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Oil Usage 496

4K views 44 replies 16 participants last post by  65Vette 
#1 ·
Hi all,

This is my first posting here and I have a question about my newly acquired Vette. I bought it about a year ago and the owner said it had a std 454 with a cam. I was changing the oil and saw a dent in the pan so removed it and learned the following.

496 cu. in. (From a previous owner)
Chevy bow tie alum. heads
Eagle H Beam Connecting Rods
SRP 73F 4032 Alum. Forged Pistons
Roller hydraulic lifters and roller rockers
Crane cam (?)
Holley double pumper 4779-9
Headers

I was told the engine was put together in 2002 at a cost of over $10k. It’s got good power, don’t know how much HP, but it pulls well.
My main question right now is oil usage. I have to add a quart about every 100 miles. I never see any smoke, the spark plugs are a nice tan color, no oil. Have a few leaks but not enough to account for that. I was using conventional 20w50 until a couple of weeks ago changed to full synthetic 15w50. Didn’t seem to make a difference. Is this normal?
 
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#7 ·
Trying to figure out how to respond to these messages. Yes, I have a PCV system and I assume it’s working. Haven’t done a compression test yet but will. Oil pressure is 30-40 except at idle, 12. Can’t hear a rattle, side pipes. What do you think?
 
#8 ·
Try disconnecting the PCV and see if it gets better, just vent both valve covers.

It might be the intake leaking, that one is hard to tell until you take the intake off and see the oil path on the gasket.

I put low tension rings in a BBC I built for myself, the very first BBC I ever built. It ran good and never really had any visible smoke but when cruising on the highway with high vacuum it would suck up a quart of oil every 100 miles or so.
 
#10 ·
I do a proper compression check first. I had a Pontiac 400 one time that I had bored out and apparently the guy doing it had his machine mess up during the work and had to Dismount it and take it to another shop to finish it. He didn't bother to tell me this I just assumed it was in spec when I measure the ring end gaps. However they were not bored round and some spots were as much as 10 to 12 thousands out of round. It ran super strong but had tons of blow by and low compression on two of the cylinders. I had to put a rag or a Sweat Band around a breather in the valve cover and if you pulled the dipstick out you would get a mist of oil coming out of it.
 
#11 ·
Time for a compression test.
That kind of consumption has me thinking rings. The engine could have been assembled "loose" for a potential boosted application then changed direction.

Are you running a cat? That can catch a good amount of smoke and then burn it off slowly and you will never see it.


x2 on the oil. Driven is some great stuff and if your flat then the amount of Zinc in there oil is worth the $10-15 a quart.

Start with a compression test. Maybe your lucky and it is just bad valve seals.

Oh and fix your leaks. Tappet cover, timing cover, oil pan, rear main, and maybe a few others. Good gaskets are expensive I get that. But when installed correctly you won't need to touch them for years. I buy felpro blue gaskets and my junk does not leak. It might smoke, might shake your windows, and might burn some unspent fuel. But it is clean. A clean engine runs better and it is easier to spot things before they become issues.

Clean your engine and blow out your hoses. A new pcv valve does nothing if the hose going to the intake is full of gunk.
 
#12 ·
I had a 350 SBC that used about that same amount of oil. I couldn't see it smoking out the exhaust either. Without the PCV hooked up the blowby was noticeable.

I tried and checked everything mentioned in this thread. It was the oil control rings. Ultimately concluded that the fuel pressure (which we found was way too high) to the dual quads caused constant washdown of the cylinders


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#14 ·
Disconnected the PCV, no change, still uses oil, but there was no blow by, breathers are clean and oil free. I also haven’t done the compression test yet. Right now it needs oil and I’m tired of paying for expensive synthetic oil. I thought it would make a difference on oil consumption if I used a synthetic, but no.
Do you guys think it would be okay to use a name brand high mileage diesel 15w40 oil?
 
#15 ·
The only vehicle I've ever seen use less oil with synthetic are the old original Saturn's because there was a design flaw with the oil rings getting gummed up and stuck in the pistons. I would be using conventional 10 W 30 10 W 40 or 20 W 50. I used to run almost everything on 20w 50.
 
#17 ·
What intake?
Can you take the carb off ans see down in the intake runners of the heads to see if there is any oil there? Might use one of the snaky cameras.
Its either sucking it through the bottom of the intake at the gasket, or its lost the oil rings. Oil rings dont affect cranking compression much at all.
 
#22 ·
Might be a situation where you need a double thickness intake gasket too, so maybe get the feeler gauge stack out and see what kind of space you have between intake and heads on all four corners with no gasket there, just the old end rail gaskets, if you are using them and not just a silicone bead on the end walls of the lifter valley
 
#25 ·
No way to check this except a tear down, as it won't show up on a compression or leak test....but the second ring installed upside down will use a large amount of oil and tend to reverse pump oil film into the intake ports during cam overlap.

I've seen that a couple times, doesn't show much oil on the plugs but the piston crown will be very dirty and wet, and the intake manifold will be oily darn near clear to the carb if the cam has a lot of overlap.

The second ring is called a compression ring, ...but it really isn't, it is actually the final oil prep ring for the cylinder and the top ring, scraping off the remainder of what the oil rail set leaves and leaving just a micro thin layer for the top ring to run on. If the top ring fails, the second won't hold compression for but a very brief time, as it isn't face shaped to do so.
Due to its either being reverse twist taper face, or Napier face style, if installed upside down they turn into an oil pump up the cylinder, rather than a scraper down the cylinder.

It gets confusing on left behind signs, because a leaker of an intake face gasket will give the same oil symptom in the manifold and oil consumption problems....but if you get the intake sealed up and still have a problem this might be something you;ll want to investigate.
 
#31 ·
That's a strong indicator that oil is getting down the guides. Then take system sees a lot of vacuum which will pull a lot of oil down the intake valve stems if the seals are worn and/or the the stem to guide clearance is too wide. The exhaust side sees a lot of heat and pressure which burns what oil gets down the guides but also the pressure tends to dry out the stem to guide interface which really accelerates wear on these parts.

Not that these are the only possibilities but are strong contenders. Another that has been mentioned is intake fit to the heads. Anytime the block has been decked, heads milled, or the engine has a combination of aftermarket heads,
block, intake, etc. the fit up can result in sealing problems with the intake to the heads. A common one being where the ports are leaking with the valley side, this pulls a lot of oil and is hard to detect unless the manifold vacuum is much lower than you would expect with the cam used.

Bogie
 
#28 ·
Check the fit/clearances with no intake gasket at all, to see if intake face and head face or parallel or angle to each other, and get an idea of the gap size...then make a gasket decision.

Was the inside of the intake manifold oily too, and not just the head port and back of the valve??
 
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