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  • MGB Gearbox

    Does anyone know whats involved in using an MGB Gearbox in a Marina based Roadster? I've read that the tunnel needs widening but by how much and where along it's length? Is the size of the footwell reduced? Is the non-overdrive version any easier?

  • #2
    Re: MGB Gearbox

    Message originally posted by: Stefan Carlton
    Why not go the whole hog and do a complete conversion to Ford Type 9?

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    • #3
      Re: MGB Gearbox

      Message originally posted by: Doug Campbell
      My experience is with the non od box. The tunnel does need relocating which means that the floors need to be cut down. I just opened the tunnel up without disconnecting the rear connections and bent it to suit the gearbox. The passenger side foot well ends up being very narrow but enough for both feet. The outrigger which carries the firewall on the passenger side requires cutting back approx 25mm. A new ali cover plate requires fabricating for the tunnel. I have still not figured out how to connect the gearbox mounting to the tunnel without having all sorts of ironmongery hanging below the car. Will let you know once figure out. The front propshaft flange also needs to be changed to match the B box and the prop needs to be shortened. The speedo drive cable also reqires the box end changing to a B one, or get a B speedo so you can use the B cable.

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      • #4
        Re: MGB Gearbox

        Thankyou for your replies. I don't like the idea of reducing the footwell size as I find it pretty small already. From your discription, Doug, the gearbox mounting sounds difficult too. I think I need to take a closer look before I take the plunge.
        Stefan, the Ford Type 9 does seem attractive (does it need mods to the tunnel?) but I am put off by the cost of the bellhousing etc. Maybe I could fit a Pinto engine as well! But then again I prefer to keep the B engine. I never was good at making decisions (Or was I?).

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        • #5
          Re: MGB Gearbox

          Message originally posted by: Stefan Carlton
          There was an article by Jeremy Cox in April-May issue of Pitstop, page 15 where he puts a Type 9 box into a LWB Roadster. If you don't have a copy of the mag email me via www.stefancarlton.net/index.php?type=contact and I'll sort you out with a copy (scanned in). It even lists his email address, which I must use one day as I half plan to do the conversion myself late next year when/if I upgrade the power plant to a stage 2 head and cam.

          He suggests, that it fits in the tunnel perfectly with little modification (apart from a cross member to hold it in place). The difficulty comes from changing the back end of the Marina engine to cope with the new box - you need to change the back plate, flywheel, clutch, cylinders, different and lever and finaly a pre-engaged starter motor.

          As I say, send me an email and I'll scan the article in and send it through (assuming it's only for yourself of course).

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          • #6
            Re: MGB Gearbox

            Having fitted a Type 9 to the B I can thoroughly recommend it. OK it wasn't a budget solution but I wouldn't go back to the Marina 4-speed for anything. The added beauty is it fits the existing tunnel without modification (except to the top cover), albeit you need to be a bit creative with the mount and speedo drive. For full details of what was involved check my PitStop article from a few issues ago.
            Marlin Roadster, LWB...1860 B Series + Ford Type 9
            Renault Espace 54mm front calipers, vented discs, cycle wings and adjustable tie-bars.

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            • #7
              Re: Re: MGB Gearbox

              I did read the article and I am sure the Type 9 is the better solution but I still think it is a little expensive (Am I right in thinking it was the Hi-Gear kit you used, Jez at around ?600?). As my Marina engine is also in a bad way I was hoping to pick up an MGB engine and gearbox together hence my original question.
              I'll not give up on the Type 9 yet though - it would be nice wouldn't it.
              Thanks again for the information and encouragement.

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              • #8
                Re: MGB Gearbox

                As my soul-baring ramblings in the last few issues of Pitstop may have revealed, it's not that easy. The solution for the rear gearbox mounting was fiddly but seems OK. The o/drive means that the drivers side tunnel is a bit narrower just forward of the seat, but I haven't had to alter the passenger side as Doug has ( perhaps I've got it all in the wrong place) but altering the tunnel is a relatively small problem.
                If you do get an MGB engine and box, DO NOT buy them separately as I did - get the lot together still joined up. There are so many bits eg box-engine bolts, clutch slave, starter motor that don't transfer. Also, to keep the same engine mounts as the Marina you need to change the engine front plates which involves timing gear etc.

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                • #9
                  Re: MGB Gearbox

                  That sounds like good advice, Peter. I must admit I didn't know about the engine front plate. Maybe I am worrying too much about widening the tunnel although it's interesting that your tunnel mods differ from Doug's. Perhaps Marlin tunnels are not all the same to start with?
                  Anyway, I think I've pretty much made up my mind to go for it so thanks for all the help everyone.

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                  • #10
                    Re: MGB Gearbox

                    Keep us informed, Rob! You are welcome to any amateur help I can give.

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                    • #11
                      Re: MGB Gearbox

                      I converted my 1992 LWB Roadster from 1700 "O" series to MGB engine and overdrive gearbox in 2003 and its certainly been a worthwhile exercise, I was fortunate enough to buy a dead "BGT" which I scrapped after removing all the parts I wanted including wirind loom and instruments, I did not have major problems with the transmission tunnel just a little widening and a new cover, if you want any info or photographs of the convertion please contact me I would be only to pleased to send them to you. i.jac(at)btopenworld.com

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                      • #12
                        Re: MGB Gearbox

                        Message originally posted by: Gordon Thompson
                        I know it's probably too late for this article but I went throught this problem a year ago. Once I realised how much space I was going to lose in my SWB Roadster with the MGB box I opted for a rebuilt Marina 4 speed box with a Spitfire OD grafted onto the back of it. Minimal tunnel/floor wideneing was required though the extra weight of the box plus the Marina 1800 lump meant making a new cross member and brackets to carry the box on the chassis as it broke the tunnel sides. Drop me a line at Thomps537(at)aol.com if I can be of help.

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