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MG MGB GT V8 Factory Originals Technical - V8 Conversion

I'm contemplating the long, winding and potentially expensive route of a V8 conversion. And I have the idea of trying to limit the size of those last two points, hence I'm putting a post here.

I know there are books that will tell me what bits and pieces I'll need; I have both Roger Williams' books. But I think they lack the human side of things and the experiences some of you may have had.

Basically, what should I be doing from here on in. I have a standard spec 1977 Roadster that has been chrome bumpered. It's replacing a 1976 Roadster that's had nothing done to it. I fancy something with a bit more go about it and I figured while I could fit an uprated 4-pot, why not do it properly and fit a V8.

I'm assuming:
Stage 1 is to uprate the suspension: lowered to chrome height (V8 suitable springs all round), poly-bushes, tele-damper conversion front and rear and an uprated roll bar (neg camber wishbones a good idea?)
Stage 2 is to uprate the braking: 4-pot calipers, uprated pads and V8 discs at the front, uprated drums at the rear, braided hoses.
Stage 3 is to uprate the cooling system: I'll be fitting a Kenlowe anyway, but a V8 rad and larger oil cooler.
Stage 4 is the transplant: 3.5, 3.9 (or possibly 4.0) V8, 5-speed G/B, V8 suitable clutch, V8 drive shaft and a V8 rear axle.
Stage 5 is details: V8 spec speedo & tacho

How much of this would be sensible for me to do myself? So have I missed anything obvious? I know this route has been done before and there are many things that I need to know before starting but you can't beat actual experiences.

Appologies for the long post but better ask the questions now rather than in the middle of something drastic like "the engine is out, what do I do now?"

Rick Haynes

You have got the stages about right but I would leave the uprating of the anti roll bar until you have the engine in place as the exact location of the bar is dependant on where you mount the engine.
Chris Betson

Reading it again I wonder why you want a tele-conversion front and rear. Neg camber arms combine nicely with uprated lever arms and a 7/8" anti roll bar. No need for teles as long as your levers are fine.
Same for uprated rear drums. 80% of braking is front.
The rear axle ratio makes the V8 for what it is and makes it so relaxed to drive (Andrew is right).

Frank de Groot

I've just finished a 3.9 EFI/MG and it goes like a rocket when I want and just cruises easily along in fifth when I'm not in a hurry, just really nice.I used a '95 Range rover motor with the front off an '86 3.5 range rover motor (like the RV8).I used a Supra W58 gearbox with a Dellow bellhousing (mentioned in Rogers 2nd book), but I expect you'll use a rover box as they seem to be readily available over there (not so here). If you hunt through the archives you will find detailed instructions on how to (very easily) convert your speedo yourself with one small variable resistor), Zac's V8 conversion I think it's called.

The people who hang around this site are tremendously knowlegable and helpfull, and will be able to answer most of your questions. I am not especially gifted mechanically but was able to do this conversion with their assistance, and much trawling through the archives.

Things not mentioned in the archives that I've found out for myself are;
-I had to length-en the throttle arm on the EFI air intake manifold in order to use the full length of the MG accelerator pedal, otherwise I literally couldn't press the accelerator lightly enough in wet weather,wheels would spin madly. God knows what a high comp' 4.4 is like. The '95Range Rover acellerator cable fits perfectly if you run it through the bonnet hinges along the back of the engine compartment, no big deal but a nice bonus.
-There is much comment in the archives about overheating problems- I cut out the front tray to level with the upper slam panel which gave me room to put a big electric fan behind an alloy radiator. Fans work more efficiently when they suck. Even on a 45 degrees Celsius summer day in peak hour traffic, never a problem.(The offset water pump from the '86 front leaves more room for the electric Fan. )
-If you place your remote oil filter head a little lower than usual and use the type of filter with the antiflow back valve you won't have any problems with low oil pressure on start up (a common problem apparently).
-I used the harmonic balance off the range rover and one of the pullies from an Rover SD1 harmonic balancer which lined up nicely with the water pump and gave pleanty of room for the antisway bar and saved having to machine the SD1 harmonic balancer as per Rogers excellent book.

