1968 Barracuda 318 Smoking....good compression

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jamesromeos

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Just picked up a barracuda convert with what appears to be the orig. 318. I ran a cold compression check on the motor revealing 5 cylinders at 150PSI, 2 at 130 and 1 at 140. When I looked at it there was only mild white smoke eminating from the tailpipe, Not uncommon in cold climate, plenty of power and idles nice. I took it home about hours on a trailer, and when I took it off the trailer it started with a puff of blue grey smoke. As I took it for a ride it seemed to almost smoke out our street. I immidiatly called the PO to ask what the issue may be. He said from time to time the car would do that, but it would go away as soon as the car got warm and was driven for a few. I have not taken it for a good ride yet, but I also know the car has the orig. single exhaust, and it has a carb issue as well, you need to manually open the butterfly to start if it has been running for some time. I know what oil looks like burning, this is a little lighter grey in color versus the blue oil looks like. And I think the compression looks fine as it was tested cold, and the numbers were within 20%, any help or direction would be much appreciated.

Thanks
Jim
 
Pop the oil fill cap and see how much blow by you have. If good you can assume rings are good. I would also replace the intake valve guide seals, no telling how old they are. After you get that done and the chock adjusted properly take it out for a nice long highway cruise. Pull the plugs for a good plug read and redo the compression check with the engine warmed up.
 
How did the Plugs look when you removed them...any cleaner than the others. Might pressure test the cooling system for a possible Head gasket problem.
 
Do an oil change and see what is in there. I bought a Jeep once that ran good at the purchase site but started acting like what you describe a few days later. Turned out the engine was toast and had a very thick oil mixture to make it through the sale.
 
Or, if the car has been sitting and has had very little use,when driving it more it may stop smoking on it's own. my 79 Chrysler would puff blue/grey when I first got it. After 2 oil changes (about 1500 miles total) and a 2000 mile road trip it cleared up on it's own. I've had several do that from lack of use.Also you may find that the compression may balance out too. Just a thought.
 
The plugs were black and wet looking, i changed the oil to no avail. Can you tell with the valve guide seals if they are gone bu look if i pop a valve cover off?
 
There under the valve springs. Black sooty plugs are almost certainly overly rich condition.
 
Darter6 said:
Or, if the car has been sitting and has had very little use,when driving it more it may stop smoking on it's own. my 79 Chrysler would puff blue/grey when I first got it. After 2 oil changes (about 1500 miles total) and a 2000 mile road trip it cleared up on it's own. I've had several do that from lack of use.Also you may find that the compression may balance out too. Just a thought.
Click to expand...

This^^^^

Before you spend a DIME, drive heck out of it for a while. It may stop on its own.
 
jamesromeos said:
The plugs were black and wet looking, i changed the oil to no avail. Can you tell with the valve guide seals if they are gone bu look if i pop a valve cover off?
Click to expand...
Yes, where the material has failed significantly. Look through the valve spring to see the nipple where the valve stem comes through the cylinder head. If you see a complete rubber dome around the valve stem, the seals are probably OK. If a chunk is missing there's a potential problem.

I agree that getting the engine up to operating temperature for a hour or so is a good way to get rid of condensation in the exhaust system, crankcase, and valve covers. Another way to check is to have another person follow at a distance. Get the car up to ~ 45 mph in high gear, drop down to second and let go of the gas pedal. This produces maximum vacuum in the engine. With the throttle plate shut, the engine is going to suck air down any available path. If the valve seals are gone, this procedure will produce smoke that can be seen from the following car.
 
Another possibility is sludge buildup. If sludge is restricting the oil drain back holes in the heads, oil is backing up over the valve guides and running into the cylinders. But, you've seemed to indicate that you don't think it's oil smoke. Maybe if you could post a good quality video, that might help.
 
I think I am going to try to post a video tomorrow. That is interesting about driving the car to 45 and then downshifting.....never heard of that but I think Im going to explore the possibility of the seals as well. what about a carb. issue?
 
This may sound strange to ask, but do the valvecovers have any leaks?
We had a 70 Coronet that smoked pretty bad after it was running for a min or so and then after about 5 min it would clear up.
It would smoke out the entire block and after 5 min of running it didn't smoke at all till the next time it was started.
The valve covers leaked and the oil was seeping into the exhaust gaskets and burning in the manifolds.
Once the Valve cover gaskets were changed it stopped completely.

I got it for $300 bucks because of it, and knew why it was doing it. :)
 
The carburetor MIGHT be an issue, but if it is running well, I would not suspect it.
 
Could be a badly clogged heat cross-over passage in the Intake Manifold.

Not uncommon for old small-block 273 and 318 Engines, which can prevent
heat from transfering thru the passage way to the Carburetor base.
 
From my previous experience, the valve seals and valve cover gaskets would cause those symptoms.
 
I tend to agree with Rob above, if it hasn't been driven, change the oil and drive it, bring it up to temp and see if it doesn't clear up.

Secondly, your compression test was done on a cold engine.

It should be warmed up, as soon as it cools enough to pull all of the plugs, do that, block the butterflies open with a screwdriver, hook up a battery charger to the battery, unhook coil wire.

At least three revolutions per cylinder recording the highest number. If your numbers are low at that point put a squirt of oil in #1 cylinder and repeat the process again on all 8, putting a squirt of oil in each cylinder just before you test.

It could be a stuck ring, who knows.

An old boy once told me, "if it smokes going uphill, rings, if it smokes going downhill, valve seals".
 
rebuilt carb this week. rather dirty inside. clean now. the car is blowing black carbon out the exhaust.....and is running rich. no more blue. I dont know what to do now. idle's nice, just smokes like a mack truck. The plugs were black and chalky, a box sitting behind the exhaust is blackened, covered with carbon.......what next??
 
jamesromeos said:
Any way to test an intake heat driven choke
Click to expand...

Sure. Heat the choke coil & watch for movement. Take a temp reading when movement starts and when it ends.

How to do this, you ask? Remote, non-contact temperature gun, young Grasshopper. Something like this: http://www.amazon.com/HDE-Non-Contact-Temperature-Thermometer-Targeting/dp/B002YE3FS4/ref=sr_1_18?ie=UTF8&qid=1418528258&sr=8-18&keywords=Remote+Temperature+Sensors Need to be sure it has the range for testing the choke.

The maintenance people at work have a couple of these to test A/C at vents that are hard to reach. They are within a couple of degrees of thermometers they can put in the air stream.
 
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