BT7 tri-carb linkage set up

[Deleted member 21878]

i hope to get a part this week that will allow me to start setting up the carbs. i have read a few articles including the manual on set up but they all seem to show the two carb linkage and nothing matches the tri-carb. i did see a video on you tube but felt like he was doing it a lot off feel and experience. neither of which i have...
so here is what i think i need to do and please chime in if i missed something or am doing something wrong.

step 1:
hook up the return spring to each carb.

there is supposed to be a 1/16" gap between the fire wall and the linkage when the pedal is 2-1/2" off the floor. i found a 1/16 thick washer and put it in place to set the pedal.


Step 2:
now i am assuming the linkage has to hold the 1/16" gap since nothing on the pedal does. so after the return springs are hooked up; my linkage is in and attached to the carbs, i need to adjust the arms (A) so that the stops (#2) are against the heat shield and tighten. this adjustment should hold the 1/16" gap and i can pull the washer out.

(i realize the A arm on the left has to be turned around)

Step 3:
next i need to stick a .012 feeler gauge between between the stops (#2) and the heat shield. then adjust the arms (B) for each carb so the peg just lays on the bottom of the fork they set in and tighten. this should allow for the right amount of play in the linkage once i pull the feeler gauge out.

i know i stll need to balance the carbs and i will probably need to adjust the OD kick out switch once i am done the setup. but is this the basic set up for the tri carb linkage? what did i miss?

Thanks

 

[elrey]

Re: BT-7 tri-carb linkage set up

Do you have the three ring factory manual for your car or Bentley reprint?

 

[Deleted member 21878]

Re: BT-7 tri-carb linkage set up

Bentley manual.

 

[Keith_M]

Re: BT-7 tri-carb linkage set up

TL,
I'm out of town at the moment. I'll be back over the weekend. I have some information from when I set up mine. I'll look it up then.
Keith

 

[elrey]

Re: BT-7 tri-carb linkage set up

Follow the ddd section to the T and that's about it, make sure the ball joints have little slop (if they are worn and or the retaning clip is fried or lost and you are in the field, I have looped wire around them in such a manner as to keep them close), then continue on to the start and balance ( three card monte comes to mind). I have used the flexible tube hiss listening technique to great effect at the start, then proceeded to the unisyn type tools for the final check. (The tube is easy to move and one does not have to look at a moving ball or indicator while fiddling with the adjustment screws. You just listen while you work). Tuning these three carbs is not really any more difficult than tuning two. Just takes longer with more back and forth fiddling. I'm certainly no expert, and am interested in learning whatever Keith brings to the party. Just do what the book says,
jet.centering piston drop check and all, and you should be fine.

 

[steveg]

Re: BT-7 tri-carb linkage set up

DD - with your carbs off, now would be a good time to install vacuum ports for manometer syncing. Better and easier than the other methods - you don't have to remove the air cleaners! Either of these types of ports can be removed and the holes plugged with a metric screw. I'm using the lower style and have left them in place and plugged with small allen screws.

 

[elrey]

Re: BT-7 tri-carb linkage set up

Steve! If you keep on making these improvements we will never be able to say, "I gotta go to so & so's to work on the car, honey." again!

 

[Deleted member 21878]

Re: BT-7 tri-carb linkage set up

Steve
i think maybe i will hold off the manometer plan for another time. right now i plan to use my flow meter and hose. i added some weatherstrip to the end so it should seal off the carb. probably will tape it to some sort of holder so i can hold with one hand while i adjust with the other. we will see how it goes.

Keith
i would appreciate any notes you may have. please send them on.

elray
i have been following the book but i felt it left some gaps as far as setting the linkage. as far as the carbs themselves these are rebuilt carbs the PO had done. not sure how long ago but cartainly long enough the pistons had gotten sticky with the oil. so i cleaned them out with carb cleaner along with the dashpots. everything slides really easily and i get that little bit of a clank when i drop the piston from the top. i feel like they are fine. i set the mixture nut two full turns down and the idle screws are turned in one turn.... per the book. i worry more about getting the mixture right than anything else.

