I have a 1953 Caddy 331 motor. I have a finned valley pan and my question is this... the original valley pan had a HUGE vent in it. I'm talking an elephant trunk. It came strait up, made a quick 90 then turned down and went off the side of the block. The new valley pan doesn't have one at all. I'm wondering if this is going to be an issue or if I should consider machining some breathers into my finned valve covers. current photo.....
The elephant trunk is a road draft tube. Same function as a PCV valve. The air blwing across the tube going down the road creates a vacuum in the tube, drawing out toxic acid gases (blowby is mostly partially burned hydrocarbons, which will condense to acid in the oil and eat the bearings). The fresh air inlet breather is the oil fill cap. The valley cover you have should have a boss cast in to show you where the tube goes. I would look at a later car, with a provision for a hose to run to a PCV valve and then to the carb - more modern (late 50s?) but 10X more effective, especially if your car will spend lots of time idling / crawling and has a fairly mild cam (lots of vacuum at idle). Oh yeah - your thread title is a little off - this only has to do with cooling if you run no evac setup and the acid eats the bearings, and then the coolant temp starts going up because the oil temp is way high. Right before it seizes ;-)
in idiots terms now... what do you think I should do. I can order one with the provisions for a PCV valve set up. But I'd rather not get another carb if I don't have too. Mine's rebuilt and running good. I'm trying to keep this engine as clean as possible. It will get driven a lot and it will do long miles and traffic from time to time. Stock cam. Stock everything. Only difference is it's got fresh heads and it's .60 over. I'd hate to have to stick that ugly stock set up on there.
I have a 331 with a Moon finned valley cover. It came with a flat spot to put a small vent. I drilled and installed a vent. Might have to wipe a little bloby off but it relieves the back pressure. Gary
I'd get a stock late vent fitting with the hookup for the PCV hose from a 390 or 429, and drill the cover to fit that. On that setup, the hose runs to a PCV valve under the intake plenum, then another hose to the vacuum port on the front of the carb spacer. If you want it really clean and un-obtrusive, you could drill and tap the bottom or rear of the plenum for pipe thread, and screw in a 90* hose barb pointing towards the vent fitting on the valley cover. Use a really short piece of hose between the intake and PCV, so the PCV is mostly hidden by the plenum, and then run the hose from there to the vent fitting on the valley cover. You could also use the carb spacer from the later engine to provide the vacuum fitting. There are a veriety of different aftermarket setups for providing a fitting to hook the hose to the valley cover, an a variety of different looks. There is even a no-name chrome mushroom breather looking thing with a built in PCV valve inside. I agree on the ugly factor of the stock road draft system. However, A PCV valve will make your bearings last several times longer than the old road draft tube, and is much less ugly. Even the road draft tube will extend bearing life many times what you can expect with just breathers. If you want to run just a breather, then there is no need to drill it at all - it already has a breather in the oil fill cap, which should handle venting pressure unless you have excessive blowby. I would not recommend running with no evacuation system on any car that is going to see lots of miles, but some guys prefer the look of no evac system. Lots of guys never have a bearing problem with just breathers, but lots of guys put less than 300 miles a year on their hot rods...
Here is the stock late setup. A picture is worth 1000 words... PCV Valve, and where it hooks to the carb spacer: Vent assembly on the valley cover that the other end of the PCV hose hooks to: I'm sure you can find a way to do it cleaner, but it often helps to see how the factory did it
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