On a newly rebuilt engine i am lossing about a quart of oil every 400 miles. about a cup every 100.

I went with iron heads and the builder recommended a very small valve seal for the double springs. I can look up the spring part numbers if it will help.
I have driving about 7000 miles so the rings should have seated. they are moly rings so i shouldn't have had a problem.

I know for a fact that the intake gasket is not leaking.
any ideas?
this is driving me nuts

 

What do the plugs look like? How do you know the intake isn't leaking? You looked at the outside of the engine? What about internal leaks? Look at the plugs.

The next thing to do is a leak down test. After you look at the plugs.

 

externally the engine looks fine as far as oil loss is considered. No oil on the engine under it or around it.
the plugs do show some sign of ash on them. This is why i think it is being burned. I also found out that the faster i run the engine the more oil it uses. again leading me to think it is a oil burning issue.

the intake on the outside looks fine.

maybe a bad PCV valve?
any input?

 

and what is a leak down test?

 

I would suspect a leaking intake gasket first.

A leakdown test pressurizes the cylinder with a gaged amount of compressed air. The cylinder pressure has another gage to check it's percent of air leaking out of the cylinder.

If there is a head gasket problem that leads into the cylinder, that test above all others will usually find it. It will also tell you if you have a leaking valve or a cylinder/rings problem as well.

To test a bad PCV system, you use a manometer to measure crankcase vacuum at the dipstick tube. If the PCV where bad, you would usually get oil in the intake.