How bad is mild blowby that is in the form of mild intermittent smoke out of an open valve cover breather??? It doesn't puff out smoke all the time and is very mild when it does. I'm trying to gain an understanding if the blowby is costing me fuel mileage, power, etc. I have a pcv routed to the base of the carb, and an open breather on the opposite valve cover, and both covers have baffles.

Again, it doesn't appear to be much. Any product I could try to help elimate the blowby completely? Swith to synthetic oil help?.....Thanks

Only a leak down test will tell you how bad a problem you have if you even have one.

Thanks Bill. Can I do my own leakdown test? Is this similar to a compression test?

You'll need a leak down tester and an air compresser. It's fairly simple. Set engine to TDC (hot is best), set air to read 100 psi, any drop in the reading of the second guage is the % of leakage. i.e. 98 psi would be 2% leakage.

For real world readings, do all cylinders at TDC and BDC

Thanks. What would be the max percentage of leakdown that you'd allow before a rebuild

When you hit each cyl with air,in addition to the percentage, to find out WHERE the leakage is, listen at the tailpipe-ex valve, carb-intake valve, radiator-bad head gasket/cracked head/block, in your case- breather cap-rings/cyl walls.

For my race motors I shoot for less than 10%. I light up a cigar if their all 5% or less

You'll never see 0% across the board. At least I've never heard of it.

On a daily driver I would be ok W/ #'s in the 10 to 17% range. Anything greater and I'ld be looking for the cuase.

Smokey said in his book that anything over 5-6% was junk.

Mine smokes like coal plant, yet it doesn't show smoke from the tail pipes till i floor it, runs very nice, engine restore is said to work ok