The Stovebolt Site Forums The Shop Area Engine Shop 383 Small block oil issues

I have a small block 383 that i just built and i'm having issues with it using oil. There is no sign of it anywhere. No leaks, no crud on back of car, plugs look great, yet its using oil. Anybody have any ideas or experiances with this issue?

How much oil are you using? How many miles since rebuild? There are a few things to check. Does is smoke on start up or deceleration? That would be valve guide seals. Does it have a extra bit of blow-by? That would be unseated rings. Disconnect the pcv and remove the oil cap to see if you have excessive blow-by. What heads and manifold are you running? Could be a leaky intake manifold gasket but that would usually show up on one or two plugs. When you say the plugs look great I would bet on valve guide seals but it really depends on just how much oil you are using.

SimS

I'll side with sims assesment of the vlve guide seals.I learned the lesson 55 years ago of the value of proper valve guide sealing of the engines which liberally oil the valve stem area of which the "oil through the pushrod engines" are a major player.The need is compounded when this heavy oiling is increased by higher than normal oil pressure which many performance engine builders go for as a bit of added insurance for their bearings.
Many times the plugs may look normal short term but run the engine 5000 miles in daily driving conditions and the telltale ash/carbon will be there bigtime.
What I don't understand is why engines without the good seals will many times have very good oil control.Probably has to do with natural sealing ability of the deposits on the stems--and that leads to a thought of the enthusiasts myth that prompts the fear,"I shouldn't do a valve job on my old engine because it may start using oil".I assure you if the cylinders/rings are doing a proper job of oil control as they are, the correction of valve sealing is not going to hurt--but disturbing the valve stem sealing can.(just my 2 cents worth-other opinions are encouraged but may be ignored).
The factory didn't machine the guides for Perfect Circle type seals untill mid 60's and I'm not sure when they started installing the seals from the factory.
Some of the worst engines for this problem for me was the 170/200 CI sixes from the blue oval.I've cured several in mustangs and falcons--they would usually have acceptable oil economy and no smoke but would build a "clinker" in those plugs and short them out.Probably was related to the oil additives used in those days(not to mention the blue oval creator).

Thanks for the quick replys. Its been 1200 miles since the rebuild. Its using about a quart in 200 miles and it doesn't smoke anytime. I would love to say that its the valve guides but these are freshly rebuilt by the same shop that did my Big Block heads. If it was valve guides wouldn't it smoke horribly? How would I get the rings to seat if they haven't already? It seems after 1200 miles they would be but, eh, maybe not! As for the plugs, they are all golden brown. I used this head/intake combo when it was a 350 and no problems. Here is what I've been thinkin, maybe crankcase pressure. Is that a possiblity? Its leaking in small weird places. For instance, the first leak was a the seal around the harmonic balancer. I replaced it and thats fine. Then is started to leak around the bolts on the fuel pump. I got that sealed up. Then it started to leak out the breather in the valve cover and PCV. I replaced the PCV and haven't driven it since. Kinda frustrated at this point! Its been sitting for two days and there isn't any oil under the old girl. Where is it going? I feel like the engine has a personal vendeta against me. I hope all this extra info will help you guys, help me. I'm baffled and have never had this problem before. I've built plenty of motors and this one takes the cake. FYI I'm gonna do a compression test on the cylinders today. Wish me luck.

Just one other thought how do you drive it ?Just stop and go ,full pedal to the floor ? Also what was the engine built for street ,strip ? Compression check I would do after another test drive since you changed the PVC.Good luck .

ok compression check came back 160psi all eight.

Sounds like too much blow by for sure. Pushing out oil from the fuel pump bolts is a sure sign of excessive crankcase pressure. The compression sounds real good but it's leaking by the rings. What kind of rings? Are they installed right side up, etc.? Do you have a tube from a valve cover to the air cleaner? Maybe the PCV can't keep up. When it's running, pull the oil filler cap and see if you are getting a lot of smoke/vapor pouring out. Is the oil consumption getting worse or tapering off? 1200 miles should have seated the rings. I'm stumped. I would be looking hard at the rings or the crankcase ventilation system. Good Luck.

SimS

Have someone follow you and get on it. Often, you won't see smoke from the drivers position.

Just an internet guess, but maybe not guides, rather seals. I've seen them make one eat a quart in 200 before. I almost have to take a spring off to get a good look at them, but at least you can change them without removing the heads.

I'd say valve guide seals too but that is a lot of pressure. My '75 uses about that much and it smokes only on start up after setting for awhile when the seals contract. No smells of oil from the exhaust after the smoke goes away and nothing wrong with the plugs either.

I got everything all sealed up and new plugs. Tried 2 PCV but it was too much. We're gonna run it for a bit and see what happens. BTW it has the chrome moly rings. Should have went cast but didn't for some reason. I heard that the chrome moly ones take a while to seat too. Thanks for all of the input and help. I'll keep you all informed.

