Vac-u-pan effectiveness

Anyone have any data on what crankcase vacuum they get with a vac-u-pan at 7000-7500 ?

Any data on loss of power by disconnecting the system?

1/16” ring line up with low tension oil ring.

I've heard some say they are good and some say no good
I tried a Moroso set up one summer, the only thing I saw was more moisture in the valve covers when I removed them to check the lash
Vacuum in the crank case can help stop tiny leaks and make power above 6000 RPM on a several good engine dyno tests that I know of
The more crankcase vacuum the better the power gains above 6000 RPM

I've never got those to work but other people have. All I ever got was exhaust pressure in the crankcase. (I know that doesn't make sense but that's my experience.)

Are you sure your entry into the exhaust is correctly shaped?

They do work but the vac is low(about 3" to 5" vac).. if running a full exhaust you have to check the back
pressure

I'd agree the pan-evac effect is weak at lower RPM based on my own experience, but an exhaust past the collectors could be a factor.
Briefly, installed a fresh engine that included a low-tension setup, otherwise very similar to the previous unit (cam, heads, intake, + 1.0 CR).
Has a huge, deep pan, mesh tray, 10-W30 oil well away from crank.
Had previously added 3.5" X-pipe & Race Bullets, ending @ rear axle. Had pan-evac with proper 1-way valves & angled suction @ collectors.
New motor would smoke a bit through the exhaust in the lanes & such, 1500-2000-ish RPM range. Would clear up downtrack. Shift points 7500.
Changed to an electric GM vac pump & puke tank, no smoke. Checked vacuum via fitting in opposite VC, 5" vacuum.

What I showed is the easiest to construct and install. If you have a detachable section of collector, a better method (higher vacuum, some vacuum at lower RPM) is to make the insert a cone parallel to the exhaust flow, with the wide open end facing downstream. It's going to get really hot, so choose your material carefully.

I always used nipples with the whistle cut - as supplied from Moroso - and installed them with the end cut parallel to exhaust flow - i.e. turned 180 degrees from your illustration - and deep enough to get the whistle cut well into the flow.

Never checked vacuum but they worked well I thought. Could free rev the engine and feel the pull on the hose. Cleaned up the moisture in the valve covers after the engine warmed up. Had to keep an eye on the check valves. They would fail fairly regularly and need to be replaced.

The addition of mufflers - even just the collector style - substantially reduced the effectiveness of the system.

Data logger and a pressure sensor will tell you for sure. I don't think that old school setup is very effective but it is probably better than nothing. You don't see any high dollar guys running that setup anymore. Even bracket racers run vacuum pumps these days.

Vacuum pump is the better (more expensive) option. Vac-u-pan is better than nothing with rags wrapped around the breathers.

ON MY SONS MAGNUM, HE SEING ABOUT .5 TO A HAIR UNDER 1" AT IDLE. SEES 5-6" ON THE HIGHWAY OR GOING THRU THE FINISH LINE

THE KEY IS HE WELDED BUNGS ON HIS VAVLE COVERS AND EVERTHIS IS AN LINE. NO RUBBER GROMMETS ETC THAT CAN LEAK. WORKS BETTER THAN I THOUGHT IT WOULD

Sealing the engine helps. Including removing the dipstick, tapping and plugging the hole. No vents.

I put one on my e/sa 340 Duster years ago. My car was scienced out completely so I know if something I tried worked. It was worth ZERO.

There are 2 variables not considered which make the conditions you want to fix: high crankcase pressure producing blowby.
1. what is the original crankcase volume in inches?
the empty space in the oil pan, but above the oil level
the empty space surrounding the crankshaft
the empty space inside the bores below the pistons (including the pistons’ interiors)
The engine’s total internal volume also includes the empty space inside the valve covers and under the valley cover
2. how much larger displacement is the actual engine than the smallest original version (for a 340: 273", for a 400 B: 350", etc.)?

