It's a nickel now due to inflation.

Arrightee... It was just a thot.

 

My engine builder has a machine for doing it, looks something like this:

 

I've got one of those machines too. That pic of your dist looks like a dual port advance with the retard part tube pulled (round opening nearest dist). I'll have to check my 78 and 9. 351M ? 400?

 

79 F150, 351m, C6.

Ive come to notice that theres a bit of off idle stumble when I only press the gas a little. Acts similar to how it does when I decelerate- rpm drops, vacuum level drops.

 

BTW, the vacuum diagram attached to the hood only shows one vacuum line going to the dist.

 

Yes, I checked my 79/351M looks like yours.

 

Any chance you could do me a huge favor and try turning your rotor counterclockwise against the advance springs and tell me if it returns completely?

 

In the AM, dark out there now.

 

Thanks

 

It depends on whether you have it hooked to full manifold vacuum or ported. If it's at ported it will let off when you let off the gas completely. If it's hooked to full manifold vacuum it will pull the vacuum advance mechanism full steam ahead because vacuum is at it's highest during deceleration.

Neither one should cause a problem though.

 

Once the throttle blades are cracked open full manifold and ported vacuum are equalized, the only time they're different is at idle, off idle they're one and the same vacuum signal.

 

Its hooked to manifold vacuum, which is what the vacuum diagram calls for.

 

Wait a minute....

Your picture in Post #7 shows the distributor connected to a temperature-actuated vacuum control valve:





I'll bet there's also another one of those control valves (perhaps the teal-colored device forward of the gooseneck?) and they both work in conjunction to switch the distributor from ported vacuum (where it normally is) to manifold vacuum when the engine is overly-warm so as to increase the idle speed (drawing more air across the radiator).

 

I was wondering if anyone was gonna say something about that. The 4 port PVS had been bypassed by one of the POs and all four of those hoses connected, which doesnt seem like a good idea since it was connecting ported and manifold vacuum.

Anyway, I got a new PVS and ran it the way you see it. Only problem was, no vacuum was supplied to the dizzy until the engine was warmed up. Theres supposed to be a bypass around that switch that allows a limited amount of vacuum to the distributor, but some genius PO removed that vacuum part, and no parts vendor has it.

So right now the two hoses on the end are off the switch and connected, supplying full manifold vacuum to the dizzy all the time. Makes startup a little harder, but gives more power during warmup. I was thinking about maybe taking the main jet out of a small engine and finding a way to stick it inline with a vacuum hose so I can meter the amount of vacuum getting to the distributor during warmup.

Oh, and Im pretty sure that teal switch you referred to supplies vacuum to the EGR system after warmup. It does open...

 

Yeah, I misread the post. I thought he said "does the vacuum let off on deceleration"