Stumbles shifting into 2nd while heavy into the throttle

[DoubleDingo]

Oh yeah, forgot to mention the rebuild of the carb from the truck. It appeared to unmolested. There was minimal tarnish or anything inside the carb. The gaskets were shot and gas was everywhere in the carb, but it looked amazingly clean in there. The kit I ordered for it was from Cliff Ruggles, and he sent #73 jets to put in it to replace the #72s. Was going to drill the baseplate and install the bushing kit, but the throttle shaft doesn't have a lot of slop, I left it alone until the next rebuild if it'll need it. The rebuild alone got back the more pronounced suction sound it had right after the vortec swap. Can't wait to drive again after replacing the booster.

 

[DoubleDingo]

That is good info, I feel comfortable saying the truck has JB7.

 

[350runner]

Yup that suction sound is one of the best things you want to hear from a qjet. Yea what till you get into it

Sent from the dust in front of you!

 

[DoubleDingo]

Yup that suction sound is one of the best things you want to hear from a qjet. Yea what till you get into it

Sent from the dust in front of you!

Definitely. After looking over the vacuum hoses for the cruise control, those are getting replaced. I am going to make the engine vacuum system as a whole, as leak proof as I can make it.

There are 2 vacuum hoses from the cruise control unit mounted on LF inner fender, and those lines appear to go into the cab. Does anyone have a schematic of the cruise control vacuum lines for a 1981 Silverado camper special? I am hoping there is something out there that shows it. And hopefully it will show the sizes of the various hoses.

@chengny @HotRodPC @bucket @RetroC10Sport @Old77 @raylanr @BADAZ

 

[chengny]

You must be registered for see images attach

 

[HotRodPC]

Figured Jerry would have a diagram. I know I don't. All mine with Cruise are mid 80's and don't use that system.

 

[MadOgre]

My 84 doesn't have that either

 

[chengny]

The Cruise Master system was used on all 1980 through 1982 models (also on 1983 Caballero and El Camino).

The Custom Cruise III system was used on 1983 - 87 models (except 1983 the Caballero and El Camino)

 

[DoubleDingo]

I got a Cruise "Master"...lol... it sounds so regal...lol...

Thanks Jerry.

I was able to view it but then I click on it so I can print it and it takes me to a log-in screen. Hopefully I can figure out a way to print it. Before I click on it, what I can see, I saw a difference in the vacuum manifold that comes off the servo.

 

[MadOgre]

click on it and save picture as. Then you can print from your saved copy

 

[DoubleDingo]

Thanks, was able to get it and print it. I am guessing it is just what is shown in the pic and nothing beyond that?

I just saw a video on youtube and a guy had issues with stumbling in his caprice and it turned out to be the check valve on the booster. I may have caused it to leak when I moved the booster vacuum line around yesterday. The more stuff I fix and reseal, the more something else begins to fail or leak. My guess is there is now more vacuum being created by the freshly resealed engine.

I am going to have the GF press the brake pedal while I am under the hood listening near the check valve on the booster. It may very well be that causing the hissing sound when I apply pressure to the brake pedal. I am assuming it could make enough noise inside the booster from the air leak to be heard inside the cab. All I know is the pedal slowly goes to the floor as you press down because of the vacuum leak. With the engine off the pedal will hold firm.

 

[DoubleDingo]

Not the booster. It is in the vacuum system of the cruise control. Unhooked and plugged the new line I added from the manifold to the transducer and the brakes work fine.

Lunch was delivered as I wrote the other part above. After looking at the info Jerry provided, and another source online since I now knew which system I have, I saw the vacuum line that goes into the cab plugs into a vacuum release valve mounted on the brake pedal. The only thing I did different when I installed the carb was add a new vacuum line from the manifold to the cruise control transducer, which energized the cruise control system with vacuum. So, when I applied pressure to the brake pedal it caused the release valve or the hose running to it to leak. Release the pedal and everything went back to normal. The vacuum line I replaced was not connected since the vortec swap last year, and the brakes worked fine before taking out the carb. So it was odd that adding a rebuilt carb to the truck would suddenly cause the booster to go bad. Glad it was something simple. That saved me some money in parts and now I can drive the truck again. And it runs way better when it's cold now. No more spitting and sputtering and feathering the gas pedal to keep it running, so much nicer having a choke system that works.

Now to fine tune the carb again and readjust the timing now that the vacuum leak was removed from the equation.

 

[DoubleDingo]

After work I ran some errands and the first part I was able to get on the freeway, and man oh man what a huge difference in performance. Wow!

Got home with it good and warm and checked timing, it was good at 10* for the moment, and then readjusted the idle mixture because it was running rich and loading up at traffic lights. Got it adjusted and took it for spin......Primary take offs are neck snapping and quick, and Secondary take offs are even better. I am not concerned with roasting the tires, I want it to grab and go, and it is doing that very well.

I still have some work ahead to get the entire vacuum system as leak - free as I possibly can. And that includes getting the cruise control fixed, it was nice when it was working properly and I want it back for highway cruising.

Just filled both tanks so the plan is DD it for a while and enjoy the truck and V8 rumble.

 

[350runner]

Add a can and a half of b12 to both tanks bud it'll clear and clean err up good.

Sent from the dust in front of you!

 

[DoubleDingo]

Yeah clean is good, I'll grab some tomorrow.