Things I would do differently;

-I wish I had used an "in tank" variety of fuel pump. The external variety was lots of trouble and is a little noisy.

-I wish I had ceramically coated the headers, the stainless discolours rapidly, which was unexpected.

Thats my two cents worth, good luck and allow about three times longer than you think it will take.

I expect others will have more useful comment.


Interesting comments - What problems have you had with external fuel pump? I was considering using one of the facet high pressure ones with a regulator. How noisy are they?
Stuart Robson

Peter, Stuart's using fuel injection, and the pumps are noisier than a carb pump. It's only really noticeable on start up and perhaps on idle, mine's in a SD1 rubber box in front of the tank, but I can still hear it if I listen hard.

Michael barnfather


I would consider the Holye NG/Hawk cars front suspension (with 4 pots and adjustable camber etc) and rear IRS with discs(although expensive the conversion to live V8 axle is also costly).

I would go Aly rad and also 5 speed box and custom made prop.

Also a new 4 or 4.6 about same price as decent rebuild of 3.5 or really go for it with a LS1.


Not very noisy at all, but given the location, in the battery compartment (just like Rogers book) definitly audible with the top up, but not loud, just annoying.Sounds like a wasp trapped back there. You can't hear it with the top down. However given that you are likely to have a swirl pot (antisurge baffle) welded into your tank, and a return fuel line, you may as well have a flange welded in and fit an in-tank style of pump. Since you can't weld the fuel tank yourself (unless you really like to live on the edge) you may as well hand the entire problem to someone else to solve, and get back a nice quiet fuel delivery system.
Apparently there is a Volkswagen with an in tank fuel pump which comes with its own swirl pot, I don't remember the details, it's a model not available in Australia (see archives again!).
If you're determined to fit an external type pump (ie already bought one) you do need to run a half inch fuel line to it. Any constriction in the line makes the pump very noisy indeed. Also a filter prior to the pump is a MUST as I found to my cost. The smallest bit of debris destroys these things.You can buy high flow filters that are external versions of those normally found on the uptake pipe in the tank (a circular piece of plastic mesh). This filter needs to be arranged so that fuel is fed from the bottom and exits the top(I used a loop of fuel line). If the filter is on its side a vapour bubble will form above the outlet which will now and again be sucked into the fuel line and break the syphon (over the back axil), which briefly makes the pump once again suck noisily. Unlike Michael I'm using the MGB back axil which doesn't make mounting the pump next to the tank an option, no room.

If you wish to ovoid having anything done to your tank at all then another option is to use a small external tank in the battery compartment (relocate battery) or boot, mounted directly above the high-pressure pump, fed by a low pressure pump. (Many people do this and that would be my second option.)

beg pardon that should be Stuart, not Rick

Cheers for all the replys guys. Most helpful.

Peter, there's a company over here called Frontline Spriget that sells fuel tanks that are designed for conversion "attempts". It's got the fuel in and fuel out connections and is baffled and (I think) has the possibility of having an internal pump. I'll have to contact them to find out costs, I only saw the ad in a magazine and can't remember the details.

For those that went "blue skies suggestions" on me. I'd love to have IRS with coil overs at all four corners, but I'm not made of money. Unless of course I go down the line of doing a bit of the conversion at a time (set up suspension, then set up brakes, collect drivetrain parts, then convert) but there have been notes of concern over this method. I've got a feeling I'll be staying with (for the mean time, or until I win the National Lottery!) the standard axle albeit uprated for V8 use.

Interesting note about no need for teles. It was just something I was thinking about, but if the general concensus it uprated lever-arms would work then they're definitely cheaper to start with. Would it be work considering teles for the rear just to keep it under control?

What about cooling, I know I live in Scotland (not Oz like Peter) but in stationary traffic there's always the chance of overheating. With the car being a 4-pot at the minute I'm probably going to install a puller Kenlowe fan kit in place of the single electric pusher fan. Can this be kept with the larger V8 in place or would I have to switch to dual pusher fans?

Lastly (sorry about the number of questions), ride height. Currently r/b height, but there's always the option to drop it to c/b height. It'll be running on 15" minilites with 195/60 tyres.

