"Bandit" (2bandit)
05/22/2014 at 16:48 • Filed to: Emma
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"Bandit" (2bandit)
05/22/2014 at 16:48 • Filed to: Emma | 0
| 18 |
I wrapped the fuel line that runs along the engine block in 2000 degree wrap trying to prevent possible vapor lock. I think it worked. Now I just need to get the transmission tuned. I ghetto mounted my 700r4's tv cable and I need to get it set correct-ish.
BondoSpecial
> Bandit
05/22/2014 at 16:51 |
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Make sure it's set correctly and that the mount is rigid and won't move or bend. Because the TV cable on a 700R4 controls line pressure (it's not just a kickdown cable like older transmissions like a TH350, C6, etc, that had a separate vacuum modulator for line pressure) if you don't have it set right, you can fry one of these transmissions in a few miles by not having enough line rise. You are better off waiting and buying the correct cable and mounts than improvising, test driving it, and ruining the trans, if what you have currently is not really right. Also note that you need a 700R linkage geometry corrector bracket for most carbs, because the stud provided on the throttle arm for a TH350 does not have the correcr range of travel for a 700R.
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Bandit
> BondoSpecial
05/22/2014 at 16:54 |
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I'm running a quadrajet. There aren't any good mounts that work with my pontiac manifold. I got one but it didn't fit in any way.
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BondoSpecial
> Bandit
05/22/2014 at 16:55 |
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What year is your qjet (if you're not sure, what is the number stamped on the side, running vertically)? Later year Qjets will have the correct stud location for a 700R because they came in vehicles that used 700Rs. An early year Qjet won't, and won't have the right range of travel for a 700R cable. Although since you have a Pontiac engine and not a chevy, I'm not sure if the 1980s non computer controlled Qjets that would have come on pontiac V8s, and used with THM200 trans, would have the same ratio TV cable stud as a 700R
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BondoSpecial
> BondoSpecial
05/22/2014 at 17:11 |
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Here is what I am talking about. http://www.jakesperformance.com/TV_Cable_Setup…
The relevant excerpt which describes what is going to happen if you try to use a 1970s Qjet with a 700R4 is this:
"The issue here is that the geometry on the carb linkage is not correct. It has a different radius of arc than what is needed for the TV cable. The TV cable needs a 1.093-1.125" measurement, the older TH350 kickdown is closer to 1.375". This creates a condition where the cable is adjusted correctly but since the geometry is wrong, the overdrive transmission has correct pressures at WOT, but becomes farther away from correct with every degree of throttle less than WOT. Not really an issue at WOT or even 3/4 throttle. It becomes an issue just off idle, where a street car operates more often than any other throttle angle. What the pressure gauge will show you is little or no pressure spike on very slight throttle movement. This is the killer of automatic overdrives in retrofit applications. The radius is a simple measurement that can be done with a caliper, a machinist rule, or even in a pinch a tape measure to get an idea. You measure from the centerline of the throttle shaft to the center of the TV stud. It should be approx 1 and 1/8th inch or slightly less. We prefer to see if on the short side. 1.100". You also want to see the TV stud rearward of center approximately 20-30 degrees. The OEM spec was 23* but this is not all that critical. It does have some effect on the rate of initial pull of the cable but a properly calibrated performance overdrive transmission will not be overly sensitive."
crowmolly
> BondoSpecial
05/22/2014 at 17:15 |
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Beat me to it. You can't really screw around with TV cables. Set it right the first time, and if you can't then don't drive the car until you can.
Good 'ol Jake! Knows his stuff cold.
I just recognized you as BondoSpecial from NastyZ.
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BondoSpecial
> crowmolly
05/22/2014 at 17:17 |
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Yes, that is me! It's odd seeing actual tech content on here, and not just kids talking about miatas huh? lol.
RamblinRover Luxury-Yacht
> BondoSpecial
05/22/2014 at 17:20 |
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Extremely interesting. Why is it that they changed the range of motion - changes in as-equipped intake setups that made for a need to space-save, or just whim of the valving manufacturer? I'd have expected changes to run the other direction because a longer throw magnifies the motion, but maybe a more miniaturized valving setup needed to cut overall size.
That being said, I'm not a huge fan of 700R4s from those I've encountered - though if you're not putting too many miles on them, the OD might be nice. Are they that common for retrofit?
