Do the pan e vac systems really work or provide any benefit? Vacuum pump out of question.

I wouldn’t say it’s worth any power over open breathers, but you need to vent the crankcase in some way.

Also improperly installed or maintained evac systems will pressurize the crankcase!

Your not comp racing, add a vac pump or use breathers...

quote:

Originally posted by maliciousintent:
Do the pan e vac systems really work or provide any benefit? Vacuum pump out of question.

I ran a whistle in the collector for years back in the 1990's methanol, worked fine. Nobody had vacuum pumps. Keep the valves fresh, install the whistle in the collector correct location it'll be fine.

Mine worked, sucked all the moisture out 7 round race. Oil looked great. I ran a clear hose, slightly bigger diameter.

This message has been edited. Last edited by: Mike Rietow,

I run the old 2 stage system with a vacuum gauge in the car. I don't run alky but I like having a negative pressure in the pan. I'm pulling 4-5 inches right now. I know guys that use electric pumps that can be mounted anywhere.

quote:

Originally posted by maliciousintent:
Do the pan e vac systems really work or provide any benefit? Vacuum pump out of question.

Definite benefit but I don’t remember the dyno numbers. I just bought dual PCV breather separator canisters to try at the track on the stock motor. If we could run pan e vac I would!

I run a PCV valve in my junk. AC Delco CV736C or CV746C right off the carb base.

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AC Delco CV736C or CV746C...

If I may ask, what makes them the "correct" PCV?

This message has been edited. Last edited by: Canted Valve,

I don't have a vacuum gauge on mine, but the pan-evac setup definitely creates some amount of vacuum in the crankcase. Engine is sealed really well, but over a full season it used to get a very slight film or mist of oil buildup all over the pan and lower part of the engine, that stopped once I added the evac system. That being said, I doubt that it makes .01 on the timeslip.
As for PCV valves, I don't know about being the "correct" choice for a race engine, but for many years most of the guys I raced with just used breathers. Those who ran PCV valves would use the GM/AC-Delco P/N 19303069, which was the OEM version used on both the 1969 L88/427 and 1970 LS6/454, (closest things to racing BBC's that had a PCV).
The common logic said that this version was calibrated to accommodate the additional blow-by and crankcase pressure from the high-compression, large-displacement engines that used forged pistons with greater bore clearances. Whether it made any difference I have no idea. Still available from O'Reilly for under $4. OReilly High-Perf BBC PCV
Most of them ran a breather filter on one valve cover, with the PCV drawing from the other cover. Probably did a much better job of purging blow-by vapors than the breathers did.

This message has been edited. Last edited by: FootbrakeJim,

I tee off one valve cover header hose to an oil separator, to a GM brake booster valve, to manifold vacuum. The other valve cover goes directly to the header. I used to put front and rear seals in backwards and it would pull more pan vacuum but I stopped doing that back in the late 80's. After shutting the engine down, I can watch how fast the needle drops back to zero to determine how well the engine is sealed, including ring seal. No pcv in this system.

quote:

Originally posted by Canted Valve:

quote:

AC Delco CV736C or CV746C...

If I may ask, what makes them the "correct" PCV?

Low flow, specified for HP applications with mechanical cams and such.

I see Footbrake Jim covered it...

I run mine with a non vented fill cap on the other side.

I've also never had to drill holes in the throttle blades to get a good idle, so there's that.