M20 Dreaming

Russ Noble

GT40s Supporter
Lifetime Supporter
Great stuff Leon.

But I rather think with 500+ cubes that your 2nd gear will make a great 1st. Approx 80 mph @7000. Probably about what you'll want. That stump puller first will only be good for manoeuvering around in the pits!!

I think your maths are a bit out! If a 0.62 gear is 225 mph, then a 0.75 will be 186. For 205 you will want 0.67.

Edit: Actually Leon, now that I've had time to think about it, would not the easiest, cheapest, most effective way to achieve your goals, be to change your QC drop gears to give you your desired 205 mph? Doing that would then give you a 2nd gear of 77mph which would still be a pretty handy effective 1st. 3rd is not a bad filler at approx 135, and whammo, 205 in 4th! A racing, effectively dogleg first, three speed with those ratios would not be a bad thing, particularly if you're going to hook 565 cubes up to it!!!!
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Hi Russ, sat down with the gear calculator you sent me and ran some numbers. Opion ( 1) with the gears I have and 15% OD in the drop gears @ 7000rpm 1st 47mph, 2nd 82, 3rd 144 and 4th 218. Opion (2) 10% OD, 1st 45mph, 2nd 78, 3rd 136, 4th 207. the bottom line is 1st is useless for anything other than the pit road, as you said. But it gives me a start and with big cubes and the Torque that comes with it, it will be drivable and I can play with custom gears later. I was very impressed with the alloy fab work you are doing and I hope to get some done myself the next time home which will be the 6th October. I didn't get much done on the uprights as my time was confined to the trans but I'm quite pleased with the result so far I will probably finish the casing moulds and then leave it for a while and get into the tub and suspension next. Well there won't be any progress for the next month so I will be relying on you, Leon and Jac Mac to put something on here for me to look at and keep the inspiration going. Look forward to hear from you Cheers Leonmac
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Just read all posts on your project from start to finish as I haven't checked the forum for a while, all I can say is inspirational mate love your attitude. We have been planning a sports car project with some wacky drivetrain ideas and scratch built body for some time, I think we should pull our collective fingers out and get on with it after seeing this.
Great stuff.
Hi guys, I'm home again and doing some more work on the project. the plan this time is to get the Gearbox casing finished, including bell housing which I'm working on today and to aid in getting everything alined, I have run a piece of tube through the crank tunel in the engine jig on the table and then the bell housing, diff casing and G/box casing can be lined up on this, So far all the vertical surface's are true and the shaft mountings are parrallel. At this point it is only wood and when these are alloy and machined properly any discrepencie's will be corrected, if I can get it close in the mould making process it can only help with the end product, When I have the casings all mounted to the engine block I'll post some pics. Just finished my lunch, so I'd better get back to the garage. Cheers leonmac
That's pretty amazing mate. I'm a machinist myself so I understand the size of the task you set yourself with that transaxle. Hope it all works out well for you. Fortune favours the brave :)
Well Jim, I always do as Im told so I have got some more progress for you. Yesterday was spent on the bell housing and the main frame work is done and now I have to fill in the gaps. I sat it all on the shaft that I installed the other day and Im happy to see it all seams to line up very well. At this stage I have built the bell housing to accommodate a full size flywheel and wet sump with 4" of ground clearance, this gives me 15" axle height. I can easliy trim 1-3" off this by using the small Flywheel and dry sump or drop to 3" grond clearence. With 27"-29" rear tyres this will give good level haft shafts and minimal axle plung through the full range of suspension travel. I have attached some Photo's.
Cheers Leonmac.



What is the total length of the box going to end up.

With the input shaft are you going to make that 2 piece,original input sliding into a secondary input.

It might be deceptive but is the bell housing longer than it needs to be or are my eyes playing tricks.

Keep up the good work.

It look's good. I have a couple of quick questions. I was looking at your earlier posts at your rear uprights. I see no tabs to mount calipers, so I take it you are running inboard brakes. I was wondering how you are going to mount them. I also don't see any tranny mounting points in your pattern. Usualy the diff side covers on Hewlands incorperate these into the casting. Just a little food for thought.
Yes Jim, your eyes are fine and the bell housing is long. The reason for this is that when the M20 was being designed at McLaren, they were really getting into "Polar Moments" and Chassis dynamics and weight distribution. So they increased the wheelbase by 2" and moved the engine forward from the rear Axle line by 8.5". To do this they simply made the Bell housing 8.5" longer. this also pushed the driver forward and the net result was that with the hip mounted raidiator's most of the cars weight was between the wheels, and better weight transferr to the front axle line.

