Thread: 55 thunder bird carburetor

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hihave a customer with a carburetor that has no vacuum at carb venturi to activate advance in dist.It has plenty of vacuum at manifold showing maybe 2in at carb revved up or at idle .Cust said was fine all of sudden quit but this was 8 yrs ago car cranks fine after new points and condenser .Also need points gap and dwell settings .thanks I

single point gap is .014-.016 for 28* dwell

thanks I guessed and set them at .015 any ideas on no venturi vacuum

Originally Posted by wakes

thanks I guessed and set them at .015 any ideas on no venturi vacuum

Welcome to CHR.
The venturi vacuum is simply an open port to the throat of the venturi, above the throttle plate. The only thing that could cause reduced vacuum is having that port blocked, or having the hose that's connecting to the port blocked. Look down the carb throat and see if you can see any crud blocking the tiny hole, and clean any deposits with carb cleaner. If that doesn't do it I'd take some carb cleaner and spray it into the connection tube on the back of the carb using the little tube on the spray can, then take an air nozzle and blow through the tube, towards the carb throat.

Thanks I'll try that after reading other posts that seems like only solution.I've already checked metal line and it is clear.

which carb do you have?

you said 2in vacume revved up or at idle---------which port------either way manifold should be higher at idle, less as revs/load goes up

Ported should be low or zero at idle but go up with r's

He can make the engine run much better by getting a dist with dual advance------think they maybe came out in 1958?

Also---check to see that the advance plate is moving in the dist-that old could be stuck

I believe Venturi vacuum is above throttle (also called timed), usually has little to no vacuum until the throttle starts to open. And, if I remember correctly, the older Ford motors vacuum advance worked backwards of the GM. I believe Jerry is familiar with this.

I had already checked vacuum advance in dist with a hand held vacuum pump .it works fine just no vacuum coming from carb at idle or revved up thanks for all the help .