Welcome to our resource for MG Car Information.



MG parts spares and accessories are available for MG T Series (TA, MG TB, MG TC, MG TD, MG TF), Magnette, MGA, Twin cam, MGB, MGBGT, MGC, MGC GT, MG Midget, Sprite and other MG models from British car spares company LBCarCo.

MG MGB GT V8 Factory Originals Technical - Should this 1969B get a V8?

I have had the car for two years. A former California car with no rust or rust repair. I just had the motor rebuilt and, put in over drive while I was at it. The car is very correct and, runs great but, I want to step up to a V8 now. I have done some reading and know about many of the tasks involved to make this happen but, would like some input on this. The Rover V8 is what I want and, I would like to stay with chrome bumpers. Would I be better off selling this car as is and looking for one that is done? Would a Heritage shell for my year (1969) come ready to accept a V8?

Being an older B the steps involved in converting to a V8 are quite drawn out and can be rather costly if you are not able to do much of the work yourself. Skills such as welding and metal working might be needed to do a proper job. That being said it is my opinion that if it's in as good of condition as you say it is then I'd just leave it "B". (bad pun but I couldn't resist) As far as I know the heritage body shells have the inner fenders of the later model B's with the large depression for the V8 exhaust and the forward mounted radiator but if you use an earlier chrome-bumper cross member you may have clearance problems with the bottom pully on the engine. If you have your heart set on a V8 MG then you could always keep the '69 and buy a rubber-bumpered one which would be easier to convert. You could always convert a rubber-bumper car to chrome-bumper if you prefer the chrome more. That's just my two cents worth.
Chris Mowris

FWIW I'm with Chris - it sounds like your car is too nice to start chopping around. If your pocket is deep enough go for a Heritage shell (having ensured you can get the V8-style bulkhead and inner wings on a shell suitable for chrome bumpers). Otherwise I would be looking for a non-running rubber bumper car from a rust-free state...I get the impression these are still plentiful.
David Smith

I don't know about this; I was able to get a Rover 4.2 and an SD1 5-speed into my '74 CB car very cleanly with just one weekend of sheet metal work and fiddling with the steering column. It probably _is_ a little easier in an RB car, but the difference in overall effort just isn't significant. It's the difference between spending 315 hours instead of 300 hours on the thing!

I'll have to agree with Chris and David. The '69 was, in my opinion, one of the best "B" packages. With the described condition of the car, and work already done which would become disposable, I would strive for originality. The CB vs. RB is a complex issue and one really needs to decide what one wants in the final product. You'll not likely rest easy unless you do it right in the first place. There are solutions to all of the problems encountered with conversion of various models and parts. It is no doubt the easiest to convert a RB car and lower it--perhaps with a modified CB X-member for the best handling. How much does the thought of a hood scoop bother you? (not that it would be absolutely necessary). I have seen V8 shells advertised. Well done Ron!

Thanks for all input folks. Angus, the thought of a hood scoop does not bother me at all but, I will probably not put one on. I am afraid if I do, every guy with a little something under his hood may want to have a go at it! What I am reading so far, I sort of knew already. Yes my present vehicle is quite nice and it might be a shame to cahnge it all around but it is so nice that what ever car a get to replace it is gonna have to be darn nice because I don't want to be kickin' myself after letting this one go. I know some of you are probably thinking "just keep it and have two!". That is a great idea but I have limitted space and I can't drive two cars at once. I would prefer to just have the one. Is there much body work involved to make a RB look like a CB? Body work is not my thing but I am pretty good at welding and I think I do a lot of the under hood mods myself.
Ron, you mention a Rover 4.2. is that the same block as the 3.5?