Cheers guys,
Rick Haynes

After I had fitted my large aluminium radiator (5cm thick, and extending below the tray)) and very large fan (10cm deep, 16 in diameter), I had a look at an RV8 and was suprised to see both RV8 radiator and fan were about half the size (ie massive overkill on my part) . I'm not too upset though as there is nothing worse than sitting in traffic anxiously watching the temperature guage.
I now believe the high efficiency aluminum radiator is probably unnecessary if the cooling fan is set up right, ie behind radiator, close coupled and RV8 "through the wings" style exhaust extractors. If you have your fans at the front, or maybe "block hugging" style headers, then there probably would be a need for the better radiator.
However there is sure be be an RV8 somewhere nearby that you could have a look at, then take that as your minimum. Given the cost of big aluminum radiators ($600 australian)and giant electric fans ($300), and the fact that you've not much room, this is well worth doing .

Thanks Peter.

I'll take your advice onboard. Incidently I think all the VWs with the Jetronic (Bosch) fuel injection have in tank pumps with swirlpot. I changed a pump that was getting a bit noisy in a Passat. Took about half an hour and cost me £5 from a scrappy. Tanks are weird shaped though...

Stuart Robson

You will see from the archives that there is much info (too much in some cases!, as there are often 2 or 3 solutions to a particular question or problem). I would recommend spending many hours searching & reading before finalising your solution or committing any money. Starting with a 1977 shell, you do have the option of the staged approach you describe. Given that your stated objective is to avoid a long project and minimise expense, you may want to consider keeping it can always upgrade later. Poly bushes, tele-dampers, 4-pot calipers, upgraded anti-roll bars are all "nice to haves" on a modestly powered conversion. Providing that all suspension and brake components are in tip-top condition, you can be selective in what you upgrade. You may also wish to consider the approach I have a rusty/good runner Rover Vitesse...£500-£800. This provides many of the major components and has the potential to minimise cost, uncertainty and project timescales considerably. Pete
Pete Green

Nice to know about the Passat,I hadn't realized there was an EFI version, wish I'd know earlier. Something to file away for future reference.

Audi 5 cylinder engine in the old Passat GL5s...
...Was very underated. My old man had one that did 350K. Wonderful motorway cruiser that was at 2100rpm at 70mph and at 4000rpm...... ;¬)
Stuart Robson


My radiator is OK with single large Kenlowe fan, but I do have rear facing louvres in the bonnet for stationary cooling,and wrapped RV8 manifolds. The fan rarely cuts in when the car is moving, but there's not much room around the engine and gearbox to let hot air out when stopped.

Michael barnfather

Just incase you've missed this somehow, the radiator on the post '76 MGB's have the same core as the MGBV8 .
so you need not buy another one.
One other thing I would wish having done otherwise (which infact I HAD to do otherwise)
I initially bought a second hand 3.5 motor (that's where I got the '86 front from) and I had intended to recondition it. This motor turned out to to have cracks around the main bearing bolts. This is infact very common, the bolts work lose and the crank moves a little and hence the cracks. The cost of welding, machineing, reconditioning, resleeving (and putting studs inplace of the bolts) with this old motor was the same as a brand new short 3.9 motor. ie.not worth it. That's here in Australia, might be different where you are though.
I did eventually find a good, very low km, hot wire 3.9 motor with all the gear, however If you are considering buying a second hand motor insist on removing the sump and having a look either side of the crankshaft main bearing bolts. You will see one (or more) fine cracks on one or both sides of the aluminium that these bolts screw into (if the motors a bad one that is).
I looked at half a dozen 3.5's (all cracked) before the 3.9 came along.

Thanks for the info, could be useful when I get round to looking for engines in ernest.

Having looked around briefly with no real intention of purchase quite yet, there are several 3.5l & 3.9l from Range Rovers & SD1's in various breakers yards around the country. Plus, as a bonus, I could get hold of a 4.0l TVR V8 from a write off for £1700 (AU$5000). With the potential of a 5.0l from a TVR Griffith 500 including a gearbox. Problem is that while that would be great in Oz where petrol is a bit cheaper, that would be a bit like trying to put a fire out by spitting at it over here.

