PITA - Single Weber

[James_Douglas]

After days of trying, I cannot get the new DGV (Manual choke) Weber progressive 2-BBL to run correct on my 251 flathead.

I have been playing with the idle jet, main jet, and air correction jet. I am starting to think that a single weber cannot be set up to match a 251 cubic inch engine that was designed to idle at 450-550 RPM.

Setting the Weber at the required settings for mixture screw (2 turns max) and throttle blade position (1.5 turns out max), I cannot find a combination of jets and air bleeds that will allow the engine to idle.

If I open up the air bleed and then up the jet size to match, it runs too rich.

If ANYBODY is running one of the Holley or Carter Weber Clones, would you please tell me what size jets you are using.

Best, James

[greg g]

Is this a weber that is a progressive 2bbl with a small primary throttle bore and a larger secondary??? Not personally familiar with the webber deal but a lot of folks ran them on four cylinder cars back in the 70's and 80's. Opels, Alfas, Toyotas and Datsuns, and others of that period. I recall a fellow trying to run one on a 240 Z and not having any luck with it. The prmary throttle bore was too small for low rpms, and the secondary was barely large enough to feed that 2.4 litre.

Just thinking any of these that was designed to run as a single on a 4 or as duals with 3 liter 6's are going to be to small for your 4 liter 6. If its sitting on an adapter maybe try a holley or carter 2bbl from a small v8. Holleys have some adjustability and are easy to change jets on and sized maybe more to your engines liking.

[James_Douglas]

Greg,

I am thinking that a single one is just too small for a 4.2L engine. I have a couple of emails out to some "experts" and it will be interesting to see what I get back.

I have my Edmund's duel 1BBL manifold. I may have to just get another one and do the blueskies thing...

James

[James_Douglas]

After talking with the weber experts, the consensus is that on a 4L engine a single weber DGV may not have enough venturi area on the primary side alone to properly tune the carburetor to the engine.

They recommend installing a synchronous kit which will open the secondary and primary together.

Given that the guys running the duel carbs have both primary venturi's running at idle and having success with that, this makes some sense.

They are shipping me up the linkage to make the change and I will report on what happens. I do have the Edmond's Duel manifold and I could run twp progressive duel carbs if need be.

Best, James

[BeBop138]

After talking with the weber experts, the consensus is that on a 4L engine a single weber DGV may not have enough venturi area on the primary side alone to properly tune the carburetor to the engine.

They recommend installing a synchronous kit which will open the secondary and primary together.

Given that the guys running the duel carbs have both primary venturi's running at idle and having success with that, this makes some sense.

They are shipping me up the linkage to make the change and I will report on what happens. I do have the Edmond's Duel manifold and I could run twp progressive duel carbs if need be.

Best, James

James do you have the part# for that kit---I will be running two of these and if more fuel is needed with the cam I will be using I may need to put these on my carbs.....Lee

[James_Douglas]

It will show up tomorrow and then I will have the part number. That said, I doubt that you will need it if you are running 2 carbs. The problem at is that the weber 32/36 carb design is apparently for engines up to about 2500CC. Since out flatheads are around 4000CC, a single carb using PROGRESSIVE linkage is just too small to get it jetted correctly at idle. Remember that the webers use the idle circuit up to about 2200 RPM.

In the case of two of these carbs the normal jetting procedure should work just fine.

James

[Don Coatney]

James;

Let me know if you still want me to disassemble a carburetor and send you numbers next week. Sounds like you have already figgured out the problem.

[James_Douglas]

Don,

Time will tell. The synchronous kit is due in tomorrow. If it does not work then I may pony up and buy a second carb and use the Edmond's manifold.

I can tell you that between 1800 ans 2200 RPM with no load the engine runs smoother than with the Carter.

I will keep you posted. In any event, it would be interesting to see how the clones are jetted. I know Pete has had good luck with his set up and I would be curious as to what all his jet specifications are.

Best, James

[Don Coatney]

James;

How can you tell your engine runs smoother between 1800 ans 2200 RPM?

[James_Douglas]

With the Carter there was en ever so subtle miss in that RPM range. Driving under a load you could not feel it, but sitting still without a load you could feel it and hear it.

I have four carters that I have rebuilt, all to the same specifications, and they all work a little different. One has the miss between 1800 and 2200. Another has a stumble on WAT off of an idle. Yet another has a part throttle bog on mid-throttle high load situations like going up a short hill.

I think that the internals of the carburetors, the small passages, of the Carters have varying amounts of wear from over the years. Carbon that will not come out and/or lead that opened up some of the passages over time.

That is the only thing I can come up with to explain the differences.

In the middle RPM range with the Weber, the engine sounds and feels dead steady. I am sitting here waiting for the sync kit to see if that will take car of the idle issue with the weber.

I have to say that I like very much the mechanical installation aspect of a single weber. It is a very clean and easy installation. One friend thinks that it would be easy to re-work a stock air-cleaner so you would almost not see the carb at all. Interesting thought.

Best, James

PS, Where are you this week. I was thinking of you when I saw a 60 Minutes interview with the Fed Chairman and they showed the robotic fork lifts running large amounts of $$$ at a time down a hallway.

[hkestes41]

It will show up tomorrow and then I will have the part number. That said, I doubt that you will need it if you are running 2 carbs.

James, I agree 100%. I am running dual Carter/Webers and Offenhauser intake on my 0.060 over 218. I think they are running just a hair on the rich side but it is a very slim hair so I haven't done anything to correct it.

[martybose]

James, I agree 100%. I am running dual Carter/Webers and Offenhauser intake on my 0.060 over 218. I think they are running just a hair on the rich side but it is a very slim hair so I haven't done anything to correct it.

