Gearbox transplant on a standard upright Prefect
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  1. #1
    Official RnS Addict Perfect65's Avatar
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    Gearbox transplant on a standard upright Prefect

    I have a standard upright E93A Prefect that I am restoring as original with sidevalve 1172 engine. I would like to do a subtle gearbox conversion to 4 or even 5 speed. I have read recently of a conversion using a Reliant box but this meant the engine had to be pushed forward a few inches. Does anyone here know of a very compact modern gearbox that I could look out for. I am quite prepared to make a new bellhousing and rear bearing converter to take the torque tube but the main thing is that it must slot into the original space eventuelly. The donor box could be from a small capacity car as power transmission is minimal - 25 BHP if you are lucky. Dave

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    Official RnS Addict scooder's Avatar
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    I doubt very much there is a 5 speed out there that will fit in the same size hole as the original 3 speed. Its a very short 'box. Have you driven it yet? The E93A box has got fairly well spaced gears. Nothing like the pile of **** thats in the 100E. The 100E feels like a 4 speed that someone nicked the 3rd gear. The E93A feels a lot better.
    Be carefull of old 4 speed box's. The early ones (such as A30 and Standard 10 n such) Often have the top 3 gears placed fairly close to the E93A box, but with a stupidly short 1st gear added on. That would lead to a lot of efort for no real gain. As for a 5 speed, I realy dont think the engine has enough beans for an overdriven top gear (5th gear) You'd be forever changing down when the wind blows harder.
    I'd first try an Acuaplane head and a single 1 1/4" SU (I think you'd have to fab an inlet manifold for this), This would probly make more differance than a box swap, better power everywhere, better mpg, better hill climing ability, better top end.
    Martin.

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    I'm Not Jed Clampett stueeee's Avatar
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    Almost any gearbox change is going to be really difficult if you don't go over to an open propshaft setup which really means a back axle change. What about using one of the 100E overdrive gearboxes on the back of the E93A lump -as well as giving you a taller top gear, the overdrive can be used on second to remove the huge ratio gap Martin mentioned. There were several overdrive conversions made back in the day; some are listed on this website: Ford Popular 100E - XVJ 392 - Murray My brother had a Nordec manufactured overdrive on his 100E van, worked really well along with a mildly tuned sidevalve motor.
    Stuart.
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    Official RnS Addict Perfect65's Avatar
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    All good fodder for thought. My reason for looking to fit a 4 speed was the good report from the person who implanted the Reliant box - rave review quoting better acceleration, economy as well as top speed. My own experience racing motorcycles was when I transplanted a Suzuki 6 speed box in a 4 speed 250 2 stroke that made it feel as good as my 1105 tuned Kawasaki. I dont expect the same sort of improvement from the Ford but the Reliant box project seems to be a sound improvement. Perhaps add an SU and a higher compression?. I really didn't want to tune the car just make it better to drive - less strain. Dave

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    Official RnS Addict mygasser's Avatar
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    assuming the ford and reliant boxes are both 1:1 top gear how did your source get better top speed? if he's wrong on that can you trust his enthusiastic reviews enough to carry out such an involved conversion?
    need a job done on your project? i may be able to help.

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    Official RnS Addict Perfect65's Avatar
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    I have just read through the article again and what he is saying is that the car achieved better maximum speeds under the varying conditions, better up hill having a suitable third gear instead of having fourth to struggle with or to take a big drop to third and rev its nuts off. So yes Neil, top speed on the flat is going to be the same but getting there quicker and being able to maintain momentum under road conditions - thats sounds good to me. Dave

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    Official RnS Addict scooder's Avatar
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    Got a bit here about Aquaplane heads from an old Pitmans book.
    "Acceleration, hill climbing and maximum speed in the gears and in top gear are all improved. For example, the time taken to accelerate through the gears from 0 - 30 m.p.h. on the standard saloon in good condition is just under 9 seconds. This can be reduced to under 7 1/2 seconds when a high compression head aluminium head is fitted. Similarly, the 0 - 50 m.p.h. can be improved from about 25 seconds to 19 seconds. Maximum speed in top gear is not raised very greatly but nearly 70m.p.h. should be obtainable. Of greater importance, however, is the improved speed obtainable in second gear, in which it should be possable to reach nearly 40 m.p.h. In a typical test of the maximum speed obtainable up a hill having a gradient of 1 in 15, the speed of the standard Popular was about 44 m.p.h. With an aluminium cylinder head 52.5 m.p.h. was atained"
    This sounds to me like this is what you want to achieve. Got to be easyer than swaping in a different 'box, which is going to be a lot of work to sort. Dont think of the high compression head as tuning, just mearly correcting the compression ratio to what it should have been.
    Martin,

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    I'm Not Jed Clampett stueeee's Avatar
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    Or, if you don't want the expense and/or the "modified" look of an Aqauplane head under your bonnet, get hold of a Ford 8 head, it bolts straight on; fitted to the 10 HP E93A it bumps the compression up a fair bit.

    Ran a Ford 8 head on my E93A motor when I was yoof, along with some porting and a bigger carb it was much more lively than the standard motor.
    Stuart.
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    Official RnS Addict scooder's Avatar
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    That is a very good alternative there, forgot about the Eight head. Any idea what it bumps the comression up to?
    Martin.

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    MR UN-POPULAR sqweaka's Avatar
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    i think you can also get a better crown wheel and pinion for the axle to improve things.. these things are bolt on improvements, tried and tested! id be doing them first see how it perfomed, the T i had had an su fitted and it went well enough and gave great fuel mpg

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