Mystery bump on bell housings

[alexiskai]

What is the purpose of this bump?

[rotorwrench]

It's appears to be an unfinished boss. It could have been for a bolt to attach something there but I have no information other than that there were different castings for the early multi-plate clutch and associated transmission. There may have been other changes to the bell housing design that I'm not aware of. I don't know if the right hand drive vehicles used it for some purpose or not but Ford put it there for some reason. Maybe someone else has more information.

[alexiskai]

The bump also appears on the multi-disc clutch housing but has no apparent purpose there either. Nothing about it in the JS. Doesn’t appear on any SB diagram. No one seems to know why it exists.

[Will N]

Could it have been there as a clamping point when the part was having its mating surfaces machined?

[Phil Brown]

Something for a righthand drive car ?

[Bob C]

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Here's a picture of a RHD and nothing there just the hump.

[alexiskai]

The fact that it’s on every variant and yet has no apparent function is itself weird.

[nkaminar]

It was put there to confuse future Model A owners.

[J Franklin]

Maybe something to aid alignment during manufacture.

[mcgarrett]

I'm gonna take a semi-educated guess about this mystery bump.

On Vince Falters' website he has a page showing all of the timing cover differences and mentions that some very early Canadian built export models did not have a timing pin hole in the timing cover - he shows a photo of one. He states: "the the engine was timed by a hole in the flywheel housing". Could this casting bump be the place where a timing pin was used to access a timing dimple in the flywheel he alludes to? I'm gonna say yes...and be proven wrong later!

https://www.fordgarage.com/pages/timingcovers.htm

[alexiskai]

Originally Posted by mcgarrett

I'm gonna take a semi-educated guess about this mystery bump.

On Vince Falters' website he has a page showing all of the timing cover differences and mentions that some very early Canadian built export models did not have a timing pin hole in the timing cover - he shows a photo of one. He states: "the the engine was timed by a hole in the flywheel housing". Could this casting bump be the place where a timing pin was used to access a timing dimple in the flywheel he alludes to? I'm gonna say yes...and be proven wrong later!

https://www.fordgarage.com/pages/timingcovers.htm

That was my theory too, and in fact my flywheel has a divot in what looks like the right place for it. But sadly in the JS, in the section for Early 28s, it shows the flywheel housing variant that had the timing pin hole in it. So it really was in the flywheel housing. Good theory though, definitely fits (some of) the evidence.

[dave in australia]

Alignment point for the machining process. Even modern castings have them.

[alexiskai]

Originally Posted by dave in australia

Alignment point for the machining process. Even modern castings have them.

Is this the same thing as a "datum"?

[Herb Concord Ca]

Not to high-jack this post, but notice where the accelerator pedal is in post #6.

[Synchro909]

Originally Posted by Herb Concord Ca

Not to high-jack this post, but notice where the accelerator pedal is in post #6.

And our cars have round pedals. There is not enough room for the elongated pedals and a central accelerator.
I prefer the RHD setup because it is not that difficult to use the brake and double de clutch a down shift at the same time. Ball of the right foot on the brake, heel on the accelerator - hence the term heel and toe action.
Notice also, the bracket on the back of the block to reach the starter and how the clutch pedal goes down between the engine block and the manifold flange clamp. There is not much room there - that's why we changed the clamp to one that does not need a nut and bolt. The nuts had to be positioned just right or they would stop the clutch pedal being depressed fully.

[dave in australia]

Originally Posted by alexiskai

Is this the same thing as a "datum"?

Yes, same thing.

[dave in australia]

Originally Posted by Synchro909

And our cars have round pedals. There is not enough room for the elongated pedals and a central accelerator.

The RHD multi plate clutches used the oval pedals, but changed to round right near the end of multi plate clutch use. It was the single plate clutch that used the round pedals on RHD cars.

[Herb Concord Ca]

Thanks Synchro and Dave for the education.

[WTSHNN]

Originally Posted by mcgarrett

I'm gonna take a semi-educated guess about this mystery bump.

On Vince Falters' website he has a page showing all of the timing cover differences and mentions that some very early Canadian built export models did not have a timing pin hole in the timing cover - he shows a photo of one. He states: "the the engine was timed by a hole in the flywheel housing". Could this casting bump be the place where a timing pin was used to access a timing dimple in the flywheel he alludes to? I'm gonna say yes...and be proven wrong later!

https://www.fordgarage.com/pages/timingcovers.htm

The pre-production Model A's did have the timing pin located in the flywheel housing; not the clutch (bell) housing.

I got this photo from Facebook, it's a shot of Bob Martino's pre-production chassis that was displayed at the Model A Restorers Club Morgantown Meet in 2022. You can see the boss is present even on a pre October '27 Chassis and the timing pin is just in front of it on the flywheel housing.



-Tim

[mcgarrett]

Fascinating stuff. I love learning new things about these old Fords. I gave it my best shot!