vacuum pump,why pull off valve covers

[nyesgym]

Trying to get every once of horse power out of my 383 sbc. I want to put a vacuum pump on it. I see most racers pull off 1 valve cover ? Is it better to pull off both valve covers ? How about pulling vacuum from under the intake ? When I got this motor it had not evac system on it, when i put a header evac system on, right away i went 2 tens quicker. now a 3 vane pump will pull alot more then a header evac, so it should give me more power. I figure I have about 615 HP, running 9.12 et, i want to hit the 8.99, so i need about 30hp to do it. any thoughts

[Kevin Johnson]

Better to pull from the block/crankcase area but more problems arise. Use the valve cover for your FILTERED vacuum relief valve.

[A Atwood]

What about pulling from the fuel pump block off plate?

I have wondered if this is a good place for the vacuum source location.

ARN

[Rick360]

I've found pulling from the valve covers will carry less oil out of the engine. It can be from either side and doesn't need to be from both covers, use which ever is closer to your pump to make the lines shortest. Then put the relief valve as close as possible to the line, or in the pump/line would be even better.

Rick

[Kevin Johnson]

What about pulling from the fuel pump block off plate?

I have wondered if this is a good place for the vacuum source location.

ARN

Make a block-off plate with an interior baffle so that windage is not blasting directly into it. Use a large diameter hose and connect to the top surface of the end of the valve cover directly over it. Baffle the entrance but keep the cross sectional area of the exit from the baffle at least as large as the CSA of the hose (follow this design cue on the entrance to the hose as well)-- you may need to install a coil inside the hose to keep it from collapsing. At the other end of the same valve cover make a baffled vacuum draw source but with a significantly smaller hose or csa. On the opposite bank valve cover install your filtered vacuum relief valve. Everything nicely damped and you will be doing the least amount of interference to draining of the oil from the heads. Be aware that some engines have significant issues with secondary windage/blowby flow paths (Ford Modular V8, for example). If you perturb the OEM system then you must be prepared for unintended consequences. Just look at what they went through with the Coyote.

[nyesgym]

Thanks Guys, Kevin, i am going to try to do it your way,larger hose ? 1" dia ? trying to understand what you wrote.you say at the other end of my valve cover[ near my firewall] make a baffled vacuum draw source, with a smaller hose, this is do now understand ? what does this do ? where am i running this smaller hose to ? will a 3 vane pull do fine or should i go with a 4 vane ? thanks terry

[Kevin Johnson]

Thanks Guys, Kevin, i am going to try to do it your way,larger hose ? 1" dia ? trying to understand what you wrote.you say at the other end of my valve cover[ near my firewall] make a baffled vacuum draw source, with a smaller hose, this is do now understand ? what does this do ? where am i running this smaller hose to ? will a 3 vane pull do fine or should i go with a 4 vane ? thanks terry

It is probably easier to make the larger tube from preformed mandrel bent header tube sections with some kind of air-tight joint. Particularly since you will probably pass near a header (so heat shield as well).

Yes, you understand what I mean about the smaller tube. A vacuum pump manufacturer can advise you on which pump to use. I would not use one with an integral vacuum relief, though (or block it off), as that would defeat everything else you are doing with respect to flow. By the way, you might want to look at the internal construction of the Studebaker type R drain tube. If you go to the Studebaker forums I think there are people there that can direct you to original engineering drawings. I think the Granatellis' were responsible for it.

[Rick360]

That sounds way more complicated than it needs to be. Keep it simple.

I also don't like putting the relief far away from the vacuum pump line. Any relief air that comes in flows thru the engine that way - not good and carries more oil with it. Open the drain holes big enough in the block and heads and if your rings seal good you wont have enough air flow out of the engine to be a problem.

