1984 4.9L carburetor hold down bolts/nuts...

[1986F150Six]

I have owned 3 vehicles with the 300/4.9L carbureted engines and all had the carburetor held down with two nuts. My son's 1984 is the same and I wondered why a lock washer is not used?

Thoughts?

Thanks!

[85lebaront2]

I never saw a problem there, the issue I always saw was the throttle body to float bowl/main body screws coming loose.

[ArdWrknTrk]

Lock washers are next to useless.
If you're really concerned use distorted prevailing torque lock nuts.
They will not come loose.

[Tarheel Blue]

I’ve run my YFA w/ star washers for over 15 years now. None of the traditional “wobbling loose” problems, ever.

[1986F150Six]

Tarheel Blue wrote

I’ve run my YFA w/ star washers for over 15 years now. None of the traditional “wobbling loose” problems, ever.

Thanks, that was what I was hoping!

[FuzzFace2]

85lebaront2 wrote

I never saw a problem there, the issue I always saw was the throttle body to float bowl/main body screws coming loose.

Yep that is where I have seen them come loose also not the carb to intake manifold.
Dave ----

[85lebaront2]

Dave, now you know why every YF/YFA I rebuilt had those loctited.

[Ford F834]

David, I don’t have a technical answer but I have a theory…

When you go to remove the carburetor, the nuts don’t suddenly “crack” loose… they release gradually and evenly.

I assume this is due to the very fine threads combined with some rebound on the compressed gasket material. Also the carburetor flange is soft metal so the nuts seem to bite into it just a little… like I said, it isn’t a scientific engineering answer, just an observation.

I have never had one come loose at the mounting studs, but I have had the bowl come loose from the base plate!

[1986F150Six]

Thanks, Jonathan!