11/69 Vacuum Switching Valve, Carb and Vacuum Retard Distributor Questions (1 Viewer)

[ryanwk628]

Running a 1970 (11/69) stock F engine and am going to a Trollhole carb. The new carb only has one vacuum port compared to the three I had before. I also have a vacuum retard distributor with petronix. The FSM (1972 F egnine) actually shows a Vac advance dizzy (page 8-25 or 160 in the pdf.) So I did a lot of searching and am reading to cap the vacuum retard on my dizzy and set the timing at 10 degrees. Supposedly this dizzy has enough mechanical advance to be serviceable without the vac. In the carb thread Trollhole said to cap the vac line on the carb. I know that I should be looking for a Vac advance dizzy.

Vacuum retard distributor

Old carb

New Carb and Vac Switching Valve

I have two questions:

1) When I cap these lines, based on how the PO plumbed it, I wont have anything going to the vacuum switching valve. What do I do with the vacuum switching valve? Just disconnect it? Does it need to be wired up?

(not mine but similar)

2) If I get a vac advance dizzy, is there a diagram like the one below but for my vacuum switching value? Mine has 4 outlets, this diagram shows 6. Does it matter or would I need a newer vacuum switching valve? Right now my intake has the port plugged where this digram has manifold vacuum. Im trying to determine what I would need to run and from where. The posts Im seeing deal with vac on the dizzy side but not the switching valve or routing. Pics would be helpful

Any insights into the logic behind this stuff is appreciated. Im trying to not just find out what to do but to understand why it works that way. Thanks!

 

[thebigredrocker]

Marley, the engine is 81-87 2F. Carb is 70-72 F. Dissy is 70-74 with a vac retard delete, so is now mechanical advance only.

Delete the VSV and emission computer.
Leave the CB connected to manifold vac.
Connect a hose from PCV valve on pass side of engine, over to intake manifold side plate (currently blocked off) or the big PCV port on the F carb insulator block.
Connect breather hose from air cleaner lid to clean air fitting on top of valve cover.
Set base timing to 10*, adjust idle mix for best idle speed/quality, set idle speed to desired RPM.

If it doesn't run right, then pursue further diagnostic: pull plugs & inspect, compression test, fix manifold leak issue due to headers, rebuild carb & jet to run right, etc...

Not an in depth of why to cap the VSV, but confirmation nonetheless that our VSV's aren't necessary. You probably know this, but FJ40Jim would be a good guy to contact if you end up wanting a Vac Adavance dizzy. Pretty sure he rebuilds dizzy's and is meticulous.

I would be curious to hear FJ40Jim's thoughts on pertronix in a capped of retard dizzy vs. petronix in a non-USA advance dizzy.

 

[thebigredrocker]

Pretty sure @Coolerman runs with his VSV capped off. He might even have an in depth explanation of why on his webpage.

 

[ryanwk628]

Pretty sure @Coolerman runs with his VSV capped off. He might even have an in depth explanation of why on his webpage.

Thanks! Ill check it out.

 

[65swb45]

I routinely remove the VSVs from this vintage. You simply cap the advance port on the carb until you get a vac advance dizzy.

The early '70 carb you took off had a vacuum port capable of running the throttle positioner. The new carb does not have this provison, so you will need to make one. I don't believe the intake manifold had a boss for a vacuum filter until '71, so it will take a little more work to set it up.

Best

Mark

www.marksoffroad.net

 

[ryanwk628]

I routinely remove the VSVs from this vintage. You simply cap the advance port on the carb until you get a vac advance dizzy.

The early '70 carb you took off had a vacuum port capable of running the throttle positioner. The new carb does not have this provison, so you will need to make one. I don't believe the intake manifold had a boss for a vacuum filter until '71, so it will take a little more work to set it up.

Best

Mark

www.marksoffroad.net

Thanks Mark! Is this the Vacuum filter? I picked up some parts off craigslist from someone who was parting out a seized F engine and this and a matching exhaust manifold were part of the lot. My 11/69 intake does not even have the boss on it for this part. Two ports here, they would go to where with a vac advance or vac retard dizzy?

Thanks!

 

[65swb45]

Yes, that is the part I am referring to. And as you noted, your manifold does not have provisions for installing it. If you have the port behind the carb, there's a mod to add a vacuum port there. I have a special fitting for it. We can talk offline if you have a telephone.