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Exhaust Pan Evacuation on the Street

General engine tech -- Drag Racing to Circle Track

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skinny z
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Exhaust Pan Evacuation on the Street

Post by skinny z » Fri Jun 19, 2020 12:13 pm

I've nosed around here looking for someone whose effectively applied a pan evacuation system on a fully mufflered dual purpose vehicle.
While I'm aware of the negative pressure pulses induced in the collectors (as in pressure wave tuning) and my understanding is the flow of the exhaust creates a siphon at the pan evac tips. I'm also aware that many full exhaust systems have a positive pressure due to the restrictions created by the entirety of that system.
So, what's the word on this?
To put it in context, this would apply to a street/strip/open road event car, your everyday 450 HP carbed SBC with a 2 into 1 single muffler arrangement. Cutouts for track days but otherwise corked up. This is in an attempt to eliminate the PCV system. Not that it has to be done but wanting to know if it CAN be done with effective results.

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Re: Exhaust Pan Evacuation on the Street

Post by Coloradoracer » Fri Jun 19, 2020 12:57 pm

Those work poorly when combined with mufflers or exhaust plumbing. They work "ok" on open headers. Unless you are having issues, a pcv system will not cost you any hp or performance, and you have nothing to gain by going to a header evac system. If you want the ultimate crankcase evac setup, install a vacuum pump system instead...Depending on the application, gains of 10-70 hp have been documented when using one.....

Header evac systems are "old school" and really aren't a great solution.....
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Re: Exhaust Pan Evacuation on the Street

Post by skinny z » Fri Jun 19, 2020 1:01 pm

That's my understanding as well with respect to ALL of the points you've touched on.
It's more part of a conversation elsewhere that prompted the post here. Some say yes. Others say no.

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Re: Exhaust Pan Evacuation on the Street

Post by BobbyB » Fri Jun 19, 2020 1:23 pm

Coloradoracer wrote:
Fri Jun 19, 2020 12:57 pm
Those work poorly when combined with mufflers or exhaust plumbing. They work "ok" on open headers. Unless you are having issues, a pcv system will not cost you any hp or performance, and you have nothing to gain by going to a header evac system. If you want the ultimate crankcase evac setup, install a vacuum pump system instead...Depending on the application, gains of 10-70 hp have been documented when using one.....

Header evac systems are "old school" and really aren't a great solution.....
How do you choose a pcv valve for an engine making 14"hg in park & 12" hg in gear? Can you suggest one?

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Re: Exhaust Pan Evacuation on the Street

Post by steve cowan » Fri Jun 19, 2020 1:35 pm

skinny z wrote:
Fri Jun 19, 2020 12:13 pm
I've nosed around here looking for someone whose effectively applied a pan evacuation system on a fully mufflered dual purpose vehicle.
While I'm aware of the negative pressure pulses induced in the collectors (as in pressure wave tuning) and my understanding is the flow of the exhaust creates a siphon at the pan evac tips. I'm also aware that many full exhaust systems have a positive pressure due to the restrictions created by the entirety of that system.
So, what's the word on this?
To put it in context, this would apply to a street/strip/open road event car, your everyday 450 HP carbed SBC with a 2 into 1 single muffler arrangement. Cutouts for track days but otherwise corked up. This is in an attempt to eliminate the PCV system. Not that it has to be done but wanting to know if it CAN be done with effective results.
you can hook a vacuum gauge in where you think the evac goes in the header,i have read on this forum where 3'' is possible on an open exhaust./header
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Re: Exhaust Pan Evacuation on the Street

Post by Coloradoracer » Fri Jun 19, 2020 1:36 pm

I've always used the oem valve for that particular engine....they do have adjustable ones though. One thing to think of is that most European engines don't use a pcv valve, they pump the crankcase directly to the intake to help pull it into a vacuum.....
Mark Goulette
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Re: Exhaust Pan Evacuation on the Street

Post by skinny z » Fri Jun 19, 2020 1:55 pm

[/quote]
you can hook a vacuum gauge in where you think the evac goes in the header,i have read on this forum where 3'' is possible on an open exhaust./header
[/quote]

Seems to me there's some YouTube content in that regard. Poor content though.
While the open header application seems pretty straightforward, it's the full exhaust when on the street that concerns me. And my exhaust system is terrible. Maybe a gauge stuffed into O2 sensor bung will give a better indication of how poor it is.

