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Vacuum for vac u pan

General engine tech -- Drag Racing to Circle Track

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Superstock
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Vacuum for vac u pan

Post by Superstock » Tue Nov 19, 2019 5:57 pm

I have a vac u pan system on my motor that doesn't draw very much vacuum, maybe 1" total if that according to my guage, what can I do to draw more vacuum , cannot use a vacuum pump according to the rules

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Re: Vacuum for vac u pan

Post by zums » Tue Nov 19, 2019 6:00 pm

What style pick up do you have and where in the collector is it oriented, is the case sealed tight?
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Re: Vacuum for vac u pan

Post by Superstock » Tue Nov 19, 2019 8:29 pm

The pipe part is in the collector at a 45 degree angle with the notch cut in it just like " they" recommend and it is right above the 4 tubes that go into the collector

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Re: Vacuum for vac u pan

Post by MadBill » Wed Nov 20, 2019 12:47 am

In his BBC book, David Vizard wrote about and showed a system he said was by far the best pan vac. he's ever seen. I forget the builder's name, but I believe he is/was a Speed-Talker. The system used a square cut ~ 5/8" tube angled in through the side of the merge collector and bending to run down the centerline to the throat. I believe it achieved ~ 6" Hg.
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Re: Vacuum for vac u pan

Post by Kevin Johnson » Wed Nov 20, 2019 1:46 am

MadBill wrote:
Wed Nov 20, 2019 12:47 am
In his BBC book, David Vizard wrote about and showed a system he said was by far the best pan vac. he's ever seen. I forget the builder's name, but I believe he is/was a Speed-Talker. The system used a square cut ~ 5/8" tube angled in through the side of the merge collector and bending to run down the centerline to the throat. I believe it achieved ~ 6" Hg.
https://www.chevydiy.com/how-to-build-chevy-big-blocks-exhaust-system-guide/ wrote:If you are looking for the ultimate in evacupan performance, it’s time to get serious about the location of the extraction nozzle. My big-block building compatriot Mark Dalquist managed to get a draw of almost 9 inches Hg (which is 121 inches of water) by finding the sweet spot in the center of the collector among the primary pipes.

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Re: Vacuum for vac u pan

Post by MadBill » Wed Nov 20, 2019 10:02 am

That's the one Kevin! Encyclopedia Johnson delivers again! :D
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Re: Vacuum for vac u pan

Post by Superstock » Wed Nov 20, 2019 11:13 am

Thank you, I will find the book and study it. Still want to know if hooking it up along with a pcv valve will work or just repositioning the pipe will do everything by itself?

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Re: Vacuum for vac u pan

Post by ClassAct » Wed Nov 20, 2019 1:50 pm

Superstock wrote:
Wed Nov 20, 2019 11:13 am
Thank you, I will find the book and study it. Still want to know if hooking it up along with a pcv valve will work or just repositioning the pipe will do everything by itself?

I run both a pcv valve and a pan evac. No reason not to. Both do seperate things and both work together at cruise.

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Re: Vacuum for vac u pan

Post by Superstock » Wed Nov 20, 2019 4:54 pm

How much vacuum does your pcv vac u pan setup have and does it plumb into the back of the carb or the manifold?

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Re: Vacuum for vac u pan

Post by ClassAct » Wed Nov 20, 2019 4:57 pm

Superstock wrote:
Wed Nov 20, 2019 4:54 pm
How much vacuum does your pcv vac u pan setup have and does it plumb into the back of the carb or the manifold?

I haven't had time to check them both together yet, but the pan evac pulled 5 inches at WOT so that's all that will ever be. I was more concerned with part throttle stuff.

I'll get some time next spring to test them together.

I run the port on the back of the carb for pcv.

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Re: Vacuum for vac u pan

Post by Superstock » Wed Nov 20, 2019 5:51 pm

Thanks, there might be some leaks in my system, I can't get that kind of vacuum, actually would be happy with that, but I would like to keep working on this and see what I could actually achieve, it is an ongoing project for me to find the most efficient system, someone said they used smoke thru there system to find leaks, would like to find out about that

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Re: Vacuum for vac u pan

Post by Superstock » Thu Nov 21, 2019 4:33 pm

Has anyone tried different size hoses, like 1" or 1/2" and what difference did it make?

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Re: Vacuum for vac u pan

Post by rustbucket79 » Sun Nov 24, 2019 8:40 pm

If you're not using a mechanical fuel pump why not plumb the inlet side of the biggest SOB mechanical fuel pump you can find to the crankcase as well?

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Re: Vacuum for vac u pan

Post by Superstock » Mon Nov 25, 2019 6:37 pm

Now were starting to think guys, great idea, unfortunately in using a belt drive and there isn't a way to hook up a mechanical pump, but thank you

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Re: Vacuum for vac u pan

Post by Superstock » Fri Nov 29, 2019 5:56 pm

Can someone tell me is a pcv valve set up with a vac-u-pan a better way to draw vacuum and how do you determine what pcv valve you need. Do you hook it up to the manifold runner or the base of the carburetor or a spacer under the carb? Thank You for your replys

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