'71 rochester idle problem

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Golden Scamp

Golden Scamp

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My '71 318 rochester 2GC idles very poorly during a cold start and then during a warm start if it has been sitting for an hour +. Tried adjusting choke spring for cold start as choke seemed too open and this worked for cold start, but drove for fifteen minutes, parked, and 75 minutes later had a hard start and terrible idle. Carb full of fuel but acts starved and will not idle without plenty of gas being given in Park. Replaced fuel pump last month but did not resolve. Fuel dripping from throttle linkage and visible fuel on both sides of intake and wondering if rebuild will remedy this. Once warmed up, this Plymouth will go anywhere with no issues, but park it after that for an hour, and it barely starts and runs like garbage at idle. Any thoughts from the veterans?
 
I'd say time to clean it, and it may have a foam float that is sinking, and or dirt in the needle/ seat, or needle worn/ damaged.

Many guys try to blame fuel dripping from the throttle shaft as worn shaft/ bore, but the fact is, fuel should not leak even IF worn, as vacuum should draw it in. This is an indication of too much fuel, dripping into the throat due to high float level.

Heck, this time of year in Kansas, you should not even NEED a choke.
 
Have been doing some reading and think you are correct 67Dart273. I guess I suspected a rebuild was in order, but didn't want to tear the carb down if something else was going on. Got a kit from the Carb Docs and a brass float. Was wondering if anyone knows the stock jetting on this carb? # 7041180 Rochester 2 bbl? THANKS!
 
Golden Scamp said:
Have been doing some reading and think you are correct 67Dart273. I guess I suspected a rebuild was in order, but didn't want to tear the carb down if something else was going on. Got a kit from the Carb Docs and a brass float. Was wondering if anyone knows the stock jetting on this carb? # 7041180 Rochester 2 bbl? THANKS!
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Andy, i have your factory jet number. It's in a adobe form chart so i'm trying to get the documents together to bring here. Has a complete exploded view breakdown and part numbers for all your carb parts. For right now the jet # is 7002654, and yes they are rochester only. Holley jets do not work. I'll be back shortly when i figure how to transfer the info.
 
That's awesome OldmanRick! Thanks for taking the time to get this to me. The jet info is just what I needed, and the exploded view will be very helpful when I tear down the Rochester. I have seen these instructions going for $15 or more online, so I am grateful.
 
Golden Scamp said:
That's awesome OldmanRick! Thanks for taking the time to get this to me. The jet info is just what I needed, and the exploded view will be very helpful when I tear down the Rochester. I have seen these instructions going for $15 or more online, so I am grateful.
Click to expand...

Your welcome, Andy. I did a bunch of those carbs back in the mid/late 70's on GM small blocks, 305/350's. GM sent them out the door so lean (emissions?) most all stumbled off idle. Ditched the A/F limiter caps and jetted up one size and they ran great. Yours being a 71' i think just a regulation rebuild and tune and it should run real well. The're one of the easiest carbs to rebuild. Ironically i found that info. under non-automotive applications......lol. Guess rochester thought Mopars didn't rate:D. Good luck gettin' her tuned up.
 
Thats what I was looking for. Stock jet size is .56 MM. Have been researching and jets seem to be changed mostly if performance parts are being used or for differences in elevation/weather. I don't plan on doing any racing anytime soon but was wondering if increasing the jet size to, say, a .57/.58, would be at all beneficial? Maybe stock jets are fine but mixture just needs tuning?
 
As far as jetting i suppose going up one size if you have it apart wouldn't hurt. Not sure if it would help? You just don't want to go too rich in a stock application. I think there is another issue causing the problem your having. Probably a good idea at some point to tear it down, clean it and install the new parts from a kit. As simple as this sounds, i've seen these carbs lose the seal at the base gasket and caused enough of a vacuum leak to wreak hovoc on how they ran. A quick snug of all the mounting screws and even the air horn (top screws) is a easy check to see if it makes any difference. Not your exact carb, but you get the idea.......
 

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Great to hear Andy, i like your Scamp. Had a 71' for a short time. Wish i still had it....:D.
 
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