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Dual Webber Carbs

I have recently acquired a 73 1.7 bored to a 2.1, with a Web Cam Street Performance Cam. It has the original distributor, vacuum advance disconnected, electronic ignition(little black box inside the distributor). I just gave it a tune-up including having the carbs set up by a pro - I hope. I have a flutter at low RPS, but goes like a bat out of heck at higher than 3000 RPMS. Is this systematic of a carb set up. I have recently purchased a .009 Distributor but have not installed it as yet. Will this help? I don't do alot of high rev driving and it is a little irritating. Short of putting back the original FI set up, any thing else I can do to make it more smooth at lower RPMs?

Thanks,

Hutch
Old 09-01-1999, 09:40 AM
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I have a 76 2.0 that had the FI replaced in 86. I just recently returned it to daily driving after sitting for 12 years.The carbs were rebuilt (Webers) and it runs very smoothly. It does pop and fart when cold due to no choke but warms up quickly. The thing I don't like is it does not rev very well. If yours does it must be the cam.My car has a lot of bottom end power just the opposite of what you describe.
Old 09-01-1999, 10:36 AM
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Neal,

Thanks for replying. Does yours have the original distributor or do you have the one with mechanical advance such as the Bosch .009 or .050? Any body.... does it make that much difference?

Hutch
Old 09-01-1999, 10:52 AM
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Sounds like the engine is not advancing the timing quick enough since the vac advance is disconnected. Look to see which distributor you have, if it has the last 3 digits as "050" you are in good shape. Look on the www.dgi.net/914/ site under tech reference and then under distru\ibutor chart. It give you the specs on different distributors. I've heard the 009 is bad news, however it is still probably better than what you have set up. If I were you I would hook up the vac advance somehow, this "should" really help your low end.
Old 09-01-1999, 10:55 AM
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JP,

Thanks for your reply. Any ideas on how to hook up the vacuum advance with a dual carb setup?

Hutch
Old 09-01-1999, 11:57 AM
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What is happening sounds like the typical Weber carb set-up that wasn't meant for that car. What I mean is that unless you have a 911 or Ferrari, etc. that came off the assembly line with webers it is difficult to get them running properly. Typiclally Webers work in two positions idle and all the way open.(or so I've heard. I use Dellorto's.) To make them more drivable the jetting is the is the sore spot. If the carbs came from an identical engine and were already jetted properly then ok. But the likelyhood of taking any set of carbs out of the box, bolting them on and expeting them to be "right" with some adjustments with a screw driver is pretty slim.

I went through five sets of jets for my Dellortos before I got the "right" set-up. I mean the drivablity that I was looking for, even now it isnt real good but I like it.

So there you go, it still might pop and fart when warming up but if you get the jets checked out you will find that it makes a huge difference in the way the engine winds up under a heavy foot.

If you have the Weber book it should tell you how to "estimate" which are the right jets for your car. You have to take into account the displacement of the engine, the cam, the heads(ported and polished etc.), and the diameter of the carb bore. Each one of these will change the requirement of air/gas mixture. The math in the book should help to get you in the right ball park.

That is my two bits
Thanks to Pelican for letting us speak out

Conrad

Oh yeah, get the 050 distributor.

[This message has been edited by Conrad W Peden (edited 09-01-1999).]
Old 09-01-1999, 12:43 PM
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What is happening sounds like the typical Weber carb set-up that wasn't meant for that car. What I mean is that unless you have a 911 or Ferrari, etc. that came off the assembly line with webers it is difficult to get them running properly. Typiclally Webers work in two positions idle and all the way open.(or so I've heard. I use Dellorto's.) To make them more drivable the jetting is the is the sore spot. If the carbs came from an identical engine and were already jetted properly then ok. But the likelyhood of taking any set of carbs out of the box, bolting them on and expeting them to be "right" with some adjustments with a screw driver is pretty slim.

I went through five sets of jets for my Dellortos before I got the "right" set-up. I mean the drivablity that I was looking for, even now it isnt real good but I like it.