I took the routing of buying a USA RB model and converted it to CB. The MGOC sells kits for this conversion but these kits don't use the original bumper brackets. It is supplied with special brackets With these brackets, the bumpers are mounted to the front and rear valence instead of the chassis. I didn't like the idea so i used the original brackets.
The most difficult job was to make the holes in the chassis for the brackets because there is limited acces. Also aligning the brackets and fitting a grille is time consuming. I also lowered the front and rear suspension.
The idea of converting it to V8 is highly recommended.
I would sell your MG and buy a mechanical tired USA import and then do the conversion. I found out that converting a mechanical tired car is a little more expensive then restoring it to standard specs. A donor SDI, i bought for GBP 250,- and i was able to sell the 4 cilinder MG engine for GBP 175,-.
Peter van de Velde

Converting a RB is sounding like a good way to go. Is it possible to put an interior intended for a CB into the RB body. In other words can a dress a 1977 to look like a 1969?

On my V8 conversion, I took a similar route. I already had a 73B, with new front suspension, new interior, etc. with a bad body. I found a 77 shell, switched front crossmembers, and put the interior (seats, door panels, dashboard, etc), from my 73. I also changed over to chrome bumpers, and lowered the 77 rear end to match the chrome bumper specs. It is pretty tough to tell my car wasn't an original 73, except of course if you look closely you can still see where the RB mounts on the front were cut off.


I was just looking through the cars for sale in the classified section. Yes there are a few RB bodies available here in the US for a fair asking price. (I was surprised that there seemed to be a lot more CBs than RB for sale.)
Anyway, I have one more question. If I were to go with my exsisting '69 body, is it neccesary to move the radiator forward like the late model body to do the V8 conversion?
Thanks again

Having done a couple of V8 conversions I have some experience of various routes, with most experience with my own 1968 V8 EFi which I converted over 15 years ago.

Firstly there is not single route to follow, there are many variations on a theme, with certain common threads.

Many have been mentioned but to sum up conversion of a pre rubber bumper car requires the engine bay of that car to be converted to the shape and spec of the rubber bumper car for the simplest fit. (Inc moving the rad forward.)

Steering is an issue in several areas. One relates to the exhaust clearance and the compatability of steering to front crossmember in terms of mounting angles. Here a number of options are viable with differing amounts of work, again the rubber bumper route can usually be the simplest.

Next is the issue of steering type in the column area and the fact that early dash boards were created to accomodate a thin solid steering column and certainly on RHD cars the later fatter collapsable column doesn't fit the gap and the larger earlier tacho and speedo doesn't allt relief in that area. The LHD dash alternatives may offer some relief here, but I have no experience to comment further.

Mounting the earlier column can be done to a later body if you create appropraite mountings and the spline size between early and late cars is the same. Note that the early steering systems had a shorter rack pinion and longer column, whilst later cars used a longer pinion to push the universal joint further up into the bulkhead. (for ease of V8 fit) This means that if you mate an early column to a later rack you have the steering wheel around another 2+inches out of the dash towards you. (This is certainly applicable to UK spec steerings and I suspect it also applies to all US specs. No doubt any variatiosn will be highlighted by other posts.)

The modifications to the gearbox tunnel vary with the chosen gearbox, but none need to have that much done to the shape of the Mk2 shells original set up. Certainly nothing that alters the general look or ability to fit trim, carpets etc.

Heritage actually now do a specific V8 spec shell for such conversions with a chrome bumper spec except for the V8 under bonnet area ready for a V8 fit. These shells are (I think) about 750UKP more than the basic standard MGB shell price.

As far as engines go all pre 1995 Rover V8's are externally identical and can all be used. Post 1995 engines have been extensively revised and updated but the basic dimenaions remian the same. However some of the ancillary fit parts do create additional difficulties. As many of the better parts can be transferred to the pre 1995 style there is little need to worry.

Standard engine capacities range from 3.5 to 4.2 litres for the original specs, but these are easily taken out to 4.6 with the later 4.6 cranks. Other conversions allow the engine to go to 5.2, with I have seen somehwere a very special 5.8litre unit. Far to big for the original design and clearly not worth the cost.

