The Ford Barn

alexiskai · 01-26-2025, 09:02 PM

This is a roundup of the current options for centrifugal advance distributors for the Model A.

Many people believe that operating a manual spark advance is part of the Model A experience. If you're one of these people, this post is not for you – do not read further and do not reply with your opinion.

The purpose of a centrifugal advance distributor is to automatically advance the ignition timing as the engine rpm increases. The graph of rpm to degrees of advance is called the timing curve. Most distributors use a system of spinning counterweights and springs to advance the distributor cam.

Product: Nu-Rex Automatic Advance
What it does: Installs in the valve chamber; replaces the lower shaft with a spinning weight on a spring; as the weight spins faster, it advances the rotation of the shaft above it. Provides 29° total timing at 1800 rpm.
Difficulty: Moderate
Pros: Retains original A distributor and manual spark control (if needed); high-quality timing curve; relatively cheap ($220).
Cons: Requires mild mechanical aptitude to install and can't be easily removed; timing curve unsuitable for high-compression heads over ~6:1.

Product: FSI distributor
What it does: Uses Pertronix electronic ignition instead of points & cam; vendor can supply weights and springs for most timing curve options.
Difficulty: Easy
Pros: Most flexible product in terms of timing curve options; no mechanic skill required.
Cons: On the expensive side ($380); can't use stock plug connectors; doesn't look stock; the Pertronix component has a reputation for failure among some repair shops.

Product: FSI Zipper distributor
What it does: Same as std FSI distributor but with outward appearance almost identical to stock A distributor.
Difficulty: Easy
Pros: Lets you use stock plug connectors; all the benefits of the FSI distributor with stock appearance.
Cons: Most expensive option (currently $600 with accessories).

Product: Mallory YL11A distributor
What it does: Vintage aftermarket distributor; 28° advance (I think)
Difficulty: Hard unless you can find one already restored
Pros: Excellent reputation for reliability; cores readily available.
Cons: Parts and expertise have become very difficult to find, so if you can't get your hands on one in good condition (which will probably be expensive), you might have a long road ahead of you to restore it.

Product: Model B distributor
What it does: Ford's first attempt at centrifugal advance was on the 1932 Model B. The distributor resembles the A distributor but has very different internals. Provides 14° of advance.
Difficulty: Moderate
Pros: A true "period-correct" modification; relatively cheap, lots of cores out there; easy to rebuild if you can rebuild an A distributor.
Cons: Limited advance means the user must adjust initial timing by trial and error; stock springs have a reputation for being too stiff; correct condensers very hard to find; only one supplier for shaft assemblies (Renner's Corner).

Product: B+ distributor
What it does: Modern reproduction of the B distributor using off-the-shelf parts; same 14° advance as the original B.
Difficulty: Easy
Pros: No mechanical skill required; good vendor support (Means Garage); cheaper than FSI ($300).
Cons: Short track record for reliability; limited advance means the user must adjust initial timing by trial and error; doesn't look stock; can't use stock plug connectors.

Product: Roll your own distributor
What it does: Take a "classic car" distributor such as the Lucas 25D or a modern one from 123Ignitions and modify the casting and shaft yourself to fit the A engine.
Difficulty: Hard
Pros: Best performance and flexibility; potential to add vacuum advance.
Cons: Requires significant machine shop skill and equipment; doesn't look stock, can't use stock plug connectors.

Did I forget any?

01-26-2025, 09:02 PM	#1
alexiskai Senior Member Join Date: Apr 2018 Location: Mebane NC Posts: 2,848	Current status of centrifugal advance distributors This is a roundup of the current options for centrifugal advance distributors for the Model A. Many people believe that operating a manual spark advance is part of the Model A experience. If you're one of these people, this post is not for you – do not read further and do not reply with your opinion. The purpose of a centrifugal advance distributor is to automatically advance the ignition timing as the engine rpm increases. The graph of rpm to degrees of advance is called the timing curve. Most distributors use a system of spinning counterweights and springs to advance the distributor cam. Product: Nu-Rex Automatic Advance What it does: Installs in the valve chamber; replaces the lower shaft with a spinning weight on a spring; as the weight spins faster, it advances the rotation of the shaft above it. Provides 29° total timing at 1800 rpm. Difficulty: Moderate Pros: Retains original A distributor and manual spark control (if needed); high-quality timing curve; relatively cheap ($220). Cons: Requires mild mechanical aptitude to install and can't be easily removed; timing curve unsuitable for high-compression heads over ~6:1. Product: FSI distributor What it does: Uses Pertronix electronic ignition instead of points & cam; vendor can supply weights and springs for most timing curve options. Difficulty: Easy Pros: Most flexible product in terms of timing curve options; no mechanic skill required. Cons: On the expensive side ($380); can't use stock plug connectors; doesn't look stock; the Pertronix component has a reputation for failure among some repair shops. Product: FSI Zipper distributor What it does: Same as std FSI distributor but with outward appearance almost identical to stock A distributor. Difficulty: Easy Pros: Lets you use stock plug connectors; all the benefits of the FSI distributor with stock appearance. Cons: Most expensive option (currently $600 with accessories). Product: Mallory YL11A distributor What it does: Vintage aftermarket distributor; 28° advance (I think) Difficulty: Hard unless you can find one already restored Pros: Excellent reputation for reliability; cores readily available. Cons: Parts and expertise have become very difficult to find, so if you can't get your hands on one in good condition (which will probably be expensive), you might have a long road ahead of you to restore it. Product: Model B distributor What it does: Ford's first attempt at centrifugal advance was on the 1932 Model B. The distributor resembles the A distributor but has very different internals. Provides 14° of advance. Difficulty: Moderate Pros: A true "period-correct" modification; relatively cheap, lots of cores out there; easy to rebuild if you can rebuild an A distributor. Cons: Limited advance means the user must adjust initial timing by trial and error; stock springs have a reputation for being too stiff; correct condensers very hard to find; only one supplier for shaft assemblies (Renner's Corner). Product: B+ distributor What it does: Modern reproduction of the B distributor using off-the-shelf parts; same 14° advance as the original B. Difficulty: Easy Pros: No mechanical skill required; good vendor support (Means Garage); cheaper than FSI ($300). Cons: Short track record for reliability; limited advance means the user must adjust initial timing by trial and error; doesn't look stock; can't use stock plug connectors. Product: Roll your own distributor What it does: Take a "classic car" distributor such as the Lucas 25D or a modern one from 123Ignitions and modify the casting and shaft yourself to fit the A engine. Difficulty: Hard Pros: Best performance and flexibility; potential to add vacuum advance. Cons: Requires significant machine shop skill and equipment; doesn't look stock, can't use stock plug connectors. Did I forget any?