Weber tuning frustration

I've owned my Pantera for 39 years and every year or two I strap on my original Webers, but after a few months of struggling I go back to the trusty Holly. I cant seem to get them balanced. With all settings the same one side of the exhaust runs cold the other side hot. without going into things I've tried to alleviate the problem, do you have suggestions?
I dismantled and cleaned all carbs.

Attachments

Photos (1)
Original Post
quote:
Originally posted by PanteraDoug:
I would suspect the linkage. What does yours look like?


The carbs are not hooked together yet, so far each carb is set up individually, independent of the others. they are pulling the same CFM. the cool bank on the right does not appear to respond to adjustments as the hot left bank.
The flow at idle on these carbs is so delicate, that you balance that flow with this device.

You sit it on top of the velocity stack, then equalize the calibration with them with the ball that floats in the glass tube.

Weber carbs have soft brass throttle shafts. Ham handed throttle construction can very often twist them.

Once they are twisted you will have un-equal flows from one throttle plate to another in the same carb. That makes it impossible to sync the carbs.

This sync device will help you determine that.



Weber linkage has to be VERY light basically relying on the throttle return springs built into the carbs themselves.

Many linkage set ups that I have seen require too many additional return springs to zero the linkage.

The return springs go on the center linkage pivot, not the carb throttle levers.

The Pantera linkage is unique to the car itself. Generally speaking you HAVE to use the center tower to make it work.



The side loading linkage that Inglese has are really for the Mustang. It is not going to work properly in a Pantera and likely will result in you twisting up the carb throttle shafts.

Believe or disbelieve but I'm the one who did the initial jetting setup on the Clevelands for Jim, with his parts, but it was me. Circa 1978.

This was all proprietary information then and no one was sharing jetting info on the carbs for this set up. You had to figure it out for yourself.



At the time, the set up was in my 68GT350 and had to use his design for the side loading linkage. Carbs had to be parallel rather then opposed as in the Pantera manifold design.

When it, mine, was transposed to my Pantera, all it would do is jamb open and not return to zero. That linkage design became useless.



The original Pantera Weber design was done by Holman-Moody for Ford and GIVEN to Detomaso.
The center tower is there for a reason. Yon NEED to use it.

Change the throttle design at your own peril. It's your car and you of course can do anything that you want to but it isn't easy being completely on your own. Because of the location of the engine the access to the set up is difficult. You don't want to endlessly be messing with it.



All I can say is that it was my observation that Jim couldn't make it work and went to the side loading.

The only Pantera that I ever personally seen him set up was Andy Carr's back in 1980 or so. He was having problems with the linkage on that car.

I know because I was riding as a passenger in it when he locked up the throttle and spun it on an entrance ramp to RT95 in CT. It was right after a snow storm and there were snow banks along the roadside.

There was no rear deck lid on the car with open stacks, no screens. No Weber cam. Carbs fuming atomized fuel like a volcano. Big Grin

First time I ever heard the valves float on a Cleveland. That was fun. Yikes!

Glad it wasn't my car. Big Grin


You have three choices now. 1) work it out yourself 2) pay someone to fix this for you 3) take my info for free.

I'm not an unlicensed MD. I don't right prescriptions. I share my experiences with others. This is not "theory". You can take it for what it's worth or ignore it completely.

"Frankly Scarlett, I don't give a dam", so to speak? Cool


I did my center linkage like this. The benefit is that it doesn't pull on the carbs themselves, just is the secondary return spring tracks require.

The throttle pedal is very light. Feels more like an electronic throttle.

I hope it helps.

Attachments

Photos (1)
To balance idle depressions on Weber, the most practical tool is a board with mercury columns. It makes it possible to see all the barrels together for a 4 cylinders engine or at least a complete bench for an 8 cylinders which is very practical because when we tune a barrel it affects all the others because the speed of the engine varies

I made one 40 years ago and I still use it.