Interesting. I've pretty much convinced myself that my Carter-Webers are a bit lean just off idle, as my car pings during light throttle acceleration, but quiets down (pinging wise, anyway!) if I put my foot in enough to get into the secondaries or the power valves.

It's really interesting if you are accelerating hard and slowly lift the throttle, as just before I get down to the throttle opening to sustain a constant speed I will get a burst of pinging.

I'm buying a book on Weber jetting theory this weekend to start pondering changes.

Marty

[James_Douglas]

Ok,

The sync kit showed up and I installed it. Idle now actually works. I ran it around the block a couple of times and it runs very strong. Better than the Carter.

I have not made any other changes to the engine.

The only problem is I can kill the engine if I go to WOT from a dead stop.

I will start to trace that problem down in the morning.

Driving down the street and then hitting the throttle hard makes the thing jump up very smartly. A noticeable thing on the 9 passenger suburban.

I have yet to take it on a freeway run to see how it work at high speed.

If I can solve the WOT problem from a dead stop this carburetor will work well. Now the question is what will happen to my gas mileage. I was getting around 14-16 around town and 17-19 on long freeway runs with the Carter.

I will keep folks updated and once I get it dialed in, I will provide specifications.

Best, James

[Don Coatney]

Interesting. I've pretty much convinced myself that my Carter-Webers are a bit lean just off idle, as my car pings during light throttle acceleration, but quiets down (pinging wise, anyway!) if I put my foot in enough to get into the secondaries or the power valves.

It's really interesting if you are accelerating hard and slowly lift the throttle, as just before I get down to the throttle opening to sustain a constant speed I will get a burst of pinging.

I'm buying a book on Weber jetting theory this weekend to start pondering changes.

Marty

Marty;

I would think the pinging is timing related and not carburetor related. I still dont understand how your engine runs well the way you have your distributor set-up with the mechanical advance disabled and the vacuum advance connected to the manifold not the carburetor port.

[kencombs]

Marty, on the pinging issue: I'd put my money on timing also. With the vacuum advance connected to the manifold I think this is what's happening from your description:

With wide open throttle you have NO advance because of the low vacuum signal. But as you back off the throttle and the vacuum rises the advance comes into play causing the pinging.

[greg g]

remember were are talking a GM style Distributor. (with the Lagdon deal) Do they not work differently than the mopar style, isn't vacuum actually a retarding influence with the GM set up. Low vacuum allows the centrifigul advance to go balls to the wall, then the return of vacuum pulls it back to "normal" as less power is being called for. I remember tha when drag racers used to run with out vacuum on GM cars, theory was that the total run was WOT and the timing should be fully adaanced for the entire run. Not lok mopar where ported vacuum actually anticiptes and advances timing based on an increased vacuum signal.

Or am I sucking wind here???

[Don Coatney]

Greg;

You may be correct. I have sucked wind many times before...

[James_Douglas]

Today I played with the Weber configuration more. I now have the car so that is will accelerate from a dead stop with WAT.

It is a little slow on the WAT acceleration, but the Carter was the same to about 10 MPH. Remember I have a fluid coupling so it is a high load WAT from idle.

It appears that the weber is VERY sensitive to float level. A few MM do make a difference.

Currently the settings are:

Weber DGV 32/36 with Synchronous barrels and manual choke.

-------------------------Primary -- Secondary

idle/progressive circuit: #60 -- #60

main circuit: -----------#150 -- #155

Main Circuit Air Bleed: -#160 -- # 165

Accelerator jet (Duel) -#60

Float level (Plastic float) is 51MM open and 33MM closed (35 is standard). This is WITH the gasket on the horn.

I am having a number 70 Accelerator jet shipped up. If that does not do it, then I may have to DRILL A PROGRESSIVE PORT TO THE MAIN VENTURI to extend the progressive circuit a little more up the RPM range.

I will keep people posted.

James

[martybose]

Marty, on the pinging issue: I'd put my money on timing also. With the vacuum advance connected to the manifold I think this is what's happening from your description:

With wide open throttle you have NO advance because of the low vacuum signal. But as you back off the throttle and the vacuum rises the advance comes into play causing the pinging.

I hear what you (and Don) are saying, but I don't think so. Right now I am running 2 degrees static and only 13 degrees total with vacuum. Ironically, I think part of my problem is my 9 to 1 compression and my mildest of 3 grinds cam. If I had gotten a longer duration cam it would have bled off a little more compression.

I could be all wet on this, but I'm pursuing the carb tuning angle anyway. If it turns out I'm wrong, I'll fess up.

Marty

[bts_dodge49]

Just wondered how James Douglas made out with his Holley Weber? I'm trying to use the same carb on a 230 CI and running into similar issues. James, did you scrap it and go with 2 webers, or did you find the single sufficient?

Thanks,

Todd

[TodFitch]

Just wondered how James Douglas made out with his Holley Weber? I'm trying to use the same carb on a 230 CI and running into similar issues. James, did you scrap it and go with 2 webers, or did you find the single sufficient?

Thanks,

Todd

Guess I'll have to start signing my posts with "Tod from the old forum"....

[james curl]

On a Cheverolet V8 you disconnedt the vacuum to set the timing. Most 350 cu in engines set the timing at TDC,4 degrees or 6 degrees before tdc with the vacuum disconnected. If the vacuum retarded the ingition when connected then some would be running ATC which I think would not be to good.

[Plymouthy Adams]

in most cases your cam duration would have to be at or exceed 290 degrees for the the overlap to lessen you compression..