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MG MGB GT V8 Factory Originals Technical - V8 Conversion Help

Ok, over the years the info and advise from this site has been very helpful. The engine on my 1980 B has finally had it. It's time for a V8. I like my mechanic and he said he would work with me to do the conversion, but can I source out everything he'll need, and I mean everything. With that in mind, is this a good idea or will I wind up in a position of tracking down motor mount from one source, rear end from another and shocks from a third. My mechanic's is great, but he's not going to read a manual or start manufacturing custom mounts.

Hi Ric- Today you have choices unknown 5 years ago. Bill Guzman and Brian McCullough both over full conversion service, including packages for any level of fast you are after. Good luck Vic
vem myers Ric-try these links. Vic
vem myers

I'm not sure they have V8 conversion kits though. Pete Mantell would be a good call, as would some of the other V8 vendors. Check the V8 Newsletter for sources. Most offer a pretty complete package. These days you can do a Rover/215 swap as a bolt in job. The SBB is just a trifle more work, and the Ford swap is possible as a bolt-in as well, though more expensive as you have to change out the front suspension or crossmember. Your mechanic should have a relatively easy time of it.

Jim Blackwood

Jim wrote: "Check the V8 Newsletter for sources."

This page lists the best sources:

As I answered on the MGB board, for everything in one location you could try D and D but I forgot about Glen Towery who is one of the British V8 sponsors as well and comes highly recommended by a good friend who did a V8 conversion a couple of years ago.
Bill Young

The toyota supra (W58) gearbox set up I use doesn't need any tranny tunnel mods.
Dellow Automotive can sell you all the bits. Ships internationally

Towery (and others) can sell you two sorts of brackets and a variety of other bits.
You want the through the guards, RV8 style headers.
AA Automotive in Adelaide sell the best ones

, Clive wheatly in England will sell you a nice RV8 copy headers.
Other useful stuff here

Peter Sherman

Should also have mentioned that Glenn used to come to your place and do it in a weekend!

If your back axle is a salsbury one (row of bolts around the back cover only, not on the front.
It is VERY strong. You don't need to replace it unless you want to.
I recently read a thread where a number of people were writing that they had used up to 400BHP engines with it. I think it's a very safe bet up to at least 250BHP.
I still use it with my 3.9EFI and never a hint of trouble. Other than axle tramping, and thats the springs and can be fixed with antitramp bars.
It was origionaly designed for some sort of delivery van and was adapted for MGB's.
I prefer the 3.9 diff ratio to the 3.0 etc. I put a V8 in for the fun factor of powerful accelleration, not highway economy. However, thats pretty good as well with EFI, I get almost exactly 10km to the litre at 110km/hr,top down.
Peter Sherman

Peter, That's a really low ratio.....what is 10k per litre in 'real' money... about 23 miles per Imperial gallon at 68 ?

Your fuel taxes must be much lower than ours, my Efi 3.5 with a 3.08 axle gives me just over 30 miles per Imperial gallon at 70/75 and I think I'm hard done to !!!

I'm paying £0.99 for a litre of 98 octane here, and that's quite cheap by UK standards.

M Barnfather

30 is pretty good.
I think you might be calculating with US gallons!
Lets see , there are 3.7854 litres in a US gallon,
And 4.5461 of the British (real?) sort.
1.60934 km per medieval Mile.
So thatís 28.2 miles per Britsh and 23.5 per US gallon. Not quite 30, but close enough for me. If I had the roof up Iím sure that would get better, however I never have the roof up if it is humanly possible!
I have no complaints about economy.
This was during a 10-12hr drive down from Sydney to Melbourne on a 8 lane, very good road/freeway. A steady 110km/hr seeing what it would do. I filled up a few times out of curiosity. Some times it was about 9 and a bit and sometimes 12 and a bit. A way of passing the time on a long long drive.
The fifth gear is a 0.78 ratio.

We are actually a bit horrified to be paying $1.35 a litre.
Peter Sherman

Too late to matter, but my bad-sorry. Yes, Jim, Bill and Brian are v-6 swappers extraordinaire....not v-8
vem myers in Canada carries
most of Clives items and they have been very helpful
I used his aluminum RV8 brackets and mounts and I made
a trans (TR7-8/SD1) mount and didn't have to move the trans cross member and no welding.

