21 stud pilot motor vacuum takeoff

[pooch]

No clue if inlet manifold is original to motor or not, but has no vacuum take offs.

Need vacuum for crab dizzy and power booster .

Any ideas for the correct place to drill and tap manifold ?

[51 MERC-CT]

Not "correct" but any convenient spot that is accessible. Worked for me.

[Talkwrench]

Maybe use a vacuum
plate under the carb , like one for a Columbia its what you'll need for the power booster.

[flatheadmurre]

The big trucks had vacuumplates to for brakes.
Think about where you drill for the fitting, seen people drill over a single inlet runner and hook up wiper/powerbrakes and dizzy to it...just has to affect the A/F mix...

[51 MERC-CT]

Originally Posted by flatheadmurre

The big trucks had vacuumplates to for brakes.
Think about where you drill for the fitting, seen people drill over a single inlet runner and hook up wiper/powerbrakes and dizzy to it...just has to affect the A/F mix...

If the booster or the distributor vacuum brake were drawing outside air (that may affect A/F ratio) then how would they even work?

[pooch]

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Originally Posted by flatheadmurre

The big trucks had vacuumplates to for brakes.
Think about where you drill for the fitting, seen people drill over a single inlet runner and hook up wiper/powerbrakes and dizzy to it...just has to affect the A/F mix...

That was what I am alluding to.

Not running a vacuum wiper, that would let air into the manifold constantly when working.

The dizzy would be negligible, but upon starting the vacuum booster needs to be emptied, so if it was drilled into a certain inlet chamber, it would affect that particular 4 cylinders upon the first revolutions of starting and minimise vacuum thru that side carb barrel..

I doubt the action of applying the brakes would matter much when the engine is running, even at idle, even then it would only be a puff of air in, as the pedal is pushed, then the air would stop.

I do have one of those truck plates, but wanted the takeoff to be right at rear of manifold so no large pipe showing.

[flatheadmurre]

Powerbrakes are momentary only so not a big problem.
When you press the brake its just the movement of the diapragms volume of air coming into the intake, same amount is coming when brake is released to restore the vacuum again.
Wiper is the big issue affecting the lean cruise mix.