Fresh Rebuild Losing Oil

[Step'67]

So my dad and I recently did a mild rebuild on a 350 for my 67. Stock bottom end, new cam, lifters, Vortec heads, intake, etc. I was doing it on a slight budget and just went with Summit brand piston rings, possibly the problem. Anyways, dad has done tons of motors over the years, in his own Chevelles, Camaros, a 71 Blazer, he has been around the block and is no stranger to car restores and engine mechanics. However, he has never had an engine use oil, and no where near the magnitude as this one does. It seems to be losing a quart every 2 weeks, possibly sooner, although it does seem to vary a decent amount. It seems to have traces of oil coming out of the timing cover seal, but in very pitiful amounts, no where near enough for that to be the main issue. It is also leaking between the engine and transmission, but on further inspection, the rear of the engine, behind the flywheel is perfectly dry, i think its only the nasty 4 speed transmission (new overdrive from Bowties is on the way here soon). I also installed an oil separator inline with the pcv valve, and again, a very small amount is collected in the separator. Upon start up, a slight amount of smoke can be seen from the exhaust, so we were thinking possibly the valve stem seals, and I've got new ones of a different material I have yet to install. The thing is, with it using that much oil, there is no burning smoke visible in the exhaust at any rpm, after starting of course. However, the oil consumption seems to speed up when at higher rpm (freeway vs town driving). Another thing to add is when ordering parts I accidentally ordered a Melling high volume oil pump, which places the oil pressure off the gauge when cold, and at the very highest point when driving while warm. Sorry, just trying to generalize here, but any ideas on where this oil could be going? We had the cylinders honed and all machine work done at a reputable machine shop, and used high-quality break in oil. Could it be that the Summit cast rings just never seated? It's been at least 800 miles since the rebuild, so I figure they would have already. Any comments would be helpful, thanks guys.

[Fldawg]

cast rings will seat up faster than moly rings , did you check the ring gap , i.e. slide rings in where they normally ride and check the gap, sometimes the machine shop will need a set if they bore engine out or the paper work that tells you what the gaps should be for certain applications like running nitrous , or a turbo or super charger , i'm not a big fan of honing out cylinders and putting new rings in because most of the time you set yourself up for trouble. As far as 800 miles they should be seated in. as far as the cranking up and buffing that sounds like a stem seal, as far as the vortex heads go check the oil drain back holes, sometimes they get clogged with sludge and do not allow oil to go back to bottom of pan and will cause oil to blow out tailpipe, maybe this will help you maybe it won't , but these are things that i have run across over my years of being a mechanic

[Step'67]

Thanks, we did check the gaps, and the cylinders were honed to spec.

Also, another note to add, when driving to school I would let it warm up for a few minutes before driving in the morning. The concrete would be wet from water from the exhaust when I would leave, and later when I would come home, after the water evaporated, there would be black sootish stuff that stained the concrete. Could this have anything to do with it? I just figured it was just running rich due to the choke being on and the excess fuel was depositing on the ground.

[Fldawg]

that's the lovely fuel we are running full of water that's called ethanol, that's nothing to worry about. hope you figure it out, it's hard to do over the computer, you might also had the ring gooves line up i've seen it happen or a broken ring beause cast rings have been known to do that. Good luck

[GASoline71]

Originally Posted by Fldawg

that's the lovely fuel we are running full of water that's called ethanol, that's nothing to worry about. hope you figure it out, it's hard to do over the computer, you might also had the ring gooves line up i've seen it happen or a broken ring beause cast rings have been known to do that. Good luck

What he is describing is normal water vapor that builds in an exhaust system when going from cold iron to warm/hot after start up.. The black stuff is just soot from inside the system. If anything he might be runnin' a little rich. I don't think it has anything to do with the ethanol in the fuel. Ethanol CAN attract water... and it will be in the fuel tank, and make the truck run poorly. But that's only from sitting for extended periods of inactivity.

Gary

[Step'67]

Sorry guys for not getting back sooner.

Originally Posted by 71STPSDE

Have you done a compression check and see if all the cylinders are equal?

I have not yet done a compression check, although I agree I need to.

Originally Posted by Marv D

And the obvious, did you use a regular dino-juice oil for the first 500 miles or so? Synthetic will actually be so slick that the rings will take a long time to seat,, especially plain cast rings. If you had used a good plasma-moly ring then the inlay is soft enough it's not as big of an issue.

I used, and am still using, Amsoil's High-Zinc Engine Break-in Oil. So yes, it is a synthetic. http://www.amsoil.com/storefront/brk.aspx Dad is an Amsoil dealer, so naturally that is what we used. After reading so many good reviews about it, I figured why not. You bring a good point.

Originally Posted by Marv D

I'd suggest you see where you stand after the new valve stem seals. If there loose enough to allow oil til weep down and puddle when the engine is off, imagine what happens when the vacuum of a running motor does!

I agree that I need to change the seals first, then report back.



For those of you asking if the covers have baffles, yes they do, and the pcv is pulling from a baffled port. Keep in mind I did put a separator inline with the hose so I do know that the oil is not being pulled through there. There is maybe a drop of oil in the separator after 2 weeks of driving. Anyone think that the high volume oil pump is a bad thing and that I should pull it and replace with a standard pump?

Thanks guys again for your input. There are a few more things I need to check into, and any other suggestions would be awesome. Unfortunately, it is my daily driver, so the time I can work on it is limited to weekends mainly. I'm almost tempted to just do a quick rebuild of the cylinder walls and rings while I'm installing the Bowtie trans. We'll see though.

[Lee H]

I would start with monitoring how much oil you are really using and over how many miles. What kind of valve covers do you have, real GM covers with baffles or after market without baffles or cheapo baffles? If your collecting oil in the PCV hose you either don't have baffles, have very cheap baffles, or blow by. Did you bore then hone or just hone old bores? To what spec? With your engine up to operating temp pop off the oil fill cap or the PCV and see if you have vapors coming out. Work on getting the external leaks fixed and see if that makes any difference in your consumption rate.

[71STPSDE]

Have you done a compression check and see if all the cylinders are equal?

[cdowns]

do you have a PCV system with baffeled valve covers?

[MARKDTN]

Originally Posted by cdowns

do you have a PCV system with baffeled valve covers?

My question too. If you don't have baffled valve covers, you can have issues with oil consumption. I would also change the PCV valve itself as it may be leaking.

[Marv D]

And the obvious, did you use a regular dino-juice oil for the first 500 miles or so? Synthetic will actually be so slick that the rings will take a long time to seat,, especially plain cast rings. If you had used a good plasma-moly ring then the inlay is soft enough it's not as big of an issue.

I'd suggest you see where you stand after the new valve stem seals. If there loose enough to allow oil til weep down and puddle when the engine is off, imagine what happens when the vacuum of a running motor does! Obviously anything wicking down the guide of the exhaust valves makes more smoke at startup and then pressure of exhaust helps hold that at bay while running. So oil consumption through the guides is typically more on the intake side. Look closely there when your changing seals.

[storm9c1]

I'm running a HV oil pump in my 383 -- I ran 10W30 dino oil (plus proper break-in additive) for the break-in period. The stock oil gauge is pegged until the truck warms up (needs to get nice and hot), then it falls down to a little over half at idle. I expect this to be normal. Lots of guys run HV oil pumps. I couldn't see how this could be a problem. But perhaps it could agitate another problem?

[j1970GMC]

Sounds like you checked the timing cover leak, but I had a timing cover leak that was very small at idle but when driving got much worse. Probably not your problem, but it happened to me when my mechanic used the wrong gasket....