Oil burning 393

I have about 2000 miles on my 393 now and it is losing about a quart of oil every 100 miles. I wasn't too alarmed at first but it doesn't seem to be improving. I have torqued down the intake manifold again. The heads were not new but were only supposed to have a few hours run time on them so I didn't bother getting them reworked. I do see smoke when I rev it up and then let off but thats the only time. I used Keith Black Hypers and chrome moly rings. The engine sounds somewhat like a diesel till it warms up but I think it is the roller rocker arms causing this. I rebuilt my 351W truck engine a few years ago and it consumed oil for a few thousand miles but nothing like this. Any ideas or do I just need to be more patient?
Thanks,
Kywookie

I have always heard that if you have the throttle plates in carb open (low manifold vacuum) and it smokes then the rings aren't sealing. If you have the throttle plates closed (high manifold vacuum) and it smokes then the valve guides are worn.

Sounds to me like your bore is too large for you rings to seat and or pistons. The rings aren't 'large enough' to have the correct tension against the cylinder walls to control oil and to scrape the oil off the cylinder walls.

What do the plugs look like? Are they oily and wet looking?
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Kiwooki,

This summer I put together my roller 302
and used the old 'shedder' type valve stem
seals that don't grip the valve guide bosses.
These were '90 E7TE heads. That sucker used
a quart of oil every 200 miles or so and smoked when you wound it up past about 3500.
At about 1500 miles I changed the seals to
the correct seals, the type that grip the
guide bosses, and it cleared up the problem.
I think you need really primo valve guides to
use those shedder seals without sucking oil.

Bruce

The heads are Windsor Sr. They have whatever seals that they come from the factory with. I wish now I had spent the money to have someone go thru the heads so at least I could have ruled that out if it's not the problem. Being Keith Black Hypers, I installed the top ring in each cylinder and filed the prerequisite amount. All the rings measured the same gap so I think the bore size is correct. The plugs look great, not oily at all. I do not relish the thought of tearing the engine down again.
Kywookie

<font size=-1>[ This Message was edited by: kywookie on 9/25/02 8:30pm ]</font>

Those pistons should be a tight fit. The roller rockers should not make any noise if you have a hydrolic cam. If it is a solid cam it would tick. I think you maybe have a piston clearance problem if it sounds like a diesel.

Does it sound like an old 6.9 Ford diesel? If so, I'd say that the bore clearance is too loose. That's what my truck sounds like in the morning when I start it, but then it goes away after it warms up a few seconds. Sounds exactly like an old 6.9 diesel for a while. I know for a fact that the bores are loose in my truck, as I set them up that way when I built the engine.

Mavman, I would assume that even with the loose bore that you have in your truck it doesn't burn the amount of oil I am talking about here. I ran roller rockers on an Olds 455 I built years ago and I experienced alot of noise with those too, although not specifically a diesel sound like this. I keep thinking (hoping) about it possibly being a leaking intake gasket, letting oil get sucked into a cylinder or two. The engine runs great, it just burns damn near as much oil as gas. I can detect smoke coming from the exhaust at idle and it will smoke more when revved, but I can't tell if it is worse under a low or high vac situation because it is tough to be in two places at once. I am going to give it a few more thousand miles but if there is no improvement I guess I will pull it back out and do an autopsy.
Kywookie

remove a breather from the valvecover. If you get a lot of pressure/vapor from it, I'd think that the rings arent sealing very well. That's the easiest way to check for excessive blowby.

My fresh 393 consumes oil,too.About a quart every 300 miles or so.I have SRP pistons with moly top rings.Cylinder walls were honed with very fine finish( they were almost polished)- do this kind of combo use oil?
I have double checked every normal thing like sucking oil from the breathers, retorqued the intake manifold etc. Heads are new AFRs.Can the fine cylinder wall finish be the reason?
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Kywookie....

My 408W uses about a quart in 1200 miles (calculated) and I understand that correct honing of the bores is essential to good ring seating??!! In addition, rich carb condition can also keep rings from seating.

Do you have a PCV system?? If so it may be the culprit. Rev high and decelerate and high vacuum can suck oil into the intake if baffling is not good in your valve covers.

Oil consumption is not a big deal in high performance engines if they run good, but smoke out the back REALLY SUX!!!

My $.02 worth!!

Good Luck,
Cobrajack
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