You did good on the ring selection for long service and less wear on the cylinders.
The cast iron may have run in quicker but the oem went away from cast iron top and oil rings on cast iron cylinders in the early 50's.The ring manufacturers claimed 3 times the cylinder life for the chrome plated.Your Moly sets normally use a top ring with a moly filled groove which reduces wear in high heat and marginal lubrication that the top ring sees.The oil rings will have the wearing surfaces chromed.The 2nd ring is usually cast iron and plays a large part in oil control.But the package is engineered to give long life with minimal special run in required required.
Cylinder finish and cross hatch form can affect the run in needs and since the comp sealing rings are gas operated(expanded harder to the cylinder wall surface by combustion pressure
) in modern ring sets they need to be worked sufficiently hard to start this close mating of ring sealing surface to cylinder sealing surface.
So: avoud short trips, make it run near 200 deg temp, no oil additives during run in, basic oils only and as light as you can be comfortable with, make it work as hard as possible(combustion temps and pressures are up with larger throttle openings/heavier loads).
War story: we rebuilt a 6v53 Detroit used in the upper on a P&H crane to lessen the oil leaks and consumption using all GM cylinder kits so the finish and material was proper.When put back in service the leaks were cured but the oil consumption was much higher than before the rebuild.We put up with this for approx 6 months and saw no improvement so pulled the engine out and sent it to the manufacturers shop where it got I think 2 hours on the dyno at increasing loads.After reinstalling the engine now had an oil appetite like a good engine.The upper engine in a crane sees long periods of idling and is usually running a bunch of pumps which are not heavily taxing on engine output most of the time.
Run it hot and hard and ask your head builder what guide seals he installed.Some don't install wiper type seals on the premise that the guides are not properly lubed but the factory has used them for quite a while now and these modern OHC engines would not be acceptable without good oil control at the stem/guide.

We got another 100 miles on it and it seems that we got it. Knock on wood! Thanks for all the input.

If you don't mind, i would like to piggy back on this, since it seems to have been finished. I have basically the same problem. I have 1960 283, 230 h.p., stock,9.5:1,500 cfm. It was a motor that had not been opened up, and I had a shop rebuild it and give it back complete. Run the car 4500 miles, and kept having the top half of the plugs dark ( black in color but not built up). Wound up pulling a head, and 3 chambers were caked full of crud. The cylinders had vertical lines about 3/8 apart wher the rings rode, but not in between. Crank was scored, cam gone, etc. Did a another rebuild with different shop. Running .0025 piston clearence, everything else new. Hone job looked good. I had them put the pistons in (Cast Iron Rings), and I did the rest. I now have about 2500 miles on it, and I am getting I assume blowby from the rings since rebuild. Heads have new guides and seats, and rebuilt twice. Does not smoke at start up, but will if I lug it backing up or starting out. I have a road draft tube, but it will push oil out the Oil Filler neck which has a breather in it. I tried a pcv instead of the road draft, but did not help. I started it using detergent oil with some GM rebuild juice because of the cam. I'm about at my whits end, and I really don't care to pull that thing out again. This is not a race motor, but I drive it, not baby it. It usually doesn't run above 3500. Any help or suggestions would be greatly appreciated.

We built a 383 SBC for a friend and it used 7 quarts of oil in 400 miles. I looked at it and the custom valve covers he was using had the PCV directly over a rocker arm. The oil was squirting straight into the PCV valve. I machined a new PCV hole and the problem was fixed.

Take a look at the hose going from the PCV to the intake manifold.

Ron

I hope you're not using sythetic oil.

Why not do a leak down test on it and stop guessing?

This is a stock motor, stock valve covers, road draft tube and pcv come out a hole in the block behind the distributor. No synthetic, 10w30.

As far as the leak down test, I know what your talking about, but I don't. Could you please give me a nickle run down? Thank you.

A cylinder leakdown test is done by putting air into a cylinder through a spark plug hole with a quick-connect air line fitting brazed into a spark plug shell. Get each cylinder to top dead center on the compression stroke, and lock the crankshaft by putting the transmission into high gear and setting the parking brake, or using vise grips on the flex plate of an automatic transmission car. Listen for air leaks at the intake and exhaust, indicating leaky valves, or at the crankcase filler, indicating ring leakage. Bubbles in the radiator show head gasket leaks and/or cylinder head cracks. If you've got an adjustable air pressure regulator, adjust it to 100 PSI with the air line blocked off, and the pressure with air going into the cylinder will show you the percentage of leakage- - - -85 PSI=15% leakdown rate, etc. A good cylinder will have less than 10% leakdown, and a really good one will be under 5% leakage.
Jerry

Thank you, I'll check it out. I suppose the million dollar question is, if I do find leakage past the rings, is there any way to cure this short of another rebuild? It seems to have gradually gotten better, but I would have thought after 2500 miles the rings would have done their thing.