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Anti Pulse Valves
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speedbuggy714
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PostPosted: Tue Jul 08, 2008 6:35 pm    Post subject: Anti Pulse Valves Reply with quote

Anyone know who sells or where I can find an anti pulse valve for the vacuum line on a vacuum advance dizzy? CB Perf. no longer has them or at least that's what 1 salesman told me.
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Alan_U
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PostPosted: Tue Jul 08, 2008 6:59 pm    Post subject: Reply with quote

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Last edited by Alan_U on Wed Jul 09, 2008 12:21 am; edited 1 time in total
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speedbuggy714
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PostPosted: Wed Jul 09, 2008 12:12 am    Post subject: Anti Pulse Valves Reply with quote

I think a check valve would only allow air flow or vacuum to travel in 1 direction. If that's the case then once you pulled a vacuum on the dizzy vac canister and it advanced it would not release so your timming would stay advanced. Like holding your finger over a drinking straw with liquid in it. The liquid dosn't drain back out. I believe the idea of the anti pulse valve allows air (vacuum) to travel in both directions but doesn't allow fast surges or pulses to advance and retard the timming in an irratic way. They smooth out the vacuum for a more steady, smooth advance and retard.
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Alan_U
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PostPosted: Wed Jul 09, 2008 12:19 am    Post subject: Reply with quote

Please disregard my ealier post. I dont know where my head was at.

I still dont see a noticeable driveability improvement with such a "device" You will never see such things on older vacuum advance distributors on other car makes.
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speedbuggy714
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PostPosted: Wed Jul 09, 2008 1:08 am    Post subject: Anti Pulse Valves Reply with quote

You don't see them on many vehicals here in the states but I have been told they were used on cars over seas. Actually, up until about 3 years ago CB Performance sold them for use with the Dellorto and Weber carbs when using vacuum advanced dizzy's. Since the EFI has become so popular they claim they didn't sell enough to keep them in stock so they no longer offer them. They mention and reccomend them in the Dellorto Superforformance book and the Weber Tech Manual both written by Bob Tomlinson. I saw them 18 plus years ago on some VW's set up for racing but I wasn't into the Hi-Po stuff then and didn't know what they were for. Now, when I want one, there all gone Crying or Very sad
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lostinbaja
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PostPosted: Wed Jul 09, 2008 3:42 am    Post subject: Reply with quote

I used a .030 mig welding tip in the vacuum hose to smooth out the pulse to the MAP sensor in a fuel injected application. It works great.
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dubkrzy
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PostPosted: Wed Jul 09, 2008 4:32 am    Post subject: Reply with quote

I ported both carbs and ran a tee to smooth out the signal. Works great!
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speedbuggy714
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PostPosted: Wed Jul 09, 2008 10:37 am    Post subject: Anti Pulse Valves Reply with quote

dubcrzy,
When you combined the two carbs do you feel this gave you a stronger (more) vacuum as well or just a smoother draw?


lostinbaja,
I may experiment with the .030 mig tip. I have plenty of those laying around.

Thanks for the replies!
Mike
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myb356
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PostPosted: Wed Jul 09, 2008 12:53 pm    Post subject: Reply with quote

I have a 4 vac lines hooked to my Dells. With a K8 cam it seemed to be necessary. My timing light was jumpy before I hooked all 4...now she is smooth. I also have a lighter weight spring in the can and it also happens to be adjustable. As far as driveability goes... my power now feels stronger around 500 rpm lower when just lugging it around town.
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speedbuggy714
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PostPosted: Wed Jul 09, 2008 2:11 pm    Post subject: Anti Pulse Valves Reply with quote

myb356,
Was it a big deal to drill and tap the Dells for the extra ports? I'm not looking at mine right now and can't remember if there are blocked off spaces for the vac tube on each carb barrel or not. Did you drill and insert a short metal tube then epoxy it in place or just a tight fit? Did you then run short hose from each barrel on 1 carb to a "T" then "T" both carbs together into the vac canister? I too am running a large dual lobe cam and I don't have much vacuum and it's a bit irratic below 1500 rpm.
Thanks,
Mike
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dubkrzy
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PostPosted: Wed Jul 09, 2008 3:47 pm    Post subject: Reply with quote

Smoother Confused

Is that a word?
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martyrg
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PostPosted: Wed Jul 09, 2008 8:25 pm    Post subject: Reply with quote

I too have dual Dell 45's with a large cam and a Mallory Unilite. Vacuum signal was very erratic at low speed, causing the timing to jump all over the place.

I drilled the second carb for PORTED vacuum (NOT manifold vacuum -very important!! Check out aircooled.net technical artical for more about this.) It was easy to do as there is a spot cast in the side of the carb body for the hole.

Just carefully drill through the hole, deburr the carb throat where the drill came through. Go to a hobby, craft, or hardware store and find their display of K&N brass tubing. Buy the size to fit the hole you just drilled. Use some JB Weld to glue it in place, just make sure that it doesen't get inside the brass tube and plug it up.

I tee'd the two carbs together and then went to the vacuum port on the distributor. The vacuum signal was a lot better, but still somewhat erratic. I e-mailed John at aircooled.net and he suggested putting an idle jet into the vacume line to help smooth out he vacuum pulses. That seems to have done the trick.

Good Luck!
Marty
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Hotrodvw
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PostPosted: Wed Jul 09, 2008 9:01 pm    Post subject: Reply with quote

dubkrzy wrote:
Smoother Confused

Is that a word?


More Smoother? More Smooth? Smootherest? Laughing
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myb356
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PostPosted: Wed Jul 09, 2008 11:17 pm    Post subject: Reply with quote

All of the 45's that I have are already fitted with a fitting on one throat. I have done 2 sets of 40's by making a threaded brass fitting and drilling and tapping the carbs. Be sure the throttle plates are open before drilling! Thinking back mig tips screwed into the casting would have neen easier. The trouble is with 45's the casting is thinner and would require a different approach ( example brass tube from hobby store ). Good luck with obtaining your smoother results.
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speedbuggy714
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PostPosted: Tue Jul 15, 2008 2:42 am    Post subject: Anti Pulse Valves Reply with quote

Found them here: http://www.dellorto.co.uk/merchandise/products_det...ctionID=71

Thanks Samba member BerT3 !
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