I've got a 1967 Fleetwood that developed "a problem" with its stock Quadrajet, and being a carb with a very short run I couldn't find anyone willing to rebuild the thing at anything approaching a reasonable price. Too many unknowns about what specifically was going to be involved. Lacking the energy and funds to deal with it, I picked up a Edelbrock 1406 and adapter and I'm going to roll with that until I find someone who can handle the Q-Jet.

All the work on the car (which extends beyond the carb) is just about done, and the one lingering detail is control of the switch pitch TH400. The factory carb has a rotary switch which controls both the kickdown and torque converter, and that switch a) won't connect to the Edelbrock and b) is old and doesn't work very well anyway. I need to concoct a replacement, but am not having any luck.

Here is the carb, with the old switch laying on its side:



I need something that:

A) Applies 12v at idle
B) Applies 12v at approximately 60% throttle

The problem with all modern TPS is that they work on resistance, I just need something that opens and closes. I could do something with a microswitch for idle, but that would not handle the "60-100%" scenario very elegantly without some sort of cam to drive it. I am not readily seeing how that cam would work, so I'm just throwing the term around conceptually.

Obviously the car will run and drive without this working, but I'd like it to work. I'm wondering if the combined wisdom of PFF can think of a good solution to this problem... I've been staring at it for a year without good result.

Here is the car - I am really anxious to get it back on the road!

And here is video showing the linkage in action...

https://www.youtube.com/watch?v=aXqd9BWP-y8

That is a beautiful Fleetwood, love it.

Thanks! It's a fantastic car and I'm dying to get some wheel time!

Can't see your pics at work, but the video shows what looks like the electric choke spring. Every switch pitch I ever saw had a switch on the brake pedal that energized the solenoid for the torque converter stator (changing the pitch) to keep the car from creeping while stopped at a light. Never seen one with a switch on the carb. Was it on the driver's side of the carb (By that connector?)

EDIT- After a little Googling, I see that some had switches on the brake, some had vacuum and some had it on the carb. I think Caddy was using it to make the car cruise smoother and maybe get a tad bit better MPG on the highway instead of raising the stall speed to eliminate creep at stops.

Sorry I can't help with the switch setup, but maybe a simple momentary on switch with a spring attached (like a motorcycle rear brake light switch)? You can adjust it to do it's thing at a particular throttle position?

[This message has been edited by tesmith66 (edited 09-10-2015).]

Yeah, I know how the system is supposed to work, and how it worked on the stock carb. What I am trying to figure out is how to replicate that on a non-stock carb. The stock setup used a rotary switch, like a primitive throttle position sensor, to control the stator at idle (eliminate creep), control the stator at WOT (to increase torque multiplication), and to control the downshift solenoid at WOT (to force a downshift). Getting the idle behavior out of a simple switch isn't all that difficult, but controlling both kickdown and TC pitch at %WOT (I believe 60% WOT is factory) is a little more difficult.

The biggest issue is the Edelbrock throttle arm sucks. There is no place to attach anything, and it's not a useful shape to actuate anything over a range of motion. I know other GM cars with a standard TH400 used a pedal switch to activate the kickdown, but unfortunately the accelerator pedal in the Caddy is not like other Chevys, there is almost no pedal arm inside the car, no place to attach anything without actively getting in the way of pedal movement.

I've been looking at using the throttle linkage in the engine bay, but that's tough too. It may be my best bet, this is a terrible mockup illustrating my idea:



I can make a bracket to attach a flat piece of whatever to the intake manifold or the back of the head, then use a pair of microswitches activated by the arm as it passes by. There isn't much to provide stability there, and I am worried about mounting the switches to the engine since its relationship to the throttle arm isn't exactly fixed, but the approach seems reasonable.

Maybe you could do a kickdown switch like this:


...and use a brake switch or just the 12V feed from the brake light switch for switchin the pitch at stops.

Summit Racing sells that switch, but it's too freakin' expensive

http://www.summitracing.com/parts/bmm-20297

You could probably build a setup like that for less than 10 bucks.

[This message has been edited by tesmith66 (edited 09-11-2015).]

Jeez, yeah, I saw that thing and a similar part that PCI (PCS? Something like that) makes that's $120. How do these people sleep at night charging $50 for a $2 plunger switch and a spring?

