Compression test shows 165-170 all cylinders. New timing gears, very careful to line up dots correctly. New PCV # 2072 to air cleaner and PCV to carb base. New plugs, wires, cap, rotor, ignition module, EGR, vacuum advance. Seemed to be running good then blew intake manifold gasket and saw oil on valve covers from PCV's and breather and out of dipstick. Replaced intake gasket but can't cure oil blow by. Carb line to PCV sucks strong, no sign of blown head gasket, water temp good at 185. Started engine today with PCV's & breather out and oil fumes blowing out strong. Many Chevys over the years since 1970s but never this problem. Beautiful 4WD Silverado but useless to me like this. Any ideas?

 

It has two pcv valves? When did this issue start, or what's changed since this issue begain?

 

I think the one pcv valve to the base of the carb, the other should be atmosphere vent, that's the one to the air filter. Not that the pcv valve on the air cleaner side is at vaccum, it isn't, but it probably is closing off the vent.

 

Thanks again for the reply. Been working to replace the 350 with the good 305. I see that the 305 has 4 bolts at the torque convertor while the 350 has 3. Wondering if there will be a problem. I'm hoping I can swap the flywheels but haven't got the motors out yet where I can see for sure. The 350 is a 1986 model and the 305 was bought by me from AutoZone for a 1980 model. Any thoughts?

 

Cancel that..pulled both engines today and both convertors have 3 bolts...on to install