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MG Midget and Sprite Technical - Datsun 5 Speed modification

I have been running a Rivergate Datsun 5 speed kit for the last 100,000 miles. I have the engine out for a rebuild and clutch replacement. The Rivergate kit uses the original midget clutch with a slight modification. Researching on line, there was a similar kit produced by Morriservice that used the Datsun clutch, which is a larger diameter and mates properly with the original Datsun release bearing. Apparently the Morriservice kit required a flywheel modification, drilling and tapping new clutch cover assembly mounting holes. I would like to try a Datsun clutch but do not know if the flywheel requires machine work to reduce the thickness, and if the flywheel height would be compatible with the Rivergate mounting plate currently in place. There is geometry involved that may be more subtle than I first considered.

On another note, the engine rebuild needs to take into account the additional load that the 5th speed overdrive gear places on the engine in the 3,600 RPM range for holding speed around 75 MPG on hills. I am considering 9.75:1 pistons and a more aggressive cam. Any suggestions for increasing midrange torque?
Glenn Mallory

Glenn,

I've had the Morriservice setup for years. When converting, I sent my flywheel to Paul and he drilled and tapped it for me. There was no other work done to it. You just have to center the pressure plate on the flywheel and mark the location of the mounting holes. Note that the pattern of the Datsun plate mounting holes is not symmetrical so once you've drilled the holes the pressure plate will go on only one way. There's also the locating/orientation pin. The nice thing about using the Datsun clutch is that there is no mixing and matching of disc and pressure plate. Everything comes in one box including the throwout bearing. Any engine size in the 210 from 1979 to 1981 will work since they used the same clutch for all years.

I don't know about the Rivergate mounting plate but mine is about 1/2" thick. It's in the garage and it's cold and dark right now but if you can wait until tomorrow I can measure it. I'd guess that they would both be the same thickness.
Martin

Thank you Martin.

The thickness of the Morriservice backing plate would be important to know. The Rivergate plate is exactly 2cm thick, 0.787 inches. If the Morriservice plate is 0.500" thick, this means I would probably need to take at least a 1/4" off the flywheel surface to approximate the Morriservice clutch cover to release bearing distance. Maybe it doesn't matter since the release bearing can be adjusted at the pushrod.

I found that the transmission bearing cap collar was broken off. The clutch had a slight vibration in the pedal so that mystery is solved. I don't know what caused the bearing cap extension to break loose. The release bearing slides easily on the collar and the pressure plate levers show no damage. The bearing itself turns easily. In any case, if the Rivergate backing plate is thicker than the Morriservice plate, this would leave the release bearing farther out on the bearing cover collar.

If you can measure your backing plate when it is convenient and let me know, I would appreciate it.
Glenn Mallory

Glen you could try contacting James Barratt at Barrrat Engineering in the UK. He sells a superbly engineered kit to fit a Suzuki 5 speed box into a Spridget. This kit requires the original flywheel to be machined and he may be able to let you know how much you can turn off without affecting strength or tickover.

Jan T
J Targosz

Glenn,

I measured the plate while it's in the car so a bit awkward but I got .640" .
Before you go cutting down the flywheel I'd fit everything together and see what kind of clearance you've got. Since the two pressure plates are different you probably will have enough room for everything to work and the Rivergate plate would put the gearbox a bit farther back. The input shaft splines are pretty long so the .137" difference should not be a problem.

A few years back my collar also broke but my clutch didn't work well so you were lucky there. Ebay is your friend although I got mine from Gerard's Garage. My understanding is that he is no longer doing business but his web site is still up. I wonder who if anyone took over the Datsun conversion part of the business. There was a place called Double M Ranch up here in Port Townsend, Washington that restored Morris Minors but they don't show up on Google maps and I saw a query on a MM web site asking about them. They would have been a logical successor.
Martin

This thread was discussed on 30/01/2023

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