Quote:
Originally Posted by Kilohertz
Well thank you DD and Heard for your excellent work here, super good info.
I have a scenario which I imagine could be quite common. I have found an Offenhauser 1079 4bbl intake which is for the early 32-48 Flatty, mine is a 1951 Flatty. As you see in the picture the 2 ports at the front are not drilled out, but are easily cut out to fit the road draft tube and oil fill/breather tube. My plan is to install the oil fill/breather and then drill/tap the road draft area to fit the PCV valve....and the million dollar question ($600,000 CDN) is...do you know a good PCV valve, similar to what you have chosen, that has a threaded base on it rather than utilizing a rubber grommet?
Appreciate any guidance you may offer.
Cheers
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Kilohertz .....Your positive critique is MUCHO appreciated. One thing to remember about PCV valves is that they are affected by engine displacement, and by expected vacuum levels. IF the camshaft you are planning on running is of any performance types, your vacuum levels will likely be diminished from a stock cam's vacuum levels. This is one reason to TRY to find a valve somewhat CLOSE to a match for your particular engine's characteristics. In our case, I believe Heard's engine is at 284 cu. in. displacement. I like the GM PCV valves because of the all metal, well-proven design. In our case, the only GM engines that I could think of even close in displacement, and with a performance cam was the '67-'69 Z-28s at 302 cu. in., and yup....they did have a rumpety-rump cam, for sure! That particular PCV valve is a Delco 19303069. IF running a stock cam, I'd source a PCV valve for a 283 Chevy engine, say 1965-ish.
Just about all of the PCV valves I've looked at which have a male threaded end are built such that the direction of flow through the valve is opposite of what you are trying to do, assuming that you want to drill and thread that blanked-off draft tube location. Those threaded ends usually thread into a vacuum port on a carburetor.
I might suggest carefully drilling a hole in that boss sized precisely for a rubber insert/grommet designed to receive a specific PCV valve. You'll want one similar to the one (in configuration) that we used in our project. The LARGE diameter end would fit down into the manifold, with the other end plumbed to a "MANIFOLD" vacuum source.
REMEMBER...To run a set-up like this, the vertical tube must be in place at the front end of the valve chamber, underneath the manifold.
The Dorman web site shows a VERY extensive line of different PCV rubber grommets which your local parts store can order, if not in stock. These examples below can be seen at many sources on line. I know it's not what you wanted to hear, but you can still make the installation look tidy with just a little thought and planning. Hope this helps! DD
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