k mi. the intake manifold cracked on the underside...ran like crap until it got warmed up. used a qt about every 700mi. I replaced the manifold and all was good again.
 
Interesting. I'm hoping my problem is simpler and maybe the result of increased vacuum now that its running better. Gonna do some more digging on it...
 
JoeliusZ28 said:
Interesting. I'm hoping my problem is simpler and maybe the result of increased vacuum now that its running better. Gonna do some more digging on it...
Click to expand...
It is unlikely you have a piston ring problem since the smoke goes away after warm up.
Valve stem seals are very likely to cause this type of problem.
Also, sucking oil through the Positive Crankcase Ventilation system, particularly with aftermarket valve covers in which the baffle is missing or poorly made.
The fact that you added horsepower should help, rather than hinder, piston ring sealing against the cylinders.
Don't ignore the brake vaccum booster either.
A tiny amount of brake fluid can create massive amounts of smoke.
It is possible for a master cylinder to leak and vaccum booster to draw brake fluid into itself and then the intake.
Rare.
But it happens.
You'd think it would suck all the brake fluid out but it takes a long time and makes an inordinate amount of smoke, on startup, in the process.
Check the inside of the vaccum line to the brake booster for residue.
 
I didnt consider the brake booster thats a good idea. I know the symptom is typical of valve seals but im finding it hard to believe it could be only that since its burning so much for so long and then it eventually all goes away. I know brass guides can expand/contract with heat but seems like that problem would have developed over time instead of all at once.
 
JoeliusZ28 said:
I didnt consider the brake booster thats a good idea. I know the symptom is typical of valve seals but im finding it hard to believe it could be only that since its burning so much for so long and then it eventually all goes away. I know brass guides can expand/contract with heat but seems like that problem would have developed over time instead of all at once.
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Valve seals can leak down after shutdown and then smoke alot at startup.
Would also suck a lot of oil on deceleration down hill.
That brake booster leak is a really unlikely but not unheard of thing.
Happened more than once to my Dad's car collection though.
 
Whatever is leaked into the cylinder shluld burn off right away on startup though right? Is it typical for valve seals smoke for 15-20 minutes? I guess one thing i didnt mention is it does NOT puff on immediate start if its stone cold. (It will on a warm start). On a stone cold start it seems to take a good 10 seconds of run time before it starts breathing a steady stream of smoke. I do not notice any burning oil while driving, even on decel.

Edit: also forgot to mention these are stock valve covers.
 
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JoeliusZ28 said:
Whatever is leaked into the cylinder shluld burn off right away on startup though right? Is it typical for valve seals smoke for 15-20 minutes? I guess one thing i didnt mention is it does NOT puff on immediate start if its stone cold. (It will on a warm start). On a stone cold start it seems to take a good 10 seconds of run time before it starts breathing a steady stream of smoke.
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That sounds like valve seals.
On startup, top end is dry.
Takes a few seconds for oil to start dripping out of rocker arms, leaking down onto stem seals.

The acrid smell though, that makes me think it's brake fluid possibly.
Because burning brake fluid is vile smelling.
Could be too rich a fuel air mixture combined with valve stem or piston ring oil leak, or intake gasket leak to valley area, making the catalytic converter stink.
That is far more likely than my brake fluid leak.
Just wanted to mention it because it is possible.
 
I'd start it up cold.
Run until the smoke is at it's worst.
Shut it off and pull the spark plugs.
Keep them in order.
See if any exibit oil fowling.
Maybe they all do or just one.
Even if it is just one or two; could indicate a leaking intake manifold gasket.
If they are all clean; id run a compression test followed by a leak down test if poor compression was indicated.
 
It doesn't seem to smell any different than typical oil burning it just seems to get to me a lot more than other experiences I've had. Maybe its the zinc additive. But pretty sure if i put my face near the tailpipe it would end my existence pretty quick I felt like crap after that few minutes of diagnosing yesterday.

Good idea on the plugs. I have all the parts to do the intake gasket and even the valve seals. I was just hoping its something more to do with the oil in that vacuum line.
 
JoeliusZ28 said:
It doesn't seem to smell any different than typical oil burning it just seems to get to me a lot more than other experiences I've had. Maybe its the zinc additive. But pretty sure if i put my face near the tailpipe it would end my existence pretty quick I felt like crap after that few minutes of diagnosing yesterday.

Good idea on the plugs. I have all the parts to do the intake gasket and even the valve seals. I was just hoping its something more to do with the oil in that vacuum line.
Click to expand...
Ahh, zinc and catalytic converters don't mix.
Particularly the phosphorous and zinc compounds found in those oil additives.
They coat the inside of the cat and can make it smelly.
But that doesn't explain your smoke issue.
That is something else.
Most likely engine oil.
But gotta find it.
 
No cats on it anymore. Its definitely engine oil... consumption on the dipstick aligns as well. Oil level has gone from the top to the bottom of the operating range in just the last 200 miles or so.
 
Get a good valve spring compressor.
I bought the cheap one from Summit and regretted it.
Got the job done but wished for a better tool.
 
You got the better one.
I got the small hand wheel version.
Kept slipping off the valve springs.
The arms deflected under load too much.
It did fit easily in the engine compartment though.
A lot of cussing.

I pulled all the spark plugs and inserted a piece of rope into the cylinder I was working on while it was at TDC.
the rope kept the valve from falling down.
 
I have an air compressor adapter for the spark plug port. However Im not looking forward to this job because it looks like both the AC compressor and brake booster are in the way.
 
JoeliusZ28 said:
I have an air compressor adapter for the spark plug port. However Im not looking forward to this job because it looks like both the AC compressor and brake booster are in the way.
Click to expand...
I was lucky my AC had been lost to the ravages of time.
Now that crappy valve spring compressor I got did help being small enough to fit between the brake booster and cylinder #7.
About the only advantage to it.
 
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