Carb problems mid trip - help!

[ctsandb]

I’m in need of some advice. I was driving my 71 c10 (with a stock 307 with a Rochester 2 barrel carb) to the Nashville airport on Sunday (over 200 miles each way). I stopped to get a bite to eat at a drive through and the truck suddenly started to idle up and down. It would go away if I kept the RPMs up and would get close to dying if to didn’t do anything.

After I got my food I pulled out on the street and drove it down the block to a Kmart parking lot. It drove ok but as soon as I took my foot off the gas, it would buck and idle up and down and sounded like the vacuum advance was swinging wildly.

In the parking lot, I left it on and checked all the vacuum hoses. There didn’t seem to be any leaks. The only thing that seemed to get the engine to run better was to manually adjust the butterfly but it would only fix it for about 10 seconds.

I got some carb cleaner and starting fluid from Kmart and sprayed the outside of the carb. When I sprayed the back of the carb, it made a big difference but I couldn’t figure out where it was going into the carb. At a certain point, while I was trying to figure this out, I sprayed so much the engine almost stopped running. After that point, the engine evened out and seemed to run ok. I ended up getting back in the truck and driving another 100 miles to the airport (and made my flight!).

I took one picture of the back of the carb when it was not running well (just to try and get a look) and then again after it started running ok. You’ll notice that there is a small rod or screw (with a flat screwdriver type end) with a spring around it on the back of the carb that was in when it was running rough and then out (and loose) when it was running ok. Is this what was causing it to run rough? What is this part?

I plan on rebuilding the carb when I get home but thoughts on driving it home on Friday when I come back from my trip?

thanks!

[geezer#99]

Hot idle compensator.
Post #10 here explains about it.
http://www.hotrodders.com/forum/what...rb-208423.html

Maybe yours got sticky and some carb/choke cleaner cleaned it out.

THere's a diagram here at the bottom of the page that shows it.
Part 57, 58 etc.
http://www.carburetion.com/r2.asp

[ctsandb]

Thanks! I have never noticed this part before. The link you provided talked about this was typically for trucks with AC, which mine does not have though who knows if this carb is original. Hopefully it will be ok to drive it back home on Friday!

[LockDoc]

Originally Posted by ctsandb

Thanks! I have never noticed this part before. The link you provided talked about this was typically for trucks with AC, which mine does not have though who knows if this carb is original. Hopefully it will be ok to drive it back home on Friday!

I'm betting you solved your problem with the carb cleaner....

LockDoc

[Ironangel]

Originally Posted by LockDoc

I'm betting you solved your problem with the carb cleaner....

LockDoc

Agreed with the above

[ctsandb]

Thanks all! I'll give an update tomorrow when I get home...I hope.

[davepl]

Originally Posted by geezer#99

Hot idle compensator.
Post #10 here explains about it.

I'd say the odds of their bimetal spring changing the mixture at the same temp at which fuel boils would be hit or miss at best! Clever idea, I guess, but one that didn't stick, as they ultimately gave up on it.

[68Gold/white]

Carb base gasket can be a problem, or PCV valve sticking.