Manifold w/oil tube

[akart]

If I change to a manifold with an oil fill tube and breather can I loose the pcv valve, block off the pcv inlet at the carb and use no hole valve covers. I am in an emission free zone. THANKS

[ray_mcavoy]

PCV is not just an emissions system. It provides a means to actively draw harmful moisture and blow-by gasses out of the crankcase. A simple breather alone won't do that. And if the moisture and blow-by gasses are not removed you'll end up with rust and sludge inside your engine.

The older small blocks with the oil filler tube in the intake manifold also had a second vent hole in the back of the block near the distributor. It was connected to an oil separator baffle inside the lifter valley.


On the outside, that hole was originally connected to a road draft tube that would draw the blow-by gasses out of the crankcase when the vehicle was driving down the road. A vented oil filler cap allowed fresh air to enter the crankcase.

Then around 62/63 or so the road draft tube was eliminated and replaced by a PCV valve plumbed into that rear vent hole. Open PCV systems still used a vented oil cap for fresh air into the crankcase. While closed PCV systems used a sealed oil filler cap and drew fresh air from a tube connected to the engine's air cleaner assembly.

Around 68 or so that vent hole near the back of the block was eliminated along with the oil filler tube in the intake. That's when things were moved to holes in the valve covers.

So to use the older no-hole valve covers on a newer engine, adding the intake with an oil filler tube is only half of the equation. You still need some way to plumb in a PCV valve. The easiest way is probably to drill a hole in the back of the valve cover (facing the firewall) where it won't be all that visible. Install the PCV valve in that hole. Be sure to use some sort of baffle to keep oil from being drawn into the PCV valve. And use a vented oil filler cap to allow fresh air to enter the crankcase.

[akart]

Wow, what a wealth of information. Thank you very much. I will leave the pcv alone, valve cover breather too and add the front tube oil fill manifold. Just like to add oil up front instead of popping the breather.