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MG MGB GT V8 Factory Originals Technical - 3.5 which one of these

Gooday all.

just about to start the collection for 3.5 conversion. i have just come across a bloke with 3 running motors for sale at $100 ea. question is do i go for the carburetted versions. (about 1982 i think he said) or the injected one (lucas injection) about 1985. all from rover3500. Im not sure which path i will take at this stage ie. injected or carb running gear. will look at lowering the engine in the bay a little more than standard conversions so i have the option. Maybe i should buy all 3 at that price. no doubt , they will require rings and bearings at minimum but might be handy to pick the best of the bunch and on sell the other two. Not needing a race car but a daily driver. the old 4 does around 30,ooo kls a year and has finally gotten smoky and tired.. Also , and without going through archives, does the rover timing case suit the conversion, or is it the range rover one that is easier.


PS to above.

budget is almost zero so need to keep costs down. Have read somewhere in archives that using the original gearbox is ok and understand that it has its weaknesses. Is there an adaptor plate for the 3.5 to the original box? its a 69 mk 2 overdrive and what clutch would be suitable for the original box ? (need to save money for rv8 style exhaust) and radiator. And if someone would like to donate 5000 for a good conversion, please feel free to do so (laugh)


if these are coming from a rover 3500 and if one of the engines has a 5 speed attached, then you should go with that entire setup.

I cannot recommend using the MGB 4 speed. You will probably break it pretty quick;y with the stock 3.9 rear.

But if that's what you want, there has been threads on here about it.
Richard Morris

Gooday Richard

Unfortunately, all 3 were autos. Using the original box isnt a choice based on anything other than costs. Mind you, i do have time on my side as its winter here now so will keep an eye open for rover box or toyota at fair price. Have also just spent the last 2 hours going through the archives and cant beleieve we have any more questions to ask that havnt already been answered in here. and it does appear that the original gearbox might do the job..just. Not sure i could resist the temptation for the occasional suirt though..think ill keep looking for a box


To use the MG gearbox you need not just a VERY solid 'box and the adapter plate but also a machined flywheel adapter with spigot bush, an MGC clutch assembly, a modified MGB flywheel and you must saw the starter mount flange off of the Rover block meaning there is no going to a different 'box later on. All that expense and you'll likely break the B 'box anyway if you get aggressive very often.

Why not consider the automatic for your commutor? I don't know how congested your traffic is but I wouldn't mind an automatic B V8. (I'll duck for cover now)
Willem van der Veer

Hi David.

Point taken about the block being made unusable for a different gearbox at a later stage. Also given the expense of the other items you have mentioned, looks like a rover box might be the better option now. I;ll continue searching the archives as im convinced of other alternatives.

Willem.. mmm auto is a possability but i would prefer the manual with 5 speed. i live in the country and travel 160 klms a day to work through the mountains and would like to maintane reasonably good economy. thankyou for the thought


Toyota 5 speed box (Supra or Celica) with a Dellow conversion package is the best option since you live in Oz. You'll need a flywheel whichever way you choose with a manual box.If any of the autos are 4 speed, it might be worth considering, as the 3.9 diff should work reasonably well with it. Barrie E
Barrie Egerton

Gooday Barrie

In regards to the rangerover flywheel, is any model range rover suitable ? and the motors have no auto;s with them. just motors. Have also notied that the supra box is availiable with different lever extensions. 21" i beleieve is suitable for the mg... does the celeca box have the same options re different models?

Hi Cactus, The RangeRover fly wheel is your best option but it needs to have about 10 - 12 mm machined off the face & be redrilled & tapped to accept whichever clutch plate you use. As far as I can tell the difference between the Supra & Celica boxes are , the Celica has a cast iron case & the Supra, an alloy one. Some of the ratios might vary a little but not much. The extension arrangement is the same for both. The 21" is the most suitable for the MG but the others can still be used with a bit more tunnel work. The P76 flywheel won't fit. Barrie E
Barrie Egerton

At $100 each I would take all three.
This way you have the time to check each in detail later at your place and pick the best from each.

