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I just converted my road draft tube over to a PCV system on my 1950 Olds 88. 303ci. Now it looks like a traded my oil spots on my floor with light oil spray out the breather. The PCV valve I used was for a Chevy 350 with 1/2" fuel line to the carb base plate. My assumption is it all works fine until I stand on the throttle and loose all the vacuum. My vacuum at idle is 20 inc.hg.

Has anyone done this conversion and have advice? My next thought was to get a breather with a port to connect into the air cleaner to create a completely sealed system. My breather is on the pipe from the timing chain cover, not valve covers.

I did rings about 3k miles ago. No smoke or oil consumption. Compression is 110# across all 8 which is only 10# off spec. I assume some blow by is normal so I'm mostly just trying to keep the motor clean. I have noticed what looks like front and rear main leaks after I switched from 20-50 to 10-30 oil as well. with 10-30 I was running around 35# of pressure on the road and 50# with 20-50. If the leaks are driven by pressure build up than I'm not sure what my next move will be. Strangely, when I first finished the motor and for the first few thousand miles it did not leak at all. It all started rather suddenly.

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First off, this is how it was done on my 32. A direct scavenge from the valve cover down to a bung welded on the exhaust. It was always scavenging (vacuuming) as the engine was running. I doubt if you're going to go this route though.

I presume you are talking about removing your old draft tube, and you put the PCV valve into where the old road draft tube was????

You then ran the hose to your carb to the ported side? and are getting your fresh air drawl from your filler cap?

Question, Why did you run 20-50 wt oil? To raise your oil pressure reading?????

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You beat me to it John,

Also..On the Olds, if you just put in a PCV valve in the old road draft openings, and port it to the carb, it's going to suck up some liquid oil. That is going to get sucked directly into the intake..Because there is no baffling there.

If you use a valve cover, and place a PCV valve there,, there is already the lifter valley splash pan on the Olds engine, which will prevent the PCV valve from sucking up the liquid oil.

So, the suggestion would be to PLUG the road draft tube, and drill out a hole for the size of PCV valve cover and grommet, and plumb it that way...You are going to be drawing the fresh air in from your old oil filler cap....Which sucks (PUN) because it's really going to be unfiltered air.

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When Chevy went to PCVs for '67, they had a neat little metal cap which screwed down where the road draft tube went. It had a hose nipple on it, to which an inline pcv attached and then it went to the carb base plate on the backside. You can probably find these items (tin cap, long bolt, inline pcv, etc.) in the Corvette restoration parts industry or perhaps Classic Industries catalog. Not very ornate, but it apparently worked.

There are also some push-on breather caps which have a conversion set-up to attach a pcv to them, I believe. Several different ways to accomplish adding a pcv to a vintage engine . . . the Chevy method is pretty good.

Just some thoughts,

NTX5467

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