Still there's plenty around. Can't get onto V8 conversion quite yet as the current MGB is giving me a little grief that has to be dealt with.

Rick Haynes


Pete Green has some interesting points: indeed a lot of things look nice, and are used by people to their benefit, but not really necessary.
Brakes - use V8 pads (greenstuff or OE) on your normal brakes, perhaps drilled/slotted discs. Stops well enough.
Handling - you can stick to standard. If you want to improve the handling, fine, but not necessary. If you want to improve step by step: remove rear arb. Uprate front arb. Neg camber arms, uprated levers and uprated springs (perhaps lowering, but take car of speed bumps).
Rear teles work a bit anti-tramp, but cost money and if you really need anti tramp (big torque, big engine?) you'd better find some anti-tramp bars. I run my V8 without and it works just fine.
Handling and braking can be addressed when you finished your conversion; can be done while you keep your car driving. Be sure that your system is in good condition.

Of course if you can lay your hands on an SD1 it is nice to use as much parts as possible. Pitty an SD1 is to be scrapped; they're such fine cars.

Frank de Groot

Just a example of what not to do on rear dampers and ride height. I had a few problems (fairly well known), but thought a bit of hindsight might be of help........

(I was going to do the conversion to V8 on my old MG, but then realised that I didn't have the time / the cost was disproportionally high, so bought one.~£6-8k)

The car I bought had been lowered considerably (which did improve the handling compared to my old one) however a simple speedhump took off my exhaust. So I replaced it with a nice big-bore stainless steel one (highly recommended). However I then had to fit new dampers and took the tele route (which do improve the ride considerably), but there are big issues with clearance that took a blowtorch and a hammer to solve.

There are some ways to help this, for example oval box and smart routing improves clearance, but worth bearing in mind if you're choosing handling options....

Might be worth considering the combination that you intend to have in advance (I know this because I didn't)....

3.9's common! Wish it were so here, very rare second hand as all those thousands of folks with 3.5 Range Rovers snap them up. The disadvantage of having aluminum bodies that never rust away.
As for economy, I haven't fully tested this yet but I believe that the 3.9 EFI is not costing me any more to run than the old 1800. I used to put my foot down a bit and those twin SU's tend to guzzle petrol.

Well, as far as I can tell there are plenty of Rangie's to be torn apart over here. Is there any downside to choosing a Range Rover V8 over an SD1 or even a TVR?

Also, would I be better off going for and EFi assisted lump or carbs?

Rick Haynes


EFi or carbs......that should start a discussion (once again)


Less expensive to buy.

Mechanically simpler

fit under bonnet easily


More efficient (power and MPG)

Stays in tune

cleaner exhaust

You pays your money...and takes your choice......there is no right answer....just different opinions (I'm 3.5 efi)

Michael barnfather

The TVR approach is sound, if you can get your hands on one for reasonable money. Going the Range Rover route does give you more engine(size)choices, but there are other considerations. Low power output (low compression ratio etc) can be overcome if you plan to re-build the engine...but your orginal posting said you wanted to minimise cost & time?? In addition, the Range Rover will not give you the bell-housing, flywheel, clutch & slave cylinder, prop-shaft and gearbox. All these will need sourcing separately = more time and money! If the Range Rover is old (pre '86?), you'll end up with only 3.5, the weak block, poor performance and won't even get the EFI set-up...surely the worst of all worlds? My advice for what it's worth...if you really do want to minimise time & expense, break a running late SD1 Vitesse. If not, anything is possible given the money....5.0L TVR?!!
Pete Green

Pete, (or anyone)
Off hand, do you know how much people shave off the heads to get the compression ration up to SD1 vitesse?. I intend to do this at some stage.
Rick , he's quite about right about getting a Manual Vitesse if you can. Here they are virually unobtainable unless you really open your credit card full throttle.
I got the Range Rover engine because it was only $2400 Australian, had only 20,000 Km on it and had all the EFI gear. Too good a deal to pass up, and I figured that I wouldn't(and don't as yet) miss the 7 or 8 BHP.

