Oil Leak I guess

[jolobo64]

Got a 64 chevy c10 350 engine and tranny seems to be from mid 70's. She looks good and runs good but I notice when I return from a drive there is a small oil drop in the driveway. Worst than that I can drive about 40- 50 miles and I am clearly a quart low. Thought it was valve cover or intake gaskets, changed those. Still same problem. There is no smoke when driving , of course early morning there is very light( not bluish) white smoke, that seems to be normal on any car just starting up in the morning.

Sitting idle no oil leak, Oil pan gasket is my next task, just wondering where can that much oil be going? Oil is clean, once again no smoke to indicate its burning oil, but I am lost for ideas???

[Rich 5150 69]

Several questions arise here, which trans and rear gear ratio are you running, are you using a PVC valve, is it clean, what oil are you using, some brands tend to simply slip past rings more so than others, how often are you changing oil..?

[jolobo64]

Gear Trans Ratio got me on that one?? New PCV Valve is installed, oil change just done about two months ago. I've only had the truck for about 4 months, shipped it overseas. I noticed it back in Atlanta before shipping and that's why I changed those other gaskets. The weight I put is 20w50 I think I tried castrol in the states and over here I put some other brand, cant remember. But even with the Castrol had same issue.

The engine clearly is set up for 1/4 quarter mile racing. My mechanic back home showed me some like lifters on the valves when we changed the valve cover gaskets and also has a sports clutch. Thats all the info I can think of on the truck.

Thanks for your reply so quickly.

[Evan's 1965]

Only thing I could think of is the rear main seal or pan seal like you say, but it would likely be throwing some oil underneath the truck while driving if the rear main seal was bad I'd think & throwing oil onto the exhaust. Another thing that happens is the oil ports on the heads get clogged up with sludge & the oil doesn't return back into the crankcase, making the oil level on the dip stick read low. It could possibly be that along with a slow leak, a drop
or two doesn't seem like much.

[Rich 5150 69]

Assuming yoy have 3.73 gears or 4.11, you need to determine this, engine rpm`s with a standard three or 4 speed is going to be around 2800, I would run straight 30 weight valvoline, when spinng the motor to those levels at a constant rate the crank will airate the oil especially multi viscosity oils and pulled thru the PCV valve to be burned off. You can install a windage tray to alleviate some of this but this will mean dropping the pan and changing out main bearing bolts, other than this would be loose clearances on rings and or valve guides. You can run an extra long tube from the valve cover thru a plastic see thru fuel filter so that it hangs lower that the valve cover ( this is tempory ) just to see how much oil you are actually burning thru the PVC valve, then you can do a leakdown test on valves and rings.

[jolobo64]

Thanks Evans for your reply as well, Now Rich I'll try that test and see how much is going through the PCV, not a mechanic but I am assuming there should not be a lot of oil passing through correct? If so then there is a problem? I have the tools for the leak down test I'll see if I can do that test as well.

[AcampoDave]

I once had oil from the valley, (where the lifters are on a v8) getting sucked thru the motor due to a faulty intake manifold seal. I only noticed the smoke upon taking off from a long stoplight. If my pipes didn't exit out the sides I may not have even noticed it. I also had black oily residue in my tailpipe outlets. I decided to re-seal the intake and discovered the heads weren't sealed properly either. The gaskets were an oily mess. It's strange because a shop built the motor so I took it back. He resealed again with Felpro and the problem persisted, so back to the shop again, this time with Victor Reinz gaskets and a leakdown test. 2 years now no troubles.