Weber setup?

[foster461]

The CANNON manifold ( USA ) is a third option not given in the above link. The tales of woe therein are a surprise to me, as I've no complaints about my systems after 74,000 miles. TWM make a better looking linkage but the stamped and plated arms worked fine for me too.

 

Balancing idles may require fitting throttle levers to the outboard ends of the carbs and fitting extra springs thereto as the butterflies don't quite close concurrently; if the outboard closes ahead of the inboard ( i.e. the one attached to the arm ) no extra spring is needed. The Cannon manifold with its balance tubes addresses this in any case. Here's what the CANNON set up looks like with TWM linkage:

 

 

I reckon RHD cars have little option but to use a cable; my LHD cars both use factory carb linkage to the CANNON supplied bell crank

 

Good point Tom, while I have been critical of the **** Cannon Linkage I think what you have is a good compromise with the cannon manifold and the TWM linkage. After experimenting with the Ratco cable I'm slowly coming back around to perhaps fixing my bell crank issues as the throttle return for the cable is going to be a project and since I'm LHD I have the option of going with the bell crank and rod.

 

BTW did your maniflold come like that or do you have somewhere north of 100 hours invested in converting the original pitted cast aluminum into that shining masterpiece ?

 

Stan

[Guest ntc]

Hello Tom

First of all what a fantastic looking engine bay, I am somewhat confused are you saying that USA spec cars have a mechanical throttle linkage ? and no cable

Regard's

Neil

[Quark]

Hello Tom

First of all what a fantastic looking engine bay, I am somewhat confused are you saying that USA spec cars have a mechanical throttle linkage ? and no cable

Regard's

Neil

 

Here is a scan of my linkage assembly "instructions" and the source of my conundrum - my car is a US import (converted from LHD), my Webers and linkages are also a US import - just need to work out how best to convert/fit them!

Edited June 25, 2008 by Quark

[foster461]

Hello Tom

First of all what a fantastic looking engine bay, I am somewhat confused are you saying that USA spec cars have a mechanical throttle linkage ? and no cable

Regard's

Neil

 

Neil, the US carbureted TR250 and TR6 have a bar that goes across the engine bay and a lever to operate the throttles via an adjustable bar. You can see it here:

 

http://www.mossmotors.com/Shop/ViewProduct...amp;SortOrder=1

 

Stan

[Tom Fremont]

BTW did your maniflold come like that or do you have somewhere north of 100 hours invested in converting the original pitted cast aluminum into that shining masterpiece ?

 

I had it polished - toyed with removing the CANNON lettering but decided not to. Not cheap, but rough cast it would have stuck out like a sore thumb in the company it's keeping

[foster461]

I had it polished - toyed with removing the CANNON lettering but decided not to. Not cheap, but rough cast it would have stuck out like a sore thumb in the company it's keeping

 

Well it all looks great.

 

I bit the bullet and fettled with the bell crank to get it to work. The cable was a cool idea but the throttle return issues were more than I was prepared to deal with and I thought why mess with your proven design and used the adjustable rod from a spare set of strombergs. I did have one question.. is your throttle return just dependent on the spring from the lever arm to the body or do you have something else going on ?. The stromberg rod has a local spring near the carb end which I discarded for this application but I'm wondering if that one spring on the lever is going to do the job ?

 

Stan

[Tom Fremont]

I did have one question.. is your throttle return just dependent on the spring from the lever arm to the body or do you have something else going on ?. The stromberg rod has a local spring near the carb end which I discarded for this application but I'm wondering if that one spring on the lever is going to do the job ?

 

Just the one you mention - but there are those inside the carbs working for us too. Still, it's necessary to keep the ball joints ( Rose joints - see archives ) lubricated, and every other pivot point as well. Otherwise, you may have to slip your foot behind the pedal and pull back gently to get that 500 rpm idle conventional wisdom ( but not my experience ) says can't be done with these. Try that with a cable...

 

I use TriFlo bicycle chain spray lube with Teflon. Same little can for the last 14 years

Edited June 25, 2008 by Tom Fremont

[foster461]

Just the one you mention - but there are those inside the carbs working for us too. Still, it's necessary to keep the ball joints ( Rose joints - see archives ) lubricated, and every other pivot point as well. Otherwise, you may have to slip your foot behind the pedal and pull back gently to get that 500 rpm idle conventional wisdom ( but not my experience ) says can't be done with these. Try that with a cable...