This is why a stroker 400 has more problems than the same size 440: higher pressure and higher pressure cycling due to a smaller container.

This is another advantage to a deep pan: the extra air volume buffers the pressure cycles.

Sometimes we just do what is helpful and/or cost effective. Maybe not the optimum solution or technique, but helpful.

Is a vac-u-pan system helpful in relieving pressure in the crankcase and maybe even pulling a negative pressure? Yes. Is it better than a simple pair of breathers in the valve covers? Yes. Is it the best solution? No. Is it a fix for leaking rings? No. Is it much cheaper and easier than a vacuum pump system? Yes. Does it have any negative side effects if properly installed and maintained? No. Easy decision.

Especially since it does not compromise future mods or limit engine strategy.

My car blows the one way valves out in the headers at least once a year. I always carry 2 spares. Engine braking in the shutdown just blows the plastic out.

Its annoying - I'm thinking of switching to the gm air pump For Chevy Express 1500 00-02 GM Original Equipment Secondary Air Injection Pump.

I dont think I have room for a dry sump and just need a little vacuum on my little 383.

Do you have the pan evac before or after the muffler?

Will an electric do the trick ? Anybody have any real life experience. I don’t have space for mechanical .
G

I bought a electric one but havent put it on yet

They don't look big enough to do it.
A 12 volt car vacuum (locate in the car's interior, pulls from hose through the firewall and dumps under the car) is way bigger, cheap, designed for continuous duty.

I bought a unit designed for a engine... should pull 8" to 10" on a SB

I use methanol and am looking for ways to evacuate moisture. I have seen guys connect a shop vac in the pits after a run. I thought employing an Electric pump on the return road and at the trailer after a pass could help.

Could you not run a brake vacuum pump ? Like subaru's run ? Also Aus holden commodores run them , sure be the same on chevys . They will pull up to 20" vacuum . Use an adjustable pressure switch to set .
Plus the holden type , hella makes them i think , is quite small

Tex

Try this

Tex

Hey Tex,
Thanks for this. I was not aware that any of these pumps could draw that kind of vac. . Would need to come up with a trap for the oil/water pre pump. I will look into it.
Alot of folks run methanol in your parts?
G

Here's a link to the hybrid pcv/electric evac system I designed, been using it for around 10 years now with no issues. Worth a look if you have a street/strip car like mine...

Hybrid PCV/Electric EVAC System

Grant

Not a deal breaker , but that is a man sized amp draw.
Just something to be aware of.

I'm not seeing any electric units capable of moving the volume of air required to do the job, unless you're just trying to make power brakes work. Maybe my search skills are lacking.

As per GZ Motorsports:
"At best the electric pumps I've tested are about equivalent to a pan-evac system. I'm not current with the latest electric pumps because I abandoned that approach based on our testing. The Pontiac pump which has a lot larger motor than the Corvette pump would run the battery down very quickly if there was no alternator to keep the it charged. Again most of these pumps are designed for low air volume and an oil free environment, they might work adequately for a while, even as well as a similar to a pan-evac system, but they won't likely last a long time."

This was a few years ago, but I don't know that anything has changed...

Except for this which I know has been used on Pro Stock motorcycles...

https://quartermax.com/electric-vacuum-pump-kit/

Did you notice that it only draws power when making a nitrous pass?
Although I power the pump from the car's electrical system, it could easily be powered by a cordless tool battery pack. I have also converted one of these pumps to brushless power to get even more rpm/volt, but the pump on my car still has the stock brushed motor.

Grant

No mufflers. Possibly too many whoomps at the finish line on occasion though. 🤷‍♂️

This is what I found out years ago when I was in need of a vacuum pump for my hemi. I bit the bullet and put a belt driven pump on it. Had some issues w/ the Aerospace pump (didn't pull much vacuum and had 2 pumps fail), but once I got a Moroso pump it's been trouble free. GZ & Star also make good pumps.

Star is top shelf. Aerospace I'm not so fond of whether it's brakes, pumps, whatever.