That's a 235 carburetor, but if that is really a 51 size jet it is no wonder at all why you need your choke on to keep the engine running and why it sputters and stops without the choke halfway engaged. That is a small jet and will cause the carburetor to run pretty lean to very lean. 58 size was a common jet back when we had real gas. 59 or so might be better with ethanol. Your power piston does appear bent...straighten it, please or it may stick and hang up in your power valve opening. Which would interestingly cause you to run too rich or...if the bent piston was causing the power valve never to engage, you would be running way too lean when you needed power.
However, the 58, 59 jets were for the 235 and not for the 261 (but you don't have the right carburetor for the 261 so just changing to a much larger jet might or might not help you).
Last edited by Jon G; 08/13/20233:25 PM.
~ Jon 1952 1/2 ton with 1959 235 | T5 with 3.07 rear end
Looks like problems pretty well solved. I drilled out the .051" jet to .063" and (after tuning) she will idle perfectly with choke disengaged. However, she will idle up with choke out to near 1/2 engaged, but then she falls off after that. So i'd say .067 may be the ideal jet size. But im happy with how she is for now. I wont bother with. I'll try and run rec. gas and see how she responds.
Thanks for all the input. That solved the issue.
"Commonly quoted life advice I dont even try to live by." -Famous Person
Once you get tired of tinkering with a Rochester, put a Carter YF for an AMC/Jeep 258 cubic inch inline six on it. Those carbs are 30-something years newer, much better quality, and are factory calibrated for an engine almost exactly the right displacement. Jerry
"It is better to be silent and be thought a fool than to speak and eliminate all doubt!" - Abraham Lincoln Cringe and wail in fear, Eloi- - - - -we Morlocks are on the hunt! There is nothing noble in being superior to your fellow man; true nobility is being superior to your former self. - Ernest Hemingway Love your enemies and drive 'em nuts!
The power piston must push up & the spring pushes it down to knock the ball off the seat. Turn it around to make sure it will work in all positions. You may have to bend it to go into the center of the hole. Don't go larger than the .063 jet size. If you have to do that to get it to run right, something else is wrong. If a little is good it doesn't mean a lot is better. The choke is made for cold start & run. It is not for regular driving.
George
They say money can't buy happiness. It can buy old Chevy trucks though. Same thing. 1972 Chevy c10 Cheyenne Super In the Gallery Forum
Possibly a lean condition created by vacuum leak(s).I use carb spray while running and make short shots at critical areas, those related to manifold vacuum. Anything between the base of the carb and head. The idle rpm will change if you hit a leak, usually stumbles a little. You'd be surprised how many you may find with a hand-held tach that you may not notice by ear. Keep spray from carb throat and just small, short sprays. 2 cents RD