i got my linkage bearing in today. (thanks to Moss for going ahead and sending me another one once we figured out the USPS must have lost the original order.) So i decided to go ahead with getting the carbs mounted. actually it went a little smoother than i thought it would. i had a small (looked like from a kid's set) 1/2" open end wrench which worked well tightening the carb bolts. the only issue i had was my own fault. i had painted my linkage and the paint makes the ends too thick to fit in the carb bushings as they should. so i had to sand the ends back to bare metal so they were free. i followed my plan from above and i think it worked as expected. linkage is hooked up and all seems to work. the .012" gap at the stops (again per book) i thought seemed a little small when doing it. but after trying the linkage at the pedal, i think it allows for some play in the joints. it felt pretty good when done and all the carbs open at the same time. guessing i may have to go back and redo that part after i get the carbs balanced.

still have a bit to finish up tomorrow but for the most part, it was not all that bad a job. Keith, i would still welcome any input. i can certainly jump back and change anything i may need to. pretty simple and i can't fire anything up until i get my rocker assembly back from Rocker Arms Unlimited. So i still got time. Need to call them tomorrow and see what it going on. they said two weeks and that was just up today.

 

[Deleted member 21878]

Re: BT-7 tri-carb linkage set up

continued with my connections today. added the balance tube and connected the choke cables. nice to finally get some of this stuff off the shelves.

Going thru my check list, one of the last things was checking for WOT. and there i ran in to a problem. my pedal set at 2-1/2" from the floor bottomed out i would say about 85% to WOT. So i took off the arm that connects arms A and B on page 55 of the Bentley manual. i decided to lengthen it to give it more travel. i raised the pedal to about 3-1/4" from the floor about a qtr inch at a time. each time it helped but i never did get to WOT. right now if i pushed the pedal all the way down the stops are about a 1/16" off. i can manually move the linkage all the way by turning the main rod by hand. but can't get there with the pedal. it could be play in the old joints?

Maybe Keith's notes will have some advice on this. otherwise all seems to be hooked up and operating as one would expect. i checked today with Rocker Arms Unlimited and they expect to ship my assembly out Monday or Tuesday. Need that and an exhaust system before i can fire it up and run a true check.


had to slide the air cleaners on just to see how it would look. couldn't resist.


while thinking about the rocker arm assembly i wonered how you all adjust valves... well i mean how do you turn the engine to adjust the valves? do you just bump the starter? i can't seem to get my hand in there to get anything on the dog nut to turn it which is how i used to do the TD.

Thanks

 

[steveg]

Re: BT-7 tri-carb linkage set up

When I had a generator, used to remove the plugs, press on the belt and use the generator nut to turn the engine over. I would locate TDC on #1, then remove cap and rotor and put a timing disc in place of the rotor, then adjust the valves in the firing order. You can also push the car in a high gear.

 

[elrey]

Re: BT-7 tri-carb linkage set up

We called that last move "walking it forward.".

 

[Deleted member 21878]

Re: BT-7 tri-carb linkage set up

Well i am still waiting for my rocker assembly and to get an exahust system before i can get the engine running. i have spoken with the Rocker arm people and they say i should have it by the end of the week. That will be nice to get moving on. i do not want to mount the alternator / coil until i button up the front tappet cover and i don't want to do that until i have the rocker arm assembly installed and make sure all my push rods are in place. i am going to order my exahust system this week as well and should have early next week. then i will have a few days to get it fired up before heading south for a few weeks.
To pass some time today i decided to check out the O/D solenoid travel and adjust the kick-down switch. i had seen where a number of people had used a bolt to put on top of the ball bearing and under the dial gauge. i decided to use a shear pin. it is hardened and hollow so it sits on the ball and the top fits over the tip of the dial gauge. it worked quite well. i did not have any issues with it jumping out or moving around. i adjusted the travel to .036. (according to my guage anyway) then i measured a the distance from the seat to the gass pedal and cut a board to prop in there to hold the pedal app 1/3 the way down. i cut the power off at the switch and then disconnected one wire on the kickdown switch. i checked for continuity thru the switch and adjusted it until it just broke the connection. hooked it all back up and tested it kicking out the OD with the dash switch off. all seems pretty good but a drive will be the best test i guess. probably have to wait until i get back home.

 

[Healey Nut]

Re: BT-7 tri-carb linkage set up

Interesting add on to the fan shroud . Do you think it will have any additional effect on the cooling ability?

