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MG Midget and Sprite Technical - Type 9 installation - correct preparation?

FINALLY started my 3-phase project to:
i) install Type 9 'box
ii) get engine bay painted
iii) complete engine re-build, including cam change.

As per attached pic, I have now got the engine out, necessary for all of the above.

I know it's been written many times before BUT can you please confirm the piece that I need to cut out of the transmission tunnel? I believe it's the channel that runs across the car, through which two bolts passed into the original gearbox mount? In my photo, it's the piece immediately below the heater box. Do I only need to cut out this channel between either side of the transmission tunnel and as such, no sheet metal needs to be removed?

Sorry, I know this has been written in many threads before BUT I don't want to get it wrong tomorrow when I go in with the saw...

Glynn


Glynn (1275RWA) Williams

Glynn
When I do conversions I take out 7 inches of the top hat cross brace chassis member - where the original gearbox mounting bolts are. I then cut back 8 inches taking that part of the floor of the transmission tunnel out.
Alan
Alan Anstead

Alan - thanks for your reply.
To clarify, cut out the cross member plus the next 8 inches of the transmission tunnel? i.e towards the axle from the cross member?
(can you tell I'm nervous about doing this???)

Glynn
Glynn (1275RWA) Williams

Glynn
That is how I do it. If you are nervous and a midget & Sprite Club member then delay. Accessible on the members section of the main club website are back issues of the club magazine in which are several articles , with pictues, of T9 conversions that I can direct you toward.
Alan
Alan Anstead

Here's a good website showing what it should look like when removed, obviously you don't need to remove the heater box tray - as shown here for a K series:

http://ktu661c.com

The third photo down is the one you need.

Over the years I've extended the cut out in the rest of the tunnel lower skin to the point where I can now lower the back of the gearbox without lifting the whole engine/box assy off the front mounts.




john payne

Thanks John - that photo is really clear.
I'm going to start cutting NOW!

Glynn
Glynn (1275RWA) Williams

This is how it looks now - hope I got it right??


Glynn (1275RWA) Williams

Lookin good!
Alan
Alan Anstead

Glynn - have you got the gearbox mount and plate? Are you using FL parts or making your own?

When I did mine I whacked some heavy box section into the open ends of the crossmember before welding the ends up - not sure whether it was necessary but seemed to be the done thing (about 15 years ago now).

If you need info there's a load on the twin-cam/16 valve archive on this site - just do a search and there'll be all-sorts. Most of the K-series conversions will have had this done.

Cheers, Lloyd

L McInally

Lloyd,
The only items I have so far are a MMC bellhousing and a good type 9 'box.
I was planning to thump some box section into the open cross member and make up a mounting bracket along the lines of some I've seen posted on this forum and other websites. That bit doesn't look too difficult...
I'm also planning to go concentric slave cylinder route as per many others on the BBS.
Thanks for your input

Glynn
Glynn (1275RWA) Williams

This is the replacement cross member that I made for mine. Very simple! The "shoe" in the centre takes a Fiesta engine mounting rubber block that screws directly to the T9 box, with shims to provide height adjustment.

The commercial items seem to only bolt to the inner chassis frame rails, which to me doesn't properly replace the function of the original cut out section. I feel it is important to provide rigidity across as much of the width of the car as possible, so mine was just limited by the position of the exhaust pipe. Its about 22" long.


Guy W

Guy - I like your cross member.

2 Questions....

1 - is that 60x20 3mm thick box ?
2 - Do the middle 2 bolts go all the way through or do you have larger holes on the other side to get a socket etc in.
3 - did you have to trim the channel that runs underneath the stell pressing that runs down where the seat bolts.

Ok that was 3 three questions ;-)
Dean Smith ('73 RWA)

Hi Dave,
1. Sounds about right. Actually, no I think it was deeper than 20mm. Probably 30. Its too wild outside at the moment to go and measure!

2. It is bolted up into the box sections on both sides - all 4 fixing bolts. I used some 3mm thick angle irons that slide inside the cross members and have captive bolts welded to them. The bolts protrude down ready to fit the blue cross member onto. It makes it easier to fit this way, can be clamped up tight and no problems of aligning bolts in dark holes to get threads started.

3. Yes, I cut out a small notch from the inner seat runner channel at either side. Didn't seem to weaken anything too much!

One modification - if I were doing this again, or rather when I next take that off, I will weld a couple of extended lugs (100mm?) to the trailing edge of the cross member and add another fixing bolt through the floor at each side of the tunnel. It has worked fine, but after 70,000 miles of use I can see that there is some slight floor distortion from the 60mm wide box section trying to rotate - probably under braking
Guy W

Sharp eyed will spot the photo was taken pre concentric clutch slave days!




Guy W

Guy - I like the look of that bracket! Unless I come across an even better idea, I'll think I'll do something very similar, including the addition of the extension pieces as you describe.
Cheers

Glynn
Glynn (1275RWA) Williams

I lost nearly all my pics of my conversion (I took loads!)but here are a few, if it's any help.

First, tunnel from underneath - before cutting.


Nick Nakorn

After cutting.


Nick Nakorn

With the gearbox installed.


Nick Nakorn

That mounting plate is the same style, as far as I know, as normal commercially available ones. But to me although it is clearly robust, it doesn't properly replicate the structural function of the original (cut out) cross member.

The original is a box section across the full width of the car, providing rigidity from sill to sill. This forms the lower section of what is a large D (on its back) shaped structural unit formed over the top by the A posts and the scuttle/ bulkhead unit. In fact there are 2 such structural D shapes, one within the other, the smaller one being formed by the gearbox/transmission tunnel. The strength of these relies on the rigidity of the full width cross member along the base of the D shapes.

