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MG MGB GT V8 Factory Originals Technical - How did they do it??
|Everyone says use the rubber rack and x-member for the V8 conversion but how did Costello and Leyland do it on pre-rubber bumper cars? If my extractors go through the inner fenders will the stock chrome rack and x-member work?|
|Quite possible could work with the through the fender headers. I have also seen it done with a couple of u-joints in the steering shaft.|
Costello used a second steering column U-joint just aft of the steering rack, as well as the OE joint near the firewall. I think he also repositioned the point at which the column comes through the firewall to a point lower down to clear his headers.
The Factory GT V-8 used the first incarnation of the rubber bumper crossmember and steering rack, in fact, the later RHD rubber bumper crossmember will interchange with the chrome bumper GT V-8 one.
|The problem is the top UJ on the steering column.|
The chrome bumper one is too big and is in the same place as the exhaust manifold bolt has to be.
So you need to move the UJ nearer the driver, which is what the rubber bumper cars did to standardise with
the V8s. Hence the suggestion to use RB crossmember.
I have used the RB steering rack, shortened the CB steering column to match and still used the CB crossmember. The mounting of the steering column is as per CB original
To mount the RB rack on the CB crossmember I have cut and extended the rack mountings on the crossmember - this also brings the rack down and forward so it sits in the space between the front of the V8 sump and the crankshaft pulley.
This allows the engine to be mounted at the right height and still gives an inch or so clearance between the sump and the crossmember.
|OK many points here. First the original Costello engine mounts sat higher than the later rubber bumper type. This enabled the front of the sump to clear the memeber. On conversions it is quite probable that a little 'dressing' of the front of the sump may be neded to slot the engine in.|
The steering issue is as said one of being able to 'shove' the original UJ position further into the bulkhead to provide the clearance needed for the number 8 cylinder exhuast header. Addind the extra UJ provided the extra 'shove' and also added an extra degree of flexibility to align the pinion shaft with the column. Of course the effective lengthening of the pinion shaft also pushes the steering column up towards the driver by the same amount, unless the inner and outer column are shortened. The lower column mounting also has to be redone.
Use of a later rubber bumper/V8 steering rack on an earlier crossmember leads to the pinion angle being all wrong and the shaft pointing into the brake master! The angles of the mounts have to be altered, but onece done then you achieve the same end of 'shoving' the UJ out of the way for the exhaust. The amount of extra length this way is actually longer than when using the extra UJ, so the shorteneing of the inner and outer column becomes a more pressing issue and one that raises it's own problems. (I had to do the same a Chris)
The rubber bumper fit is the same as the RV8 and here the engine sits lower than with the early Costello conversions. The engines position is otherwise the same so the actual holes in the inner wings for the exhausts is the same. If there was to be a clearance problem between the exhaust and inner wing it would be with the Rubber/RV8 set up as the engine is closer to the panel in this application. One clearnace problem that may be present is that if the engine sits higher then the downpipes drop may be too little before turning through 90 to flollow the floorpan. There may be a need to add an inch or so of drop.
Of note is the fact that all factory V8s used the rubber bumper set up and in fact pioneered the later cars standard suspension and steering pattern. The RV8 followed the same route so only early chrome bumper Costello's and some other conversions followed the chrome crossmember route. I did origibnally, although I am now with a rubber bumper one.
One other point that has not been raised, yet is a critical consideration, is one of overall engine height and the clearance required to fit the induction system of your choice. There is small enough space for a carb and less for injection so any consideration of engine mounting not only has to allow thought for the actual engine, exhaust, steering fit, but also the induction.
|There is certainly a lot of misinformation about crossmembers & steering racks from people who have never done the conversion but think they know a lot about it.|
There is no problem using the chrome bumper cross member in either the early cars or swapping one in a rubber bumper car to lower the ride height. Using the rubber bumper engine mounts or their equal will allow a Rover engine & deeper oil pan to clear as well as the shallower Buick//Olds. You may have some air cleaner clearance with the early bonnet(hood in the US) as it has less "crown" than the later ones.
I prefer the later rack, as it has more turns lock to lock, & I run oversize tires- 195/65/15 or 205/60/14, & it takes less arm power when parking.
To make things work, start with a rubber bumper steering U-joint. It is smaller than the earlier unit. It is not necessary to modify the rack mounts on the cross member, but it is necessary to modify the mounting pads on the bottom of the rack to change the angle of the shaft to meet the U-joint. This is hack saw or belt sander work. The steering shaft will have to be shortened about 2" & resplined. I also slotted the mount where the steering column goes through the firewall & lowered it about 3/4".
|Jolly good show, Jim - I feel really enlightened by your post! You may recall, I used a chrome-bumper x-member, rack, u-joint, and a Buick oil-pan - all unmodified. To make it work out on my car, I too lowered the pass-thru in the firewall. My engine position is probably different than anyone else's - made my own mounts. Also, I fabricated my own steering column, because I wanted to move the seat position significantly rearward. (There are LOT's of ways to skin cats...) |
The information about racks having different gear ratios has me excited. The factors you mentioned, combined with my down-sized steering wheel, make piloting my car quite an upper body work-out. And - if I sneeze - the car changes lanes. I hadn't thought about changing racks before!