The standard MG box is marginal in this application and will probably fail in short order especially if you are going through the mountains on a regular basis.
I would opt for either the Supra or Celica box and the Dellow housing to mate it to the Rover as suggested above.

Another alternative is the Borg Warner T5 from the Commodore V6 or V8. Cheap , strong and easy to find.

Carbs or EFI is a purely personal choice.
Which are you more familiar with? Which of the engines you are getting has the better set up in terms of wear and abuse by previous users?

Cheers , Pete.
Peter Thomas

Afternoon Barrie and Pete

Barrie, thanks for the info on box;s. Any idea on which year? will source one from the local wreckers i think. And i believe a ford pressure plate and a ??? clutch plate.

Pete. I agree after reading hours worth of archives. the original box looks like its out. Do you know if dellows make a bellhousing for the T5?

As to carbs or injected. Much more familiar with carbs although with help i would attempt the injection although not sure on the costs. also i have read that the plenum chamber needs machining to get it to fit under the bonnet with the injected set up.

Think i will need to do another few hours of reading to come to a decition. basis is cheapest way out but do realise it wont be all that cheap to do. thats why the collection of required parts over the winter.

thanks cactus.

Ps pete. im down the otways so hills aren't huge.

I,m about 5 or 6 months ahead of you in conversion terms and here,s where I am at;
I,m using a 3.9 EFI rover,LT77.The rover box was by far the cheaper way to go as Dellow quoted me $2600 for a supra kit,ie. bellhousing ,spigot bush etc..
Triumph and Rover in Adelaide had a LT77 for $995 delivered to my door.The bell housings are $600 on ebay here and like hens teeth around OZ in general,but in the UK (Im an expat)they are far more common so I imported it and the whole thing cost $300.
EFI, this has to be cut down, but the Rover castings are of the school of thats close enough.So there's alot of stop and check going on for the 28.5mm or so that has to come off.My EFI has been in the workshop for weeks and I should have it back soon.
Headers/Extractors/Manifolds-What ever you call them are not cheap! $1000- $1200 I have been quoted and at present I'm exploring the US or UK for a cheaper pair.
The whole thing wont be a cheap or quick exercise as I,m finding out, but look at the end result !
Hope this helps,Good luck.

While you're reading, consider the EFI type. 1989 on were "Hot Wire" which are generally preferable to the earlier "Flapper" type.

Also, most prefer the later 14cux controller.

If money is an issue, get the car up and running with the carbs (ugly as they are) and then you can look forward to building a good EFI system. Good luck!
Edd Weninger

The mid '80's 3.5 EFI inlet manifold on range rovers is the almost same as the 3.9 hot wire. If should be the same shape as this
first photo.

Since this comes with the motor, You might be able to save a bit by fitting the hot wire electrical gear to the mid '80's manifold. A simple bolt/plug in. As the above person has done. You need the computer, airflow meter, fuel and water temperature sensors, throttle position sensor and idle controller.

Usually the Hot wire specific manifolds have a big "3.9" caste into the cover.
It cost me $100 to have the trumpet tray vacuum take offs welded up and 16mm machined of the bottom and 11 or 12 mm machined off the top. Engine improvements opposite the St.Kilda town hall. I let them take their time and do it in spare moments. Another guy offered to do it for $70. I have a spare machined tray that I would swap for a tall oil filler and a "air con'" water pulley (the cast one) if you end up with a few spare parts. They could also do your Fly wheel I believe.
Don't go and buy a pre Hot wire (federal or "flapper" style) set of electronics. If you've already got the flapper (has a weighted flap/paddle that measures air flow, think backfire consequences) by all means use it. But its no where as good/ reliable as a hot wire.
With EFI you also need to buy a couple of fuel pumps. A "feeder pump" $95 Peirberge pt #12001, and the main bosh pump $155. The feeder sucks though a large filter (that acts as an antisurge tank/filter) and supplies the main pump (which is no good at suction).

