carb making loud noise

[bobbyray27]

Ford Holley 4160 carb making loud hum/whistle sounds as if its being created by vacuum. Really loud never heard anything like it. Any thoughts of what it might be. Seems to go away when the rpm's come up off idle. All vacuum ports are capped off while trying to find the problem.

 

[Rockin69er]

Had this same problems years ago on a 460 in a F-250. It would go from a hum/whistle to a banshee wail at ~ 1000 rpm and then go away. Finally traced it to the gasket between the main body and the jet plate. The gasket was one of the early Nitrile ones and I put a cork one back on. That stopped the air leak. I have used Nitrile since then with no problems.

 

[broncnaz]

Are you sure all the vacuum port caps are in good condition? other than a missing or bad cap the only other thing it might be is a base gasket leak.

 

[bobbyray27]

Yes all caps are new and I removed all of them one at a time to try and locate the problem. I will try and check all of the internal gaskets.

 

[Bronchopper]

got a pcv valve on it? reason i ask, is i had a pcv hose that would collapse under vac conditions. it was tough to find since it did not do it all the time. replaced the hose and it was all good.

 

[bobbyray27]

I do have a pcv valve but its capped while I'm trying locate the problem. I have a hose for the brake booster that is connected to manifold. I will take a look at that one to see if its the problem.

 

[BronCowie]

Get a short length of hose, put one end to your ear and then move the other end around the carb, you might find the area of concern. The also make stethoscopes for this type of troubleshooting too that work even better.

 

[bobbyray27]

I've tried that in the past and haven't had much luck but I guess its worth another try.

 

[ugly74]

grab a can of carb clean, and mist it around mating surfaces. if there's a vac leak, the rpms will come up when you hit the spot.

 

[Bronk]

I don't know if you fixed the problem yet or not but did you try a different carb?

Reason I asked is... I had a aluminum intake on my 400 m with a rusted metal welsh plug and thought it was a carb problem till I put a known good carb on and still had the problem.

 

[bobbyray27]

changed all gaskets and while doing so found to screws missing from the bottom that hold the throttle plate to body, dam the PO. Adjusted the floats idle screws pump and now it runs great