Using the brake light switch and a plunger switch is a solid idea. I had not seen the B&M kit installed, but that was very helpful. I didn't understand how it was actuated - the spring lets it activate at a lower throttle opening without restricting it. Good deal. I hate spending $50 on a switch, so I guess I gotta go spend some time on Newark/mouser/digikey and see what they've got there.

I am not sure about the merits of actually combining the kickdown and the stator shift functions as I think you want stator shift before kickdown, but at the end of the day if the 60% throttle stator shift gets dumped, it's not the end of the world. This isn't a performance car, I don't need to improve throttle response.

If you go that route, be sure and insulate the switch. That 12V terminal sticking up naked in the sea of grounded metal is a bit scary.

I have a TH400 that may end up in my El Camino. I had a gas pedal switch eons ago, but haven't seen it in 30 years. Always thought about using a switch setup like that, but $50 is just plain mean.

Here's a switch:
http://www.elecdirect.com/p...ovKhq7gBEiQAEvsBZ_S_

All you need to activate it is a spring. That cable setup B&M uses is superfluous. Of course, you could run a cable inside the cabin to keep the switch dry.

quote Originally posted by thesameguy: I've got a 1967 Fleetwood that developed "a problem" with its stock Quadrajet, and being a carb with a very short run I couldn't find anyone willing to rebuild the thing

What do you mean "carb with a very short run?" You mean short production run?
Also, can you describe the "problem?"

I've got a bit of Q-jet experience (from long ago), but I might be able to help. Some of the old hot rodders on here as well may know. If you were going to replace it, why not go with a rebuilt Q-jet or at least another spreadbore carb so you don't need an adapter. Holley makes the 4175 as a Q-jet replacement.

You may spend more time and trouble getting that 1406 to work than fixing the original carb or replacing it with another Q-jet.

All the carb stuff is in the past - there is a brand new 1406 w/ adapter installed, plumbed, and tuned on the motor, I just need to make it control the transmission properly. It just wasn't worth paying $500 for one of the other options when a $240 1406 does the job just fine - unless a more expensive carb would have simplified installation... which they wouldn't. The 429's Q-Jet is unique to the Cadillac in just about every way except the bore layout. Going 4175 for example would save an intake adapter but none of the other work. It just wasn't worth $260 to save an adapter.

Where I am now is a carb that needs transmission control features. And, of course, the switch-pitch TH400 is also a very short-run transmission so there aren't any off-the-shelf solutions there, either. At least not in 2015. I understand in the '80s this would have been less of a problem.

If you do know someone who will rebuild a 1967 Cadillac 429 Q-Jet I'd love the name. The best I've gotten so far was from Jet, who very nicely told me I could send it in and they'd see what they could do. Most people just said "Sorry, we don't have parts for that."

At least you'll hone your fabrication skills. Good luck with your project.

True enough!

Feeling pretty good about the result...

https://www.youtube.com/watch?v=GJepufdV1ao

Looks good. Have fun cruisin!

I am looking forward to it. I bought the car in 2010 in Denver, CO and drove it 1400 miles back to Sacramento without incident. In '12 I parked it for the winter and when I came back in '13 some stuff was not right... it's taken a long time to clean things up, but I'm on the home stretch. This weekend I'm replacing the old v-belts, a failed exhaust manifold gasket, and hopefully reinstalling the dashpad. After that, I am waiting for remybattery.com to deliver a right-angle battery terminal and some ebay guy in Germany to deliver some Tesa electrical tape. I think that's all there is left before I get some wheel time in one of the best cars GM ever made.

Nice car.
regarding Qjets
I've had good experiences with
http://www.cliffshighperformance.com/

Thanks for the tip - I will definitely look into them when it's time to put the qjet back on.

In in the interim, I actually put 30 miles on it today, the first time it's been driven since 2013. Took a few miles for the front drums to unstick themselves, but following that not a single hiccup. Felt good driving 5500lbs of American luxury again. Got a few loose ends to tie up but the big work seems to be done.

Without the Fleetwood to work on, I'm not sure what to do!

Cruise that bad boy out to Illinois and I'll put you work!