Just picked up a 352 powered '66 that runs awful. It has a new carb and ignition system tune-up including the coil, cap, plugs and rotor. The previous owner was trying to get it running right but found it easier to sell it to me than actually fix it. haha. I was mostly interested in the perfect, rust-free body, but I would like it to run. He even told me to drive it the 600 miles home and I'm glad I didn't. I ended up finding a shipper to bring it 500 miles of the way because he needed to fill his rig and I took it the last 100. It barely made it.

It runs inconsistently like timing is wildly fluctuating. So I assumed that the vacuum advance was either going out or causing issues. So I put the vacuum hand pump on it and started testing the advance only to find the diaphragm completely torn and trashed. But before I replace it, I wanted to make sure the distributor wasn't also bad. I checked it for axial play on the shaft by trying to jiggle the rotor back and forth and didn't find it to be inconsistent with old Fords. I didn't measure it, but movement was slight. My concern is that with the distributor secured, you can move the rotor about 22 degrees or halfway to the next cylinder. So I pulled the distirbutor and checked the gear and it looks normal with no crazy wear. That's the back story.

Answer this:
Is any play clockwise or counter clockwise normal for an FE engine? It would seem that while the engine is running, some play wouldn't be a factor unless it were somehow inconsistent (as in if the bushings were worn letting the dizzy shaft float around). Let me know your experience. Presumably, it's normal or the cam in the engine is shot. I also thought that maybe since the distributor is mounted to the intake that if the intake were spaced up too high due to bad gasket installation, that might cause the dizzy gear not to mesh well with the cam. Again, I don't know. Just listening for feedback here.

Also, interested in feedback on other potential causes. Carb is a newer 2bbl holley and appears to have been replaced when the previous owner was trying to figure out what was wrong. We had nothing for vacuum advance because the diaphragm was torn. (Other than a timed vacuum leak that a broken diaphragm causes).

 

My gut feeling, based on your description, is that this is a vacuum or carburetor problem, not one caused by fluctuating timing.

The play you mention in the distributor seems to be the mechanical advance, so that's good to go.

I suggest you check for vacuum leaks using an unlit propane torch. Play the gas stream around the base of the carburetor, the intake where it mates to the heads, and anywhere else there could be a leak.

Best of luck, these can be hard to track down, but fortunately, it is a simple engine.

 

The truck definitely ran like there was a vacuum leak. The diaphragm in the vacuum advance canister being torn accounts for that. Also the PO had connected the line from the advance canister to a standard vacuum port on the carb, not a ported one. There's not a ported place on the side of the Holley metering block. I need to figure this out. Then I can properly tune and make sure there's no vacuum leak anywhere. The truck has power brakes and Cali smog so after I work out the supply for the vacuum advance, I'll disconnect the booster and make sure there aren't any other leaks anywhere else. It has the itty bitty Bendix booster.

 

2 bbl Holleys don't have the ported vacuum on the metering block afaik. There should be two vacuum ports at the base on the passenger side. The larger one is ported, the smaller, lowest one is constant manifold. The large port at the rear of carb is for PCV or brake booster.

So long as they are plugged there should be no vacuum leaks and just keep the vacuum advance disconnected till it gets replaced. It will decrease fuel economy but vacuum advance alone wouldn't cause the symptoms.

Many people wouldn't notice a disconnected vacuum advance, so long as the hose is plugged. Distributors are fairly inexpensive and if there is any slop in the bushings now it will wear further very fast. Gummed up and worn out stops could cause problems. A reman might be $50 or $75 and includes a new vacuum can.

 

Guess I should add that the truck has a bunch of vacuum stuff since it's Cali emissions and power brakes/auto trans. I tested the brake booster by putting a vacuum on it and it doesn't hold for longer than about a minute so I'm sure there's a leak in the booster. Plus the line that attaches it to the manifold is original rubber and isn't even tight around the nipple. If it stops raining this weekend, I'll have to get it sealed up so the carb can figure out what to do.

