I have a 340 stroker (418 cid) in my 68 dart gt. It now has about 7000 miles. It has been using about 1 qt of oil every approximately 500 miles since I got it a little over a year ago. The builder had it over the winter and changed some things but the oil usage continues. It has a 600cfm Edlebrock carb. with electronic choke, Edlebrock intake and aluminum Edlebrock heads with headers. The fuel pump is a Holley 110gph (brand new). There is no dripping or visible leaking of oil. The exhaust tips are black and sooty and there is always a light coating of soot on the back of the car. There is no visible smoke on start nor while cruising. The engine runs well and has good power and acceleration. The compression and leak test were very good. The spark plugs are not fowling and are burning light tan. There is an occasional oil splatter on the passenger inner fender adjacent to the alternator but no obvious source of the oil. That was the reason for changing the fuel pump, but did not solve. Not sure this related.

There is a pcv valve connected to the front of the carb and a breather attached to the air cleaner. I had blocked off the pcv valve and disconnected the breather from the air cleaner, but the usage continued. There is no oil in the coolant system nor coolant in the oil. The vacuum advance for the distributor has been disconnected. The engine had trouble cooling until I installed aluminum radiator this spring.

Just giving you everything I can think of to help explain situation. Anybody have any ideas? I am leaning toward a problem with one of the heads where oil is being blown directly into an exhaust port and being carbonized in the headers. It may leak a little into a cylinder when off but not enough to create visible smoke when started. Could be fault or crack in head or valve guide. I do not know. Running out of ideas. Thanks,

 

Who built the motor(reputable)? You didn't say what kind or weight oil you are running either.

I would investigate this further.

 

I had my 1971 Demon 340 stroked to a 419 and I used 20w-50 oil in it.

 

I have a resolution to my oil consumption problem. There were at least four bad exhaust valve stem seals in the new Edlebrock heads. The oil leaked directly into the cylinders during the exhaust stroke and was mostly carbonized in the headers creating the fine soot. There was also some unburned oil that coated the rear bumper with an oily residue. New heads and new seals took care of the problem. Ditched the Edlebrocks. Well, they were supposedly stolen from the builders shop. Anyway, much happier with the new ones. Thanks for looking.