 

[Deleted member 21878]

Re: BT-7 tri-carb linkage set up

honestly, since i have never had the car running, i have no idea. the addition was all born from reading other threads about cooling... and having too much time on my hands. figured it can't hurt and it is not too hard to remove if it makes noise or turns in to some other kind of pain. the fan shroud was just part of it. i also made a piece to seal under the radiator and i made a scoop to help funnel air in to the radiator at the bottom.

 

[jeffyfarley]

Re: BT-7 tri-carb linkage set up

I have been working on tuning my BT7 tri-carb for the last few days after finally getting the air filters off with a custom stubby 1/2" wrench my mechanic made up for me. I have read all of the workshop manuals and handbooks and they all say it is necessary to disconnect the linkages from the shaft that connects the three carbs before proceeding. However all of the instruction videos I have watched on youtube seem to omit this step. They just go ahead and adjust mixture and idle without disconnecting or reconnecting the linkages.
My car seems to be running pretty well now but I can't seem to get the idle to drop much below 1000rpm so I wonder if the linkage is preventing me from lowering the idle speed. Does anyone have any advice on this one way or the other?

 

[Randy Forbes]

Re: BT-7 tri-carb linkage set up

To synchronize the butterflies to operate in unison__an important step__you need merely to loosen the clamp-nuts securing the bell-crank to the shaft. The linkage isn't so much disconnected, as it is rendered temporarily inoperative.

GREAT CARE must be taken when tightening up those nuts to insure that each butterfly reacts exactly the same as its mates; there is slack in the take-up, so be sure that the slack is equal amongst the three units.

 

[Deleted member 21878]

Re: BT-7 tri-carb linkage set up

as Randy said abve,
the arms in the following picture can be loosened to balance the carbs effectively disconnecting them from each other.

i also had an issue with my carbs (newly rebuilt) that the nuts holding the new shafts were too tight and that caused them to stick. the return spring could not pull them back fully to the stop. even one carb can raise the idle a little.

two other linkage issues that could affect your idle speed at the carbs.

one of course would be the choke screws. make sure they are not hitting the cam and holding the throttle open. just reach down and back them off to see if they change the speed.

next is the throttle arm at the firewall. make sure at rest, the arm is not hitting the firewall. there should be a 1/16 clearance there. you will need to adjust your stops for this.


i start with my throttle stops first. then i believe the book says to put a .012 feeler gauge behind the stops before setting the carb arms. put one under each stop and then lightly hold the arms to the bottom of the forked lever as you tighten them. as randy said above, make sure the play is the same for all of them and they operate together.

 

[Deleted member 21878]

Re: BT-7 tri-carb linkage set up

Oh, keep in mind that if you do need to adjust that lever off the firewall, you may want to adjust your kick down switch for the overdrive.

 

[dcarlg]

Jeff,
Great advice above.
I've been learning to adjust my triple HS4s this summer.
Some random suggestions:
1. Loosen linkage as described above.
2. Push choke cable in as far as it goes.
3. Check that the jet springs have returned the jets all the way up.
Reach under each jet and push up. Should not move.
4. Tighten linkage with feeler gauge as previously described.
5. Back off fast idle screws until they almost touch the cam that they ride on.
6. Remove dashpots and pistons. Measure depth of each jet inside the bearing.
7. Add depths, divide by 3. Set each jet depth to that number.
8. Try to adjust idle by backing out idle screws evenly.
9. If idle is still too fast, lean out mixture evenly 1 or 2 flats on each jet adjusting nut. Counter clock-wise looking down.
I found that using a small flashlight in one hand and the little SU wrench in the other allows me to be more effective.
10. Repeat as needed. May need to reset linkage.
11. If idle speed won't drop, spray carb cleaner around throttle shafts each side of carbs.
If idle speed drops, you have air leakage caused by wear and will need new throttle shafts. Maybe bushings too.
If your engine warbles and pops during test drives, adjust mixture nut to be richer one flat each. Clock-wise from above. Repeat as needed.
I can't get constant idle speed due air leaking around throttle shafts. Another fall project...
My engine ran better, but smelled rich. When I checked jet depths, the jet in carb #1 was dropped 2X the other carbs.
It's much better after averaging jet depths.
I'm still fiddling with the mixture and idle.
Apologies if you already know this. I'm just sharing what I have learned.
Good luck.
Douglas

 

[Deleted member 21878]

And best to make sure your timing is set properly before you begin.