Vacuum pump vacuum levels

[gnfan231]

Looking for some information/help with my vacuum pump setup. I have installed a gz motorsport VP and I wanted to know what are safe levels of vacuum I can run on the GN motor? I have 4 " at idle and 17" at 3,000 RPM without any boost. I still need to put a Vac gauge somewhere I can read it under boost. Any help appreciated.

Bill

 

[earlbrown]

Are you running hellfire rings or some other goofy arrangement where you need to vacuum out the crankcase?

 

[gnfan231]

Are you running hellfire rings or some other goofy arrangement where you need to vacuum out the crankcase?

Nothing goofy, just wanted to keep everything sealed up. The VP was free and it fit right in the AC compressor bracket.

 

[earlbrown]

Unless your engine's in need of a rebuild, you don't need it. (and if it is in need of a rebuild, it needs a rebuild)

No reason to add complication to an engine that already likes to be an ass from time to time.

 

[gnfan231]

Unless your engine's in need of a rebuild, you don't need it. (and if it is in need of a rebuild, it needs a rebuild)

No reason to add complication to an engine that already likes to be an ass from time to time.

 

[gnfan231]

Unless your engine's in need of a rebuild, you don't need it. (and if it is in need of a rebuild, it needs a rebuild)

No reason to add complication to an engine that already likes to be an ass from time to time.

 

[gnfan231]

Looking for some information/help with my vacuum pump setup. I have installed a gz motorsport VP and I wanted to know what are safe levels of vacuum I can run on the GN motor? I have 4 " at idle and 17" at 3,000 RPM without any boost. I still need to put a Vac gauge somewhere I can read it under boost. Any help appreciated.

Bill

 

[gnfan231]

Engine is fresh...but a simple I don't know would have been fine.

 

[Nick Micale]

With my mechanical vac pump the normal setting I use is 10-12".

My RPM range is from 6600-7000 RPM.

Many racers do not usually want to pull more than 15". There is an external regulator I added at the pump so I can adjust the vacuum.

I also use a 2 bar MAP so I can log these readings with my XFI.

My unit is a custom design with lots of help and advise fromSteve at Star Machine.

 

[SS/GN]

With my mechanical vac pump the normal setting I use is 10-12".

My RPM range is from 6600-7000 RPM.

Many racers do not usually want to pull more than 15". There is an external regulator I added at the pump so I can adjust the vacuum.

I also use a 2 bar MAP so I can log these readings with my XFI.

My unit is a custom design with lots of help and advise fromSteve at Star Machine.

Nick we tested some of this years ago and anything over 15 hg we were told could suck the oil off the wrist pins and cause big time problems We never saw an advantage of more than 10 to 12 HG Then NHRA said we couldn"t use them

 

[earlbrown]

Engine is fresh...but a simple I don't know would have been fine.

Not a problem. I'll try my best not to answer any more questions for you.


(but just for curiosity's sake when you say ''fresh'' does that mean recent rebuild that has proven itself, or recent rebuild that only has a few miles on it? bonus points for a flat tappet cam and non hardened lifters)

 

[ijames]

www.speedtalk.com is a forum where lots of top professional engine builders chat, and vacuum has come up many times. The consensus seems to be that even with very low tension, skinny rings they don't see gains past about 10" of vaccum on the dyno or track, and between 12 and 15" they start to see wrist pin and other oiling problems. Most recommend 10" max. Oh, with standard rings they don't see much if any power gain, but with the low tension rings they can pick up 50+ hp on a 650 hp n/a sbc. Even with std rings you still get the benefits of cleaner oil and no leaks.

 

[Nick Micale]

........ Oh, with standard rings they don't see much if any power gain, but with the low tension rings they can pick up 50+ hp on a 650 hp n/a sbc. Even with std rings you still get the benefits of cleaner oil and no leaks.

As you said Carl, no power gain on a N/A engine, but with a turbo or blower much more crankcase pressure is generated, and there is a noticeable HP gain with a vac pump.

We found this to be true at the track when my car would loose a tenth and a couple MPH when the electric pump was not working, and this is not acceptable in competition where you win or lose by a thousand's of a second!