Thank you for the additional advice. I did use a sync tool and the CFM reads nearly identical. but I will dial it in better. However the difference in the two sides appears larger. Maybe that small difference is the key. I can feel the header tubes and they are not identical temperature as they heat up after starting. More fussing will follow. I like the challenge, but will pull in a third party if all else fails.
thanks for all the input, it's half the fun of trying to go it alone. I am getting closer, the heat of the header tubes gives me some fuel delivery information, however now I'm still running too rich which runs contrary to the basic tuning settings I found in various locations. Unscrewing the needle valves by 1+1/2 to 2 turns as a base setting appears way out.
Hi Tom, I've seen the 'hot/cold' issue before, although with individual cylinders, not the entire bank. At least on my setup, minor adjustments to the idle mixture screw at the base of the carb can bring a cylinder with 'cold' exhaust to idle properly. (There are of course eight - one per cyl - and none end up in the exact same position; I must dial-in each cyl individually to give maximum revs at idle at a given throttle setting. As they get dialed in, engine idle rises, so the throttle setting for all carbs must be reduced collectively to a normal idle speed.

I use a homemade extender to reach the screws (pic 2) - small nail in an aluminum tube - on my obscured LH carbs. RH is easy w/ this side-pull 'reversed' setup. On your car clearly no adjustment screws are easy to reachSmiler

If your carbs are not linked together that complicates the above idle adjustment...I guess you could throttle an individual carb back down once 'best' idle mixture settings are found, but then the sync setting is messed up again. I would connect the linkage, sync all carbs (ideally with a setup like Rene's), THEN adjust idle mixture.

The only other thing that came to mind was fuel pressure. I know everyone says you need c. 3 psi for Webers but I have accidently run 8-10 at times due to a hair-trigger Filter King pressure limiter, and the engine doesn't seem to care much(!). So maybe it's not a HUGE deal but surely best to run c. 3-3.5 psi.

Please let me know if you know of a Weber expert in our area, I'd like to have my system evaluated at some point, once everything else on the car is good to go....

Attachments

Photos (1)
Sorry just now saw your comments re. mixture. Agree 1.5 - 2 turns sounds like a lot - - THINKING mine are generally around 1 turn out. Whatever the case the difference of 1/4 turn away from exact 'best' idle setting seems to be enough to shut down idle on that cyl.
To synchronize depressions the procedure is as follows:
- close ALL air-screws completely and adjust the linkage so that all carburetors are just completely closed.
- screw the general idle-screw so that the engine can just idle
- Carburetor per carburetor, open the air-screw of the barrel which has the greatest depression until the two depressions are the same.
- Adjust the linkage between the two carburetors of each bank of cylinders to obtain the same depression on the four barrels. It may be necessary to retouch the air-screws but always acting on the same screw
- adjust the linkage between the two banks of cylinders. Again it may be necessary to retouch the linkage between the two carburetors of a bank and possibly air-screws
- after each adjustment, give a short throttle and let the engine come back to idle then adjust the speed of the engine with the idle-screw


At the end, each of the four carburetors must have one of its two air-screws fully closed.

Then adjust the richness of each barrel with the gas-screw to obtain the highest engine speed but on an 8 cylinders, it is necessary to have a very fine ear or a lot of experiment, from where the utility of lambda probes.

I installed lambda probe nuts on the exhaust of each cylinder of my Westfield (2 liters Opel 4 cylinders engine with two Weber 45 DCOE) and I confirm that 1/8 turns on the gas-screw makes the lambda vary significantly. It's a very fine tunning.

I do not know in the US but in France there are almost no mechanics who still able to do that, the good repairers of motorcycles, when they agree to work on a car, know how to do.

It is already long to properly synchronize a four-cylinders, I do not imagine what it is for an 8. Good courage.
quote:
Originally posted by René #4406:
To synchronize depressions the procedure is as follows:
- close ALL air-screws completely and adjust the linkage so that all carburetors are just completely closed.
- screw the general idle-screw so that the engine can just idle
- Carburetor per carburetor, open the air-screw of the barrel which has the greatest depression until the two depressions are the same.
- Adjust the linkage between the two carburetors of each bank of cylinders to obtain the same depression on the four barrels. It may be necessary to retouch the air-screws but always acting on the same screw
- adjust the linkage between the two banks of cylinders. Again it may be necessary to retouch the linkage between the two carburetors of a bank and possibly air-screws
- after each adjustment, give a short throttle and let the engine come back to idle then adjust the speed of the engine with the idle-screw


At the end, each of the four carburetors must have one of its two air-screws fully closed.

