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Old 10-07-2010, 05:27 PM
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venting of old engine

I have an older (1960)cadillac engine in my rod. It probably needs overhauled,but it runs good,so I don't want to go thru that expense. It has the breather on the oil fill tube and the old downdraft tube in the back. What bothers me is at stop signs and when going slow it puffs a lot of smoke out the breather on the oil fill tube,and thats not the worst part--If I get on it then it blows oil out of the filler pipe breather (and probably out the downdraft tube also) but I cant see that one when driving. This car is hoodless and the oil is going on the firewall,cowl, and windshield. I'm wondering that if I convert to a PCV system if that would help at all,and what about a baffle where the downtube is and then a hose to the intake without a PCV valve? Would that be any different than a PCV valve in the hose? Mainly I just want to stop the oil from coming out of the breather on the oil fill pipe. ANY SUGGESTIONS?

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Old 10-07-2010, 05:50 PM
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What is being run on the Bonneville roadster is breather caps on the rocker arm covers with hoses running to the headers so any oil goes into the exhaust system. that may help your issue..

I have tried most all of it and now do what is known to work..
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Old 10-07-2010, 05:58 PM
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I think you can fix this problem without too much effort. I would take the draft tube off the engine and clean it out. When they get plugged the engine lets all the blow-by come up the fill tube.
But to answer your question. To change to a PCV system, take the draft tube out of the engine and plug the hole with a rubber expansion plug. Drill a hole in one of the rocker covers and install a PCV valve in it. Run a hose from the valve to a vacuum port in the intake manifold. That is all you need.
Vacuum from the engine will draw air from the rocker cover and fresh air will enter the crankcase through the vented fill cover.

Good Luck
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Old 10-07-2010, 06:10 PM
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I checked the draft tube---its clear. I really don't want to mess with the valve covers unless it is absolutely necessary could I take out the draft tube and put a PCV valve from there to intake vacuum? Anotherthing,this car has 6 duces with a split manifold with 2 rubber hoses between the manifolds. Would I have to plumb a PCV to both sides of the manifold ,or possibly into one of the crossover hoses(only runs on 2 center carbs others blocked off)The only vacuum source right now is a fitting on one side of the manifold for the tranny vacuum modulator
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