1937 ford flathead won’t rev up

[Derek1937]

I have a 1937 ford pickup with the 21 stud 85hp motor and a Stromberg 97 carb everything has been rebuilt it idols perfect but when you go to rev it up it wants to die until you do 3/4 choke then it revs up and drives but stinks like gas around it with the choke on. Is there anything I might need to do to stop this problem? Thanks

[Chester Leighton]

Sounds like the power valve in the carb is plugged. Rebuild kits come with new ones. I had the same issue with a friend's 49. Bought the rebuild kit and put the new power valve in and problem solved. I was going to suggest checking the timing or possible a bad condenser but if it will rev up with choke on, the problem is fuel. It could also be that you don't have the float bowl setting right and there isn't enough fuel in the bowl.

[rockfla]

I would suggest doing a search here on the barn, upper right of the forums section in the red boarder. There have been "numerous" discussions here on the barn in various post, as you will find, on power valves, what to look for AND where to purchase them.......ALSO many qualified opinions on them Most notably CharlieNY, who you will want to make note of AND quite possibly end up sending your carb too IF you cannot make it run right....Charlie is "The Man". Just start your search with "Power Valves" and then maybe come up with a couple more iterations using "Power Valve". I "might" also PM CharlieNY here on the barn as he is, ONCE again, THE go to man for all things carburetors.....I am sure he will advise you on your issue!! Are you also sure your carburetor is not "worn"??? Not familiar with 97's but wear in the shafts and other parts can cause similar issues that even SOME rebuild kits will not fix.

[Terry,OH]

Check engine vacuum also.

[Derek1937]

[QUOTE=Chester Leighton;2130882]Sounds like the power valve in the carb is plugged. Rebuild kits come with new ones. I had the same issue with a friend's 49. Bought the rebuild kit and put the new power valve in and problem solved. I was going to suggest checking the timing or possible a bad condenser but if it will rev up with choke on, the problem is fuel. It could also be that you don't have the float bowl setting right and there isn't enough fuel in the bowl.[/QUOTE

I did buy the rebuild kit and rebuild the whole thing again because it’s had this same problem for quite a while so I put new everything in it but it still has the problem when it’s running and you look down the carb you can see it over fueling it when you open up the throttle and no choke but then you choke it and it’s fine

[Flathead Fever]

Sponsored Links (Register now to hide all advertisements)

If definitely sounds like a fuel issue. It's time for a carb overhaul. Closing the choke to get it to run eliminates everything else. I worked with a guy that was the carburetor rebuilder at a Ford Dealer in the 1960s-1970s. He took a regular air blow gun that has the threaded safety nozzle to reduce pressure. Unscrewed it and replaced it with a brass adaptor that accepts a foot-long piece of the smallest brake tubing, 3/16". He blew-out every passage with that tool. Then he took a spray can of carb cleaner that has the red plastic straw nozzle and forced it against each passage to make sure it sprayed out the other end of. I never saw one of his carb rebuilds not work perfectly. He always put a little white grease on the base gasket so that if you had to remove the carb later on the gasket was reusable and you didn't need to scrape it off the intake. The other thing is to not gorilla tighten the screws and strip them or warp the pieces. Just snug them. Check the carb base and carb top to make sure its flat and the throttle-shaft for play, a tiny bit of play is okay. A lot of play will give you a vacuum leak at the shaft. If you know every passage is clear, the carburetors have no cracks. you replace everything that is not metal. the gasket mating surfaces are flat, throttle shaft play is okay, float level is set correctly it should run great when your done.



Air fuel adjustment is the fial adjustament that is done, First the points dwell, then the timing and lastly air-fuel-ratio. It must be done it this order. Adjust final air fuel mixture using a little camping propane bottle. Its not necessary but it works great. Gently bottom out the A/F screws, if you overtighten those precision needle and seats you can damage them. No matter what carburetor I'm working on I always back them out equally 1 1/2 turns. With the engine warmed up adjust the idle speed. Open the propane bottle a little and pass it over the top of the carb. If the idle goes up the mixture it too lean, If it goes down it's too rich. When you have the mixtures screws turned equally, adjusted close to where they need to be the rpm will not change with a "little" propane. Because atmospheric pressure, temperature and altitude vary while driving you want to set the idle mixture slightly to the rich side. Give the screws a n additional 1/8" to a 1/4" turns out and your air fuel mixture will be perfect. Anybody can do this. "Always", work outside when working with fuel systems so that if there is a fire (you forgot to tighten a clamp and a hose comes off,...) you don't burn your garage and house down. That also applies for starting engines for the first time.t is real easy to get distracted and leave something loose. Its good idea to double chek it before you start an engine.

[rottenron36]

If I remember correctly, 97 carbs do not have a power valve, 94 carbs have a power valve. Ron

[A bones]

Charlie's no. is 716-662-9159

[Lawrie]

97,s have a power valve,But is mechanical.
Lawrie

[rotorwrench]

If a person has to apply choke then the mixture is too lean. If it idles then you know it's not in the idle circuit. Most likely it would be in the high speed circuit, ie main jets or flow tubes plugged. The accelerator pump is the acceleration circuit and the power valve is the power compensation circuit. There could be flow blockage in the power compensation circuit or a problem with valve function. The accelerator pump is easy to see if it's working as a general rule. It either squirts good or it doesn't.

[flatjack9]

You can rule out the idle circuit and the power circuit.

[alanwoodieman]

size of jets?