That type of plate introduces weak points at either side of the transmission tunnel - in effect creating two hinge points allowing the body to flex in a way that it wasn't intended to. My interpretation is to use a replacement section that is much wider across the width of the car to avoid creating those "hinge" points. Ideally mine would have extended sill to sill as well, but the problem then is that it gets in the way of the exhaust pipe, so that is what limits the width.

All theorising I suppose, but that is my take on it.

Oh, and mine was made from a bit of scrap section that I fished out of a skip so it cost nothing. Maybe that's really why I justified using it! ;-)
Guy W

I followed Guys crossmember design sort of faithfully :) and I later added a rectangular tube to hold a rubber block which helps control any lateral twisting under drive

This works so well that I haven't even replaced the engine steady rod I added to the back of the engine years ago


bill l

Only two mounting bolts on yours Bill? Or are there other holes that don't show in the pic?
Glynn
Glynn (1275RWA) Williams

two does it, though I have considered bunging a second set in

No problems yet so far
bill l

Guy, I think it would be a hinge-point were it not for the transmission tunnel. Without the original cross-member the hinge-point is in the middle of the tunnel. But even then, the bulkheads are pretty good structures that should hold things together. The admittedly crude heavy plate supplied in the kit is thus to stop a lateral arc movement of the two sides of the car around the tunnel 'hinge' as well as providing a gearbox support. I think it's OK.
Nick Nakorn

Nick l am sure the commercial design is fine. Just that l think mine is better! Its certainly easy to make if anyone is going down the diy route. My complete T9 installation cost just on £220, including the gearbox (2001 prices) You wouldn't get it done for that sort of money these days!

I do have a rear engine steady as well.
Guy W

Guy, I think mine is even better! Like yours it was free but only because I copied the 'ground anchor' that was the the Frontline one but out of ally. I can't remember the figures but it saved a lot of weight and does the job. Like Nick I think the Frontline design is more than up to the job - just a pity they didn't make it a bit lighter.
john payne

Guy, I agree the Frontline version could be much better. Next time around I think I might make my own too.

I was so tempted not to buy the expensive Frontline kit but after doing a big spreadsheet and putting in prices I was almost about to spend nearly as much on 2nd hand gearbox plus all the bits with no guarantee that the box would be any good. £220 is good Guy! Mind you, in 2001 you could by a whole car for £100, take out the box and sell the rest for £50... those were the days. I just think of the scrap yards I used to walk around when I was a kid in the 1960s, one had a Hispano-Suiza in it one week but it had been crushed by the following week... another yard in the early 1970s had a straight 8 Packard in right hand drive. It was there for years and years.
Nick Nakorn

How/where/why, is the rear engine steady?
Lawrence Slater

On mine l have an adjustable, rubber mounted tie rod between a bracket fixed to the top bell housing bolts and the top inner corner of the n/s foot well, which is reinforced. The gearbox is only supported on a single point at the rear, with little lateral support so l added the engine steady to resist torque reaction.
Guy W

Usually in a similair location/orientation as you find on a Mini - from the rear of the engine across to the passenger footwell.

because with a type 9 gearbox that only has a single mounting point low down, and the 2 original engine mounts there is less resistance to the engine rocking under power than with the original gearbox mount that provides more support against that motion.

Also popular with racers I beleive where higher powers and more strain can also cause more movement than is desired.

Picture is from Peter May
http://www.petermayengineering.co.uk/specialistProducts.htm

(Posted as Guy was typing)


Dean Smith ('73 RWA)

And my rather less stylishly engineered example!


Guy W

A good idea Guy.
Nick Nakorn

A good idea then.

I used rubber blocks inside the g/box tunnel, snug against the sides of the T9, to achieve the same thing. It's worked perfectly well since, without ever needing adjustment in over 13 years.

However, I may re-visit that and apply the version of stay shown here. I'll decide when I pull the engine for a rebuild, and when I pull the current T9, to install and test several T9s I've accumulated.
Lawrence Slater

Not my idea at all. It was a commonplace addition to minis. In fact with the early minis with the long pudding stick gearlever it was almost essential if you uprated the engine and still wanted to change gear!
Guy W

Was certainly standard by the time my 1984 Mini Mayfair was built. Zircon Blue with blue velour interior. You could feel the luxury ....

(Guy you sure you dont want to claim the idea at least ;-) )
Dean Smith ('73 RWA)

Mmm, I don't have an engine steady, the rear g/box mount and the two engine ones seem to cope ok. Not had to replace them in the ten years since conversion anyway.
I'd be interested to see how much it moves when being thrashed though, those engine mounts seem quite soft.
john payne

John, l don't think its that critical either. Its just what l chose to do. I had fitted a LCB exhaust and found that it was knocking where it passes by the chassis rail as the engine twisted a bit when l blipped the throttle. Perhaps l should have just renewed the engine mounts but l just like playing with things like that!
Guy W

I had the same experience that the Ford gearbox mount is quite soft in comparison to the A series gearbox mount when I fitted the earlier Ford 4 speed gearbox to my car, IIRC the same mount is typically used for the type 9 conversion as was fitted to the RWD Escorts. I think FL even used it for the engine mounts on the K conversion. I had to place some thick rubber mat below the mount to stop the mounting bolt banging the original gearbox cross member. The up/down/ sideways motion of the gearbox and gearstick was more than with the A series but could be lived with.
David Billington

This thread was discussed between 10/01/2015 and 14/01/2015

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