318 OIL LOSS WITH NO SMOKE OR LEAK

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K

KCS

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Hamlin, N.Y
My 71 Swinger runs great but every 5 to 600 miles I am having to add at least a quart of oil. There is no smoke and just a tiny trace of a leak. The motor was built in March. Here are some of the specs: 1968, 318 block, Wisco pistons at 0 deck, Scatt connecting rods, Ported and polished 360 heads, stock 340 intake manifold, Edelbrock 650 CFM carb. Compression is 9.5 to 1. Where the heck is the oil going?
 
I had the same issue with my 318 but, I had an Edelbrock intake. I did leak down tests, changed valve stem seals twice, checked top to bottom. I thought I didn't have any smoke but, I followed the car while accelerating and decelerating and noticed a trace amount. The two things that solved my issue were oil creep up some intake bolts and the intake gasket.
 
An engine uses oil three ways. Leaks, burning and passing through the crankcase as a mist. That third is difficult to pickup on, because it involves the crankcase vent system......if there is one and the PCV system, if there is one.

If you have no PVC, that could be the whole issue, as the PCV puts a vacuum on the crankcase and helps the rings to seal. If you see no leaks to amount to anything and see no burning to speak of, I would inspect the crankcase breather and PCV system.
 
Have you put cardboard under the engine compartment when you park it to see if any drips???
 
New valve guides ? If not, it will suck oil right through them on deceleration. Then a good puff of smoke at acceleration. For many years the unleaded engines were expected to pass as much as half quart over a 1000 miles. You're passing more than twice that amount so....
 
At that usage rate, it can easily be going down the valve guides or being sucked into the intake ports or going past the rings and no smoke will be readily seen. I had a car with a toasted turbo seal that sucked oil about 1 qt per 400 miles and I never saw smoke.

I would seriously suggest that you have someone in the back seat, turned and looking back, and go through some accelerations, and then slow to a stop and then take off at normal speeds several times, while that person in the back watches. They will see smoke from the exhaust a LOT more readily than a driver using the mirrors.
 
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