Then adjust the richness of each barrel with the gas-screw to obtain the highest engine speed but on an 8 cylinders, it is necessary to have a very fine ear or a lot of experiment, from where the utility of lambda probes.

I do not know in the US but in France there are almost no mechanics who still able to do that, the good repairers of motorcycles, when they agree to work on a car, know how to do.

It is already long to properly synchronize a four-cylinders, I do not imagine what it is for an 8. Good courage.


On 48IDA's it is unusual to be able to get all 8 cylinders to idle equally.

You can't even get the same carbs equal. Once cylinder usually will be higher then the other.

You need to experiment to see if the dominant cylinder on each carb is the higher or the lower setting,

For me it normally works out to be no more then one gradation mark on the sync tool.

Then it is balancing back and forth until you have them close.


The plugs should be a dark brown. Some describe that as a rust color. They should not be black.

On my engine, the idle set screw vary slightly from cylinder to cylinder but are in the 5/8 to 3/4 turn out.


It's very common to foul a set of plugs up while doing this. In fact, maybe two.

I have found that with the ida's, the ignition likes a slightly hotter plug but also remember that I am using different cylinder heads. Aluminum, not iron.

They have different requirements.


Also, in case you have not already discovered it, the engine likes an idle jetting of .60f/.85a.

Depending on the camshaft configuration, you may also be able to lean that out to a .90 idle holder.

For a long time, the only idle jetting available was a .70f/1.20air (idle jet holder). The seemingly sudden availability of small air jet holders made leaning down the idle possible along with adding a third transfer hole to reduce the transfer flat spot.


Forget about trying to get a lean idle with the carbs. About 12.5-12.0:1 at idle is as lean as you can go without the carbs popping through the exhausts at idle.


You HAVE to install the linkage before you do any of this and you are going to need to work back and forth from the idle screws to the linkage to zero it.

This isn't easy AND if your linkage does not have the right geometry, once you drive the car, the idle will be all wrong again.


The set up of Nate's car is using Inglese's re-orientation plates. That was Jim's solution to removing the over/under linkage working off of the center turnbuckle and tower.

It worked on my '68GT350, but not on my Pantera. My Pantera I could only make work with the center tower.

The ONLY reason that you use those reversing plates is to simplify the linkage.



When you reverse the one bank of carbs to put them all in parallel throttle positions, you loose power in the engine because you loose line of sight from the throttle to the intake valve.

How much I can't say scientifically because I never dynoed all of these possible combinations but I can feel the difference as a driver.

I would SUSPECT something like 25hp loss or the difference of running a Holley carb with a factory air cleaner or an open carb.



Mine idle now at 775rpm, with 15 degrees initial advance and a non Weber camshaft with 245 degrees duration @ .050 and 72 degrees of overlap.

You will also see the idle vacuum change as you make these changes and adjustments. I can only get about 11.5-12 inches at this idle speed. More if I idle up. Probably 14 at about 1,000 rpm?

I don't worry about that any more since I put a vacuum pump in the car and that gives like 18-20 inches for the vacuum accessories.



So it is possible to get them "civil" (depending on your definition), it just takes a lot of patience and as I remember about 2 weeks of work to get it right.

I remember Inglese making the final comment to me on the Shelby, "if you think they are right now (or you are happy with them) LEAVE THEM ALONE!"



I don't see how you can save all of the settings when you take them off of the car. You are going to have to go through this every time you reinstall them. Settings are so sensitive that just one bump in disassembly changes things.

Others I am sure have different experiences? These are just some of mine and solely intended to save you some of the pain. However, if you are into pain and love the challenge, challenge away! Have fun.



Oh...I have found that the P-E iginition is a gift from "Heaven" with the Webers. If will fire and clean up a completely fouled plug. NO other system will do that. Not the Ford or the MSD.

In fact, it was the MSD that kept failing and wouldn't start the car after sessions of "Weber tuning". That just compounded the issues and made it near impossible to determine where the problem was.
There is a vacuum outlet on each body of each carburetor.

Yes, it's better with 8 columns than with 4 but we can do the two benches one by one and balance them after.