Rick

[nyesgym]

Pretty sure my rings are sealed good, i know i am still getting pressure in my crankcase, because it was still pushing my dip stick out ,until i got one of those locking dip sticks. some of this advice might be over my head alittle, i do want to keep it simple. and i sure want to pull as little oil out of the motor as i can. But , I really like this speedtalk, it is very nice to get advice on things. I am not to old to learn new things, Thanks Guys. All I learn here I pass one to may son, who is a Turbine Helicopter mechanic, stationed at Hunter Army airfield, in Savannah,Ga . then he tries this on his race car
terry

[Ernie's 5oh]

If your rings are sealing good, you wouldn't have your dip stick being blown out by blow by threw your rings.
What make of pump are you looking to get? and you should always run a regulator, depending on your combo and oil pump pulling too much vacuum will make your motor starve for oil.

[Kevin Johnson]

That sounds way more complicated than it needs to be. Keep it simple.

I also don't like putting the relief far away from the vacuum pump line. Any relief air that comes in flows thru the engine that way - not good and carries more oil with it. Open the drain holes big enough in the block and heads and if your rings seal good you wont have enough air flow out of the engine to be a problem.

Rick

At high rpms, oil with air entrained in a moving engine rather than on a non-tilt dyno, is like soda water when it emerges from the bearings. Foam does not flow so easily as neat oil. I think there are many examples of "oil filling the heads" which are explained easily with increased bulk due to decreased density which are attributed to the drain holes not being big enough*. Drawing air down through the drain holes via the crankcase encourages the evacuation of the heads. Just like the suction water basins on airplanes.

The flow of oil to the heads is essentially a constant past a certain rpm. It will drain under gravity or with an assist. Put the vent on the left bank as you look at the crank pulley. This will actively work to combat oil being driven up the drain ports which is useful.

* Keep in mind that OEM testing includes hundreds if not thousands of hours cycling back and forth between peak torque and hp on a dyno. If the drains were not properly sized this problem would show up quickly. Oil pump flow only increases very gradually after the pressure relief is hit. Of course, if you have done something to deliberately increase flow to the heads that is another story. Often it is just the opposite in racing engines.

In addition, the head which has no venting will have more stress on the intake and exhaust valves/guides. Exhaust pressure will try to flow out and expel oil and fouled gas from the guide and being in local proximity/communication to/with the intake valve guide this will encourage more oil being taken in and burned in the engine but with unfiltered atmosphere to boot. For the changed local conditions to communicate with the vacuum-pump-with-close-proximity-relief-valve requires transit through the crankcase. So in trying to make something simpler the complexity of the system increases. By providing a properly sized relief valve, it should preferentially provide additional atmosphere to the interior of the valve cover and reduce the proclivity of the exhaust valves to provide same. This is all assuming excellent ring seal. There is no doubt that there are less expensive ways to do things but overall simplicity is not so straight forward to achieve as one might suspect.

[Kevin Johnson]

... i know i am still getting pressure in my crankcase, because it was still pushing my dip stick out ...

It would be a good investment to obtain a leakdown setup so you can determine the health of the engine. Good Xmas present for your son.

[nyesgym]

WOW Kevin, i will have to reread this 10 to understand it. not sure whos pump to buy, areospace has one ? ok, i am going to put mny relief valve in my other valve cover. i understand now how to install my fitting that i am going to draw from., the only thing i do not understand is[ i had a typo befor] what is the small hose for on the firewall side of the valve cover, . i know i will get some pressure in my crank case form the rings, but i am sure i get some pressure from that crank spinng at 8000 rpms. the color on my plugs,exhaust ports and my headers are light gray. plugs only have light gray at the very bottom of the porcelin, so not using any oil thanks for all the info

[Kevin Johnson]

The small(er) hose is where to draw your vaccum from. The manufacturer of the pump should have very realistic suggestions on what size it should be. By being smaller than the tube connected to the crankcase and having the intervening volume of the valve cover it will dampen and steady the flow. A similar technique is used with some mechanical oil pressure gauges so the needle doesn't jump around so much.

[nyesgym]

i am slow, reread this info alot, I got it ! I will build this system, will i pull much oil off the fuel pump block off plate ? I will baffle the hole for sure at all holes.has anyone done it this way ?