This engine is in a street rod. Here is my frustration. The engine uses a quart of oil every 400-500 miles....the compression is good....it has no oil leaks....it doesn't smoke... it runs very well...... The baffle in the valve cover has enough clearance.....Someone suggested using synthetic oil which I did around 1000 miles ago but it still uses the same amount of oil. Does anyone have any wisdom they can offer?
Thanks
Doug

Excess oil consumption comes from it getting around the rings or down the guides.

While holding good compression is a good sign, oil consumption around the rings is also dependent upon the oil ring set and the second compression ring doing their job. Problems in this area will not show on a compression test and most like not on a leakdown test either. That said, a leakdown test is most valuable as it does give a pretty good indication of compression ring seal to the wall and piston. The rings not only do their work against the cylinder wall but also must perform properly within the ring groove.

The valve guides, especially the intake are sensitive to clearance and quality of the guide seal. Worn guides and or valve stems allow space for oil to be drawn into the intake. Hardened seals especially those of O ring and umbrella will allow oil to flood the stem and upper guide, the vacuum inside the port will do the rest. Unfortunately there isn't a good test short of disassembly and measurement.

Bogie

 

if you pull the plugs , any difference in any ?
pull the header and look to see if one is black sooty looking .
you say no smoke , even on start up ?
no leaks , nothing wet back to rear ?
you may have seals damaged from not enough clearance .

 

How many miles are on the engine?
At what milage did you start using synthetic?
Did the engine reach very extreme heat levels during break in?
What type of rings are in the engine (cast iron, moly, plasma-moly,etc...?)
Who honed the engine and to what RA?

After you do the leak down and if it comes back poor, then mix some comet with gas, pour it down the carb and keep doing it until the rings seat. Or some Bonami, if you can still find it. Not a great solution but a easier one than tearing it back apart.

 

are you runnign 6" rods? If so you can expect taht kind of oil consumption as the result of the pin going through the oil groove on the pistons. One of the primary reasons to avoid a 6" rod.

 

383 stroker using oil

thanks to everyone. now i am more confused than ever.....ha..ha...... the engine doesn't smoke at start up....doesn't smoke when i put my foot in it. I guess I will keep scratching my head......synthetic oil is cheap.

 

If you are using an aluminum intake, what gasket are you using? This is a common leak point if you are using gaskets meant for an all iron combination (such as Felpro Permatorque Blue that have a steel shim core) I have seen this too many times to count. It's a slow, steady loss that never shows any smoke because it is a tiny constant leak whenever it's running ( but will sometimes show on a longish decelleration in gear from a high rpm).

 

383 stroker using oil

the engine is as clean as a whistle.
doug

 

You won't see what I am talking about until you pull the intake off, it is leaking from the lifter valley into the bottom of the intake ports in my description, so the motor is sucking oil. That is why I wondered which gaskets were used, type IS that important.

 

you have to test the pcv baffle to know your not picking up oil...
every time you let off the gas there is instant 25Hg+ and max oil pressure at the baffle to siphon oil...

drill 2 holes seperated in a plastic peanut butter jar lid (any brand is fine) so you can mount two 3/8" fittings in the lid...

so you can connect the jar and lid in series using hose with the pcv valve and carb connects....
(just for the idea a pic' attached)

many after market valve covers have the pcv directly aligned with a push rod (DUMB!) so more better baffles are needed

simple project that may well give the answer...

edit:
petg plastic peanut butter jar can take "some" heat but a glass jar is maybe better

 

I'd give Red65's idea a go first, but I'm still wondering what intake gasket you are using?

 

CRS=forgot to say

make the fitting from the pcv valve extend further by a inch (piece of hose whatever) into the jar so that any oil picked up will be directed toward the bottem of the jar,,,,only air continues out the other fitting on to the carb....

there can be a super small intake leak due to alignments or gaskets....
do correctly re-torque all the intake bolts,,,hot and cold cycles do make parts move....