C6 vacuum modulator

[loman]

I've finally been able to work on car a bit after back surgery. When I removed the motor and trans a few months ago I found the adjusting screw for the modulator valve laying on the floor. I have no idea as to how far to screw it in to start with. I was thinking screw it all the way in and back it off about 4 or 5 full turns. Anyone have any suggestions?

[poboyjo65]

Where ever you start turn it 4 times on your first adjustments. takes that much to be able to tell if you're going the right way. after you see which way to go you can go less ,to dial it in just right. Thats all I can remember, never could remember which way to start out so thats how I remember the 4 turns right off the bat to see which way to go

[loman]

Thanks Johno for the reply. I'll keep that in mind. I did some looking around on the web and it seems that turning the screw in clockwise raises the shift point and counter clockwise will lower the shift point. Also, I did turn the screw all the way in and then counted the full turns as I backed it all the way out to see how much adjustment there is. I came up with 15 full turns to completely remove the adjusting screw. I also found this comment from an old thread from a different board see below.

"3 turns +- depending on where the adjustment screw is, if it is flush with the vac outlet you should be able to go 3 to 4 turns in, if you need any later or firmer shift than that will produce then you will have to go into the v/b and or governor."

[poboyjo65]

Thanks Johno for the reply. I'll keep that in mind. I did some looking around on the web and it seems that turning the screw in clockwise raises the shift point and counter clockwise will lower the shift point. Also, I did turn the screw all the way in and then counted the full turns as I backed it all the way out to see how much adjustment there is. I came up with 15 full turns to completely remove the adjusting screw. I also found this comment from an old thread from a different board see below.

"3 turns +- depending on where the adjustment screw is, if it is flush with the vac outlet you should be able to go 3 to 4 turns in, if you need any later or firmer shift than that will produce then you will have to go into the v/b and or governor."

I use to call my buddy who was a rebuilder to ask him about the adjusting but I'd forget which way before I got around to adjusting it. he knew about how many mph change it would shift at per turn. & he would be dead on. I suppose that was with a fairly stock motor with plenty of vacuum. the last time I adjusted one was with little hotter motor with about half the vac of a stock motor & my buddy had died so I had to trial & error it .

so when you say raise & lower you mean the rpm's right? he called it shift quicker & later with later being firmer shifts & quicker being smoother or softer.
It just amazed me how he knew the mph a turn would change a car. I always wondered were all cars/trans the same or did he know each one or what. just like when I went to a lawnmower shop to buy a tool to set the carb on my weed eater,it would only run right about half choked, so I knew it was out of whack. the guy was out of the tools to sell but he had one he used so I asked if he would set it for me, he said yes in just a few minutes so I set the weed eater down & was turned around watching guys load a mower & heard him say ''try it''. I turned back around & he looked at me & said ''try it''. It cranked up & ran like a new one. I said how much do I owe ya & he said we dont charge for that & took off walking,I had to chase him down to ask him how he set that carb without cranking the motor. & he laughed & said running good half choked usually 1/2 turn on a certain one of the screws does it. he'd been doing it a long time. guys that do something day in day out know things,they know all the tricks of the trade.