flathead question
 

just bought a '36 with later motor. i noticed it has a small copper tube going from a raised boss on the front cover to a boss on the intake manifold. my other flathead has nothing like that! anyone know what this is for? thanks!

Re: flathead question
 

It's to supply a source for the vacuum brake on the distributor. DD

Re: flathead question
 

on my other motor, the tube goes to the distributor,not to the timing cover. why is this different ?

Re: flathead question
 

It's called 'design change'. Just a different route to the same destination.

Re: flathead question
 

The 3-hole mount '37-'41 "helmet" distributors have the vacuum line attached to the distributor. The '42 and later "crab-type" two-bolt distributors have the vac line attached to the cam cover. DD

Re: flathead question
 

Ford re-engineered the distributor to make it as short as possible. They shortened the cam, had the distributor bushing extending back inside the motor and used the crab cap. everything possible to cut down the length. One innovation also introduced was to run the vacuum through a drilling in the timing cover.

A simple, elegant design.

Mart.

Re: flathead question
 

was not aware of that change. thanks, everyone!

Re: flathead question
 

Re: flathead question
 

Every street engine needs two ignition advance curves, one for cruise and one for power. The vacuum brake provides that by allowing max advance st cruise and preventing detonation under hard acceleration.

Re: flathead question
 

There is no vacuum brake on the distributor you show which is a 49 to 53 distributor. The vacuum brake was used on the earlier engines as a way to limit centrifugal under acceleration.