Pete-Good tip about the Peugot by the way!

Changing pistons is the way to go I believe. If you can't get them for sensible money locally, try Real Steel in the UK...+44(0)1895-440505 (approx £137 a set, less the tax = £116). Shipping may be a killer?
Pete Green

I've just noticed Mikes comment on EFI.
Like Pavlovs dog I can not fail to respond
Rick the thing is most 3.9's (or larger) come with the EFI already attached & you've got to go out and buy Carbies.
It's very easy to make the plenum fit. Balancing advice (from the people who contribute to this site) I had 16mm machine from the bottom of the trumpet tray, 12mm machine from the top of the tray and only 5mm from the cover. Gives me about 1cm clearance top and bottom.
If I was doing it over I'd take only 10 from the top of the tray and 7 from the cover instead, also only 15mm from the bottom.

It cost only $230 Australian to have this done.
Thats got to be cheaper than Hollies and low rider filters etc, certainly cheaper than MGBGTV8 plenum copies and SU's.
The main expense with EFI is the fuel tank alterations, and you're probably due to do something about that anyway given the age of these cars.

I rather suspect that your Carbie type conversion is done mostly for the sake of style, and hang the cost.

Not a bad second option, and to be born in mind however our pernicious customs like to add back on 10% general service tax and a further 15% if it comes in a box with "car parts" written on the side, add on shipping and multiply all of that by the exchange rate (about 2.6 I think) then I start to get sharp pains in the hip pocket. Local providers know all of this very well (of course) and so levy steep prices and sometimes it can be a little cheaper to import if you watch the exchange rates closely.
At this point I've still got a spare set of heads from the 3.5 dud motor sitting around doing nothing. Idle heads makes the hands work like the devil, if I might parraphrase horribly.

OOps... forgot about the tank conversion that was a problem (only because I was too mean to pay the local Rover dealer for an RV8 tank ) !

I was fortunate in that our local Rover SD1 dismantler is a friend and he had a scrap SD1 Vitesse in his I had it. They still are about (he had a twin plenium one in last year) but getting rarer, but it does make the conversion easier in some ways (and harder in others).

The simplest route is to find a scrap V8GT and transfer the parts into a new Heritage shell....I've seen this done several times but there cant be many left now.

Good luck anyway.... you've certainly come to the right place for's often conflicting but generally good natured..


Michael barnfather

About the discs: 505 Turbo had two different discs. The 604 Ti consistently used the discs you want.

Frank de Groot

I've got the Peugeot part number somewhere if yoy want it.

Michael barnfather

Yes please, I most certainly do. There can be no mistakes then.
(& any advice would be good).

MG B Roadster 1973
V8 Conversion

Vehicle has been owned by myself for 10 years. Was fully restored when purchased with receipts and photographs of all work carried out. V8 conversion was carried out in 1997. Vehicle was run for one year after conversion, then taken off road for respray, then due to other commitments and interests eg. MX5 and motorboat – MGB was just left in the garage.

We are moving abroad approximately July / August therefore MG for sale. Vehicle was valued at £9,500.00, I am looking around £5,000 as a quick sale is required.

Engine Size: 3.5 litre rover V8 – approximately 170bhp
Jan Speed : 4 speed manifolds
Twin carbs
Remote oil filter/cooler
V8 radiator
Twin straight through sports exhausts
Reconditioned Rover 5-speed gearbox
MGC axle
Uprated and lowered suspension
Standard brakes with V8 disks air-equip hosing, new cylinders etc
Uprated clutch
New propshaft
New petrol tank
High pressure fuel pump
Plus much, much more
Twin kenlowe system

I have a full list of components purchased and fitted from MGB conversion specialists in London, which runs into thousands of pounds.

All conversion and restoration work carried out by professionals to a very high standard.

The engine insulation brief was to make it look factory installed, which has been carried out successfully.

Due to the low price there has been quite a lot of interest, so I imagine it will sell very quickly once inspected.

County Durham

For more details please don’t hesitate to contact me 07778 411 904

Pictures attached.

This thread was discussed between 06/03/2003 and 23/03/2003

MG MGB GT V8 Factory Originals Technical index

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