Technical Information (MGB 1A)
(3 Main Bearing Engine)
Last Modified - 10/03/00
This article should be read in conjunction with technical article MGB1.
Attach your existing engine backplate to the all synchro transmission assembly, drill and tap the upper starter mounting bolt hole to 3/8" USS (use 3/8" x 1.3/4" bolt and lockwasher for starter motor attachment). Next use a 3/8" drill bit and drill a lower starter motor mounting bolt relief indent in the transmission flange to a depth of 1/4".
Remove the engine backplate and helicoil the bottom starter motor mounting hole to 3/8" USS (the existing hole is conveniently sized, use 3/8" X 1" USS bolt and lockwasher for starter motor attachment).
Additional hardware required to attach the transmission to the engine backplate is as follows: 6- 5/16" X 2.3/4" SAE bolts with nuts and lockwashers.
Fitment of your original starter motor will require that the transmission housing be bored out (2.5" +) to clear the starter motor bendix. You can also use the MGA starter motor, which will require a smaller hole of 2.1/8".
There are 2 ways to solve the problem of matching the transmission pilot shaft with the crankshaft pilot bushing.
If you are in the engine rebuilding stage then it would be more convenient to counter bore the crankshaft to a depth of 1.5" to 1.625" X 1.123" diameter. Due to small variations in pilot bushing outer diameters, be sure to supply the machine shop with the actual bushing you are going to use. Use the 1" long pilot bushing as used on the MGB 18V engine (22H1416 Moss 330-415). Before installing new pilot bushing soak in 10W oil for several days or weeks. Longer is better.
Alternatively, retain your original size crankshaft pilot bushing and have the transmission pilot shaft machined to the following dimensions: .6215"-. 622" OD to a total length of 1.5"-1.625". Be sure to install a new crankshaft pilot bushing who's dimensions should be .814"OD X .6875" length X .625"-.626"ID for a working clearance of approx. .003".
MGB models 1968-1973 fitted with non-overdrive or overdrive all synchromesh transmissions, had no provisions for an engine restraint system. Angled brackets were fitted atop the engine mounts to prevent the engine from moving too far forward in the event of a front-end collision. Unfortunately, they did not work to well, evidence by the number of radiators and fan blades I have replaced.
We have manufactured an engine restraint kit, which allows you use your existing crossmember assembly. Click here to see illustration.