General Category > Quadrajet Carb Talk and Tips
th350 detent valve travel question
stevef:
--- Quote from: Cliff Ruggles on March 13, 2019, 02:53:54 AM ---The cable on a TH350 is not a player in shift function in the "normal" driving range. It is for forced heavy/full throttle downshifts so shouldn't come into play until pretty late in the travel of the throttle.......Cliff
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Thanks Cliff. Right now, with the q-jet at WOT, the detent valve still has about 3/16" undepresssed, or 3/16" travel left until it would bottom out. It sounds like I might have to make it so that last part of the valve gets pushed in some more at WOT for the kick-down to work.
I just had a idea. I have a 73 El Camino with a th350 that I installed over 20 years ago, and the kick-down has always worked. I'm going to drop the pan on it and see how far the valve is pushed in at WOT. It's been a while since I changed the filter on it anyway :) . I've put in quite a few th350's over the years and never had this problem, so never really paid attention to the valve position.
stevef:
--- Quote from: tayto on March 13, 2019, 04:41:35 AM ---Is it aftermarket cable or AC delco? i have not had good luck with aftermarket TV cables for the 2004R/700R4s. Ac delco ones are the one to use IMO.
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It's an aftermarket, but I compared it to the old original cable, and didn't see any difference in length or function. So, I can't see a reason it wouldn't work. The original one is old and ugly, but I might reinstall it to see if there is any difference in how far it actuates the detent valve. Thanks for the thought.
tayto:
was the qjet you are using originally from a car with a th350? if it's from an OD unit the "swing" might be wrong. I had a 2004r a long time ago that i used with a th350 carb and the trans only last 2 years. was behind a 305 in a 64 impala that i drove mainly highway miles.
stevef:
Good question, but yes, it's actually the original q-jet and engine that came in this car. So, it's correct.
I've found my answer about the travel of the detent valve. I dropped the pan on my El Camino and when it's at WOT, the valve is completely depressed. On my TA, at WOT, the valve still has about 3/16" travel left to go. So, the TA cable is not completely depressing the valve at WOT for some reason.
I've been using a new aftermarket cable that's supposed to fit my application and looks the same as my old one. I looked up the GM part number for my application, but they're no longer available from GM, or anywhere on the internet. So, aftermarket or used original is the only choice.
So, I have a couple options. I still have my original cable, so I think I'll put it back on and see if it makes a difference. Another option is to shorten the front of the cable slot on the new cable, so the throttle lever starts pulling it sooner so it can push the valve in completely at WOT.
I'll let y'all know what happens. Any other thoughts are welcome.
Cliff Ruggles:
For most set-ups and my own car I don't use the transmission kick-down feature. The last thing I want to happen is the transmission seeking a lower gear during a heavy throttle passing scenario. I'd rather manually shift it if/when needed....but my engine does make over 550hp and 600ft lbs torque, so it really doesn't need high RPM's for any sort of "normal" driving........Cliff
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