1963 MG Midget - Nissan CG engine & 3D printed manifold

Fantastic work, wonderfully informative.

Great update - thanks for sharing the video 👍 Car sounded spot on and seemed to be making rapid progress - are you planning to use it more competitively?

Last year I gave the lever arm dampers a service with new oil and gaskets which certainly improved handling. On removal the rears had been very low on oil, whereas the fronts had still been full. When I took the suspension apart over the winter the rears where showing signs of leaking and on inspection had low fluid levels. As a quick fix I fitted a pair of later dampers from eBay to get the car on the road and allow me to focus elsewhere.

Damping is a bit of a hot topic in Spidget circles with the general consensus being lever arms bad - telescopic good with very little to back up either viewpoint that stands up to anything more than bar talk scrutiny. While telescopic dampers are technically a better solution the car is not designed for them, so the kits on the market all have compromised mountings that either load the damper incorrectly or put stress into the shell in ways it was never designed for. I also like a challenge so decided to try to stick with the Amrstrongs.

The rear dampers from my car are of a slightly different design to the later cars, apparently only normally seen on Frogeyes. Like the rest of the rear end there was nothing to suggest they had ever been removed so I was very keen to keep them with the car. Unfortunately they were pretty banjoed.

Years of running with low oil meant there was no lubrication to the shaft (snurr) which had badly worn the soft casting case. The steel shaft with the lever attached runs directly in the casting with no bushings so when they get this bad they are normally scrapped when this happens. I didn't want to do this so spent a lot of time refurbishing them. I couldn't find any decent guides on how to do this so took plenty of photographs.



On the bench



Cover removed and oil drained



The shaft is a push fit into the rocker arms. The back of the damper body is plugged. This was quite tricky to removed - I used a small cutting disc and a pry bar.





With the plug removed I put the damper on the press and carefully pushed the shaft out. I took a lot of care to support the body to prevent distortion.







The rocker / piston assembly was then removed and the felt seal picked out from the body.

With the body completely stripped I mounted it onto the faceplate of my Myford and clocked in the seal bore. I used this as a reference because the main bearing journals were too badly worn to be of use. These were bored out to accept some acetal bushes and the seal bore was also bored out to accept a lip seal.



It's a close fit!











With the machining finished the body was washed and put through the ultrasonic cleaner before being reassembled and filled with Motul 20W Heavy Fork Oil

And repeat for the other side...

The dampers were finished off with a set of adjustable valve bodies. Again I could find very little about these online but they are apparently used in racing series where the lever arms need to be retained. Adjustable lever arms were made by Armstrong but are extremely rare and expensive.



These weren't cheap either but are a straight swap for the original valve and are adjustable on the car with 16 clicks. Fully wound in the damper is basically solid. I found 8 out was about the same as standard and 4 out was great. Ride wasn't really any worse - certainly not something I could detect, but the body control was massively improved, especially at the rear. Before undulating road surfaces could catch the car out and cause the axle to hit the bump stops - with these fitted (and combined with properly working dampers) the handling is great. Highly recommended!

I bought them directly from Suspensions Supplies Limited www.suspensionsupplies.co.uk/ They were on offer elsewhere but SSL were cheapest and, I believe, actually make them.

Thanks for looking

James

Thanks for the write up and pics, excellent job I had a 1969 Midget ( Red) and later a 1970 B roadster (BRG) both had lever arm dampers, but I've never seen them in bits

worthidlj
Possibly? A telescopic damper will likely have a bigger reservoir of oil, but a lever arm is typically bolted to the body of the car with a large area in contact, acting as a huge heatsink, whereas a telescopic is reliant on air to cool it.

Lever arms do offer advantages for packaging, especially for the really clever combined upper arms (single arms were fine for the original application in an A30 - less so in a Midget)

A big problem for performance is the leverage / force applied to the pistons changes as the arm moves though it's arc

I suspect the main reason for telescopics being widely adopted was down to cost, and then mass. Levers are much more complicated, harder to make and have more parts.

Excellent write-up, all the way through reading was sayin' "adjustable valves, when's he going to mention the adjustable valves" ...

Well done ! be interesting to see how your 'seals' stand up, looks a really elegant solution.

Sharing space with a lightly scratched XK...that speaks volumes!! 😁😁

Fantastic build, bookmarked from here on!

Hannibal Rally, Day 1

Up at the crack of dawn to put another 5psi into the rear tyres, check fluids and adjust the clutch cable. I think the cable had just settled and didn't take much to get the biting point back in the right place. All done in time for breakfast and the briefing.

The event is a point to point with a vague map with checkpoints to tick off / photograph, the route between them down to the crew. Starting was on a handicap based on experience, age of car and power-to-weight. This meant we set off second, following fellow novices in the straight six Mustang.



'The office'. Bluetac worked really well for holding a phone. Later we used a pair of phones were signal was intermittent with a GPS app on one and Google maps on a second.



The roads were empty, twisting and beautiful and the little MG ate the miles. The extra tyre pressure helped greatly and we were able to push steadily harder as the day got on.





A quick pit stop in Mont-sous-Vaudrey before getting back on route



As we drove into the afternoon the temperature really started to rise but the car took it in its stride. We were always aware of the all-round drums but did not experience fade. The tyres really improved with temperature with cornering speed notably higher...

With the hotel marking the end getting close the fastest cars started to catch up and before long I heard, then saw a beautiful (and rapid) blue Alfa 105 of Frank and Joost in the rear mirror. Determined not to be overtaken I obeyed the speed limit and drove responsibly until being forced to pull over for fuel. Unfortunately the combination of careful driving and the blazing sun had pushed the cooling system and the engine had got a bit warm.



Refuelled, fluids checked and allowed to cool (man and machine) I handed over the keys to co-driver Ben for the final leg.

What followed was a pretty serious climb in traffic through Mijoux. As we climbed so did the temperature gauge so we pulled over to inspect the damage. I suspected the fan had failed given how well the car had performed over the last two days conditions, but a slow but steady stream of bubbles into the expansion tank suggested otherwise. Balls. At this point the hotel was only 10k away so we decided to let the car cool down and then nurse it there. No coolant seemed to have been lost and at this point there was nothing to loose.



We arrived, demoralised and exhausted at the ski resort and joined the rest of the group for a beer.



It was clear that the head gasket was leaking so calls were made to try and source a replacement, but nothing was going to arrive for at least a day, which was too late. Figuring we had nothing to lose I drove the car down the footpath to the back of the hotel where we were drinking and set to work.



The beer, tools and help kept coming and in no time the coolant had been drained and the cam cover removed. Just the tricky bit now... The cams had to come out to access the head bolts. Not an ideal situation made a little trickier because back when I fitted the head and timed the cams I removed the alignment pins so the cams could be properly timed by the book, rather than dot to dot. This meant there was no positive alignment between the sprockets and cams. And the sprockets had to come off to remove the camshafts.

We took lots of photographs and then used a small screwdriver as a punch to mark the cams, sprockets and chain prior to removal. Lots of cable ties were employed to support the chain.



The cams came out without a fight but the head bolts had internal hexes. Nobody had a hex drive socket set, or torque wrench so an allen key and trolley jack handle were put to use in combination with my calibrated forearm. The front bolts felt looser so were tightened to match the rears, than all were given an extra 1/4 turn for good measure.

The gasket sealant had gone solid in the heat so Ben made a paper gasket for the timing cover with a notebook and a hammer.



With the sun starting to set and the table being laid for dinner the race was on to get it back together, which we managed just as the first course was served, the engine firing back into life first turn. Now food. And more beer. And wine. And sleep.

Thanks for looking

James