New engine smoking
 

Background: I recently had the 351W engine in my car rebuilt after I sloshed the oil away from the oil pump during an autocross and tore up the old cam drive gear. The engine had less than 1,000 miles on it from a previous rebuild when it happened. The cylinders and flat top Keith Black pistons were undamaged and left as is. The crank was removed, polished, and reinstalled with new main and rod bearings. A new Comp cams hydraulic roller cam (series 35000) with matching tappets was installed. I also went with new Edelbrock Victor Jr. heads and kept the existing Edelbrock Performer intake and Holley 750 CFM carb. I replaced the distributor with a billet model from MSD. Crankcase ventilation is via one hose from a fitting in each valve cover to a vented oil catch can.

Situation: I have a little more than 100 easy miles on the engine since the breakin. I can tell from the lumpy idle that this cam is quite a bit more radical than the one I had before. Now, when the engine reaches operating temperature, a small but steady trail of smoke come from the vent on the catch can while the engine is idling. I suspect it is also venting smoke while cruising, but I'm unable to confirm.

Question: Is it normal for an engine with these kinds of components to vent in the way I described? If not, what should I check as possible causes of the venting? Any other suggestions?

Thanks.

Tommy;

I do not have any answers for you, but I prefer one hose from one valve cover to the carb or intake and a breather on the other valve cover for crankcase ventilation.. Did you use the same vent set-up before and did you have this problem??????? Did you have your cylinders honed and new rings also????? One possibilty is a glazed over cylinder or the rings just have not seated yet....

David

David -
A previous owner built the car expressly for SCCA racing and he set up the crankcase vent system I described. I never noticed smoke from the vent system with the earlier tamer version of the engine. .. I don't believe my mechanic did anything to the cylinders, pistons or rings during the most recent rebuild.

yes.. you can recover the blow by via pcv (and should anyway)but this is normal.

OK, so here is my setup with similar smoke. 302 with Cobra finned valve covers. I have a tall filler tube and a key shaped hole. WOuld I put the breather on the tube, and put a grommet with a PCV vavle in the other tube?

If you can see smoke / vapor coming out the breaters than your rings aren't seated very well. But this is one of those qualitative things, a little is normal, more is indicative of poor ring seal. So it just depends on how much is coming out.

Dumb question: Are you running synthetic oil? The guy who built my last engine warned me not to run synthetic until after 500 miles, otherwise the rings will have a hard time breaking in. Just a thought.:confused:

Remember, if you are pulling oil vapor down your carb, you are lowering the octane value of your gasoline.

Tommy;

Now I do not know what to tell you to look at!!!!!!!!!! If the set-up on "other" engine was working fine,seems it should on this one... Perhaps a little leak or crease in the intake gaskets could let some smoke/blowby thru,I would seem to think it is poor ring sealing as Mr. Fixit has suggested.... If the smoke bothers you,you may want to go to the PVC set-up and burn it in the engine where it will not be noticed.....


OhBuoy;

I would leave one breather tube with a good breather on it and the other valve cover,I would put a non-breather cap on the tube and drill the correct size hole in the other end of the valve cover for the PVC grommet and then run it to the carb base plate or intake,whichever has the connections for the PVC....


David

JT - I'm running Castrol 10W30 non-synthetic oil.
David - I'm going to let things go for another few hundred miles and see if things improve as the rings have more time to seat. If a little smoke all I have to tolerate, I think it will be ok for a car that is mostly used for racing.

Thanks to all for your help.