Oil burning, what next?

[Jeff Farrar]

Okay here is the story.

Engine is a 1979 454 "hi perf" bought as a short block and built by a race shop with over 12:1 compression. The heads that were used came from 1970. When the engine was built it had a huge 1100cfm carb. The block was decked. Since then, the intake a carb have been replaced with a alum intake and a 670cfm carb. The engine has spent a lot of time just sitting and I'm sure that the owner didn't do anything special before starting it up in between the years. The engine has less than 10k miles over a 22 year span. It runs real strong.

I acquired the car this summer and have been going though it taking care of various items. The only problem that I am trying to track down is that the car is burning oil. I don't have an exact amount but it is a lot. No puddles to be found and outside of block appears clean.

It only smokes blue out the one bank. It does not smoke during start up or sitting at idle. It smokes when taking the rpm up and getting off the gas (during decel) or leaving it in gear and going down a hill. I know that at that point it is pulling a huge vacuum and is pulling in oil in from somewhere.

What I have done. I replaced all the teflon positive valve stem seals on that side with viton seals. Two of the intake seals were split. I have also pulled the intake and replaced it with new gaskets. There wasn’t any oil sitting in the runners. Although one if the runners was darker than the others. The PCV valve that was being used had a pinched hose that was running to the base of the carb. I replaced it with a 90 degree style that allows for a straight run without the pinch. It is baffled under the valve cover and there was no oil in the hose or any in the intake runners. The PCV valve and open breather are both on the side that I am having the problem with. The other side just is basically closed with just a oil cap. When I pulled the valve cover to do the seals I didn't notice any oil passages being blocked everything seemed pretty clean although there was a puddle at the back of the head. The vacuum reading is pretty much steady at 15". It does fluctuate +/- less than one deg. Normal? I have put off doing a compression check because with those symptoms I thought it would be something in the top end. I ruled out bad rings because it doesn't smoke during acceleration or at idle. But after correcting those few items I think that will be my next step. Plug #6 did look pretty bad when I first pulled it. I have since replaced all the plugs and #6 and #4 do have a slight oil look to them. The dipstick was popping out, I "think" that went away with the new PCV valve.

Outside of the rings what else should I be looking for? I am just trying to do everything I can before I have to have the engine pulled.


THANKS!!!

 

[Rowdy1]

Thread Sealer?

Just a remote thought, but if the head bolts weren't sealed properly it "could" account for excess oil consumtion. I know first hand how this can drive you crazy, trust me. I had the same problem, symptoms with a small block and went crazy trying to figure it out. Got lucky, and found excess oil in the intake sides of the heads with a mirror. Pulled the bolts, used ARP sealant, no more problem

 

[wallyknoch]

Since you have already replaced the valve seals, the next step is to have a leak down test performed. This will check the rings for each cylinder with out a tear down.

 

[allcoupedup]

I've heard that excessively worn valve guides can cause oil consumption -- even with new valve seals. The engine vacuum basically sucks the oil through the valve guides with the additional stem/guide clearance caused by wear. This would show up as a nasty caked mess on the back of each intake valve.

Brian

 

[Jeff Farrar]

Got lucky, and found excess oil in the intake sides of the heads with a mirror. Pulled the bolts, used ARP sealant, no more problem

Rowdy1,
How did you determine this? I assume that you had the intake manifold off, looked down one of the intake runners and saw oil near the valve and not up the runner top closer to the intake??? Then you just pulled the head bolt near that cylinder and sealed it?

In the cylinder I think it is, the runner had a oily coating to it but not overly wet.

 

[Rowdy1]

Correct

Rowdy1,
How did you determine this? I assume that you had the intake manifold off, looked down one of the intake runners and saw oil near the valve and not up the runner top closer to the intake??? Then you just pulled the head bolt near that cylinder and sealed it?

In the cylinder I think it is, the runner had a oily coating to it but not overly wet.

The engine was freshly rebuilt, and with 100, 200, 500 miles, the consumption was the same or worse. We did a leak down test and it was negative, so we pulled the intake searching for a clue. After we discovered the oil, I pulled the heads, installed new gaskets and used the ARP sealant like I said, all is well. I didn't want to take any chances doing one or two bolts, so I went back to the block removed the heads, cleaned, new gaskets, reinstalled, etc. I actually had a residue of raw oil in the exhaust, and with new rings, pistons, heads, we thought the rings weren't seating or we may have turned or broken one during installation. It was a tremendous relief to finally find the problem and know it was something stupid and not a poor assembly, although looking back, all you have to do is forget "one" thing and you have problems. Fixing them is easier than finding them sometimes. I agree with wallyknoch, do the bleed down first, process of elimination will tell you where the problem is
Keep me posted on what you find & most of all, Good Luck!

 

[Jeff Farrar]

After taking another look at the pictures, I am thinking about trying to redoing the gasket. Maybe this time a I could use a little RTV around the port to make up for any mismatch. What do you guys think? Is this my leak or am I grasping.

 

[Hib Halverson]

The initial post here makes reference to this engine being rebuilt then sitting for a long time with out running. Also, the first post says the guides and seals are fresh.

I'd be looking for a cylinder wall problem, ie: rust. You could borescope the oil burning cylinders, if you had the equipment. If you see any rust or pits on the walls, you can bet the ring seal isn't going to be good and the engine will use oil.

A leakage test might also be good to do.

All that said, one things that's missing is how much oil this engine is using and what kind of pistons are in it. If the engine has forged pistons and is getting 800 miles per quart or better, that's nominal for a forged piston engine.

 

[Jeff Farrar]

(Update) Oil burning, what next?

Finally did a compression check this weekend. Bought a brand new gauge and everything. I let the engine warm up for a 15 minutes, pulled all the plugs (seven of them looked ok with #6 being oil fouled), disconnected the coil and block the throttle wide open. Here's what I got, most of the cylinders were between 255 & 275 (275,265,270,255,275,265,270) with #6 reading 230. I add a little oil to #6 and it came up to 240.

My questions.

I know it’s a BB, high compression heads(over 12:1), and the block was decked. But I thought that those readings were WAY high. Maybe they are in line for something like that?????

I'm guessing that with those results I need to have ring job done? Is it possibly to pull the head and oil pan and just do the rings on that one cylinder without pulling the engine (no clearence issues that I can see)? Not in position at this time $$$ to have the engine rebuilt on something that doesn't see a lot miles.

Can I add anything to it (Restore, straight 30W, etc) just so I can just run around with it. What are the risks?

Thanks ton folks.

 

[vettefinderjim]

Leak Down test is next

Since you have already replaced the valve seals, the next step is to have a leak down test performed. This will check the rings for each cylinder with out a tear down.

First off big blocks, especially 454's, were prone to 1 qt. in 500 or less miles when all is perfect.

Smoke on de-acceleration , going down hill usually shows 'crankcase' pressure and blowby.......which is bad rings, cylinder wear etc.

The leak down check will verify the cylinder condition. But remember 12:00 to 1 puts lots of pressure on things, and most high compression engineswere built loose......which lead to oil consumption.