Remember to check for cracking in the block by taking the sump cover off and looking for small tell tail cracks in the aluminium either side of where the crankcase bolts go in. On my 3.5 (never used) I could just see five small (about half an inch long) cracks associated with some of the crank bolts. When I had the block crack tested, it was cracked all through!.I believe that this problem is primarily caused by over heating on a fairly regular basis. Aluminium has a larger coefficient of thermal expansion than steel, which would allow the bolts to work loose if it all got hot enough, often enough. Once loose the crank can move and stress the block. This is a particular a problem in Australia, but must have been a recognized problem world wide, otherwise why did rover crossbolt the 4.2 etc?. If you get a good one, the current solution is to either put in studs (expensive) or use threadlocker on the crank bolts.
Gearbox- bear in mind that you do not have to cut the transmission tunnel with a toyota box. I was quoted $300 for a supra box from a Melbourne wrecker but eventually went with one from Dellow ($700).
Triumph and rover (using Dellows bellhousing) sell the full kit for $2000.
Front cover- I went with a rangerover front because I had various bits of 3.5 engine lying around. If I had to go buy one I would get a rover front.
T5, he might, ring him and ask. If you are on dial up it will be much faster.

Gooday Warren.

Thanks for the reply. like you i dont have an unlimited budget. all work will be done by me. I may fabricate the engine mounts myself to try and get the engine low enough to allow for carb or injection without the need for machining but i have yet to place an engine in there so will have to wait and see what the easiest option will be.$2600 is out of the question for box and kit. might go with a supra box. as peter said, .$300 from a wreckers and i have a mate with a wrecking yard. hopefully less. i believe the bellhousings are around 5oo. wont have much choice there. flywheel and ford i believe clutch, hopefully around 300 so with luck, $1000 should see the transmission sorted out, including rangerover slave cylinder. Exhaust mmm. let me know what you find. ive heard the same, around a grand. i;ll definately go with the rv8 style and most likely run side pipes like the cobra. another decition to make.

Edd.I like the idea of carbs first then injection at a later stage. makes perfect sense.

Peter. Its chris here. i got those wheels of you last year. If one of the motors has the oil filler and pulley you want, their yours mate. i will pick up the motors, all 3 on sat morning so will let you know next week.

I;ll try add a pic of my car with side pipes i made up on computor.

thanks for the replies




The Dellow catalogue is available on line as a free download.

I am not completely certain but since the Commodore T5 bolt pattern is standard GM it may bolt straight to the back of the Rover 3.5 which was also originally GM.

Be worth a check.
I'll have a dig around as well sand post here if I find anything.

Cheers , Pete.
Peter Thomas

Forgot to add:
Have a look at the Castlemaine Rod Shop site as well.

They also have a free dowmloadable catalogue and an online forum for conversions.

Cheers , Pete.
Peter Thomas

OK. Just checked castlemaine rod shop and it looks like they have a bellhousing to suit supra box for $325. doubt it includes any accessories but will check it out. sounds cheaper than dellows housing

Thanks Chris,
Kind of you.
I've got my engine as low as it can go using the standard rubberbumper/V8 rail mounteed brackets. I still had to take about 23mm off the plenum. The real difficulty is the width of motor plus mounts and fitting that between the rails. The lower you go the further up the V you get and the wider the engine is.
The only way to really get the motor down that low is to put your mounts down on the front crossmember and cut the extracter/header holes a bit larger. The first has been done by someone on this board and apparently he found it very sucessful. I would imagine it would be easier to do, simply bolting sections of angle iron to crossmember and engine. Also better from a vibration point of view and much easier to get the engine in or out of the car. Also I suspect that you might not have to alter the steering. I saw a car from plus four in dandening that had squeezed the engine low enough to get the rear right pipe under the steering knuckel. That was a supercharged V8.
The problem is that you would be departing from the standard factor approach so you must check with an engineer first to see if he will allow it.
The Castlemaine rod shop used to make a bell housing that was a little thicker than Dellows. I was told it was better, but haven't seen one so can't confirm that. When I rang them three or so years ago they did not have any on hand.
Adapting a toyota or similiar fork and bearing should not be too hard. Like most, the dellow one simply locates on a kind of round headed bump. You could do something with some allthread and a dome nut if necessary but I'm sure the rod shop will have something if they are selling bellhousings.

This thread was discussed between 02/07/2007 and 05/07/2007

MG MGB GT V8 Factory Originals Technical index

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