So there you go, it still might pop and fart when warming up but if you get the jets checked out you will find that it makes a huge difference in the way the engine winds up under a heavy foot.

If you have the Weber book it should tell you how to "estimate" which are the right jets for your car. You have to take into account the displacement of the engine, the cam, the heads(ported and polished etc.), and the diameter of the carb bore. Each one of these will change the requirement of air/gas mixture. The math in the book should help to get you in the right ball park.

That is my two bits
Thanks to Pelican for letting us speak out

Conrad
Old 09-01-1999, 12:44 PM
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In answer to your question I have a stock distributor. The webers were installed because in 86 if your FI brain went T.U thats what they did. The car runs GREAT, I don't know about the jets but it intrigues me that
Conrad says the car will rev better with the appropriate jets. If it runs great then I would think the jetting is pretty close ?.
Could someone talk about the 050 and why it's better than stock. This must be the multiple question thread...thanks
Old 09-01-1999, 01:35 PM
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In my small experience with carburetors(or however it is spelled), you need to change the distributor to get the proper performance. The reason being is that the timing on the engine changes as the engine revs up. With the 050, you don't use suction for the advance...instead it is advanced mechanically. If you have the stock distributor and it isn't hooked up, then it does not advance.

Not sure what the difference between the 050 and the 009 is though.

Paul
Old 09-01-1999, 02:52 PM
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What I mean about the jetting is that at different revs the engine needs different amouts of gas and air. Jets that are good at cruising [say 2000 to 3000] may not provide enough gas at 4500rpm. If you are agressive you will want the carbs to work their best between 3500 and 5500. And so on
Old 09-01-1999, 03:00 PM
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As Conrad said, the jets change the amount of fuel going into the intake air under various circumstances. There are main jets (used at WOT and down to maybe 1/3 throttle), idle jets (used at idle and up to maybe 1/2 throttle), Emulsion Tubes (no clue), Air Correction Jets (no clue), as well as the venturis and accelerator pumps.

All of these things have to be set up correctly for your car. The easiest way to do that is to find someone who has the same motor as you and copy their setup. The most common way is to get a whole bunch of parts and start swapping until you find a setup you like.

Several of the people on the 914 Rennlist have setups they like. Personally, I think carbs are the next best thing to "black magic", and I prefer the FI setups.

The stock distributor works pretty well, even without the vaccuum advance hooked up. It has a fair amount of centrifugal advance built in (~22 degrees on the D-jet cars), and many of the 74+ cars did not have the vacc advance when they came out of the factory! According to rumor, the 009 only has about 12 degrees of advance built in, rather than 22. You can have it re-curved, but that costs...

It is tough to install vacc advance on carbs or on an FI setup that didn't have it in the first place. The distributor dashpot is simple enough, just hook up the fitting that points away from the distributor body. But you have to get a vaccuum "signal" that goes pretty high when the engine is at part-throttle. The FI does this by putting the advance fitting just above the closed position of the throttle plate, and letting the venturi effect of the air going past a small throttle valve opening (this is part-throttle, right?) create a very high vaccuum.

It's easier to hook up vacc retard for a low, clean idle. You have to tap into the vaccuum in the manifold--anywhere below the throttle plate will do. Some carbs have little air passages built in for this, some don't. Adding one to a carb or manifold that doesn't already have it is a pain, but not as big a pain as adding the vacc advance.

The 050 distributor and the stock 1.8 distributor seem to be good ones for carbed 914 motors. They have more centrifugal advance built in than the 009, and the 1.8 has more than the stock distributor. If you can hook up the vacc retard function, then you can have a lot of advance while still keeping a nice low idle.

--DD
Old 09-01-1999, 06:00 PM
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Cheap and Dirty...

You say you have a 009 in the box. If you don't plan on returning it for a 050 then maybe you should just pop it in, and see what happens. If the car gets better, than a 050 will improve things further.

