 
     |
| '67 Fleetwood - Switch Pitch TH400 w/ Edelbrock Carb (Page 1/3) |
|
thesameguy
|
SEP 09, 03:21 PM
|
|
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!
|
|
|
|
thesameguy
|
SEP 09, 11:19 PM
|
|
|
|
CoolBlue87GT
|
SEP 10, 09:26 AM
|
|
|
That is a beautiful Fleetwood, love it.
|
|
|
|
thesameguy
|
SEP 10, 12:17 PM
|
|
|
Thanks! It's a fantastic car and I'm dying to get some wheel time!
|
|
|
|
tesmith66
|
SEP 10, 01:12 PM
|
|
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).]
|
|
|
|
tesmith66
|
SEP 10, 01:27 PM
|
|
|
|
|
tesmith66
|
SEP 10, 01:29 PM
|
|
|
|
|
thesameguy
|
SEP 10, 05:43 PM
|
|
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.
|
|
|
|
tesmith66
|
SEP 11, 12:16 PM
|
|
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).]
|
|
|
|
thesameguy
|
SEP 11, 01:22 PM
|
|
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.
|
|
|
|