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MG MGB GT V8 Factory Originals Technical - Jag IRS in an MGB V8

Hi, Guys,

I'm now in the midst of converting a Jag IRS for use under an MGB, so I thought I'd toss out a request for info from anyone who has already done the conversion, or is in the process.

Any hints, pointers, things to avoid? How did you mount the diff to the MGB body? What was your hub-to-hub measurement? What size tires and wheels are you using?

Any websites to check (I've already been to Nick Smallwoods site)?

Dan Masters

A website with some info on this is MGB V8, at Jim Stabe installed a Jag IRS in his '66 roadster in the early '80s. On the site, go to Links, then A Good Collection of Aluminum V8 Articles, then to MG V8 Swap. There are some pictures, but in short it says that he shortened each side by 3", bolted the cage to the trunk floor with backing plates, and ran brackets to the rear shock mounts. Hope this is of some interest or help. Best, Joe
Joe Ullman

How expensive is a Jag IRS unit, what's the gearing, and where can one be sourced? This seems like a fun and worthwhile project.


A good used unit runs about $950. That's a complete setup - diff, suspension, brakes, cage - complete, but everything except the diff will probably need to be rebuilt. A complete rebuild kit runs around $395, and that includes everything you need except shocks and springs - bearings, bushings, brake rotors, caliper rebuild parts, pads, a pretty complete kit.

Available ratios are: 2.88, 3.07, 3.31, 3.54, 3.73, 3.90, 4.25, 4.50, 5.11 Limited slip differentials are also available.

They can be bought from Concours West Industries:

If you want to go big bucks, you can get a custom built unit, whatever width you want, polished/chrome plated, with a Ford 9" pumpkin, etc, for around $5,000.
Dan Masters

If of any moment: I have a complete setup from a Series I E-Type which I believe is 3.07; maybe it's 3.31. Includes shocks, springs, the whole nine yards. Oughta be cleaned up, but it's certainly in fine shape. It is located in Phoenix, AZ. I'll sell it for a lot less than the aforementioned figure. Email me offline if interested.

how many jag rear ends do you want @$750?...oh, nick smallwood's site is a gr4eat place to go
anthony barnhill

This thread was discussed on 06/12/2002

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