Even easier (like you said) would be to hook up the present dizzy to some vaccuum. Ummmm-ahhh, duh, I dunno. Not sure if your Webbers have vac ports, don't think hooking the dizzy up to only one would work either. The 32/36 Webber has a vac port that works O.K. so maybe see if the duels have one also. If not MAYBE (this is a guess) try taping into the intake manifolds below the carbs, "tee" the two lines together and use a vac gauge to see what kind of readings you get, or just hook it up and see what happens.

The only problem I see is if the PO advanced the base timing to try and compensate for the lack of an advance mechanism, you may "ping" (detonation) when you hook up the advance properly. If this happens take some on the base ignition out.

The point about jetting is indeed a valid one, you may be jetted for high RPM, but if the dizzy you have now has no vac line on it I think that is your main problem. Even rejetting it won't cure the bog caused by a lack of timing advance.

The difference between a 009 and 050 is proabably the "advance curve". This is the relationship between engine RPM and timing advance. "Re-curving" a dizzy is possible, but expensive. I think people prefer the 050 because the curve matches a 914 motor better than the 009 (I beleive the 009 is for the Type-I motor, and may even have a slight #3 retard to help cool Type-I motors hot #3 problem, whole-nuther-story)
Old 09-01-1999, 06:06 PM
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I had the exact same set up you described. The builder put in an 009 and I had a horrible time timing the car. It was either pinging at lower RPM's and fast as heck at high revs, or it ran like a bug - ie. no power. We installed a factory 2.0 distributor, opened one of the vaccume ports on the passenger side carb (webber 40's), and it runs unbelievable. It isn't perfect off the line until it is warmed up, but once up to temp it is as smooth as can be and pulls very hard all the way to redline. I am VERY pleased.I have heard many times that the 009 advances quicker, but doesn't have the range required to run correctly. I have also heard of some poor quality issues.
Good Luck,
Scott S
Old 09-02-1999, 07:02 AM
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Scott,

Do you know what your jetting is, exactly ?

I want to build an engine like yours next winter, 2.1 L with Weber 40s and I'm not missing a chance to learn about carbs. I'm barely getting familiar about the D-jet, now I'm gonna have learn more . . . is'nt that what we're in this for ?

Cheers

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Old 09-02-1999, 10:32 AM
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We fussed with it for along time and ended up using the original jets that were supplied in the kit. However, My home is at almost 7000 feet above sea level, so your setting will most likely be different.
-Scott S
Old 09-02-1999, 02:04 PM
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I have a 1.8L w/ Weber 40,s and a mild cam . I used the jets it came with and it ran ok but it didnt have any low end power and poor throttle response.I bought a Supertrap mufler, the small one , for $105.00 , it made a big difference . The engine must have been lean because the extra back presure was just what it needed.You can add or remove rings to get what you want but you got to get the jetting close first. It has a cheap old .009 Tiawan dist w/ crain ign and works good , maybe I will try a .050
Old 09-03-1999, 12:10 PM
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I have a 74 2.0 that the PO reworked to 2.1, autocross cam, Webers and a 009 distributor. When I got the car it was hard to start, particularly in the winter, Philadelphia PA area, and popped and wheezed in the low and mid ranges. I checked with several Weber distributors on recommendations forv rejetting, andthey all said I should go to a CD multispark ignition before trying to rejet. Put in a Pertronics unit (I've been following the recent posts here and on the Rennlist, no problems for about 5 years) and then added a Crane HI-6, PS-91 coil, helicore wires, and opened the plugs to 0.045". This made an amazing difference in the car. Easier starting and less surge and wheeze. Even starts almost immediately on 30 degree mornings, there is a ritual, but it fires right off. I did eventually change the jets a bit, now 0.45 idle and 1.20 main. Did not change the venturies (28 mm) the emulsion tubes (f11) or the air correction jets (2.00) I've found the Weber books by HP Books, CB Technical Department, and Haynes all helpful. Much of the material is repeated, but reading the slightly different interpertations and presentations made things a bit easier to understand. I understand that Weber used to have very good pubs available for all of their carbs, but I haven't been able to find any yet. Hope this info helps you.
Harvey

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Harvey
Old 09-04-1999, 05:48 PM
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