 

Here's an update so far. I still can't explain all the symptoms, but I eliminated some variables to start the tuning process.
As I mentioned, it wouldn't run without the choke on. I eliminated the Cali emissions and plugged the ports in the heads. Then, replaced the phenolic carb spacer with a non ported version. Removed all associated vacuum ports. Then unhooked and plugged the booster line and replaced the hose to the vacuum modulator. The only vacuum items plugged in are the distributor to the base of the carb on the passenger's side as a previous poster suggested. The modulator is hooked up to the port on the intake runner and the PCV is connected to the port on the carb. New gaskets on the carb spacer and carb itself were installed. I'm gonna suggest that the intake gasket itself isn't likely to cause a vacuum leak since it's under the valve covers.
I found the PO had apparently tried to tune the carb with the choke on or something. He closed the idle screws completely so starting there and moving through the accelerator circuit and power circuit and I am able to get the truck to run right. I'll introduce the power brakes back into the mix and we should be good. Thanks for the help. I think it was a combination of old vacuum lines, a bad booster and a PO who thought it's cool to tune a brand new Holley with the choke on.

 

There are centrifical advance springs under under the plate that carries the points. Sounds like they are broke or came loose. Have seen it before. They get way to much advance.

 

The original FE distributor came with two point plates, upper (B9AZ-12151-A) and lower (B9AZ-12151-B).

Ford replaced these two plates in 1972 with a one piece assembly (D2PZ-12151-A). So by now, your truck could have either type.

With either type: The nylon bushings crack apart, the point plate wiggles around.

 

I'm posting here for future searchers. FTE guys were pretty spot on concerning the advance situation. After very meticulously rebuilding the carb, which I'm glad I did, the truck began idling perfectly and responding perfectly to opening the throttle suddenly. But when I opened the throttle about 25% and held it, it would try to die and then stumble and hunt around.
When I unplugged and capped the vacuum advance, the problem completely went away. It runs nearly perfectly. What are my options for the distributor? I could get a reman unit (which I would convert to pertronix), convert to Duraspark II, or buy one of the cheap chinese distributors on eBay. I'm leaning toward the Procomp distributor on eBay just for time and simplicity sake. It's mechanical advance.
Are there any other ideas out there? I see that I can also buy a new breaker point plate for my distributor, but if the springs are broken, what then? Take my chances with a Mr. Gasket spring kit?
Has anyone had luck with the aftermarket distributors?

 

I forgot to mention that the carb wasn't helping the situation. The metering block inside it was completely cracked up and corroded. It looked like it corroded from the inside out and upon doing a little research, the problem is somewhat common for Holleys built about 10 years ago or so. Either way, the thing is running a lot better until vacuum hits the advance in the distributor.

 

get a rebuilt duraspark distributor for a 360, about 60 bucks, and convert to duraspark. 2 birds, one stone.

 

DuraSpark Electronic Ignition introduced in 1974, but not all FoMoCo vehicles have it until 1976. 360/390's cancelled after 1976.

1974 ignition module is 1974 only. 1975 ignition module is 1975 only.

Beginning in 1976, the most common module was the blue DuraSpark II ignition module that was used into the 1990's.

Blue: Modules are identified by a colored plastic square located above where the wires feed out.

btw: The 1974 & 1975 modules were such troublesome turds that Ford techs referred to them as NeverSpark!

 

I would not touch the ProComp parts with a ten foot pole on the end of a flag pole. I frequent a few FE engine specific forums and everyone that has tried or checked into the Pro Comp parts has said to stay far, far away! JMHO I would look for a distributor with vacuum advance, it helps driveability and fuel mileage.

 

I agree, unless racing and/or running WOT all the time (unlikely) you definitely want vacuum advance. Another option is to buy a stock replacement distributor and install a Pertronix module.

 

confirming my gut feeling. I have a friend working for ARP and talked about testing their engine stud lineup and he jokingly said you're better off whittling studs out of wood than using procomp.

Local Pick-n-pull has a 1976 truck with a 360, so I might go see if I can snag the whole D2 system off of it. If not, I'll fashion my own harness and buy new/reman.