Are you sure about the difference in crown of the hood? I thought I'd noticed a significant difference between my old aluminum hood and the steel replacement hood I bought - but the steel hood seemed LOWER and I figured it was either a "quality" issue, or a difference in spring-back in the material. I'd assumed they were made on the same tools (despite hearing for years that tooling for the aluminum hood was "lost"). I'd love to have just a little more room under my hood, but my catalogs only showed one steel hood part number.
|David Knowles in his 'MG V8, Twenty-one Years On' (Christmas present, signed by the author) states that the bonnet for all cars was given a greater curvature to clear the V8 engine and quotes two, adjacent, part numbers. Need more time to find the actual numbers though. Lots of other snippets and superb quotes as well. |
|Something that may interest you guys.|
My factory GTV8 has the standard r/b x-member, lowered springs and neg camber wishbone arms.
These factors combined mean that the lower wishbones do not sit parallel to the road, whch I understand from my reading (and John Bourke) is not ideal. I found a company in the States who make modified stub axles that lower the suspension an inch. I havent got around to fitting them yet, because as many of you will know, Im in Fl the cars are in England. Anyway I plan to fit uprated, standard ride height springs along with the special stub axles. If anyone is interested, I can e-mail the info about where to buy them and I think I even have a JPEG somewhere.
Drop me a note.
Happy New Year
|A cautionary note re shortening the steering column.|
I have actually followed all the routes that I describe and comment from actual experience, from the early 1980's. The first route for my own 1968 raodster involved use of a genuine V8 rack, chrome crossmember, that uses a solid column.
I also followed the shortened column route, although slightly more than 2". I also found advantage in shortening the outer column by a slightly different amount. However the main issue is the end of the column and specifically the thickness of the tube.
The ends where the splining is done is considerably thicker than the main section and shortening, depending on the amount and I can't remember what the cut off point is, moves the new splined area onto the thinner tubing and this can be subject to crush or flex. If you do this then it is a good idea to insert a plug of steel to provide crush resistance.
Having done this I covered many thousands of miles over quite a few years, before changing to a completely different steering system throughout, along with a rubber bumper crossmember. The original system is running in another V8 conversion.
|Oh I forgot to mention that the advantage of modifying the angle of the rack mountings on the crossmember over modifying the rack is that the rack is a mechanical item subject to wear, or even damage. If that is modified then it loses its core value for exchange (it would in the UK) and it also means that changing it involves redoing the previous work. |
Addings wedge shims can achieve the same, but agian is far from ideal in terms of rack location and bolt angle for the two captive nuts.
I have always said in the many features done from experience that there is always more than one route that can be followed. However I try and choose the route that involves only one conversion and easy replacement of parts 15 or 20 years down the line from the conversion. I have reached that first milestone with my car and so far the theory has been proven in practice.
|I cut my steering column in two, close to the steering box and used two u-joints. I also had to lower my steering column but did not mess with the steering box mounting. The car is a 70 GT. I used Borgeson u-joints available in U.S. as a hot rod item. No clearance problems with the motor mount or the headers. High quality and very small, they come splined for the MG box. I heard MG front suspensions were popular at one time in hot rods. Now the favorite seems to be Ford Mustang II.|
You say you cut the column in two, but I read that as being the pinion shaft of the rack assembly - correct? As a matter of interest this is the way Ken Costello did some of his conversions.
Sorry to be imprecise, I did cut the pinion shaft. I left just enough of a stub at the steering box to mount the u-joint.
| It's interesting to see that this topic has come up again -it was well aired a while back and should also be in the archives some where.|
It's not surprising as the quality of the solution used to over come the steering shaft routing in a V8 conversion is to my eyes indicative of the whole quality of the conversion at first sight.
The solution that I chose to use on my own conversion was not the easiest or the most pracical route because I wanted to use factory syle Tubular headers with larger diameter down pipes and with the engine mounted on factory mounts AND use a chrome bumper X-member.
Firstly-I cut the X-member mounts off and rewelded them at the correct angle found by tilting the rack assembly in a temporary jig welded to the X member to maintain correct bump steer.I think that filing/machining the rack housing can work but you have to consider the eccentric loadings on the 5/16 UNF bolts in single shear-you would have to make some tapered washers to under the bolt heads or they would have to bend to take up the angle.
Secondly-I removed 25mm from the pinion of my chosen 2.9 turns long nose rack pinion(74-76) and resplined it to match the original.
Thirdly-I used the steering column from a UK spec 73 car-this is the early style collapsible column with a long plastic bellows and was made originally by AC Delco (Saginaw).If you remove or break the original plastic shear pins-they usully are broken by now or have been "repaired" with roll pins and partially collapse the column to set the correct length-I wanted the joint to be closer to the engine than the standard ruber bumper position as I have big feet and have found that the RB cowling prevents me from fully depressing the clutch.
The newer Rv8 style headers give more flexibilty in positioning the shaft-it can move upwards without fouling the manifolds.
Borgeson seem to do some pretty impressive stuff on their website.
There are only so many ways to do this-to answer one of the original questions-Ken Costello in the original L/HD car supplied to Abingdon for evaluation used a countersunk Allen screw for the lower fixing for the No 8 exhaust port manifold fixing flange to make clearance for a very slender welded style column joint in the original position!
Regards John Bourke
I agree with most of what you said. The subject has been covered before but I found it to be the most complicated part of my conversion at least as far as figuring the best way for me to go and I am not surpised to see it come up again. My way is not for all but it worked for me. My car is chrome bumper but I was afraid to mess with the steering box location, I barely understand the concept of bump-steer. My car came with just the collapsable column you describe. I could not afford the RV8 headers but had no real problems with standard headers. One nice thing with Borgeson joints is that they are very small and use a set screw which is also small. No fouling problems.
This thread was discussed between 23/12/1999 and 05/01/2000
This thread is from the archive. The Live MG MGB GT V8 Factory Originals Technical BBS is active now.