Bob Fisher

I would also like to submit a cry for help!
I have three MGs, a Chrome Bumper MGBGT, a rubber bumper MGBGT and a ZR120. The rubber bumber engine is about to join its ancestors and I am in the process of re-building a Rover 3500 V8 to fit in place of the original engine. However, I am short of an inlet manifold for the two SU's and the adaptor for the remote oil filter. Due to the high cost of importing these items I could have something made up locally if I could get hold of a sketch or pictures. Can anyone help?
Chris Barrow

There is every chance that someone locally is selling the oil filter adaptor. However in My case it was cheaper to import from Clive. The MGBhive in England might be cheaper still, however they won't export to Australia(??). It cost me around $400.

To have one made would be very expensive. Essentially it is a flat block of aluminum about an inch thick that contains the oil pressure relief valves and an inlet and out let oil line. If you have access to a machine shop you might be able to adapt the existing rover one. Or use it as a template. You want essentially the same thing, except flatter.

Fit EFI, it is much cheaper and much better to do.
The 3.9 efi will go on you 3.5 engine no porblems at all.

On the advice from others, I had the 3 vacuum take offs on the starboard side welded, which allowed me to take anything up to 11mm off the top of the tray. You can get up to 16mm off the bottom and still have plenty of aluminum to locate the trumpets(Glenn Towery takes more, very successfully). This cost me around $100 to get a machine shop to do all the welding and machining. Make sure they tidy up the remnant 3 bumps on the bottom of the tray before machining.
I used two inline efi pumps.

If you really want to stick with carbies, try second hand rover or rangerover engines that have had a Holley fitted.

Couldn't you just use a spin-on fitting for remote lines? Seems that would be much cheaper.

Jim Blackwood

Chris, you can have the original Rover manifold modified to accept a Holley carb. The "SU" lump is chopped off, milled & an adaptor plate welded on in place. These adaptor plates are usually for after market mods like fitting a Holley to GM or Ford or Mopar or fitting Holley instead of Carter etc. They're normally bolt on but the casting is good enough to weld. Barrie E
Barrie Egerton

For RH steering the oil filter base lines up (with almost supernatural precision) with the highest part of the steering. The very foremost tip of the filter base precisely aligns with the upper edge of the highest bolt on the rack. It is almost as if they designed the entire car with this objective in mind, that these two things should coincide. It is so frustrating. For all you lucky LH drivers, not a problem, spin on is the way to go.

Peter Sherman

Thanks Gents,
Chris Barrow

Chris Barrow

Let's try again!
Peter, I have managed to locate an EFI manifold with Plenum and injectors, but the supplier seems doubtful about me using the Rover ECU. Did you use it?
Chris Barrow

Mine is a 4.0 motor that came with the 3.9 EFI already on it. Every thing I have read says you can fit the 3.9 efi on the 3.5. Rogers book, this site etc.
This terrific article will tell you all you need to know.

My approach as outlined above was slightly different.

The wireing loom was a different colour code to the haynes book for me, but it wasn't too hard to figure out.

It occures to me you may have located the older style of ECU. Rover went though three stages of EFI developement (4 if you could the lastest GEMS)
First was the Federal, or flapper style.
This had an air flap in the air intake monitor, and it had analogue electronics, which had some reliability problems. The flap could also be a problem if you experienced backfire. Initially this system had a simple "flat top" plenum (often painted black) with eight bolts to hold it down. No trumpets. This was used with 3.5's only.
Later they used the trumpet manifold, approx 1985, (as per the article above). However they retained the older analogue and flapper electronics until about 1989 when they introduced the HOT WIRE digital electronics set up. This was much better and reliable, however many people have used the federal style with great sucess so if thats all you can get , use it. A plus is that it is easier to get under the bonnet.
You can fit the later Hot wire EFI to a Mid '80's "trumpet style" plenum. However you do have to change all the sensors and the idle control.

Peter Sherman

Shame you are not in the UK, I have all the main bits for a conversion but no mgb roadster to put them in :-(

Liam H

Thanks again All!
The sub-assemly is at the engineering shop now, but the local spares guys tell me that they are out of stock on some of the spares. This is going to be a loooong haul!
Chris Barrow

This thread was discussed between 10/09/2007 and 01/10/2007

MG MGB GT V8 Factory Originals Technical index

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