Holley 94 - vacuum advance threads stripped
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From: Lewisville, NC
Holley 94 - vacuum advance threads stripped
I've got a 254 Mercury flathead in Elvis with an untagged Holley 94 carb. Rebuilt the carb this weekend, sounds and runs absolutely great now. Only one hitch - the vacuum advance port on the middle casting of the carb is stripped and won't hold the vacuum line. Since this is just a vacuum line, is there a repair possible on this? I was thinking of epoxying in a vacuum line flexible vacuum hose connector and grafting that onto the rigid tube going to the distributor advance. I'm not using the throttle body vacuum port (going electrical wipers), how much of a sin would it be to use that and cap off the middle casting port?
Even with the vacuum advance disabled, I'm still getting a bunch of advance out of the mechanical advance in the distro. How much of the advance comes from the vacuum and how much from the mechanical?
I used steel brake line for the vacuum line and I'm sure that inflexibility is part of the reason for my stripping out those threads...
-Scott
Elvis - '53 F100 with Mercury 254 flathead
Even with the vacuum advance disabled, I'm still getting a bunch of advance out of the mechanical advance in the distro. How much of the advance comes from the vacuum and how much from the mechanical?
I used steel brake line for the vacuum line and I'm sure that inflexibility is part of the reason for my stripping out those threads...
-Scott
Elvis - '53 F100 with Mercury 254 flathead
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From: Southern New Hampshire
The stock 8BA flathead distributor DID NOT have any mechanical advance; it is all vacuum. If you are using an aftermarket distributor then you need to plug that carb port and obtain vacuum from the manifold.
You can try a thread sealer or even a pipe joint compound but remember it is a makeshift fix at best. An epoxy such as JB Weld is permanent and brings its own problems when you need to remove the carb.
Sometimes you can find a metric size that is just enough bigger to work and use a bottoming tap. Then its a matter of adapting the steel line end.
You can try a thread sealer or even a pipe joint compound but remember it is a makeshift fix at best. An epoxy such as JB Weld is permanent and brings its own problems when you need to remove the carb.
Sometimes you can find a metric size that is just enough bigger to work and use a bottoming tap. Then its a matter of adapting the steel line end.
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From: Lewisville, NC
I couldn't read the side of the distributor for model, but when I took it apart to check it, there were advance springs in it and a vacuum advance. When installing it, it doesn't go in so that anything seals the dist. shaft to the timing cover - never did think that was right. I don't mind using the JB Weld, but is a standard "rubber" vacuum line sufficient near the engine block in terms of heat resistance?
Did Mercury use the same distributor (and carb) for their 254 that Ford did for their 239?
-Scott
Did Mercury use the same distributor (and carb) for their 254 that Ford did for their 239?
-Scott
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From: Southern New Hampshire
The stock dizzie has an advance plate & springs that are vacuum driven. That same dizzie was used on ALL 8BA style flatties, irregardless of make, country or application.
Ford didnt go to an O ring seal until the 289 in 64. Before that it was just a tight fit that kept things together. Try getting one out of a Y Block!
Ford didnt go to an O ring seal until the 289 in 64. Before that it was just a tight fit that kept things together. Try getting one out of a Y Block!
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From: NM
If you can't find a threaded fitting that is just a little bigger than the existing hole, I think I'd tap it out for pipe threads -- 1/8" NPT maybe? Smallest one that is bigger than the existing flare nut threads. Leave enough wall thickness for strength, and don't overtighten - zinc alloy is weak. Be sure to block shavings from going into the carb. Use a barbed (5/32"?) male hose x 1/8 male NPT fitting, a short section of vacuum tubing to the original metal tube (minus the flare fitting). Should work fine, mine has a short section of wiper tubing in the middle of the metal tube (from PO).
The vacuum from that port is different from manifold vacuum. It comes from two places in the carb; the venturi and the throttle bore just above the throttle plates. If you're running a stock distributor (sounds like it), this is the proper source for the distributor advance.
The vacuum from that port is different from manifold vacuum. It comes from two places in the carb; the venturi and the throttle bore just above the throttle plates. If you're running a stock distributor (sounds like it), this is the proper source for the distributor advance.
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