Anyway Panteradoug is absolutely right, it is very difficult to get exactly the same depression everywhere, especially as it always moves a little bit and I'm happy when I arrive at a difference of less than 5mm of mercury on a 4 cylinders, then on a 8 ...................
quote:
Originally posted by Marlin Jack:
...One more question, Please. Trying to stay on topic.

You say 8 vacuum ports.
Are ALL 8 Ports Connected Together at a 'union' of One (1), permanently, as the Engine is being Run?
and would this 'Help' to 'Balance Out' the Carbs?

Thanks.

MJ


No, when the motor runs the 8 ports are closed.
This was answering MarlinJacks question about the vacuum plumbing.

One MY CAR, each runner is plumbed to a common plenum. A vacuum plenum. This is how I did it. Other variations are possible.

You can't tune each cylinder for vacuum. Not practically anyway. You use the sync tool to balance (as closely as you can) the flow at idle.

Nate mentioned fuel pressure also. If it means anything to anyone, the factory Cobra "Team" cars running Webers used no fuel pressure regulator.

They were plumbed to a fuel plenum directly running from the fuel pump at 7 psi. I don't know if they were using the current glass ball valves liked used now. PROBABLY not but some of that is proprietary information that has been lost over the years.


The glass ball valves are also referred to as "the high pressure valves". They will let you run higher pressure safely and are needed to stop the carbs from flooding the intake when you shut the engine off and it is hot, peculating the fuel and overcoming the ability of the float to close the valves.

The heat tends to boil the fuel out of the bowls and it floods directly into the intake manifold.

If you were to try to start the car under that condition you would create a flaming volcano. Ask me how I know? Wink

Attachments

Photos (1)
quote:
Originally posted by Tom Kuester:
thanks for all the input, it's half the fun of trying to go it alone. I am getting closer, the heat of the header tubes gives me some fuel delivery information, however now I'm still running too rich which runs contrary to the basic tuning settings I found in various locations. Unscrewing the needle valves by 1+1/2 to 2 turns as a base setting appears way out.


You need to pull out the plugs and read them. They may be completely fouled on the cool tubes and that's the reason for the rich mixtures and cold tubes.

Don't try to get too scientific with these carbs. It just doesn't work.

It really isn't the carbs themselves, it's the IR manifold characteristics. They are not for novices or for people with little time.

Like I said, figure about 2 weeks, working day and night, with just breaks for your bodily functions. Pit stops we call them.

Also, don't tune them inside of the garage. You will never get the fuel fumes out. It will stick to everything like a skunk sprayed the place. Outside only.
quote:
Originally posted by PanteraDoug:

You need to pull out the plugs and read them. They may be completely fouled on the cool tubes and that's the reason for the rich mixtures and cold tubes.

Don't try to get too scientific with these carbs. It just doesn't work.

It really isn't the carbs themselves, it's the IR manifold characteristics. They are not for novices or for people with little time.

Like I said, figure about 2 weeks, working day and night, with just breaks for your bodily functions. Pit stops we call them.



I totally agree and if I'm certainly not an experienced man, I'm not quite a novice anymore, I've only tuned a few 4-cylinders engines over the past 40 years that did not work "too badly" , I do not say "good".
FWIW, when I was fooling with Weber carbs decades ago, I found that joining all the intake spuds together with nice hard AN lines produced zero total vacuum. Using one line to any intake and adding a 15" long RUBBER hose produced consistent enough vacuum to activate distributor vac. advance. Using a single hard line gave zero readings again- apparently the rubber damps the extreme vac/pressure pulses in the intakes.

Tuning is vital- most Weber system either produce 12 mpg and good power, or 16-20 mpg and no power. Getting the best of both requires much fiddling. Fuel pressure seems irrelevant to good running. Do NOT use ANY kind of foam air cleaners: Webers meter fuel into airflow going in both directions so the strong pulses produce a cloud of stand-off fuel-air above each carb throat. This soaks into foam air cleaners, then a cold-start backfire can catch the soaked foam on fire. ONE carb should have a Weber-built startup attachment in place of a choke.

Also, many Weber carbs have been sitting in storage for years or decades, which dries out gaskets, o-rings and seals even on carbs that have never has gasoline in them. So NOS carbs may leak profusely on start-up and need complete rebuilding. It's things like this that give Webers a bad name & try one's patience.
There isn't anyone that I know of that has comprehensive scientific data on the vacuum situation with a specific set up in the Pantera.

