McLaren M20#73

Hi Andy, I'm probably stating the obvious here, but just watch that front lower lateral link under the starter motor in full droop. I had the same Albins bell housing and starter combo, and it didn't work, which is why I had to get them to custom make the one I have now. Mind you, I have chassis members there, which you don't, so you most likely have it all worked out.
Keep up the good work.
Regards, Udo.
Hi Udo. Yes that bar will have to have small bend to clear the starter motor on full bump. That bar will definitely be 4130. The standard block mount starter position wouldn’t work for me with the small diameter flywheel & low engine position for dry sump. It’s my second bellhousing also. Please hurry and finish yours :)
Hi Neil ...noted.
Time for a progress report...Luckily there’s enough bits and pieces in the garage to carry on building the M20 during the lockdown. My job has me working from home so things are ok. We’re allowed out for exercise and a trip to the Supermarket, all good.
The Radiator Sidepods have progressed slowly and has eaten some hours up to get to this point. It’s already for the final rivet then can be attached to the car, which I can do next week. The right side panels are all cut so that side should go together quickly now I know what I’m doing. The radiators slide in from the center so the only drawback is the motor and rear suspension links have to be removed to get them out. that isn’t a big job with this design.


Hi Andy,
Yes the current situation is a bit grim for getting bits and pieces. Your build is looking really good. would put many professionals to shame. I am managing to get a few hours each afternoon on the FJ so progress is still happening. I gave the raw body a coat of Duratec hi build the other day and after an easy sand it was ready to give it a 2k undercoat which happened today. I only have enough 2k thinners for one brew of red final coat. I may try for a best effort dust wise to get the final coat of red on and then super fine sand and clear coat once out of lock down if needed. Probably better than leaving it undercoated.
Carry on the good work, never know whats around the corner.
I have a new helper, my nephew Callum is staying for the year so has had a crash course on Riveting. He’s done well, we managed to rivet the Radiator side pod together then to the tub.
Also made a Radiator support bar and bracket that doubles as the rear clip attachment point. Hopefully next week the alert level will lower and I’ll be able to get some much needed engineering supplies.
The Radiator bottom outlet pipe was also moved up 125mm to clear the rear suspension bottom drag link. Just need to fold up a cover to hold the radiator from sliding then rivnut/bolt it in place.
All in all I‘m quite pleased how its coming together. Nearly onto the right side.


I'm sure there are people on here that know.... with a team of 6 skilled people constructing and 1 person liasing with manufactures for parts and supplies, with all the right tools and equipment, working drawings, and experience of previous builds, I bet 2-3months full time would get the job done.

Howard Jones

My guess is they made enough pieces to build at least 4 cars at the same time with quite a few spares as well. That might take a bit longer but it would result in a small group of cars being completed in about the same time. Given the 2-3 month estimate and adding another month for multiple assembly the average may well have been around a month a car.

The season back then ended around October and began the following year in the late spring so that sounds about right when including shakedown and development work over the course of the early weeks in the spring and late winter.

I wonder how long it would take Andy to do a second one if he made multiple uprights, suspension pieces and generally was thinking two cars instead of one. The body would certainly be much quicker the second time I would think as well as the thinking and design time having been pretty much done on the first one.
The McLaren Trust site has a couple of articles on McLaren SportsCars, Canams and M20 that are worth a read.
Basically 3 McLaren factory cars were made each year.
Trojan then made the same/similar McLaren production cars for customers (except the M20).

Howard, if I had the whole car in Solid Works, and a package was delivered with all the pieces router/laser cut, (and no work, family or life) things would rip along, 2 months a car would be feasible with a small team. Building 2 or 3 along side each other is an economical approach. But that takes a lot investment. My goal is to get a car together as quickly as realistically possible and enjoy some track time. Andrew
Work has continued... the right radiator pod is done, I would class the chassis tub completed bar the seat back rest. The Radiators and fans are installed. The rear drag and lateral links turned up, went with 4130 1.25” bars (Neil will be happy :)
Next job is to attach the motor and transaxle. I acquired a drill mill to assist in the machining of the 20mm front engine plate. All manual.
Just looking at SS header build kits and will order that shortly.
Well.... no active cases of Covid 19 in NZ. Border shut.. all good way down under... Stay safe.


Had a bit of play milling up the front engine plate. There's plenty of meat left as the Oil pump,
Alternator, ProCharger and routing of all the pipes has to be finalised. After that it will be milled more to lose weight.
2 x 10mm 5083 end plates where also cut and folded (heated then 20mm radius bends), had to bend them on an angle so the rear engine
support tubes would fit without having to notch anything(due the standard length bell housing, a knock on effect) They're pretty solid 1.25" .120 wall 4130 tube.
I'll tap some countersunk bolts up from the underside into the engine plate to help arrest any lateral movement.
The engine floor pan will be extended to the bell housing, all adding to stiffness.

Been waiting a week for the header pipe kit to show, shouldn't be far away so can make a start on that after the rear engine stays are complete.
Its going to get busy in that space routing around tubes, drive shafts and suspension links.

Mocked up the Procharger in the rough position.


Terry Oxandale

Skinny Man
Really clean, nice, work. I did the same thing with my floor pan, for the same reason, but later changed it to a separate removeable plate (lots of removeable fasteners), but that plate seemed to stay off more than on for several reasons: dry sump had a small gasket leak that I could never fix, engine bay temperature that was causing problems with fuel temperature all the way to the tanks (recirculated system), and just plain wanting some visibility in terms of pre-race inspections.
Nice work Andy, looking really good. I've been a bit slack with posting pictures. I have slowed right down simply because of time availability.
I have still been chipping away at it. Keep it up.
Regards, Udo.
Thanks for you kind words.. your superb builds helped me take the plunge..
The exhaust finally turned up.. 2" into 4" 304 SS. Looked at 321SS but couldn't justify the cost.

Leon, have you got that bad boy fired up yet.


Hi Andy, always great to see progress and interesting to see how you are working round the differences in layout that our engine trans combo present. Looking forward to seeing how you do the rear suspension bracketry with that trans. The LG was designed for it so made life easy or the guys who used them. As always like Udo your workmanship is second to none. I'm still plodding along, Had the engine on the dyno and made 685 ft-lbs @5500 and 700hp at 7000, hoping to have it on its wheels by the end of this month and body mounted and painted soon after.
Always looking for up dates. Cheers Leon
Made a start on the rear suspension bottom bracket. There’s about 25 hours in it so far. Constructed out of 5mm 4130 with a couple of 2.5mm filler plates. Had to have a couple of folds done on a press brake and fabbed the rest, then tigged it all.
There’s a couple of 1/2” bolts to the Bellhousing and 2 x M8 to the Albins ST6M. I’m going to add another bracket that will connect to the Transaxle side plates. So it will have 8 bolts connecting the Bracket to the transaxle.
Tried to 2 inch dimple die the base plate but realise quickly I was about 100 tons short. Will get the it pressed with a bit more omph at a local engineer shop.
(Pics with transaxle inverted)


The rear suspension bottom bracket is now installed, added the extra side brackets which should be more than strong enough. The main forces involved will be pushing and pulling on the bottom lateral links.
Made a start on the top suspension tower. This has presented a few challenges. Dart don’t drill and tap 1 of the right side bellhousing holes in the engine block, probably due to its proximity to the rear head stud. so I’m repositioning slightly some block strut mount points. I’ve got the next couple of days to get a bit more done.
(The aluminium is just for mockup)