1933 Carb Idle---possible air leak

B

Bruce/CT

Well-known member
Hi Guys,
I have a friend who just installed a professionally rebuilt carburator (model unknown to me) on his 1933 Ford. He says that it idles best with the idle needle fully closed down. Makes me think that he has an air leak somewhere. How do you test for air leaks? Seem to remember that spraying a liquid on the questioned area as the test. What do you spray? Is it WD-40? If not, what is it?
Thanks for helping us out.
Bruce/CT
 
Bruce
Is this a 4 cylinder or a V8? Makes a difference. If V8, is it the original engine with a single barrel downdraft carb?
 
Sorry, I thought it was a straightforward question. I really don't know much about the car and I have never seen the car or its engine. What testing could he do on either engine? If the question can't be answered I'll try to contact him but it may take a while.
Thanks,
Bruce/CT
 
Posible the idle screw is too hi tryiny to run on secondary , close down butterfly n see if idle system comes on line?? ernie n tx
 
Spraying fluid on (WD-40 or other penetrating oil) will temporarily block the leak and it will usually change the idle rpm noticably. An induction leak will usually make the mixture lean so you would have to open the mixture screw up a bit if it is controling idle fuel flow like most older carbs do. My guess would be that the needle isn't seating properly or wrong shape for the seat or something of that nature. Most carburetors will respond if turning the needle either way from a given starting point. If they don't, something is wrong in the idle circuit.
 
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