Carb coming loose....

[rusty ol ranger]

Ive had this happen on 300s, but never on a V8.

Every 4 or 500 miles ill start hearing a whistle in the cab, its done this for a while now, and the one nut on the back passenger side of the carb would be loose, causeing a pretty hefty vaccuum leak.

Well last time i rebuilt the carb i put lock washers on, and now, after about 1000 miles i heard the whistle again, i thought "it cant be that carb again, i put lockwashers on", so i searched and searched, thought it was in the HVAC shit behind the dash.

Then it kelt getting louder and louder. So finally i checked the carb and every damn nut was a good 3-4 turns loose.

What is causing this? Im thinking about trying nylon stop nuts if it continues, but id like to find the root cause. Bad nuts? Bad studs? Its driving me nuts.

Btw its a bone stock 77 F250 with a 400 and 2150 2bbl.

 

[RonD]

I would use nylock nuts, and make sure gasket is OK

You probably have cast iron intake and carb is aluminum
These two metals have different expansion and contraction rates, so even with lock washers the nuts can get loose and then vibration unscrews them

This same thing happens on the 4.0l OHV lower intakes and some other engines that have cast iron heads and aluminum intakes, the bolts loosen up, but locktite works for those

 

[telsar]

loctite threadlocker would probably work ok for this.

 

[RangerFabWorks]

The old Lima 2.3 1bbls were notorious for the baseplate loosening up

Use nylon lock nuts and a dab of blue threadlocker.

 

[adsm08]

Agreed, blue threadlocker.

 

[85_Ranger4x4]

You might make sure it is the nuts and not the studs. Locknuts and locktite on the nuts won't help if the studs are backing out.

 

[lvwill]

I was thinking the same thing. Locktite the studs and nyloks on top.

 

[Ranger850]

EFI would fix that whislte.

 

[85_Ranger4x4]

EFI would fix that whislte.

Somebody just had to poke the bear...

 

[rusty ol ranger]

EFI would fix that whislte.

So would a bomb. But both stand about the same chance of happening.

Thanks yall. Ill give it a shot.

 

[RonD]

Actually EFI wouldn't "fix it" just move the location of the leak to lower intake

 

[kimcrwbr1]

Get some locknuts not the ones with nylon get the metal flange locknuts the threads are slightly deformed and will never vibrate loose.