1973 350 idling really high

[eriksg]

Hey, so I'm kind of a novice, kind of not when it comes to working on cars. I got most of the basic ideas and am not afraid to get my hands dirty and start figuring things out. I've got a 1973 GMC Super Custom with the Goodwrench 350 in it. But as I turn it on and leave it in park, it idles really high. I"m not real sure on how to diagnose this sort of problem or even really how to fix it. And as for searching around online how to fix it, all I can find are ways to fix newer engines. So if anybody has any starting places or tips on what I could look for that would be awesome!
Thanks!

 

[Jims86]

Hey, so I'm kind of a novice, kind of not when it comes to working on cars. I got most of the basic ideas and am not afraid to get my hands dirty and start figuring things out. I've got a 1973 GMC Super Custom with the Goodwrench 350 in it. But as I turn it on and leave it in park, it idles really high. I"m not real sure on how to diagnose this sort of problem or even really how to fix it. And as for searching around online how to fix it, all I can find are ways to fix newer engines. So if anybody has any starting places or tips on what I could look for that would be awesome!
Thanks!

I wish I could put arrows on this stuff...but you see the choke high idle cam, near the smaller green looking piece btween the carb and choke cap?
let the truck warm up for a few minutes, and try to move that down to see if the throttl steps off of the high idle cam. if it does, you may need to adjust the choke.

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[eriksg]

Alright, so I went out and let it warm up and played with the choke. It did throttle down, but then it throttled up again. The spring you can see in the pic here right about that yellow part compresses and doesn't decompress. That makes it throttle high but if I decompress it manually, then it throttles down again. Does that still mean I need to adjust the choke?

 

[HotRodPC]

Ohhhh you've got the old bi metal choke stove non electric auto choke. How about a choke conversion? Either convert to an electric choke, or an adjustable bi-metal choke, or a manual choke cable. I myself actually like manual choke cables.

 

[ben h]

just go no choke it makes ur neighbors love u on a strait piped 350 when its 10 below out

 

[89Suburban]

Wow, look at that old stove choke setup. Been a long time since I played with those.

 

[Jims86]

just go no choke it makes ur neighbors love u on a strait piped 350 when its 10 below out

People in Urban neighborhoods with straight pipes need to be strung up by their nut sack.

They also have replacement units for that thermal setup....but thats just me. You know how I feel about stock stuff nowadays!

 

[eriksg]

So, is this going to be a replacement job or will I be able to adjust the cables that are currently installed already? Also, what are the benefits of each different choke on this old of an engine?

 

[HotRodPC]

IIRC, part of the choke linkage runs inside a channel of the carb too. By the looks of the outside of that carb, and see how it's gummed up, I wonder if maybe the linkage isn't sticking just inside the carb housing. ?.? Or am I thinking of a different model carb?

 

[Jims86]

looks like that carb is due for a freshen up.

 

[eriksg]

Yeah, it is pretty nasty. One of these days I'll need to freshen it up a bit and get some new gaskets and whatnot.
But if it could be something as simple as opening up the carb and cleaning it out a bit that would be pretty neat. Are there any special considerations I need to take into account when I open it up and clean it? Anything I shouldn't touch or leave alone?
Thanks.

 

[Driver4r]

Q-jets are pretty easy and straightforward, but if you get a vacume leak when you put it back together, it will run like ****.... We have a carb that we think the housings cracked, its been rebuilt to many times and it still runs like ****.

 

[HotRodPC]

Q-jets are pretty easy and straightforward, but if you get a vacume leak when you put it back together, it will run like ****.... We have a carb that we think the housings cracked, its been rebuilt to many times and it still runs like ****.

Been there done that before. Come to find out all along, the guy who had rebuilt it before us has used a wrong gasket. We just kept matching up gaskets to what we took out of it from the kit. Finally a buddy that KNOWS Qjets took the top off and couldn't find a thing wrong with it. As he was putting it together, he says, I think this is the wrong gasket, where is one of you kit left overs? Showed him, he changed the top gasket, problem solved.

EDIT> Now that I think of it, it may even been the lower gasket. Don't recall now, but it was a wrong gasket used from the kit.