MG Sports Cars

I have been reading this forum for quite a while but I just registered and this is my first post.

I am in the process of painting a 1975 MGB roadster. While it is a bare shell, I would like to prep it for a future 215 engine conversion (although I am going to run the stock engine for now.) I would like to modify it so, when I can afford an engine and gearbox, the conversion will be as close to bolt-on as possible. I understand that the transmission tunnel and possibly the inner wings and firewall will need to be modified. I have read through a lot of the threads here but have not yet found a step by step guide. Any help and guidance would be greatly appreciated because I would like to do the grinding, cutting, and welding only once but - unless I win the lottery - it will be a little while until I can spring for an engine & gearbox.

Thank you!

Rick, the best description of the process that I know of all written down and easy to understand is here. [www.mgcars.org.uk] For your 75 there is very little modification necessary. Moving the radiator forwards could be done and still use the original four cylinder engine with longer hoses, but the motor mount mods might have to be done at the time you install the V8.

Additionally, the cutouts for the headers should probably be done at the time the engine is installed, in order to make the openings conform nicely to the headers. Since the '74-1/2 and later had the revisions to accept the V8 there should be very little else to do, depending of course on what you do for motor mounts.

JB

Considering that you're starting with a 1975, I wouldn't worry too much about making alterations to the engine bay now.



There are so many ways to skin a cat! Back when Roger Parker was writing how-to articles (like the one Bill linked to and also the better one that's in our BritishV8 article archive) most conversions used block hugger headers and "MGB GT V8" radiators that were available from a couple well known suppliers. The Rover transmission was popular then, but it's tall so people who use it tend to mount their engines farther forward and maybe also lower than might otherwise be necessary. The Roger Parker write-ups were quite good for what they were, but they reflect a British perspective and in my opinion they're dated. (Not many Americans use Rover LT77 transmissions now.) The same criticism might apply to the Roger Williams book, especially its earlier editions. I've never cared for what that book has to say about front crossmembers, for example.

In those early days, most people bought pre-made motor mounts. In the U.S., Glen Towery offered two versions: the engine mounting height was the same, but one mount design placed the engine further back to make extra room for air conditioning. If you make your own mounts - which isn't difficult - you can put the engine exactly where you want/need it.

In 1992 the MG RV8 model came out and it featured through-the-wing exhaust routing. From the mid-90s, RV8-style headers have been readily available and popular. RV8-style headers can have bigger diameter tubing and longer length primary tubes, plus bigger bend radii... so they certainly should flow better! Less obviously, their installation seems to dramatically improve cooling system performance. (Air exits the engine compartment easier. More air flows through the radiator.) I would highly recommend you ultimately use RV8-style headers, but I doubt you'll want to cut holes for them now.

It was more tempting to give advice about where to hammer and where to cut when most people were using the same motor mounts, headers, transmissions, and radiators. Nowadays, if you're looking for guidance I think it makes better sense to really study the How It Was Done articles and start by deciding which ones you admire most.

Thanks. I think I will keep it as-is right now and make the mods when necessary. Who knows when and if I will ever get to stage two.

Rick, you need to decide which transmission. Very popular is the GM pattern T5, as it will bolt direct and is light/compact. Don't sell yourselfe short on Rover V8 and T5 cost,start shopping. The deals are out there, you just have to dig for them. Welcome to the forum and don't give up, roverman.

I definitely want the T5 world class 5 speed. Everything I read about it sounds good.

All very good advice. Also regarding the motor mounts, consider the type I used on both the Roadmaster and my 340 upgrade, which bolt to the head and go straight down to a cushion on the frame rail. Simple, inexpensive and strong, plus they eliminate any need for a torque link and hold the engine very stable. I like the softer cushions as they isolate better and movement is minimal anyway. Down sides: since they sandwich under accessory mounts some fitting may be needed to get the alternator pulley to line up, and for a really strong mount a bit of welding is necessary. But get some touch up paint, you'll be wanting that anyway. The T5 is an excellent choice, as well as RV8 headers and a number of options in aluminum radiators at decent prices. Fit the most radiator that you can physically get in there, as well as the best fan you can find.

Thanks for all the advice. I actually went on the prowl looking for some parts today.

Rick,

There is a ton of information out there and you will have a headache from all the input!

The key is to tackle one issue/system at a time. For example, are you going with a T5 or an LT77? Each requires modifications to the tranny but those mods are very different if you compare the two trannies. Are you going with RV8 headers or block hugger? RV8 headers require cutting openings in the wheel well which also help dissipate heat - these should be done before paint. Block huggers don't require cutting from what I understand.

Radiator - I moved mine forward so had to do some cutting and welding.

Test fitting everything before paint is key!!

Here is my build if you are interested...
Buick 215 with Rover 3.9 EFI
GM T5 tranny

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