David, There will be suspension pick up points on the top and bottom of the diff housing, the top mount will be on the casing and not the side plates as on the LG Box's. Because of the "split case" design I will make the top mount in 1 peice and bolt it to the top once the casing is assembled as I believe this will give the case a little more strength.

Will post some pics once the brackets are done. Thanks for the interest, Leonmac.
Sorry Jim, I just reread your post and see I only answered part of your questions.
Total lenght is 950mm (700/transaxle, 250/Bell housing) this is comparable to the 930 "P"car Box and if it was to have the short B/Housing it would be within 1-2" of the 930 box.
The input shaft will be a 1 piece shaft that will be connected by a spline that will be mated to the Lay shaft (not the original input shaft).
Hi Leon , I enjoy reading your build . I notice its a few months since you added an entry . Have you stopped building ?
Hi Zed, I have not done much since before Christmas as I have another toy (4x4) that I needed to do some work on to go away at Christmas and then this time home I have been working on the 4x4 again as I'm going to sell it.
I have been working on design work for the transaxle and other ideas, but no physical work to show so hence the lack of posts. I'm off to work again next week so there will be nothing for a while yet. But hope to get back into it with a vengence buy the middle of the year and I'm aiming for the roller to be getting close buy the end of 2010. Thanks for the interest. Cheers Leonmac.
Hi Guys, Its been a while since the last post of any progress. I have finally finished the 4x4 and it has gone to a new home so have time to get back to the M20.
The first bit of work was to see if it was worth making or buying the stubs for the rod ends, I need 30 so thought if it takes me 20 minutes to make 1 thats $30 an hour ($10 each to buy) well it took me 15 minutes so I'm making them.
Next was machining the rear uprights to take the drive hubs and assemble the the complete CV, Hub and axle. This took the best part of 6 hrs machining and I learned a valueble lesson (don't leave so much meat in the mould) you just spend hrs machining it out and leave $$$ worth of alloy on the floor. Having said that the end result is good, there is still some cleaning up to be done to the upright and holes and studs for the links etc.
As you can see in the photos the axle is straight and level to the diff and will have very little plung in the CVs, the axle is fixed in the hub end and will float in the diff end CV. as there is only 4-6" off wheel travel, I expect minimal plung.
I have also done 1 of the front uprights, it has the Nissan Skyline stub axle but I'm thinking of changing this and maching my own to in clued the knock on type pin drive, also have to locate tab's for the brake callipers.
I have also started the mould for the wheels but not much to show yet so no pics.

Cheers Leonmac


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Russ Noble

GT40s Supporter
Lifetime Supporter
Looking good Leon.

That's one helluva project you've embarked on. I shall be interested to see the wheels when you put the pics up.


Not many people who can do what you are doing Leon. Scratch building a real racing legend. There might be a possibility of a commercial spin-off. Supplying uprights to customers.

The pace should pick up now that I've got rid of my 4x4 but I can't match the pace you are setting. You are really cracking along and doing a great job.

I don't have one of those flash harry 5 axis machines to make my wheel mould, so its taking a while and some innovative techniques with custom wood and plastic, Could be a while as I'm off to work again on Tuesday.

Cheers Leonmac
Hi guys , long time since the last lot of work was done but have been doing a bit this time home. I have done the the rear trailing arms and started the rear bulkhead and Mono Tub this week, will have the suspension arms and the other rear upright machined this week and should also have the tub well progressed buy the end of the week. I will have some photos up once the work for the week is done. On the engine front, I got a 4 bolt tall deck block, Venolia Alloy 6.535" rods and Wiesco 12.5:1 pistons the other day. Still need a crank, so I,m looking around for a forged steel 4.250" stroke crank which will give me 510 cubes. The top end is ProAction 360 heads (worked ports) Jessel shaft rockers, Comp mechanical roller cam, roller lifters, Jackson gear drive, and Racer Brown push rods. So I have most of the engine now and will look at getting it together later on as I pick up the final bits and peices. It will be some time before its needed but just buy the parts as they come up at the right price. Will post pics Later.
Cheers Leonmac.