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Re: Exhaust Pan Evacuation on the Street

Post by steve cowan » Fri Jun 19, 2020 3:40 pm

skinny z wrote:
Fri Jun 19, 2020 1:55 pm
you can hook a vacuum gauge in where you think the evac goes in the header,i have read on this forum where 3'' is possible on an open exhaust./header
[/quote]

Seems to me there's some YouTube content in that regard. Poor content though.
While the open header application seems pretty straightforward, it's the full exhaust when on the street that concerns me. And my exhaust system is terrible. Maybe a gauge stuffed into O2 sensor bung will give a better indication of how poor it is.
[/quote]
this is why i dont think it would work well in a full exhaust system,hence the suggestion to test for ones self.
i have just gone the vacuum pump route myself,it is a work in progress at the moment,and a huge expense because of the Australian dollar/customs etc.
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Re: Exhaust Pan Evacuation on the Street

Post by englertracing » Fri Jun 19, 2020 4:09 pm

I tried to make one work really well.
Built a extra low dp reed system and did a 5th primary tube style tube, well sorta its on a tri y, followed by a shoenfield sprint car muffler
All this is on a 410 sprit
Alloy block and methanol dry sump
Doesn't pull much at all....

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Re: Exhaust Pan Evacuation on the Street

Post by skinny z » Fri Jun 19, 2020 7:23 pm

It all kind of appears to be hit and miss.
Some successes. Other not so much.
If I lean more towards to race with this next lump, it may be a vacuum pump for me. If I stay closer to what I've been doing, and that's a heavier street/regular driver application, the old PCV gets another go. Except this latest go around with the worn out shortblock and excessive blowby, I've never had an issue with them.

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Re: Exhaust Pan Evacuation on the Street

Post by MadBill » Fri Jun 19, 2020 11:10 pm

It's definitely a challenge to get meaningful exhaust pan vacuum with a street exhaust system, but David Vizard in (I think) his BBC book shows a system with the pickup tubes running parallel down the center of the collectors and ending at the venturi throats. I believe it achieved ~ 8" Hg., which would suggest it could work with a low restriction exhaust. If anyone's interested I'll try to dig it up. I believe it was built by a then-member of ST.
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Re: Exhaust Pan Evacuation on the Street

Post by Kevin Johnson » Fri Jun 19, 2020 11:31 pm

MadBill wrote:
Fri Jun 19, 2020 11:10 pm
It's definitely a challenge to get meaningful exhaust pan vacuum with a street exhaust system, but David Vizard in (I think) his BBC book shows a system with the pickup tubes running parallel down the center of the collectors and ending at the venturi throats. I believe it achieved ~ 8" Hg., which would suggest it could work with a low restriction exhaust. If anyone's interested I'll try to dig it up. I believe it was built by a then-member of ST.
viewtopic.php?t=59218#p836083
Kevin Johnson wrote:
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: Exhaust Pan Evacuation on the Street

Post by MadBill » Fri Jun 19, 2020 11:36 pm

To quote myself from that link:
"Encyclopedia Johnson delivers again!"
=D>
(I notice I'm getting closer re the vacuum achieved...)
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Re: Exhaust Pan Evacuation on the Street

Post by GARY C » Fri Jun 19, 2020 11:36 pm

I ran them on this car with nitrous and a full exhaust system it had straight through Dyno Max mufflers, engine combos were 377, 382 and a 421... on the 377 they pulled enough to keep the rear main from leaking even though it only looked like one side was pulling.
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Re: Exhaust Pan Evacuation on the Street

Post by MadBill » Fri Jun 19, 2020 11:40 pm

GARY C wrote:
Fri Jun 19, 2020 11:36 pm
... it only looked like one side was pulling.
It's pretty common for the check valves to flake out..
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