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MG MGB GT V8 Factory Originals Technical - rover transplant I need help !!!!!

Hi guys, I am new to the board, and will be putting a 4.0 rover and 5 speed in my 74 gt. I am in the process of buying a motor, should I start with a long block and build from there, or buy a complete used engine and rebuild. The reason I am asking is not sure if I can use stock oil pan ,water pump,balancer,intake? From what I have read else where, I am not clear on what I can and can not use. Appreciate the help

Thank you


If you're starting with a 4.0L, pitch the intake, oil pan, front cover, cam, and timing chain stuff and replace them with buick 215 style units. You can use the front pulley's from the 215, but you'll need a spacer, as the crank nose is longer on the 4.0 than the earlier units. Most any of the V8 suppliers will have the stuff you need.



check with Dan Lagrou with D&D Fabrications. He will have what you need.

Where are you located in Illinois?

rick ingram
st.joseph, IL

rick ingram

Personally, I will be purchasing a used and complete 3.9 to avoid all that additional costs and effort.

Just be sure to check the engine numbers located on the drivers side, I believe..I had a used engine dealer who either did not know that you can not use the vehicle (year) of origin as a strict guide to identify the engine (size), or he was attempting to pass a 3.5 as a 3.9

...I came close (to purchasing).

Cross reference numbers...


You still gotta ditch the rover front cover unless you want to pay about 5 times more for a waterpump than for the buick version. The waterpumps are entirely different and not compatible! Pick a 4.0 or 3.9 or whatever, the only negligible difference is the oil pan. Everything else you should replace anyway.


p.s. I don't recommend one V8 supplier over another because I've purchased from all of them, and they are all great to deal with!

Rick, Thanks for the input,( thanks every one) I looked at there web site, looks complete. I am in Port byron illinois right on the border of Iowa, about 5 miles from Quad cities. What conversion do you have?

Thanks Paul

I thought the 4.0 and the 3.9 were different in their crank main journal diameters as well as the 4.0 being a crossbolted block. Any truth to this?

What is the problem with the Rover oil pan? I used the Rover pan on my 4.2 with no problems, is the 4.0 pan different?

I have used Rover pans on 215's & 215 pans on Rovers. While there is a slight difference, the right gasket solves the leak problem.

Smarten me up, as I have a 4.0 in the works to replace a 215.
Jim Stuart

The 4.0 oil pan works and clears everyting in the MGB. It may not work with the 215 style front cover. The 4.0 pan is cast aluminum and very nice. I am using a 4.0 in my most recent conversion but I am keeping the Gems 4 DIS system and using a hot wire EFI.
Evan Amaya

I have a 3.9 with the original front cover and water pump. all I did was press off the rover style flange and replace it with a flange off a standard water pump. there are no clearence problems
Jimmy P.

The 4.0 and 4.6L front covers have the oil pump built right in, instead of being out on the side. They also don't have an accomodation for a distributor. I know on the VERY EARLY 4.0's they still had the emboss for one, but the metal wasn't punched out. I'm not sure if that emboss exsists on the later models or not. Back to the oil pump, the oil filter shoots straight out at what would be our steering racks. You could probably use a remote filter to get around that. That still doesn't address the problem with the lack of distributor. How do you plan on using a fuel injection system that DOESN'T control timing (Hotwire) with a front cover that doesn't have provision for a distributor? Something isn't going to work there. You can use the gem's system, but you have to add a sensor to your flywheel, and I'm not sure how well you'll do with a different cam. The front of the block where the cam enters is different. The 4.0L block uses a metal plate to hold the cam into the block, and that cam doesn't have provision for a gear drive for the distributor. It'd be nice to have a distributorless ignition system and all, but I think it means a lot more work, and I'm not sure how well it has been covered before.

Here's an archive of a website that did a GREAT job comparing all the different options:

Jake: You are right, the 4.0 and 4.6 blocks have different size main journals. I don't think they make different size bearings yet, so if your 4.0L crank needs a regrind, you have a problem on your hands.


Can we make a slight detour?

Has anyone tried removing a Buick/Rover engine from an MGB without pulling the tranny, too?

I don't have much time to pull this off and the less I take apart, the less I have to put back. :)

Come on Carl!
I can yank the driveline in under 2 hours! Getting to the bolts around the bell housing would probably be miserable at best. I don't think the driveshaft, tranny mounts, and clutch hose aren't nearly as difficult as the bellhousing bolts..

Maybe bring it to the convention and Steve can make a tech session out of it? =)

Hi folks,

There's lots of good information on later Rover V8s in Roger William's second book, published in 2000 - 'How to improve your MGB, MGC & MGB V8' available in the Speedpro Series published by Veloce. ISBN 1-901295-76-1/UPCX: 36847-00176-6. This book originally cost $24.95 in the USA but is now being sold off cheaply in the UK. (You might try as a source.)


P L Hills

Thanks Peter, I am finding out there are many good resources on the net, just a matter of spending time looking. Thanks again!


Paul, you should consider coming to the V8 meet in Grand Rapids, MI on August 12-13-14. There will be a lot of conversions, D&D will be there, you can ask owners first hand about their experiences...

Primary hotel is the Exel Inn on the corner of Patterson and 28th Street, right across the street from the Hilton (where the UML Summer Party Reunion is based)

You will learn a LOT!

rick ingram


Come on down! Will work for beer? :)

Engine R&R next weekend.

This thread was discussed between 13/07/2004 and 17/07/2004

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