 

I use TriFlo bicycle chain spray lube with Teflon. Same little can for the last 14 years

 

Excellent. I think I have the throttle linkage finally sorted out, the only thing I'm not sure about is the pedal height and stop, I cant really set the pedal without having the seats installed. I've been sitting on a plastic bucket to drive in an out of the garage but it is not quite the same experince :-)

 

Stan

[Guest ntc]

Just the one you mention - but there are those inside the cabs working for us too. Still, it's necessary to keep the ball joints ( Rose joints - see archives ) lubricated, and every other pivot point as well. Otherwise, you may have to slip your foot behind the pedal and pull back gently to get that 500 rpm idle conventional wisdom ( but not my experience ) says can't be done with these. Try that with a cable...

 

I use TriFlo bicycle chain spray lube with Teflon. Same little can for the last 14 years

 

With a cable the above situation does not arise. In all form's of motorsport an independent return spring is mandatary with good reason

 

Neil

[foster461]

With a cable the above situation does not arise. In all form's of motorsport an independent return spring is mandatary with good reason

 

Neil

 

Neil, independent of what ?. Do you mean the carbs must have an active external throttle closing mechanism independent of the internal springs and the throttle mechanism ?. In the case of the LHD accelerator pedal/bar/lever we do have a throttle return spring that is exactly the same as when the cars were configured with the twin strombergs. The one difference is that the strombergs had an additional long spring on the connecting rod between the accelerator lever arm and the carbs that was held under tension by a bracket under the carbs (so it was in effect compressed and pushing, not streched). Perhaps this is the equivalent of your independent return spring ?.

 

Stan

[Tom Fremont]

The one difference is that the strombergs had an additional long spring on the connecting rod between the accelerator lever arm and the carbs that was held under tension by a bracket under the carbs (so it was in effect compressed and pushing, not streched).

 

Not present on TR250s, but apparently on later TR6 carb cars. The main spring is fairly strong, as discovered when installing same

 

Webers have an additional set of pivots overhead for a total of (9) from pedal to the throttle shaft bearings. The Strombergs have (6) though the throttle shaft bearings are plain vs. ball for the Webers.

[foster461]

Not present on TR250s, but apparently on later TR6 carb cars. The main spring is fairly strong, as discovered when installing same

 

Webers have an additional set of pivots overhead for a total of (9) from pedal to the throttle shaft bearings. The Strombergs have (6) though the throttle shaft bearings are plain vs. ball for the Webers.

 

Interesting that your lever to body spring is that strong. I have a new one from TRF and it takes a bit of effort to hook it up but it didnt strike me as excessive.

 

Tom, regarding your bell crank config. I think you also have it mounted under the middle carb with the throttle connection coming up between 1 & 2. Do you have the arms of the bell crank at 90 degrees to each other with one arm vertical down and the other horizontal, and assuming you have several holes to choose from, which one did you connect the rod from the lever to ?.

 

Stan

[Guest ntc]

Here is a scan of my linkage assembly "instructions" and the source of my conundrum - my car is a US import (converted from LHD), my Webers and linkages are also a US import - just need to work out how best to convert/fit them!

 

Quark that look's like a good place to have a linkage next to the exhaust manifold ???

 

Regards

Neil

[Quark]

Quark that look's like a good place to have a linkage next to the exhaust manifold ???

 

Regards

Neil

 

- hence my interest in the cable bracket that mounts on top of your carb....can these be bought anywhere?

[Tom Fremont]

Interesting that your lever to body spring is that strong. I have a new one from TRF and it takes a bit of effort to hook it up but it didnt strike me as excessive.

 

Tom, regarding your bell crank config. I think you also have it mounted under the middle carb with the throttle connection coming up between 1 & 2. Do you have the arms of the bell crank at 90 degrees to each other with one arm vertical down and the other horizontal, and assuming you have several holes to choose from, which one did you connect the rod from the lever to ?.

 

Right on all counts, and I used the middle hole on the vertical arm, which had to be opened one size for the Stromberg rod ball stud.

[foster461]

Right on all counts, and I used the middle hole on the vertical arm, which had to be opened one size for the Stromberg rod ball stud.

 

OK, that sounds like a good config. I put the rod ball in the lower hole but I dont like the immediate proximity to the exhaust manifold so I think I will move it up a hole. Re the earlier comment from Neil about this linkage design being close to the manifold, it is but then so was the stromberg linkage so I dont feel that is a big issue personally.

 

Stan

[Tom Fremont]

Re the earlier comment from Neil about this linkage design being close to the manifold, it is but then so was the stromberg linkage so I dont feel that is a big issue.

 

It's beside, rather than above the manifold, and in my experience never gets hot enough to affect the joints ( anyway, arthritics like heat, don't they? ). Once every 5000 miles or so you can spray a little of your favourite aerosol lube into the pivot points if it makes you feel better - that's what I do but it may not really be necessary

[Guest ntc]

OK, that sounds like a good config. I put the rod ball in the lower hole but I dont like the immediate proximity to the exhaust manifold so I think I will move it up a hole. Re the earlier comment from Neil about this linkage design being close to the manifold, it is but then so was the stromberg linkage so I dont feel that is a big issue personally.

