MG Sports Cars

engine swaps and other performance upgrades, plus "factory" and Costello V8s

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Argatoga
Graham Hill

(8 posts)

Registered:
02/08/2010 12:06AM

Main British Car:


Midget rearend
Posted by: Argatoga
Date: May 05, 2010 10:34AM

I'm looking for a sturdy rear end for my ~175hp Midget swap. I'd rather not build something elaborate. I've read here about using a Monza axel, but the housing looks too big (I have a 1500 lowered by an inch). Any recommendations for an easy swap?


Bill Young
Bill Young
Kansas City, MO
(1337 posts)

Registered:
10/23/2007 09:23AM

Main British Car:
'73 MG Midget V6 , '59 MGA I6 2.8 GM, 4.0 Jeep

authors avatar
Re: Midget rearend
Posted by: Bill Young
Date: May 05, 2010 12:07PM

When selecting a rear axle I usualy look at several criteria. Torque capability, ratio availability, brake compatability, drum or disc diameter, and lug pattern.
There have been several rear axles used in Spridget swaps. For your horsepower range I'd say either the Monza or the RX7 axle would be a good fit. I know the housing on the Monza looks large, but it's basically a standard GM 10 bolt unit that has a lot of ratios available for it as well as posi units. As a budget piece it's hard to beat for those reasons as well as the added benefit that the lug pattern is the same as the original axle and the rear drums clear 13" wheels just fine. Rear brake cylinder size is compatable with the stock master cylinder as well.
You could also use a Mustang II unit but the lug pattern is different there. All three mentioned were originally used with 13" wheels and small V8s or rotaries and will handle that level of power and torque.
There's really quite a bit of room under a Midget rear, the most limiting factor would be the length of the pinion area as the bulkhead is fairly close on the front side. I used a Monza rear on my 73 with 1500 rear springs and 1" lowering blocks and there's plenty of clearance, should be the same with your car.
traction bar.JPG


Argatoga
Graham Hill

(8 posts)

Registered:
02/08/2010 12:06AM

Main British Car:


Re: Midget rearend
Posted by: Argatoga
Date: May 18, 2010 12:41PM

It looks like Frontline is developing a 5 link rear end. In light of this I'd rather go a cheaper route for the time being. Has anyone here have experience with the Peter May, Frontline, and Magic Midget half shafts? What would be the best material? I'm seeing EN40B, EN24, and chromalloy. The Magic Midget EN40B ones are $180 each, while the Frontline EN40B shafts are twice that. Any idea of why one would cost more than the other?


Bill Young
Bill Young
Kansas City, MO
(1337 posts)

Registered:
10/23/2007 09:23AM

Main British Car:
'73 MG Midget V6 , '59 MGA I6 2.8 GM, 4.0 Jeep

authors avatar
Re: Midget rearend
Posted by: Bill Young
Date: May 18, 2010 01:40PM

Graham, for the most information on high strength axles for the Midget rear I'd suggest you post a question on the motorsports forum of the MG Experience site [www.mgexperience.net] or the Sprite/Midget forum on the MG Enthusiasts site [www2.mgcars.org.uk] There are a lot of guys on both sites who race Spridgets and have experience with those axles etc.


DiDueColpi
Fred Key
West coast - Canada
(1308 posts)

Registered:
05/14/2010 03:06AM

Main British Car:
I really thought that I'd be an action figure by now!

authors avatar
Re: Midget rearend
Posted by: DiDueColpi
Date: May 20, 2010 02:21AM

Hey Graham,
Back in the day (early 80s) I built a 65 midget with a full on Datsun 240Z engine. It was bored and stroked to 3.1L and ran triple webers. After breaking 3 of the strongest midget diffys available I found that a tr4 diffy was almost a direct fit. The width is good and I dont recall any major mods to fit it in. It took all the abuse that an eighteen year old road hero could throw at it.
Hope that helps
Fred


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