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Mar 28, 2013 | 09:11 PM

mdlave

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Carb questions

1978 F150 4x4 w/ 460 and C6.
Carb is a Holley 3310-4, Manual Choke. I have a few questions, as I haven't found a totally clear diagram.

Red- Timed Spark Vacuum Source - to distributor
Green- Full Manifold Vacuum Port - No clue. Currently into a plugged off short section of tube.
Blue - Manual Choke - I'm confused about how this (currently wide open) hooks up to a linkage. It is currently locked tight, but I THINK I understand which screws to release to make it work freely. The Haynes manual only refers to automatic chokes. Should I look into adding an auto choke - the kind that closes as the engine heats, I believe?
How should any of this connect to the transmission linkage?

Power brake vacuum port on the bag. This is capped off. Any use for this?

The manual references a PCV port, but there are none. PCV currently runs to the air cleaner. Is this correct? I read differing instructions.

Thanks!

Mar 28, 2013 | 09:46 PM

tbear853

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From: The Shenandoah Valley

Quote:

Carb is a Holley 3310-4, Manual Choke. I have a few questions, as I haven't found a totally clear diagram.

Red- Timed Spark Vacuum Source - to distributor

That works, I sometimes use straight manifold vacuum for distr but timing it is different. Most people find what you are doing best / easiest .... and that is what that port's for.

Quote:

Green- Full Manifold Vacuum Port - No clue. Currently into a plugged off short section of tube.

That's the one I have been known to use as stated above. If not needed, tube with screw or cap works.

Quote:

Blue - Manual Choke - I'm confused about how this (currently wide open) hooks up to a linkage. It is currently locked tight, but I THINK I understand which screws to release to make it work freely. The Haynes manual only refers to automatic chokes. Should I look into adding an auto choke - the kind that closes as the engine heats, I believe?

On my '77 I use a manual choke. Get the linkage working first that you have. I can't tell whay it won't work from pic, but normally there's a step up cam for the throttle under there so if you open the throttle a little and move that lever back the choke closes, the cam holds throttle open some for warm up.
To use, you just need a choke cable (we sell them at Advance Auto Parts) and clamp the outer jacket in that clamp behind the lever and set the inner cable in the little hole and tighten the screw. You want it set so that the **** inside the truck is pushed in when the choke is open and that lever there is all way forwards.
That way on a cold morning, you ease down on gas peddle as you pull on choke **** and choke closes some and throttle is held slightly open. Experience will teach the sweet spot to you, and how quickly to push the **** back in.

Quote:

How should any of this connect to the transmission linkage?

It doesn't.

Quote:

Power brake vacuum port on the bag. (BACK?) This is capped off. Any use for this?

You can run vac for power booster off that large rear port (3/8) or a 3/8 fitting in the intake manifold. I have used that port for the power brake. Currently, on my '77 with Edelbrock carb I have a 3/8 barbed fitting in the intake manifold near the rear that supplies vacuum for the booster.

Quote:

The manual references a PCV port, but there are none. PCV currently runs to the air cleaner. Is this correct? I read differing instructions.

If we are talking a real PCV valve, it uses vacuum signal from intake manifold to open and "positively ventilate the crankcase" when throttle is closed and manifold vacum is highest. I have my PCV valve feeding from a 3/8" barbed fitting in the intake manifold.
Breathers can be run to air cleaners.

Between the throttle plates at the bottom of the carb and the intake valves, all that area is "manifold vacuum"...
... the "timed vacuum port" get's vacuum only after the throttle plates start opening through a slot in the baseplate near the throttle plates. If you do any work on that carb, if you rteplace any parts or gaskets ..... you do yourself a favor if you stick with Holley parts.

Apr 4, 2013 | 12:57 PM

mdlave

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Well, in the process of rebuilding the carb, I damaged the threading at the base of the pump discharge nozzle.
Since that part is integral to the main body, there isn't a choke cable currently run (PO just left the choke open, and it was stuck that way until I took it apart), and I had a soon-to-expire coupon to Advance Auto, I ordered a Proform body.
Buy ProForm Carburetor Main Body for Holley 750 Cfm, Vacuum Secondary Carb 67101C at Advance Auto Parts)

I only use the truck occasionally, so having to wait a few minutes for it to warm up isn't a problem. If it is too much for a daily driver, I'll ebay it and get a stock Holley main body.

Since it deletes the vacuum advance port in the metering block, looks like I'll be using the full manifold vacuum port.
One thing I'm not totally clear on: Any problem hooking the PCV to the "power brake" vacuum port in the back of the carb? My brake booster goes to a port on the manifold.

Apr 11, 2013 | 08:17 AM

mdlave

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Got everything back in and hooked up. I ended up going with the Proform Body.
I cranked it a few times to get the fuel pump moving fuel into the carb, then pumped the gas and it started up. It idled out pretty quickly though. Also, fuel is leaking out of the primary and secondary inlet into the carb.

Anything obvious I may have missed during reinstallation? Any sequence I did wrong as far as making sure fuel gets into the carb?