 

Stan

 

Hi Stan

 

There is a lot of difference between a stromberg powered car ie 105 bhp and what you are doing ie one extractor in your word's header heat displacement up 50%, tune it and drive it like it should be 100% +

 

Regard's

Neil

Edited June 27, 2008 by ntc

[foster461]

Hi Stan

 

There is a lot of difference between a stromberg powered car ie 105 bhp and what you are doing ie one extractor in your word's header heat displacement up 50%, tune it and drive it like it should be 100% +

 

Regard's

Neil

 

I can only hope

 

A question about manifolds and linkages. Other than Cannon, is there anyone else making them today for the TR6 ?. I see lots of TWM kit on existing cars but a scan of their web site doesnt yield anything. Is the only TWM stuff available today all used stuff ?.

 

If you look at the arm (part number 32000) on the Pierce web site for example, who makes these ?

 

http://www.piercemanifolds.com/linkage.htm

 

Stan

[foster461]

Yes Tom they are and unfortunately not as well made as your's

 

Regard's

Neil

 

Neil, is it understood why the moderm Webers need to be set to 2.5 turns vs 1 or has this just been derived through experimentation and the difference attributed to the switch from Italy to Spain ?.

 

I had mine (mfg Spain) set to 1 turn and changed them to 2.5 and the engine seems much happier though not yet perfect.

 

Stan

[Guest ntc]

Neil, is it understood why the moderm Webers need to be set to 2.5 turns vs 1 or has this just been derived through experimentation and the difference attributed to the switch from Italy to Spain ?.

 

I had mine (mfg Spain) set to 1 turn and changed them to 2.5 and the engine seems much happier though not yet perfect.

 

Stan

Stan

The Spanish one DCOE that is have slightly different casting If you are adjusting the idle for a set of carbs already fitted then progress to the second stage, if the carbs are being fitted for the first time, screw all of the idle mixture adjustment screws fully home and then out 2.5 turns. If you are using DCO/SP carbs then start at one turn out. Start the engine and let it reach normal operating temperature. This may mean adjusting the idle speed as the engine warms up. Spitting back through the back of the carburettor normally indicates that the mixture is too weak, or the timing is hopelessly retarded. If this happens when the engine is warm and you know that the timing is OK, then the mixture will need trimming richer on that cylinder. Set the idle as near as you can to 900RPM.

 

Using an airflow meter or carb synchroniser adjust the balance mechanism between the carbs to balance the airflow between them, if the rearmost carb is drawing less air than the front, turn the balance screw in a clockwise direction to correct this. If it is drawing more air, then turn the balance screw anti-clockwise. If the Idle speed varies at this point, adjust it back to 900 RPM, to decrease idle speed screw in an anti-clockwise direction, to increase, screw in a clockwise direction.

 

When you are sure that the carbs are drawing the same volume of air, visit each idle mixture screw, turn the screw counter clockwise (richening) in small increments (quarter of a turn), allowing a good 5 - 10 seconds for the engine to settle after each adjustment. Note whether engine speed increases or decreases, if it increases continue turning in that direction and checking for engine speed, then the moment that engine speed starts to fall, back off a quarter of a turn. If the engine speed goes well over 1000RPM, then trim it down using the idle speed screw, and re-adjust the idle mixture screw. If engine speed decreases then turn the mixture screw clockwise (weakening) in small increments, again if engine speed continues to rise, continue in that direction, then the moment it starts to fall, back off a quarter a turn. The mixture is correct when a quarter of a turn in either direction causes the engine speed to fall. If that barrel is spitting back then the mixture is too weak, so start turning in an anti-clockwise direction to richen. During this procedure, the idle speed may become unacceptably high, so re-adjust it and repeat the procedure for each carb barrel.

 

After all the mixture screws have been set, the idle should be fairly even with no discernible 'rocking' of the engine, if the engine is pulsing, spitting or hunting then the mixture screws will need further adjustment. If the engine is rocking or shaking then the balance is out, so revisit with the airflow meter/ carb synchroniser. No amount of adjustment will give a good idle if the throttle spindles are bent or leaking air or the linkages are loose on the spindles!

 

Regard's

Neil

[foster461]

Stan

The Spanish one DCOE that is have slightly different casting If you are adjusting the idle for a set of carbs already fitted then progress to the second stage, if the carbs are being fitted for the first time, screw all of the idle mixture adjustment screws fully home and then out 2.5 turns. If you are using DCO/SP carbs then start at one turn out. Start the engine and let it reach normal operating temperature. This may mean adjusting the idle speed as the engine warms up. Spitting back through the back of the carburettor normally indicates that the mixture is too weak, or the timing is hopelessly retarded. If this happens when the engine is warm and you know that the timing is OK, then the mixture will need trimming richer on that cylinder. Set the idle as near as you can to 900RPM.

