Hey guys. Hope someone can put me on the straight and narrow path to enlightenment. I have replaced the old 600 holley on the 327 with a new one and wanted to upgrade the existing non-existent vacuum setup on the engine. Originally it had the road draft tube hanging there (which I hear is quite normal) connected to nothing, (It did have an old pcv valve in it at the crankcase end) One side of the rocker covers had a piece of hose stuck in the oil filler hole without any pcv valve. It was just hanging there, and the other side of the rocker had a simple oil cap. Now, what I have done is replace the pcv valve in the road draft tube, connect the road draft tube to a t piece, then add another pcv valve to the passenger side of the rocker cover and connect hose to t piece and final end of t piece to the front vacuum port of the Holley Does this make sense guys? The other rocker cover has a push on vented cap fitted instead of the old plain cap.
You could just plug the hole where the road draft tube was with a core plug, or buy one of the fittings Chevrolet used right after they stopped using road drafty tubes, and use that fitting as part of your PCV setup.. As long as you have a vented cap on an oil fill tube, or on a valve cover opposite of the PCV valve, you're fine. It sounds like your engine had been sucking air from under the car via the road draft tube, using it as the vent; not too good to pull unfiltered air from under a car. Just be sure to set your idle, idle mixture, and timing specs after you've straightened out your setup. I am Butch/56sedandelivery.
Okay, thanks mate. I think I'm on the right track. I was getting some mild backfiring thru the carb and thought I'd at least eliminate this problem first before I start messing with the tuning of the carbi. It hasn't backfired since, but that could be just a coincidence. Time will tell. Cheers. Peter
Like he said...plug the hole in the back of the block. Connect one PCV valve to the fitting at the front of the carb, with the PCV valve itself in the valve cover. Have an open breather in the other valve cover. That's all you need.
You have a PCV valve pulling vacuum on the crankcase and a hose hanging down in the dirty location that is pulling air in not good.
Yeah, it hasn't been on the road for two years, and is still not quite there, so it had been just sitting on the manifold, but that hose I now have connected to a T piece to mate with the hose off the rocker cover and joined all that to the front vacuum inlet on the carbi. However... My brother just looked at that setup and he reckons I have it wrong. He says "As you have it now is basically bypassing the PVC valve and getting the engine suck on 2 inlet holes" He says I need to plug that front vacuum inlet on the front of the carbi and run the hose instead to the air filter. Sheesh! I need a new brain....
Just get rid of the road draft tube the vented cap in the other valve cover will give you a 1st style PVC system.
What your brother said doesn't make sense. Please, just go back and read Squirrels post (#4). That's what you need to do. It's not that complicated.
I put a freeze plug in the hole with a rubber grommet for the PCV valve and route the hose to the carb. I use the early style intake with the vented oil filler at the front.
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