[BradM]

Hey Guys

I'm a total noob when it comes to carbs. Having a recent problem with the tripower on my '65 GTO.

High idle, like 2k-3k. Center carb will not freely return to idle stop. I can force it with my fingers to close down to regular idle, but as soon as I let up, it snaps back up.

Any ideas why this might be happening. Some foreign matter somehwere blocking the return path or ????

There is a lot of play in the entire linkage. Is that normal. I referenced a friends 65 center carb, and his snaps back to idle with authority.

Thanks!
Brad

[pfilean]

Try taking off the accelerator cable and see how it acts. There may be some wear in the cable that prevents a full return.

[MikeR64]

BradM,
Pfilean has a good idea. I too went through total aggravation when I recently changed my 64 4bbl car to a tri-power setup. Due to a series of issues, I ended up with the replacement end carbs, but the problems I had would be the same regardless.
1. As suggested, remove the cable to see if that is holding things up. Mine had a notch at the pedal end that kept it from returning all the way that did not show up with the 4bbl.
2.) Is your return spring on the front hole of the bracket or on the center hole? I had to put it on the center hole to get enough pull at idle.
3.) The linkage: Remove the slotted linkage from the center carb so the center carb is working by itself. Will it return all the way then? If so, then look at the slot for the secondaries in the picture. Is the center carb arm bottoming against the front of the slot? When you remove the linkage, will the slotted end turn freely? Mine was all brand new, and that too was causing a slight bind. Putting a bit of light machine oil on the turning joint cured that.
4.) More linkage stuff: I had to adjust the slotted linkage for the end carbs so that the center carb did not bottom out when at an idle. Make sure the fast idle cam is on the bottom step for lowest position, then *ideally* you adjust the slotted linkage so that when the center carb is WFO (wide open), so are the two end carbs. With the replacement carbs I found I had to back off on the WFO setting for the end carbs slightly and set it to where they would open as wide as possible, but not so much adjustment that it did not hold the center carb off the stepped idle cam.
That and lots of bad names finally got it dialed in to where it runs and works great. The stuff jammed in the newly rebuilt center carb idle pickups is a whole other issue for another time. Good luck.

[Kenth]

Check for swollen accpump cup that may have slipped off of the pump stem and prevents return of the linkage.

[BradM]

Thanks for the suggestions guys!

Linkage and throttle cable aren't restricting it.

Kenth -- swollen accpump cup that may have slipped off of the pump stem and prevents return of the linkage.

>> where is this and what does it look like? Is there a good schematic online anywhere?

Thanks,
Brad

[MikeR64]

In your picture, the tiny cotter pin above the throttle linkage will disconnect the accelerator pump linkage from the throttle plates just to see if that is what is causing the issue. Pull the pin and disengage the round linkage form the hole and see if the throttle returns to the idle cam. If it does, then you may have a problem with the cup as Kenth mentioned.

[Kenth]

Brad, here is a couple of manuals that might help some:

http://www.tocmp.com/manuals/Carbs/R...nual/index.htm

http://www.newagemetal.com/pages/Pon...ac0021_jpg.htm

[ahnuld]

when i rebuilt mine, it did this too but my problem was the throttle blades not being able to close freely and leaving a slight gap, they would close by hand but not with the spring, apparently they have to be perfect, good luck. Dan

[BradM]

disconnected the accelerator pump linkage and idles like a champ at 700rpm. Now to find the cup.......

[Formulas]

I see only 1 yellow return spring, SOP is 2 springs for safety so you are lacking some closing force, and if a single spring is stock on a tripower i would still use 2.

[Dick Boneske]

You have to take the top off the center carb to get at the accelerator pump. But, I've had similar problems with center carbs where the accelerator pump link rod was binding in the top or bottom hole.

Examine the rod to see that the 90 degree bent ends are parallel with each other. If not, bend the rod so they are parallel. Then, insert the ends in their holes in the carb levers to see that the rod fits and does not bind. The bend in the middle of that rod is what controls its length. It must be bent so that, with the throttle at idle, there is 1 1/8" measured distance from the TOP OF THE PUMP ROD TO THE TOP OF THE AIR HORN. If this rod is too short, it will keep the throttle plates from closing.

Or, as has been suggested, the pump cup may be swollen or there is some interference to accelerator pump travel. You will be able to tell if this is the case (without taking the top off the carb) by operating the accelerator pump lever without the rod in place. It should twist upward from about a 3:30 clock position to above the 2 o'clock position against spring pressure, but very smoothly.

Keep posting symptoms as you proceed. We'll help you locate the hangup.

[BradM]

Acc pump rod was bent. Straightening the rod a little fixed the idle problem. As soon as I applied full throttle, the pump rod bent again.

Check out the pics of the linkage to the secondary and let me know if you see something wrong.....

[Dick Boneske]

The accelerator pump rod does not bend easily. If it bent when opening the throttle fully, there is some very definite interference to full travel of the pump.

With the rod removed, try rotating the pump lever. As I said earlier, it should rotate from about 3:30 to well above 2 o'clock. If it doesn't there is something wrong inside the carb with the pump itself. I've had a similar situation where the wrong accelerator pump (too long) was installed and would not allow full throttle without interference.

If you need a correct pump assy., let me know---or remove the pump and measure from the bottom of the plastic pump cup holder to the top of the right angle bend on top of the pump. I will give you the correct measurement and/or send you a correct pump.

I see nothing wrong with the slotted rod/secondary linkage. I suggest you move the stud that slides inside the rod to the top hole in the accelerator lever "J" extension. This works better, as it allows more center-carb-only throttle opening before the end carbs begin to open. This will require adjusting the length of the slotted rod assy., but that is a relatively simple procedure. Just make sure the end carbs open fully at the same time the center carb is open fully.

[ahnuld]

i had one of my brand new accel pump rods extend out of the cup and then it wouldn't move, lucky i had another. this would cause it to break the linkage. Dan

[BradM]

Most of the pics I see of correct tri-powers have the linkage to the secondary to the inboard side, mine is attached on the outboard side. Wondering if that is making it harder to open secondaries..it's not real smooth.

I tried reversing it, but not enough clearance on the inboard side.

[Dick Boneske]

Inside or outside makes no difference. In fact, my '64 Tripower with the secondary rod on the outside works better than on the inside of the levers.

To be "correct", you would need to change the REAR CARB accelerator pump rod to the style that provides clearance for the secondary rod to operate inside the lever. The one you are using is for the front carb or both carbs if with factory vacuum linkage. With mechanical linkage, that rod needs to changed or bent drastically. PY, Ames, and others have the correct rod.