Early Herald Engine No.

[Peter Truman]

On Gumtree here relatively locally a Twin SU Carb engine and 3 rail gearbox cast iron case, with early thin Alloy Bellhousing is for sale the engine No. is KA 1750.

I can't find a ref to Herald KA engines? I assume a 948cc engine.

[DanMi]

Australian?    https://web.archive.org/web/20130726114450/http://www.vtr.org/Herald/Herald-hickman.shtml  so a 1959 948cc

just noticed your location so that makes sense.

 

Edited May 4, 2023 by DanMi

[Peter Truman]

And the answer was right under my nose! 1959 hence the very lightweight alloy bell housing 

wonder if the very early 3 rail gearbox case could be adapted for 4 synchro use? Any feedback?

[johny]

Id be surprised as when you look at the two casings theres quite a difference on one side externally...

[JumpingFrog]

58 minutes ago, Peter Truman said:

And the answer was right under my nose! 1959 hence the very lightweight alloy bell housing 

wonder if the very early 3 rail gearbox case could be adapted for 4 synchro use? Any feedback?

Why would you want to? If it's an iron 3-rail 3-synchro casing, there's no advantage over using the later (and stronger) iron 3-rail 4-synchro casing. I doubt there's much between them in terms of weight, changing the bell housing is always going to be the simplest and most effective way to remove weight.

Very early 948 cars (and Standard 8/10) had one piece all alloy gearboxes, some have used these casings with 4-synchro internals, but I believe some modification is required. Exactly what I don't recall, perhaps the 3-synchro laygear cluster is shorter? However, many believe this casing is too weak for use with anything other than a 948 engine, it's a similar story with the early "thin" alloy bell housing, very prone to cracking, and actually somewhere I've got the stronger alloy bell housing that's also full of cracks...

Edited May 4, 2023 by JumpingFrog

[Peter Truman]

It’s a matter of availability you try finding a 3 rail 4 synchro case here in Australia 

Ironically there is also a Standard 8/10 all alloy box locally on Gumtree there’s been no Herald gearbox’s for years then 2 on Gumtree but not a later 4 synchro option

The last GT6 case I brought was ex USA & unfortunately it had a crack on the output side. The cost with delivery was probhibitive

Edited May 4, 2023 by Peter Truman

[johny]

Heres the problem, left 3 synchro and right 4. The laygear is much longer in the latter because 1st and reverse are were cleverly common in the earlier design. This meant the case had to be redesigned internally to accommodate the increase although the external length wasnt changed....

 

[Peter Truman]

Thanks for that explanation and drawings I’ll have to source a case from overseas ex Vitesse/GT6 or MkIV Spitfire.

[JumpingFrog]

Ah this makes sense, I assumed if you had 4-synchro internals, you would also have access to a 4-synchro casing.

I think as Johny shows it's not possible, 3-synchro has a small hollow space in the layshaft support, I checked some photos of casings on eBay...

The main issue (if you tried to remove material inside the casing) is with the "valley" under the rear layshaft support:

4-synchro has no such valley:

The 3-synchro case has a special bolt that goes through to stop rotation of the layshaft, the 4-synchro has a dowel (roll-pin). There is also potential issue in the tail housing (only relevant for non-overdrive), the 4-synchro mainshaft uses a bigger bearing (LJ7/8 instead of LJ3/4).

Probably for the alloy cases, if you're very determined, the problem of the valley can be solved with tig welding, for an iron case, there's no real way to add material back into the case.

Edited May 4, 2023 by JumpingFrog