I recently did a PCV conversion on my '54 235 and am now wondering if the 1/8 port on the intake manifold is producing enough vacuum to remove enough pressure and let the PCV to function properly. I swapped on an old, cheap chrome valve cover and breather cap that I had on a spare engine, when I did the conversion since(since the original cover was vented) . I did notice that the chrome cover was slightly warped when I put it on, but seemed to have sealed fine on the spare engine i took it off of(the engine came out of a driver and is very clean). I've been driving my car around for the past couple weeks since the conversion and the valve cover is leaking like crazy. Thinking it's just the warped up chrome cover, I welded up the vents in my stock cover(what I should have done in the first place). I just got through swapping the covers out and while doing so I was thinking about the vacuum port and started thinking it might actually be the problem. Before I fire her up and chance wasting another new gasket, I thought I'd see what you guys thought. Thanks in advance!
Most PVC's that I have seen on stock motors go to a 3/8" fitting at the bottom of the carb. 1/8 sounds way to small to move much of the fumes.
Do you have a vent for air to enter the engine? I used a PCV oil fill cap on my 250 but had to install a moon side breather in the back of the valve cover. Are you still running the stock intake? 1/8 sounds a little small. I ran my line over to a 3/8 plug in the side of my Offenhauser intake and it seems to be working great. I had a terrible time getting my valve cover to stop leaking. I thought the cover was warped or my head. Turned out I was throwing the wrong gasket at it. Instead of the more expensive rubber gasket, I got a cheapo cork gasket and it sealed right up. I've had it off numerous times now and keep using a cork gasket. No problems and dry as a bone.
I use a new thick cork gasket under my cast valve cover and it seems to work. But it was leaking for years at the back and I thought it was the rear main. Not just a bad vc gasket, oh well, fixed now. But I too just recently added a PCV and tapped the 1/8 pipe hole on the aluminum intake to 1/4 pipe. I did that because I also have the vac advance on that port and wanted to have a big enough port. And a heavier tee fitting. But the fitting for the PCV and vac adv are both 1/8 pipe. I used a GMC-6 cylinder style oil filler/breather in place of the Chevy draft tube to get fresh air into the crankcase and pull the PCV off the middle of the valve cover. So your question of is 1/8 pipe OK is yes. I have already run PCV valves with a .060 restrictor in them to limit the air flow at idle. Unless you have a tremendous amount of blow by you are trying to get rid of. Frank
Before I did the conversion, it had the stock cover with a cork gasket and didn't leak at all. I put a new cork gasket under the Chrome cover and it leaked like a sieve. That is what lead me to start questioning my PCV functioning correctly. I'm not certain it is just my warped cover and not excessive pressure buildup. I guess when it stops raining, I'll take her out and see how she does with the welded up stock cover back on.
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