I feel the best overall capacity is 3.9 as the bore stroke ratio is at its best and the volumetric efficiency that can be created with the standard head castings is also at a peak. Larger capacities than this require a longer throw crank which enters a situation of proportionately diminishing returns for the same input. 4.6 can be made to work quite well, and along with 3.9 litres can be bought as turn key engines.

Roger Parker

Thanks for the very informative post Roger. I assume that the 1968 you mentioned is your daily driver that I have seen you write about in past posting. Before I even read your post, I was begining to lean toward starting with a CB right off rather that trying to turn a RB 'into' a CB.
Anyway, thanks to all who posted. Any additonal comments are most welcome.

This has been an interesting thread to read; I'm in a situation that would best be described by the old Vermont farmer phrase "it's the same, but different." I have a British Racing Green '69BGT which I bought for the express purpose of a re-shell project. It is a non-functional rustmobile, holes in the floor, holes in the wings, mouse living in the engine bay, rust on every panel, swiss cheese sills, etc. Total basket case. For a while I've been debating in my head what sort of set up to go for, a stock (or quasi-stock) 1.8L inline 4 or the 3.9L V8. I'm still a ways a way from make the big leap (fiscally speaking), and I'm trying to sponge up as much knowledge as I can before I do anything. I know Heritage now makes a chrome bumper V8 roadster body purpose-built for such conversions, I presume they make a chrome bumper V8 GT body too? And would a RV8 crossmember would take care of the aforementioned x-member issues?

Ricardo Dodge

Ricardo, I am glad you brought up the Heritage shell. After getting some wonderful posts about my situation, I took my car for a spin and decided that I do not wish to re-motor this car at this time. There seems to be almost no end to the things that can (should) be done to complete a V8 conversion.
My new plan (this week anyway) is to purchase a Heritage shell and build it up with the help of my mechanic. Of course this will be after I put the 3 boys through college or strike it rich. What ever happens, I still have my present 4cyl to enjoy and, I can dream about the MGBV8 that will enter my life someday.

When you mentioned "early steering systems had a shorter rack pinion and longer column". Was the shorter refering to the gear ratio or the distance between the inner ballhousings.

I ask because I am still thinking fo fitting a RB rack on my CB xmember. The extra column length does not matter as I have to cut and insert two UJ's anyway.

Nick Smallwood

I bought a '63 roadster with plans to install a Nissan 300zx v6. I started getting ready to pull it apart. I measured the spaces, read the V8 book on cb fire wall mods and steering mods and figured it was doable. Per chance I ran across a classifed ad for a 78 from Nevada that sort of ran but wouldn't pass Calif smog and didn't have the parts needed (no catalyst, downdraft weber, etc. etc.) The car had no dents and absolutely no rust. I opened the hood and saw the bigger radiator mounted way forward and the opened up fender wells and the altered fire wall and decided before I got the hood proped up that this was the car to modify. I had a 68 roadster that was beyond restoration. I am now rebuilding that roadster with some of its parts including my 78 "heritage" body shell. I stopped for about a year to get a "67 gt on the road. Now that project is completed for a daily driver I'm on to my '68 "heritage" hot rod.
Barry Parkinson

Nick - >>>>>"early steering systems had a shorter rack pinion and longer column". Was the shorter refering to the gear ratio or the distance between the inner ballhousings ?.
Neither, actually. The pinion is the bit that sticks out of the rack at 90 degrees, that the column/shaft is connected to. If the pinion is shorter the column has to be longer to keep them connected.....
David Smith

Barry, your '68 "Heritage" hot rod project sounds like a lot of fun. Good luck!


Thanks david, I understand what was being stated now.
I miss read it as rack & pinion instead of rack pinion.

I am fitting twin UJ's so the differnce in pinion and column lengths will be adjusted then.

Nick Smallwood

This thread was discussed between 31/08/2000 and 09/09/2000

MG MGB GT V8 Factory Originals Technical index

This thread is from the archive. The Live MG MGB GT V8 Factory Originals Technical BBS is active now.