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Old 09-04-2009, 11:37 PM
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Older Holley 4150 and 700R-4 TV Cable Problem Solved -- Maybe

I'm in the process of mocking up my re-built SBC to find unanticipated problems and have been very successful: I've run into a big problem.

I'm using a Weiand 142 blower "kit" P/N 6500-1 and Weiand's recommended Holley carb, P/N 80572 (it's a boost-referenced Holley 4150).

The problem is that I'm also using a 700R-4 transmission and the Holley carb, according to the instruction manual, " ... is NOT designed for use with ANY automatic overdrive transmissions." (Of course, they only disclose this in the installation instructions; it's mentioned nowhere else.) This is my big problem.

Obviously, what they are referring to is the lack of any appropriate bracketry associated with the throttle cable attachment point so that a TV cable can be attached. This means that Holley's "solution" (P/N 20-121, their 700R-4 kickdown throttle bracket) has NOTHING to mount to. Even if it did (I have one), the geometry is all wrong, only pulling the TV cable through a 30 degree arc instead of the required 78 degrees. That may be why others have had a problem with their 700R-4s even when using the Holley bracket.

Working from info at Sumner Patterson's site, I found I could modify/construct a bracket to add the 700R-4 functionality that Holley left out.

Basically, I constructed a piece of cardstock with the correct geometry like he did, located the correct placement of the TV cable stud, and mocked up a solution. I will simply cut up the otherwise-useless Holley 20-121 bracket and weld it to the carb in the proper place. Based on my mock-up, the TV cable stud will move through the correct geometry from closed to WOT. In theory, I've solved my problem (but I haven't done it yet so no pictures).

I'm posting this because
1) I haven't been able to find anything where somebody else already solved this problem;
2) There may be a better way to do this I didn't find (remember that the Holley adapter and similar adapters will not work with my particular "older" carb and the Holley adapter may not really work at all); and
3) I'd like to get some feedback and maybe a little validation of my thinking before I actually weld stuff to a brand-new carb (which I purchased 4 years ago, so there's no taking it back).

As a helpful reference, these links provide useful information:
Sumner Patterson's site: http://www.purplesagetradingpost.com...o/700R4p1.html
TV System 101 http://www.tvmadeez.com/article/index.php
700R-4 FAQ http://700r4.com/faq/faq.shtml
Speedo Gear Calculator at http://www.bowtieoverdrives.com/index.shtml
Useless Holley bracket: http://www.holley.com/20-121.asp
Pics of identical carb/blower: http://www.camaros.net/forums/showthread.php?t=152602

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Old 09-04-2009, 11:57 PM
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At the very least, make sure the TV cable is fully extended at full throttle. That's max trans pressure at max throttle- where it needs to be as far as performance goes.

Here's my Holley HP 750 connected to the 'ol TV linkage.

And for the long version:

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Old 09-05-2009, 10:02 AM
hduff's Avatar
Fix it until it breaks

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OK, that's the diagram I was working from that Sumner Patterson had at his site. I have the arc of the TV cable stud moving exactly like that.

The second critical measurement is the distance from the stud to the TV cable bracket.

After I modify the carb, I'll mock up the bracket and measure and modify as necessary.

Now I know why my BBC/Edelbrock carb/700R-4 car never drove right . . .

I'll try to take pictures and add this to the Wiki.


LOL -- this post has already been picked up by Google!

Last edited by hduff; 09-05-2009 at 02:58 PM.
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Old 09-05-2009, 09:30 PM
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Sum's web site receives many hits on it for the tech information on it. Information for transmissions to how he built his house or info about his sail boat

Sum is a good friend of mine
Dont worry how old you are... it is the mileage on your body that adds up.
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