 

Using an airflow meter or carb synchroniser adjust the balance mechanism between the carbs to balance the airflow between them, if the rearmost carb is drawing less air than the front, turn the balance screw in a clockwise direction to correct this. If it is drawing more air, then turn the balance screw anti-clockwise. If the Idle speed varies at this point, adjust it back to 900 RPM, to decrease idle speed screw in an anti-clockwise direction, to increase, screw in a clockwise direction.

 

When you are sure that the carbs are drawing the same volume of air, visit each idle mixture screw, turn the screw counter clockwise (richening) in small increments (quarter of a turn), allowing a good 5 - 10 seconds for the engine to settle after each adjustment. Note whether engine speed increases or decreases, if it increases continue turning in that direction and checking for engine speed, then the moment that engine speed starts to fall, back off a quarter of a turn. If the engine speed goes well over 1000RPM, then trim it down using the idle speed screw, and re-adjust the idle mixture screw. If engine speed decreases then turn the mixture screw clockwise (weakening) in small increments, again if engine speed continues to rise, continue in that direction, then the moment it starts to fall, back off a quarter a turn. The mixture is correct when a quarter of a turn in either direction causes the engine speed to fall. If that barrel is spitting back then the mixture is too weak, so start turning in an anti-clockwise direction to richen. During this procedure, the idle speed may become unacceptably high, so re-adjust it and repeat the procedure for each carb barrel.

 

After all the mixture screws have been set, the idle should be fairly even with no discernible 'rocking' of the engine, if the engine is pulsing, spitting or hunting then the mixture screws will need further adjustment. If the engine is rocking or shaking then the balance is out, so revisit with the airflow meter/ carb synchroniser. No amount of adjustment will give a good idle if the throttle spindles are bent or leaking air or the linkages are loose on the spindles!

 

Regard's

Neil

 

Interesting that the change in manufacturing location would have changed the way the units were cast. Good to know though if the setup of the later carbs is different from the earlier versions.

 

Thanks too for the snippet from the Dave Andrews (?) article. I have the full paper somewhere in pdf format and a quick web search yielded this link http://hometown.aol.com/dvandrews/webers.htm . Very nice writeup for the Weber novice.

 

 

Stan

[Guest ntc]

Stan

Re the casting's, over here the biggest problem is finding trumpet's that actualy fit without a lot of work are you having the same?

Regard's

Neil

[foster461]

Stan

Re the casting's, over here the biggest problem is finding trumpet's that actualy fit without a lot of work are you having the same?

Regard's

Neil

 

I bought a kit that came with 2.5 inch trumpets and they fit perfectly so I never had that particular problem. I bought some 3 inch K&N filters that fit over them and still leave some clearance with the wheel arch although I havent fitted them yet as we are still messing with the carbs this week. I set the floats, did an initial jetting config and made a half assed attempt at balancing them before I had to dash off to get the car through its annual inspection (the sticker expired yesterday) and I was amazed that the engine even ran as well as it did. The car passed its annual physical with no issues which is also a miracle given the state things were in as late as Sunday evening.

 

Had an email discussion with Tom F about linkage geometry and after some adjustments, fixed my throttle return issues. Should have paid more attention during those trig classes I guess. If the teacher had mentioned that it was important for Weber carb linkage configuration I might have paid more attention.

 

Initial impression is WOW. Immediate throttle response, a lot of power. Its been a long time since I drove an early PI car but that was my target HP for this project and it feels very similar to a supercharged TR250 that I had a ride in at VTR last year, at least up to 3000rpm where I have set the limit at this time.

 

Stan

[Tom Fremont]

Stan

Re the casting's, over here the biggest problem is finding trumpet's that actualy fit without a lot of work are you having the same?

Regard's

Neil

 

Chrome / steel trumpets by Weber should always fit. I use alumin(i)um ones in 18mm height because the 16mm steel ones can't be had that I know of. They fit like the steel ones but their bells are slightly wider which pose a little challenge when fitting the K&Ns.

 

I notice for both of you there may be a violation of the distance-to-nearest obstruction principle: this is found in Passini's book and I don't precisely recall what it is, but somewhere around 1-1/2 x choke diameter or 1x throttle size ( 40mm ) to, in this case, the filter housing. I use 2-1/2" deep filters with 18mm trumpets and they just barely qualify. Shorter filters therefore suggest to me no trumpets, and for Stan's 2-1/2" trumpets a 4" deep filter is probably recommended on that basis.