Recently ive noticed that my 403 is using oil pretty bad. I bought the car a year ago and put around 2000 miles on it with almost no oil consumption. The engine is a fairly recent rebuild with approx 20-25k. Starting a couple weeks ago ive noticed the oil level dropping and ive have had to keep filling it with oil (1 quart in 400 miles). It doesnt leak or smoke at all, so I have no idea where all the oil is going to. Any help would be appreciated.

 

It could be a bad seal on the intake, this will cause it to suck oil up from inside of the engine.

 

Check your spark plugs - 1 or 2 wet, side by side, will tell you where to start.

 

Is it sucking oil through your PCV, or vent to your aircleaner?

 

No its not. I did notice that the pcv valve wasnt securely seated in the valve cover and was just sitting there loose, but im pretty sure that wouldnt be causeing my problem. Il check the spark plugs tomorrow and see what they look like.

 

I pulled out the spark plugs today, and they all looked pretty normal for having a couple thousand miles on them. I also replaced the PCV valve but im pretty sure that wasnt my problem.

 

Ok, the problem is back again. For awhile it seemed to go away buts it back to using a quart of oil every 400-500 miles with no trace of where the oil is disappearing to. There arent any leaks whatsoever and no smoke. Im totally confused and have asked many people but no one seems to have an answer. Hopefully someone here can help me out. Not sure if it makes a difference or not but i started noticing the problem when i was told to use a higher zinc oil, so i changed to vr1 synthetic.

 

Is the engine leaking at all? Is there a film on your rear bumper, back window, or...? What weight did you go to? I wonder if your issue would go away if you returned to dino oil?

 

Theres no leaking at all. Ive been under the car and looked and felt around everywhere and no sign of oil. I did forget to memtion that when the engine was rebuilt, a high pressure oil pump was installed (60 psi). Some people ive talked to said this may cause higher oil consumption, but if it is burning that much oil that quickly wouldnt i be seeing smoke?

 

Remove the carb & look for oil puddles in the intake.

 

If possible take one of the exhuast manifolds off to see if you find any oil in the manifold or exhaust ports. If the exhaust valve seals are leaking it'll blow out the back but won't necessarily burn.

Let us know what you find.

 

i agree , the valve seats may be leaking.

 

I've read that people sometimes have issues with the newer synthetic oils in older engines - more viscosity --> more oil consumption, which went away when changing back to standard oil. No idea what the actual issue was, since they were satisfied with just not using synthetics.

Not super helpful, I know, just food for thought...

 

This is very true, as sometimes you will see residue around where the exhaust tailpipe exits the undercarriage and on the rear window.

 

I did check the inside of the exhaust pipes as far in as i could reach and found no oil residue. Is it still necessary to remove the exhaust manifolds to check for oil residue?

 

You don't need to remove the manifolds.

 

I just noticed that my pvc that i recently replaced is pretty oily so that mite be where some of the oil is going. Never noticed that problem back when i was using regular oil, so il probably switch back to that and see if it fixes the problem.

 

I would remove the PCV, top off the crankcase and drive it a while and see if that's your problem.

 

Quick question,I pulled the pcv with the engine running and i can see vapor coming from where the pcv sits in the valeve cover. Is this normal or do i have excessive blowby?

 

Normal.

 

OK, my father had this problem in his pickup several years ago. He ended up with a completely rebuilt engine. I recall reading about a similar issue in a corvette and it was do to the carb dumping excess gas into the cylinders, washing them of oil and causing excess oil consumption.

Just my 2 cents.