1931 cady roadster vacume problem. running out of fuel

[Guest Jbart]

hello new to the form and have a question? Rebuilt a v8 355 and test driving it and running out of gas. good vac at idle about

10-13 in of vac driving it falls to about 4-6 in of vac. it seens to no not be enough to pull gas into the stewart warner can and fill it up with gas while driving. anyone have this problem? thinking about a 6 volt vac pump that puts out 18 in of vac with a back up canister. anythoghts? the vac pump off the cam is only putting out about 3-4 in not enough to pull gas in under a load (drinving). good vac of manifold of idle but under a load is my problem,

[Johan Boltendal]

They didn't use an extra pump when build, no need for it now either. Make a test rig on the bench for the Stewart, if it works ok if not rebuild the Stewart or have it rebuild. and have a look at all the vacuum line connections. Also make sure the fuel tank is clean from rust and debri and the fuel line shouldn't have an air leak either. There must be a fault some where let us know what came out,Johan

[trimacar]

I agree with Johan, a vacuum tank system works fine, it just must be in excellent working order, with no vacuum leaks and all connections correct and tight, and as he mentions clean.....they worked when new and adding another vacuum pump isn't necessary if the system is correct..

[huptoy]

I am not a Cad person. Does it have vacuum windshield wipers?

My car had a vacuum leak which turned out to be a 5 inch rubber hose in the wiper line.

It was under the dash and in 70 years the ends were hard and cracked.

Had me confused as all the lines and connections under the hood were fine.

Does it have any other vacuum driven accessories?

Found mine by sealing off the vacume line to the wipers and the vacume was OK.

[Guest wombvette]

And to add to what Johan said, the filler cap must be vented for it to work.