What we have is a independent runner manifold. It has no common plenum and it gets set up as such.

I think it is safe to speculate that it came to be for racing purposes and that it is doubtful that an engine generated vacuum source was a significant consideration.


When I got my first manifold from Gary Hall in about 1978, it had one port drilled and threaded into the #8 runner on the manifold.

As I remember, it was a 3/8npt port. When I asked Gary, he said, "oh yea, that's where you connect the vacuum hose for the power brakes. The vacuum from one runner is enough."

We all are stating our own experiences with this system. I as well as others have noticed that there seems to be noticeable differences in results and issues. I am not criticizing others experiences. I'm comparing notes, so to speak?


Halls solution didn't work for me. That first set up was in my 68 GT350 and if I tell you that I was walking the high wire without a net by myself, that is an understatement.

I plugged the thing and went on to making it run on the car.

That set up eventually got traded away when I went back to the original 302 in that car...sort of...but that's an entirely different story and not for now.


Webers can be an addiction. Maybe more accurately an infection like Malaria. You think you are over it, then out of nowhere, you get a reoccurrence?

Well, my way of dealing with that was to install them on my Pantera.


The difference was that no longer was I using the iron 4v heads, now I had these nice race car set up A3 aluminum heads. The fever was getting worse.

So back to Hall for a manifold. This time with no predrilled vacuum ports.



Yada, yada, yada. Fast forward. I need engine vacuum connections.

So here's the thing, not lots of room for intricate vacuum plumbing. Halls design didn't work. Wouldn't it be great to have a vacuum gauge in the car to add more info to exactly WTF was going on back there? Sure.


This is an IR manifold. Carbs are calibrated (tuned) to operate under IR conditions. Question: how large do the vacuum lines need to be from runner to runner BEFORE they become balance tubes and create a central plenum in the manifold?

Answer: no one knows.


Question: what happens if too large a tube system is installed?
Answer: you probably screwed up the entire physics of the design and will have no choice then to go back to where you started. This is 2300cfm of carbs. You can't use that much on a center plenum manifold.
At SOME UNKNOWN POINT connecting the runners together convert the manifold into a center plenum manifold. Who finances that experiment? You only get two weeks for vacation. Don't you want to go to the beach?


Question: what happens to the holes that you drilled into the manifold for the larger fittings?
Answer: weld them up or get another new manifold. They're only $900.



All I can say is that my vacuum tube system works for attaching a vacuum gauge. Works great.

Does it supply enough vacuum to work the brakes?
Answer: no.

Solution: rather then destroy the manifold, screw that idea and just go to a vacuum pump.
Answer: done. Pump is noisy but gets lost in the noise of the solid lifter cam and 180 headers. No one notices it.


Air cleaners: I'm not sure if even with a "Weber" cam, if it is safe to run any kind of an air filter over these volcanoes?

The picture I posted is of lets say "the pre-installation engineering study". Yea, that's it. That's what I'll call it. Wink


MPG: Well this is a little difficult to nail down scientifically. For one thing, it is as difficult to keep your foot out of the accelerator as it is for Dr.Strangelove to control his repatriated right hand.

In my experience, with a 140f/160a F5 with .70/1.20 idle and 42mm chokes (auxiliary venturi) expect about 17 mpg beating the thing like you stole it, about 22 on a long cruise like to a Shelby Convention about 15 hours away.

By comparison, the Holley 4179, 750cfm "double-pumper" is as rich at idle as the Webers are, and never got more then about 12. Mileage is relative to what you expect out of all the parameters.



ONE little detail that I absolutely stumbled across that is a big factor is that the fuel cloud at WOT "hovers" over the stock height stack.

IF you extend those stacks to 5" high, the vapor cloud stays within the stacks. The Pantera is one of the few cars that can be done on and still be within the "engine confines".


IF you look at period photos of any of the Grp4 factory cars, you will notice now (now that I told you what to look for) the stacks have been extended to about 5" high. Coincidence? Maybe? Sure. Everything is just coincidence right?

This is ONLY effective on the Pantera. It's the only car that has this room over the top of the manifold. The Mustangs don't.


