Have factory AC back on my 67GS400. Running a Q-jet carb. Idle speed w/o air 750 rpm and increased to 900 still the engine falters and dies in gear witth AC on. From what I know there was no idle solenoid until around 71, So how do I compensate for higher idle with AC engagement on older 400s with Q-jet? Can a solenoid be retofit?
The later model engines had an idle stop solenoid, but it had nothing to do with the A/C, but it could be used for that purpose. It bolted to two threaded bosses on the intake manifold. Earlier intakes did not have those threaded bosses, so you would need to make a custom bracket to hold the solenoid. Is your engine COMPLETELY stock, or do you run a hotter cam?
Don't think my mild cam change 454,212 lift would affect vacuum enough to matter. Hardly notice any difference to the stock one I had. Idle stop solenoid interesting idea. Wonder if anyone has done this and how it was wired and mounted? Would it be operating in opposite manner to push the linkage when compressor engages?
My 69 400 had a stock idle stop thing on it, until I put the Edelbrock intake on it. It was not electronic and mounted to a bracket that went to the intake bolts, on the throttle side of the intake. All that it did was cushion and slow the throttle return for the last 1/8 of an inch (approximately). It was adjustable for where it picked up the throttle. My AC currently does not work, so I don't know if leaving it off has any effect on the idle with the AC on. The bracket would not fit with the Edelbrock Performer intake. Here is a pretty good picture of it, that I added:
Ames has a bracket that uses the L/Front carb. bolt to hold it in place. They also have the solenoid that increases idle speed with the A/C on. You tap/wire it into the green compressor clutch wire so when you turn on the A/C it becomes energized. Tom T.
Unfortunately Ames no longer carries the solenoid. I did get the bracket and on the hunt for a solenoid---probably any A-body idle stop solenoid close to my 67 year will be ok.
Do some research on Amazon, there are plenty of choices, https://www.amazon.com/ACDelco-214-2138-Professional-Carburetor-Solenoid/dp/B0010HG1E6 Read some reviews. None of these will immediately raise your idle with the A/C, but they will with a slight tap of the gas. Greg Gessler has some as well, https://quadrajetparts.com/carburetor-throttle-solenoids-c-228_763.html (scroll down to the bottom of the page)
