I have been restoring my '64 Vette 327/365 to the original engine configuraion while maintaining a GM 350 block from the early 70s. So far this has included the correct air cleaner, carb, aluminum intake, 461 heads, correct exhaust manifolds, water pump, oil fill tube,fan and clutch, and all the tubes and vents. In reading about crankcase ventilation problems trying to "manufacture" the right look for the wrong block, I have routed the road hole tube from the back of the air cleaner, which should go to the hole in the back of the block if there was one, down to a fitting on the upper side of the oil pan which I installed. My thought being this would accomplish positive crankcase ventilation. I am finding that the closed oil fill cap tends to pop off under acceleration and the breather style cap(when installed) tends to exhale a good deal of smoke and oil residue. My question is this. Do I have an incorrect path of ventilation or should this set up normally work? Assuming my oil tube to carb is clear and the horn is clear, what's wrong with this set up? Would a PCV valve in the oil fill tube line help? Any ideas would be appreciated. Thanks.
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Re: crankcase ventilation 1964
I had a 350 block in my 63 and as you have I tried to make it look as correct as possible. I did however use a valve cover that vents and installed a PCV in the cover and ran a hose to the rear of the air cleaner. I had no problems with that setup. I have since found a correct 327 block.
The 64 system is a little different then the 63. The hose you have connected to the oil fill tube should run to the rear of the carburator and connect to a PCV which is installed in the rar of the carb. The hole in the rear of the block connects to the air cleaner. The PCV connection is under vacuum. You need to allow air in the block to replace the the air sucked into the rear of the carb. I think a vented valve cover is the way to go. -
Re: crankcase ventilation 1964
The '64 327/365 did not use a PCV valve of any kind. The tube from the oil fill connects to a fitting with an orifice on the driver's side of the carb.Comment
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Re: crankcase ventilation 1964
The normal flow of the '64 system is air clearner to crankcase and back out the oil fill tube to the inlet manifold via the fitting in the carb, which has a .090" metering orifice.
At WOT the flow can reverse. The problem with your installation may be that oil slosh covers the pan entry, which could pull oil into the air cleaner or cause one way flow out the oil cap vent in which case it is not a "flow through system" that dilutes crankcase vapors and then pulls them into the inlet manifold to be consumed by combustion.
Early SBs with the crankcase vent in the back of the block have a "ventilator" in the lifter valley that functions as liquid vapor separator, and the early systems with a valve worked well. I don't know why they changed to the "no valve" system, but this was abandonded and replaced valve-type system on SBs in '66.
The best design is the "valve cover to valve cover" type because it vents the entire "crankcase" space, which includes the rocker boxes. IIRC the first use of this design architecture was the L-78 in '65. The early systems didn't vent the rocker boxes very well.
Trying to duplicate the "look" of the early system on a 350 block is tough without tapping into the valve covers. The best one I have seen had a hole drilled into the inlet manifold behind the carb for a valve and since that area is visually shrouded by the air cleaner is was tough to spot, but this system's architecture was like the '63 system.
Crankcase ventilation design is much art as science. Even modern Corvette engines are prone to injest oil through the PCV system, especially if they are run in track events.
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