Transmission / Overdrive: 700R4, Edelbrock Carb. Throttle Rotation

[wittsend]

I realize a 700R4 transmission with an Edelbrock carburetor isn't a standard Studebaker setup. However, I know some have this configuration whether Studebaker or Chevy powered. So,...

I am hooking up the TV (throttle valve) cable. While there is an adapter available for proper TV cable geometry it strangely doesn't fit my carburetor (perhaps the Edlebrock carb. is for a Ford or Chrysler???).

Information is available on the internet showing how to make an adapter (angles, distances etc.). Every site list the full rotation of the throttle plates at 78 degrees. Using an angle gauge I'm getting a maximum of 71 degrees rotation. Has anyone experienced this with the Edelbrock carburetors? I have double checked that the secondary lock out and the choke fast idle are not interfering (both can reduce the angle of rotation). I have also ensured that the secondary stop has the throttle blades positioning the throttle plates perpendicular to the base.

The images posted show the: proper angles, the angle of the TV cable attachment point (wide shot and close-up).

The steel ruler bisects the center point of the throttle shaft and the center of the TV cable attachment point at 23 degrees. Not noted, but critical is the 1.125" distance from the throttle shaft center and the center of the TV cable attachment point. I spent hours to get these points aligned yet it seems negated because the throttle shaft rotation stops at 71 rather than 78 degrees rotation. That is 10% less rotation.

While I'm on the subject..., I have never seen information warning about the fast idle and secondary lock out affecting readings. More so, I have never seen anything written regarding setting idle speed. On injected cars the idle is typically corrected with an auxiliary air bleed. Thus, once set at the factory the throttle position (and TV cable position) stays set for life. But not so in a carbureted car which periodically needs adjustment.

Therefore if the 700R4 is to be properly set up it stands to reason that one should never go back and alter the idle because it will affect the transmission functionality. I'd say especially so with a 700R4 because should the throttle move off idle, even a marginal amount, the pressure is also suppose to increase immediately off its base pressure (pressure measured with the cable disconnected). This is a VERY critical setting!!!

Anyway, any input is appreciated.

Thanks, Tom

[64V-K7]

What you need is the adapter and expert support from Bowtie Overdrive.
This is the adapter that controls the TV cable ratio

http://www.bowtieoverdrives.com/catalog/catalog_inc/viewitem.php?ITEMID=213

Well worth the price

[Mike Van Veghten]

Art Carr (the real Art Carr) is another source for parts and info.

http://www.cpttransmission.com/

Mike

[PackardV8]

X2 on this.

What you need is the adapter and expert support from Bowtie Overdrive.
This is the adapter that controls the TV cable ratio
http://www.bowtieoverdrives.com/cata...php?ITEMID=213 Well worth the price

I'm a CASO and an experienced fabricator and after wasting a lot of time trying to do what you describe, I paid the money.

jack vines

[wittsend]

Thank you for your replies.

Unfortunately the BowTie adapter won't work. As I stated in my original post the Edelbrock carburetor I have does not have the linkage configuration that is typical for a "Chevrolet" (See picture). The Edelbrock adapter won't work either - for the same reason.

While obscured in the picture by my adaptation, there is nothing below the upper arm other than two 90 degree bends that attach to the throttle shaft. It is in the flat between these two bends that I drilled holes and mounted my adaptation. Both the BowTie and the Edelbrock adapter require an attachment point below the throttle shaft.

The dimensions for this TV cable actuator I configured were taken from the real Art Carr website. He provides these for people like myself for whom no manufactured adapter exists. In my case I removed the piece from a Chevrolet throttle body and cut/bent to fit which helped somewhat to simplify the adaptation.

But, back to my original issue. Regardless of adapter (BowTie, Edelbrock etc.) it does not compensate that the 71 degrees of shaft rotation ( both throttle plates perpendicular to the carburetor base at WOT) is 10% less than 78 degrees I am suppose to have. I'm concern that this might affect the calibration of the TV cable.

Has anyone ever checked the degrees of rotation of their Edelbrock (mindful of the choke fast idle and secondary lock out)?

Tom

[sweetolbob]

Tom

Allow me to display my ignorance but it seems the 78 deg number is to supply the proper amount of cable length to activate the transmission. It would seem to me that the angle is irrelevant as long as at WOT the cable is pulled the correct amount.

Might it not be more attainable to calculate the length the cable would pull at 78 deg and change the mounting position on your arm to give that same number at 72 Deg?

Bob

[wittsend]

Bob, I would tend to agree with you. With the 700R4 the cable is self adjusting. This is similar to self adjusting drum brakes on cars. As I understand the cable actually "maxes out" before WOT. The cable self adjuster (sheathing) then pulls out of its housing and locks to set the correct position at WOT.

