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MG MGB GT V8 Factory Originals Technical - B rearend

I am going to put a stroked (about 289 cubes) Buick motor into my B and was wondering what the stock rear end can take? I am going to be pushing close to 300 HP out. I can design a rear suspension using coil overs and links but dont want to start if that rear isnt going to hold that power. Any suggestions?
Jarrod Hills

Sorry, but though rugged and faithful the Salisbury rear axle on the B was, it just won't take 300HP.
Steve S.

FWIW, my car was recently on a chassis dyno and apparently develops a max of 258hp at the wheels ... I have a 3.07 C rear end with a Quaife and it has been just dandy. Certainly there are no signs that it is the least bit discontent. AFAIK the C rear is exactly the same as a tube B rear but for different CW/P gears. Not that I take it drag racing, but for sure I drive it hard when I don't reckon the VA Polizei are looking (and even if they are, a bit of grey hair in a plain-looking MG doesn't seem to arouse much interest). The Salisbury axle is a pretty doggone robust design as I think it was originally intended for trucks. A local hot-rodder tells me that it is in fact quite a bit sturdier than a Ford 8" -- I guess it has more bearings(?) -- but it's of course nowhere near as strong as a Ford 9", versions of which can handle just about _anything_, but it's rather heavy. I believe you can buy uprated halfshafts for the Salisbury rear, should you so desire, from some place in the UK.

I had heard the B axle had more bearings than a Ford 8" but that is not correct. The Ford has a total of 7 bearings, the MGB has 6. I have seen a bunch of 215/rover cars with stock axles that are holding up fine. Like was mentioned they are pretty durable axles.
Larry Embrey

I have a “factory” B GT V8 which I have owned since new. The engine, built by John Eales gives 216 bhp @ 5000 rpm with 255 ft. lbs. of torque @ 3000 rpm.

I have a late Range Rover R380 (not the LT77 from the SD1 Rover) driving the standard GTV8 Salisbury rear axle through a one-off drive shaft that I had made.

No problems with the axle, or anything else, since the engine was up rated about 12k miles ago, much of which has been hard rallying - I’m off to do The Basque Classic in it in ten days time.

Safety Fast


MGA 1600 Roadster

Nigel Steward


V8 racers over here are well over 300bhp. The halfshafts can be uprated by GKN for about £400 or Quaife or Jack Knight.

The other weak link can be the Prop (US driveshaft ?) Again these can be made up for about £100 or a Land Rover shaft used.


The thing that makes the MG axle stronger than the 8" Ford is the axle housing itself which flexes under hard accelleration and somehow, so I've been told, causes the gears to wear rapidly. The problem is common to the 9" axle as well. Racers fix this by welding reinforcements from the flange to the back of the housing on the inside.

Anyway, the thing that breaks axles is not horsepower, but torque and weight. And since the MG is a light car... Simply put, an axle that will handle 200hp in a 3500lb car should handle 300 or so and possibly more in the MGB. I haven't broken mine yet, but then again I'm not running a built 289 either.
Jim Blackwood

<<Anyway, the thing that breaks axles is not horsepower, but torque and weight.>>

There is one other all important ingredient to breaking driveline parts: TRACTION.

Jim and Carl,
Right on, you guys both hit the key factors on the head. The GM T5 everyone uses for the bop/rover conversion are scoffed, snickerd and generally thrown away by the Camaro and Firebird people because they are notorious for breaking under any "energetic" use in those cars. BUT those cars are "pigs" weightwise, so they overstressed and broke trannies..

Traction, that is the great equalizer for us. We can put all the power in the world into aour B, but without working the rear end and tubbing for larger tires, only so much power can get to road. Our power:weight ratio with a V8 is better then most cars and equates to about a 10sec 1/4 mile car, but good luck ever getting that fast as you cannot get all that power down right off the strt and have to ramp up wich costs time..

Point of all this? The stock B rear "should" be plenty for most V8 conversion, unless you are specifically going to race often..
Larry Embrey

Jim, Carl, Larry - exactly!

Roger Parker

This thread was discussed between 06/10/2001 and 15/10/2001

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