This is what Inglese did on a Pantera Weber set up. He used rubber hoses. Small ones. I think this one has a vacuum plenum added to it in between the carbs in the back?

In my experience, not enough to work the brakes.

Attachments

Photos (1)
quote:
Originally posted by René #4406:
Yes, find 15 full availables days, it's something for retirees. Smiler


First time in '78 was about 6 weeks. Had to ship the jets in from Connecticut every other day.

I had a poster in the garage that I had made from an enlarged picture of Jim Inglese, and every time I would pull out a fouled spark plug I would throw it at the poster and just leave the plug there in a pile.
At my age I cant remember if I posted that my Webers are functioning great now. The forum's total advice indicated that patience and a little luck is required. I plugged all vacuum connections to start with. The brakes are being bolstered by strong but a noisy vacuum pump that gets drowned out by motor noise, and the distributor is set at a base 18 degrees with another 20 degrees of centrifugal advance for a total of 38. This appears to be fine for my needs. Power is awesome, and much better than the 650 Holly provided. Twenty five years ago I had a wilder cam installed to go along with roller rockers and higher compression pistons but unbelievably lost all the specs, so I was flying blind concerning jets and best emulsion tubes to use. I went through many combinations and must have gotten lucky. The car wants to idle best at 900 rpm, and idles reasonably lean. There is no lag when hitting it hard, and no problem smoking the 18/305 rear tires. Nothing looks as good as a set of 8 tubes rising up from the motor.

Attachments

Photos (1)
Mine plugs look like this.
I am wondering why one side is white the other brown on the plug ? Could this be because of the agressive cam profile ?
Thanks
Peter
Ps mine is not running well. Some backshouts and some shouts in the exhaust is normal.

Attachments

Photos (1)
Mine look like that as well including in my 347 Windsor.

Your plugs would indicate to me that the idle is way to heavy on your induction. The light side is about right.

This dual reading happens because one side is facing the intake valve, the other is facing the exhaust valve.


One thing that you will find as helpful is indexing the plugs. All plugs should read equal and the defining line should be right down the middle of the plug.


I define that as, the tip of the plug needs to point directly at the intake valve.

In order to do that you need to use shims under the plugs.


The racers that I know say this is MANDATORY to get the engine to operate properly and state that they have dyno proof of 15 to 20 hp differences between indexed and non-indexed plugs.


IF you are running Webers, try going to .60F/.80-.85-.90idle holders. The .70f are too heavy.
quote:
Originally posted by PanteraDoug:
Mine look like that as well including in my 347 Windsor.

Your plugs would indicate to me that the idle is way to heavy on your induction. The light side is about right.

This dual reading happens because one side is facing the intake valve, the other is facing the exhaust valve.


One thing that you will find as helpful is indexing the plugs. All plugs should read equal and the defining line should be right down the middle of the plug.


I define that as, the tip of the plug needs to point directly at the intake valve.

In order to do that you need to use shims under the plugs.

The racers that I know say this is MANDATORY to get the engine to operate properly and state that they have dyno proof of 15 to 20 hp differences between indexed and non-indexed plugs.


IF you are running Webers, try going to .60F/.80-.85-.90idle holders. The .70f are too heavy.


Shims with a conical seat ???

These pictures were made after the engine had idled or at full load? If it was fully loaded, did you stop the engine immediately afterwards and finish freewheel?
Someone had conical shims. They aren't common. I think I got them from Summit Racing but I haven't messed with the iron heads in 25 years or so.

Did I do a coast down to read the plugs? No.

The plugs should be a dark brown, not black. The tips should be clean.

You need to lean the idle until it pops. The third transition hole is necessary for this to work.

With just two, the mains won't come in until 2,800 to 3,000 rpm. Those will lean out the running mixture.



The reason the idles were originally set up with .70 f mains is that the engine runs so long into the rpm scale before the mains come in.

You only need the heavy idle for that reason and it will pop at idle if too lean.

Since almost all US v8 engines used the 289 Cobra race specs to start with, little development was done with the idles and it was just accepted the engine would idle heavily.

.60 idles are all that you need volume wise and there is now a plethora of idle air holders to mess with. .70's are just from the past now.

Add Reply

Likes (0)
×
×
×
×