The 1947 - Present Chevrolet & GMC Truck Message Board Network - View Single Post - 47-55.1 oil seperator

**mr48chev** · 03-01-2026, 12:18 AM

I'd clean it and leave it in place. You are more liable to have the PCV valve suck oil in without it than have any actual vacuum issue one way or the other. Same as the valve covers that don't have a deflector under the PCV valve

The positive crank case ventilation system works on air in, air flow through and being drawn out by the engine's vacuum

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That is one reason that V8 Chebbys with a breather in both valve covers and No PCV or draft tube always have oil on the valve covers and oil leaks. The pressure in the crankcase has to go somewhere. I got that education on the 283 that I had in my T bucket and then in the 48.

03-01-2026, 12:18 AM	#2
mr48chev Registered User Join Date: Jul 2007 Location: Toppenish, WA Posts: 16,391	Re: oil seperator I'd clean it and leave it in place. You are more liable to have the PCV valve suck oil in without it than have any actual vacuum issue one way or the other. Same as the valve covers that don't have a deflector under the PCV valve The positive crank case ventilation system works on air in, air flow through and being drawn out by the engine's vacuum URL=https://hosting.photobucket.com/c5e80f58-8b3a-4ad3-b9a8-69c8e75f6874/32a2f9c3-bed5-405a-9b44-65c54b8e337c.jpg?width=960&height=720&fit=bounds][/URL] That is one reason that V8 Chebbys with a breather in both valve covers and No PCV or draft tube always have oil on the valve covers and oil leaks. The pressure in the crankcase has to go somewhere. I got that education on the 283 that I had in my T bucket and then in the 48. __________________ Founding member of the too many projects, too little time and money club. My ongoing truck projects: 48 Chev 3100 that will run a 292 Six. 71 GMC 2500 that is getting a Cad 500 transplant. 77 C 30 dualie, 454, 4 speed with a 10 foot flatbed and hoist. It does the heavy work and hauls the projects around.