Header evac with zoomies
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Header evac with zoomies

  1. #1
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    Default Header evac with zoomies

    Would this work or is it for collected headers only?

    Tim

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    Red Blooded American The Doctor's Avatar
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    I saw multiple race boats with zoomie evac tubes yesterday so I suppose they are either being copy cats or it works. I'd have to believe the collecter of a well tuned set of headers would provide more draw but at higher rpm, an evac tube on even a single exhaust tube could provide some draw.
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    RAT PATROL rich s's Avatar
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    Hey Tim you should try and borrow a set of good headers and see what the time slip has to say, with a carb deal and zoomis i think you may be leaving a little on the table, 1/8 mile time would be a tic better with a well tuned set of headers
    just my opinion ,let the test tell you
    Last edited by rich s; 11-21-2009 at 10:29 AM.

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    Hi Rich. Ya I've been told that a few times. I tried it at Augusta a few years ago. Ran the zoomies then the collected. I don't know how good the collected were, but the et was the same so I ran them all weekend and went back to the zoomies for the wieght loss and better looks. I think the air going across the pipes may help with the scavaging. Besides I can go to fast as it is. Got that index ya know LOL. What I'm thinking on the evac is to bring the pressure down to atleast atmospheric or a little less. Don't know if that would even do any good.

    Tim

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    Quote Originally Posted by River Rat 005 View Post
    Would this work or is it for collected headers only?

    Tim
    It works. Probably not as good as a collector but it works.

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    Well it looks like I'm slow at getting things done. I finally got the tubes in the headers. I added a 6" extension so if it didn't work I didn't mess up my zoomies. My goal was to have atleast no pressure in the crankcase to stop leaks. Well it did what I asked. No more oil leaking out everywhere. So, I was wondering if there was any vacuum in the crankcase. I rigged a fitting on one hose so I could use a vacuum gage. Whacking the throttle on the trailer it showed 3". Was suprised to see any. I then put a fitting in the valve cover. Going down the track at 7400rpm, it pulled 5". This is with stamped steel valve covers. I never thought it would get that much vacuum with this set up. I don't know if that's enough for a performance gain , but it does what I wanted.

    Tim

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    Thanks for posting up the results. We ran an evac in a set of zoomies and just with it idling you could feel a pull on the hose when you put your finger over it. I am impressed it was able to pull that much. Hmmm, gives me and idea.

    Paul

  10. #8
    gn7
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    Quote Originally Posted by Fiat48 View Post
    It works. Probably not as good as a collector but it works.
    Quote Originally Posted by River Rat 005 View Post
    Well it looks like I'm slow at getting things done. I finally got the tubes in the headers. I added a 6" extension so if it didn't work I didn't mess up my zoomies. My goal was to have atleast no pressure in the crankcase to stop leaks. Well it did what I asked. No more oil leaking out everywhere. So, I was wondering if there was any vacuum in the crankcase. I rigged a fitting on one hose so I could use a vacuum gage. Whacking the throttle on the trailer it showed 3". Was suprised to see any. I then put a fitting in the valve cover. Going down the track at 7400rpm, it pulled 5". This is with stamped steel valve covers. I never thought it would get that much vacuum with this set up. I don't know if that's enough for a performance gain , but it does what I wanted.

    Tim
    We have run both on a blown deal. The zoomie does exactly what the OP said, it pulls enough vac to keep the oil in the engine. Not nearly as much as a collecter will like Fiat said, but enough to accomplish what the OP was hoping for. A dry clean engine.

    I think the reason FC Pilot could feel the vac with his finger over the line is that the vac is probably stronger due to the velocity in a single pipe as opposed to a collector, specially at idle. Most collecter evacs won't pull much vac at idle, if any. But you only get one pulse every 2 revolutions instead of 4. At speed the zoomie simply cannot pull as much as the collector.

    River Rat, don't put too much belief in the air across the zoomie scavanging exhaust. Its less than a forward facing scoop pressurizing your manifold. You'd probably have to go 300 + to have any real effect on the exhaust scavange from a zoomie having air acrossed it. If there was anything to it, collector headers would have 90* elbows on the ends, cut on an angle.
    Besides, have you ever thought about YOU being in front of one of them? If there was much to the scavanging thing, one side would be at a distinct disadvantage. You should see have fast the driver side header on a GN fails due to the driver being in front of it. One race and you can see the difference in the coating. WAAAAAY hotter WAAAAAY less air flow.



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  11. #9
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    Hey Uncle Bob. What would you say that the vacuum range for crankcase vacuum should be for max performance?
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