Timing a 1951 Ford Flathead

[51shoeboxer]

I have two questions; the first is: Is the timing mark (Bump) on the crank pulley at TDC or at 2 degrees or 4 degrees before TDC? (I've seen all three answers online.) The second is: does the 1951 distributor have mechanical advance? Thanks

[ThirstyThirty]

seems to me, the 1953 Ford FH V8 i put in one of my A coupes a whiles back... to replace the '48 with cracked block... bot it with cracked block, $125.00! 'as it sits!!' someone din't use antifreeze one winter up in WA state... had a vacuum advance on the distributor. so I did an online search on the subject for a 1951 V8 and this is what mr AI said:

Yes, 1951 Ford V8 engines used a distributor vacuum advance system. This system, designed to improve engine performance and fuel efficiency, advanced the ignition timing based on the engine's vacuum level

[38 coupe]

The bump is where you line up the initial ignition timing, the details of 2 or 4 degrees BTDC is academic.
There is not a mechanical advance in the factory 8BA style distributor. The factory distributor works very well if you have a stock or near stock camshaft, a single stock carburetor, and you hook up the vacuum advance line to the correct port on the carburetor. JWL did extensive testing and found a stock 8BA style distributor provided optimal timing for maximum power with a stock engine.

[wga]

Along with a timing light, use a vacuum gauge to check timing. Set at max vac on gauge,
then slightly back it off. Needle should be steady.

[19Fordy]

On my 8BA the timing "bump" is 2 degrees BTC. Use that as a starting point and then use your timing light and vacuum gage to fine tune the setting.

[51shoeboxer]

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Originally Posted by 38 coupe

The bump is where you line up the initial ignition timing, the details of 2 or 4 degrees BTDC is academic.
There is not a mechanical advance in the factory 8BA style distributor. The factory distributor works very well if you have a stock or near stock camshaft, a single stock carburetor, and you hook up the vacuum advance line to the correct port on the carburetor. JWL did extensive testing and found a stock 8BA style distributor provided optimal timing for maximum power with a stock engine.

Hmm...so what you're saying is just set the timing so the bump lines up with the pointer. That would imply that the bump is at the correct number of degrees before TDC. I do not find it academic to ask how many degrees before TDC the bump is.

[51shoeboxer]

Would I set the timing pointer to the bump with the vacuum line to the carburetor connected, or disconnected; like I have set static timing on most cars?

[V8 Bob]

Originally Posted by 51shoeboxer

Would I set the timing pointer to the bump with the vacuum line to the carburetor connected, or disconnected; like I have set static timing on most cars?

Disconnect and plug the vacuum line to the distributor when setting initial timing. I would make sure the point dwell is OK before making any timing changes. Target dwell is 27 degrees.

[51shoeboxer]

Originally Posted by V8 Bob

Disconnect and plug the vacuum line to the distributor when setting initial timing. I would make sure the point dwell is OK before making any timing changes. Target dwell is 27 degrees.

OK, thanks.

[38 coupe]

There is no need to disconnect the vacuum line. The factory vacuum port on an 8BA is a mix of ported and venturi vacuum. There is no vacuum in the line at idle.
I typically set the initial advance with the engine off. Rotate the crank until the pointer is lined up with the bump. Pop the distributor cap off. Loosen the distributor hold down clamp. Turn the ignition on. Retard the distributor until the points are definitely closed. Slowly advance the distributor until the points just open (the points will spark when they first open, usually I have to do the retard and slowly advance a couple times to avoid over advancing). Tighten the hold down clamp without letting the distributor move. Turn off the ignition. Reinstall distributor cap. Timing is set.

[51shoeboxer]

Originally Posted by 38 coupe

There is no need to disconnect the vacuum line. The factory vacuum port on an 8BA is a mix of ported and venturi vacuum. There is no vacuum in the line at idle.
I typically set the initial advance with the engine off. Rotate the crank until the pointer is lined up with the bump. Pop the distributor cap off. Loosen the distributor hold down clamp. Turn the ignition on. Retard the distributor until the points are definitely closed. Slowly advance the distributor until the points just open (the points will spark when they first open, usually I have to do the retard and slowly advance a couple times to avoid over advancing). Tighten the hold down clamp without letting the distributor move. Turn off the ignition. Reinstall distributor cap. Timing is set.

I've done it that way with cars that have points, but my car has Pertronix ignition. When I checked advance with the the engine idling, my adjustable timing light showed that the pointer aligned with the bump when my timing light was about four degrees advanced. That made me thing that perhaps my vacuum advance diaphragm had failed, as there was no vacuum at the diaphragm, i.e no vacuum advanced timing. From what you've said, there should NOT be vacuum advance at idle. Let me see if I understand this Loadomatic ignition. As I understand it, the vacuum port is above the throttle plate, so at idle there should be no vacuum signal in the vacuum line; and it is only when the throttle plate is cracked open that the vacuum line gets a signal from below the throttle plate...is that correct?

[38 coupe]

The Load-a-matic uses primarily venturi vacuum. There is a little port drilled into the venturi, the more air flow the more vacuum. This is also tied into a passage near the throttle plates. Hook up your timing light and watch the ignition advance while you slowly rev the engine, and while you snap the throttle open. The advance is a good match to ignition timing needs based on engine load and speed.
You must have a good vacuum advance can for this to work.

[51shoeboxer]

Originally Posted by 38 coupe

The Load-a-matic uses primarily venturi vacuum. There is a little port drilled into the venturi, the more air flow the more vacuum. This is also tied into a passage near the throttle plates. Hook up your timing light and watch the ignition advance while you slowly rev the engine, and while you snap the throttle open. The advance is a good match to ignition timing needs based on engine load and speed.
You must have a good vacuum advance can for this to work.

Thanks, I will check that.

[flatjack9]

With no load on the engine, You won't get enough flow through the venturis to get any advance.