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crowmolly
> BondoSpecial
05/22/2014 at 17:21 |
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Keep your head down! LOL.
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BondoSpecial
> RamblinRover Luxury-Yacht
05/22/2014 at 17:21 |
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The geometry changed bc the trans changed. The factory wasn't really worried about what was going to happen 30 years later when people were trying to make a mishmash of different years of parts. 700R4s can be built to be plenty strong, there are plenty of aftermarket clutches and hard parts available nowadays to make them live.
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RamblinRover Luxury-Yacht
> BondoSpecial
05/22/2014 at 17:28 |
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I know, as we have two in the family that have now been rebuilt stronger than stock - a tow build in a diesel Suburban, and a normal tough duty build in an Astro. I was just musing that it had to have taken a certain amount of will to adopt them as a retrofit in the first place, given that one a little custom would be required in most cases, making it not an off-the-shelf swap so much as some things.
I recognized that the trans changed, I'm just not sure whether the valve body had much reason to change range of motion - "The giggles" is a common enough reason for OEM changes, I suppose, but I was idly curious if there was a reason such as going to a smaller valve body overall.
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Bandit
> BondoSpecial
05/22/2014 at 17:31 |
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78.
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BondoSpecial
> Bandit
05/22/2014 at 17:36 |
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Yeah that's a problem. That will have the wrong length of travel at the stud where you connect the TV cable, because that carb was designed for a pre OD trans w/ a kickdown cable. Which is going to lead to line rise issues as detailed in that article above. A fix for that would be to relocate the TV stud on the throttle arm of the carb to obtain the correct geometry, or get a carb from a later year that has the correct geometry, if that is even available for the pontiac application.
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BondoSpecial
> RamblinRover Luxury-Yacht
05/22/2014 at 17:40 |
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The TH350 didnt even have a TV valve. The cable was used for full throttle kickdown. It's accomplishing 2 entirely different functions. So you can't even really compare the range of travel. The 700R valve body does not operate the same as a TH350. The 700R valve body basically does a balancing act between the pressure created by the TV valve and the governor pressure, along w/ other spring loaded valves specific to each gear, to determine up and downshifts. The TH350 based line pressure off engine vacuum.
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RamblinRover Luxury-Yacht
> BondoSpecial
05/22/2014 at 17:51 |
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Gotcha. A lot of travel in full-throttle kickdown makes sense (more assured to kick down *only* at full throttle), and mechanical advantage on a rig set up like you describe makes sense as well, which has an inherent way to manage precision. Completely fresh slate, so no reason to even bother to reference what already exists.
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Bandit
> BondoSpecial
05/22/2014 at 17:54 |
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How does this look? I pulled the geometry corrector bracket I got for my edelbrock.
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RamblinRover Luxury-Yacht
> BondoSpecial
05/22/2014 at 17:54 |
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I'm going to go fairly deep tech when I get into my Rover V8 performance build, but it's very true that content here tends to be more fluffy than that.
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BondoSpecial
> Bandit
05/22/2014 at 18:04 |
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That looks like that is actually going to work. It wouldn't hurt to measure the travel that the stud that is now relocated, as per the article i linked, just to verify. Since the Edelbrock would have used the same TH350 stud that your Qjet did though, it should be accomplishing the same correction. Make sure you understand how to adjust the TV cable itself. Push the metal D shaped tab on the side of the TV cable all the way in (it will take some effort) and slide the black plastic center piece all the way into the cable. Manually move the carb arm full throttle, and you should hear at least a few clicks as the TV will ratchet out and self adjust. If you get no clicks at all and the part you slid into the TV cable stays slid all the way in, you need to move the cable mount further away from the carb. If you run out of adjustment and you can't get full throttle because the TV is hanging it up, then you may need to move the TV mount closer to the carb. The angle of your TV does not look good though. It should be inline w/ the cable pull, not off to the side. I would fix that before I moved any further, plus the metal you are using does not look rigid enough.
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Bandit
> BondoSpecial
05/22/2014 at 18:07 |
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Thanks! Yeah, I am not too pleased either. I need to figure out a bracket solution, there just isn't anywhere to mount the darn thing. I'll do some re-designing and see what I can come up with..