Help-- discreet PCV for small block Chevy

But I have a baffled pcv in the rear of the intake manifold by the dizzy. that should take the place of the road draft tube and because of the vacume, it seems to me, it should even be better. I still get a small amount of crankcase pressure pushing out a small amount of oil. I would like to leave my oil wiping towel at home when I drive.

 

My pcv valve is in the alum. cylinder which is plumbed to the rear of the manifold into a baffled tube underneath. It is connected to the center carb base with a hose. Maybe the 5/16" line to the baffle is too small? Or maybe I am just trying to be too trick for my own good.

 

I was just trying to explain why you cant run just half a system, for those who think a single breather is all you need.


Obviously, you want to have some kind of positive draw on the engine. This can be done with either a draft tube, PCV setup, or even just a tube running to the air cleaner. However way you do it, you still need a place for air to re-enter the engine so you are not trying to pull a hard vacuum, which will cause all sorts of other issues.
Putting a PCV at the rear in place of the draft tube is fine. I'll be doing that on my '67 327 real soon also. Typical hose size is 3/8". If you were to add a hose from a valve cover or the fill tube over to the air cleaner, you should be able to cut down on the mess. Remember, the PCV valve is only working when there is enough vac signal for it, usually at an idle or steady crusing.

 

5/16" tube is too small, you need at least 3/8" to flow enough air, use the large port on the back of the carb to hook to ...

 

http://www.jalopyjournal.com/forum/showthread.php?t=227754

 

Fullblast, I was thinking the same thing about the 5/16 being too small. The reason I used it, beside having it handy at the time, Is the carb fitting is 1/4" NPT and the hole in the pcv is no bigger than 1/4" (maybe smaller), and I tapped the other fittings 1/4". I didn't think about the flow needing it to be bigger. I'll try the 3/8" tube from the oil fill tube to the air cleaner, also and seal up the oil fill hole. Thanks everyone for the input.

 

When using a hose to the air cleaner (non PCV), it is usually 5/8-3/4". If you are going to tie it into the fill tube, you could leave the breather cap on it if you wanted to.

 

What I'm going to attempt to do is use a 3/8" hard line from the bottom of the oil fill tube to the air cleaner. That will be difficult enough, as it is a tripower air cleaner, but there should be enough room for a 3/8 line. I would like none of this stuff be be on my engine (for looks), but I don't want the hassle of leaky oil either. I will leave the breather cap on for looks, but it will be sealed underneath. I have 5/16" lines on both the pcv and return to air cleaner on another car (347cu. in. Ford) with a sealed system with no problems. But, both are plumbed into the valve covers opposite each other. Somehow I keep thinking my problems are coming from plumbing both intake and return under the manifold. I stll have the Cal Custom covers with the Moon breathers if all else fails.