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Tripple Webers / Vacuum Advance ???

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Hey Guys, I have searched and can't find anything about running Tripple Webers using vacuum advance.

I have a 1973 240Z that is stock except for the Webers, Pertronix ignition and 6-1 headers.

The Webers have 30mm chokes installed and run pretty well. I'm just looking to get a little better driveability and maybe better mileage.

I have rebuilt the stock distributer and the vacuum advance starts to to move at 12 pounds of vaccume and finishes its "curve" at 15 pounds. The diaphram holds vacuum for at least 15 minutes, so its working OK.

I believe the vacuume line needs to be on the air cleaner side of the throttle valve, but there are no fittings to connect to. I'm not sure how close the port has to be to the valve. I have read that the Mikunis have a port for this, but I'm not sure where is it located?

If I connect the hose to the fitting on the Cannon manifold the vacuum advance pulls in right away. No good...

Has anyone modified thier carbs to enable the vacuum advance?

Thanks, Doug

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According to redline weber, you cant run vac advance with (DCOE) triples, they reccomend going with unilite dizzy or similar!

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Can't run the advance with Webers. Even on my L320 which has a single 40DCOE (w/26mm chokes) I couldn't get it to work. I ended up going with a solid breaker plate and relying on the mechanical advance. On a little 85-90ish horsepower push rod 4 cyl that's okay but I doubt if that would be satisfactory on a L6 w/triples. What would happen if you put a 280Z vacuum delay valve inline between the manifold and the distributor? That would cut the vacuum but I don't know by how much.

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The issue with triple webers is that they just don't generate enough vacuum from any one throat to pull/move the diaphragm in the dizzy. Most people rationalize just leaving this off by saying that if you were even slightly concerned with fuel economy, you wouldn't be using triples in the first place. My own experience with them bore that out.

Triples like a lot of initial advance at idle, hence a lot of people will swap a later ZX dizzy. These have less mechanical advance allowing you to start with more initial advance. I have mine set for about 17 degrees of initial advance and get a total of 35 degrees above 4k rpm.

BTW, the lack of vacuum advance shouldn't affect your driveability, only fuel economy at steady light throttle such as cruising on the freeway.

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Agree with everyone above. I got mid 20's on the highway with triple 44s. Proper jetting can get you fairly decent mileage at cruise. If you're looking for around town mileage forget it.

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Hello Doug,

I'm building a triple weber engine at the moment,and I was thinking about the same Problem. Most people disable vac advance, because the vac will not match to your dizzy anymore.

To reach +/- 35 ,you need a basic advance near 20 degree, what has disadvantages for idle and start.

I have found the ideal solution, at the moment I'm collecting the parts.

A Megajolt controller and Ford Edis wasted spark system.This Edis system is very common on Megasquirt fuel Systems. But here it works stand alone.

http://www.autosportlabs.net/images/0/0d/Mjlj_main_screen_connected.png

Cost 200-250 $

What you need.

EDIS-6 Coilpack +module (ebay/junkyard)

new wires

Controller

trigger wheel.

Here is some info

http://forums.hybridz.org/showthread.php?t=113165

http://www.autosportlabs.com/

http://search-desc.ebay.com/search/search.dll?sofocus=bs&sbrftog=1&catref=C6&from=R10&mppfqy=edis&mppfqy=edis&_trksid=m37&satitle=megajolt+6&sacat=-1%26catref%3DC6&fts=2&fmmk=&fmmd=&fylo=&fyhi=&mppfqy=megajolt&sargn=-1%26saslc%3D2&sadis=200&fpos=47669&sabfmts=1&saobfmts=insif&ftrt=1&ftrv=1&saprclo=&saprchi=&fsop=34%26fsoo%3D2

Cheers

Rainer from Germany

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I have the Mallory dual point distributor without vac and bought the Pertronix II conversion kit for it. Now I have a great fully adjustable distributor with electronic reliability

and I don't have to worry about blowing an led trigger. I just don't trust those Unilites. One good voltage spike and your on the side of the road.

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To reach +/- 35 ,you need a basic advance near 20 degree, what has disadvantages for idle and start.
What is the disadvantage of extra advance for idle and start?

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:stupid: I have a 1971 240Z with the L-28 engine. It has a ported and polished E-31 Head on it. My current carbs are the 45mm DCOE Weber carbs. I race it and do Solo II on weekends. But most of all, I street drive it a lot. I am running the 37mm chokes in it right now. I have had 30mm chokes in it, when we had the L-24 in it. It does not get tuned that often. Once I got it setup for the L-28, I lock it in and it still is running great right now. Gas mileage all depends on my lead foot. I have that need for speed. So it goes very fast and I love it. I have had SU's setup (two sets setting in the garage) and a 4-barrel carb version (just sold a complete setup to a young man in florida) on it and didn't like either one for my own personal reasons. I still love the sound of those six carb openings sucking air. I can tell you that those carbs are better for the power side of the engine. But you can pick any one of the three. Only the person driving the car has to live with it. I am starting to work on my next car and it is start out with a L-28T engine. But in the end it will have either a Chevy 350 or a AMC 401 in it with a carb in it. Can't afford the good stuff. Good Luck, Rich. PS. We have the single solid plate in the distributer right now, no vacuum advance in it. :dead:

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