This is where it gets tricky. When the cable retracts from adjusting it is "suppose" to be at the correct position for idle - and all points in between idle and WOT. Ideally (at idle) this positions the TV valve so that it is at its base (preset) PSI. However, it is also suppose to cause a PSI increase immediately upon any cable movement. So, if the self adjust position set at WOT doesn't provide this (causes a "lesser" position of the TV valve) the transmission can burn up VERY fast because the pressure increases get behind the torque increase.

It seems odd that WOT is used to set a value when it itself is rarely used. Yet idle and positions slightly upward from there (normal driving range) are based on that setting. To further the point my understanding is that the bulk of the TV valve changes are in the earlier part of its movement. I've read that pressure changes later in the travel are minor.

I think it is for this reason a lot of people recommend using a pressure gauge. With the TV cable slacked you get a base, preset value. Then reinstalled, the cable is adjusted so right off idle pressure increases. Of course this can conflict with where the self adjuster wants to position the cable at WOT. So, it can become like a dog chasing its tail.

I just want to get it right and not damage anything. It just becomes more difficult when you are creating parts to pass through and converge to a "point in space." Frankly I'd be having similar questions even with a "kit." I'd still want to confirm that where the self adjuster sets the cable, it provides the increase from base pressure just off idle.

Tom

[sweetolbob]

Tom

I'm not trying to recommend anything nor act as an expert but here are a shot of the two "carbs" that have been on my 83 Avanti with a 200R4 tranny.

This is the Edelbrock that I started with.



This is the current Holley TBI/EFI system I now run.



I measured the angle change on each today and got 72-73 deg by the same method you used.

I recall that I went through the same thoughts you are having and found the dimensions that the cable needed to be pulled and found my units did.

I used an adjustable aftermarket TV cable and it has worked well for 600+ miles. It seems to shift correctly and kick down as it should.

Again, I'm not trying to convince you that this is correct but to add data to your post so that, hopefully, some members of more knowledge than we will chime in again.

Bob

[Jackson]

I have a 64 Avanti with a Studebaker/Edelbrock 4 bbl carb and a 200 4R trans, also a 64 Daytona with a 700 R4 trans and a stock 2 bbl carb. Both cars have homemade carb linkage for the TV cable which was fabricated and adjusted per the attachment, they also have a light to indicate converter lockup. Looks like you have it right, have you had it on the road yet?

http://news.compperformance.com/Instructions/gm_tv_cable_adjust.pdf

[wittsend]

Bob, your not intruding in any way. I greatly appreciate the time spent to get me your angle readings. Getting similar angles makes me less concern about my readings.

I'm wondering is some of the angle is lost due to the need to open the throttle slightly on the carburetor. As I stated in one of my previous posts the injected cars use an air bleed to set idle. So, they don't have to lose rotation for idle setting reasons.

The linkage on your Edelbrock is not like mine. The linkage with the large hole on top - I don't have at all. The lower linkage..., invert that 180 degrees (so it is on top) and that is all I have. That is why I need to fabricate my adapter.

Jackson, glad to hear you also fabricated your setup and that it works well. I find that encouraging. No road testing yet. My car needs a windshield. Until I find one reasonable priced and local (So. Cal.) I will continue to tinker rather than drive.

I started on the bracket that holds the TV cable today. It will be two pieces (sliding) so I can adjust for cable length. The "extend cable fully then measure back to the distance + 1/16," is a bit hard to do with only two hands. The sliding bracket will become my "third hand."

I'm hoping Thursday to finish this up.

Tom

[devildog]

I have an Avanti with Edlebrock and 700R4. When I first got it, it was OK, but I read-up on the linkage angle/arc of travel, etc. i made a small plate that i screwed to the throttle and lowered (lengthened the arc travel distance). it worked better, I lengthened the radius another 1/4 inch (more arc travel distance); now it really made a performance improvement. i would suggest, do not worry about having a longer radius and the longer arc travel distance.

joe

[wittsend]

That's good to hear. The say 1.090" to 1.125" on the radius. I ended up with the longer. And, frankly that is eyeballed. I too, because of the method I used, can put a spacer in place and lengthen the radius (see image). I had planned it that way in case I came up short. Maybe the extra length works better for you because the rotation seem limited on the Edelbrock's. What is lost in rotation is made up for in length. Thanks for the input.

Tom

[wittsend]

I pretty much finished my TV Cable bracket. It is adjustable in three ways:

1. The back half of the bracket is constructed (with slots) so it slides front to back. I did this so I can fine tune the position before I let the self adjust do its job.

2. The front half of the bracket attaches to the intake manifold to two bolt holes on either side of the exhaust crossover. Since having the cable parallel to the carburetor base (at 23 degrees rotation) is stipulated I can add/subtract washers underneath to position the bracket accordingly.

3. The bracket on the throttle shaft can also be adjusted with washers to lengthen the radius and to some extent alter the initial 23 degree angle with offsetting washers.

Frankly, I'm a little "gun shy" to bolt it down and hit the throttle for the self adjust - just yet. But it will happen soon. I want to pull the pan and make sure the TV valve is positioned correctly after the adjustment.

Tom