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MG MGB GT V8 Factory Originals Technical - mgb gt v8 conversion help please

hello everyone im in need of some help i have a 1980 gt and want to put a rover v8 with a r380 gearbox
i want to know if ther are any major cutting jobs etc to be done , i know i have to make two holes in the inner wings for the exhaust downpipes but where , are ther any dimentions or just to fit

all information will be greatly appriciated dylan

dylan

Dylan,

You don't have to cut the holes if you go the "block-hugger" manifold route as the original GT V8's had. Just want to point out there is another option.

I went through the fenders with the RV8 headers as I was more interested in cooling and clearance than originality. Pros and cons to both methods. Cutting the holes was trial & error with the engine in place and gradually plasma-cutting the holes larger as the headers were lowered in. Clive Wheatley sells reinforcing rings for the holes so these can give you the shape. I had my own rings made up.

Since the R380 is a newer version of the LT77 (which I used), most of us using this gearbox have added a "tunnel extension" piece tha adds 45 mm to the height of the tunned just behind the bellhousing. The R380 and LT77 are taller than the MGB 'box hence the need for the extension. Some have managed to get the 'box in there without adding the piece.

You can use an original MGB gearbox cross-member with new brackets welded on. This new cross-member will attach to your R380 (as long as the mounts are in the same place as the LT77) and bolt into the original captive nuts in the MGB frame.

The only other small modification was to the shifter hole itself. In order to engage 5th gear, I had to remove some surrounding metal on the right side of hole so shifter would move freely. It's not much and I can still use the captive nuts for the shifter boot chrome ring. If I'm not mistaken, isn't reverse gear right and down on the R380? It's left and up on the LT77.

HTH and let me know if you'd like any pictures or more info.

Cheers
Simon
Simon Austin

Dylan
That's very good advice from Simon - I would just add that the original cast iron blockhuggers corrode and are now in a very brittle state. If you go that route, it's best to go stainless tubular.
On the question of the tunnel extension, you need about 1cm more room in the place where the seam traverses the underside of the tunnel. As Simon says, the seam can be dressed back without too much difficulty.
FWIW
Roger
RMW

Rogers quite right about the blockhuggers (he usually is, big time long time expertise! been V8'ing MG's for ever) Cutting holes in the inner guards of your favourite car is mildly traumatic but is easily done. I used an angle grinder to begin with and finished up with a hacksaw blade. When I do another one i will just use the hacksawblade, cut small to begin with and enlarge as needed. The metal is very soft. One stoke of the blade will get you about 1 cm. When I was done I went around and round the edge with a small shifting spanner and turned the edge down (belled the edge). Ended up very rigid and strong. Since there are a variety possiblilities of how far back your engine eventualy locates you might do as I did and place the engine and then drill a few locating holes. Using RV8 style (though guards)will get you an addittional 10BHP (some claim 13) cool the engine compartment and cure the starter motor overheating problems that Rovers (&MGGTV8's) have. I also think those stainless pipes look dramatic going though the sides of the engine compartment, as well as have the 'validation' of being done by Rover for the RV8.
I tried beating/dressing up the tunnel to get a little more room, bashed away for about half and hour and gave up, it's just too strong just there and would be inclined to a definite cut and weld. Mind you I did have an alternative, so there wasn't alot of motivation to keep going.
I eventualy used a toyota supra gear box ($700) which needs no cutting or bashing at all. The draw back is you must buy an adaptor bell housing from Dellow automotive for about $500 to $900 Australian. Down here all the Dellow gear plus guaranteed rebuilt supra box was about 20% cheaper than a rebuilt rover box. The toyota box is a very good box by the way, super smooth and strong as well as being light. Fifth is 0.78.
Wasn't much of a decision really!
Good luck.
Peter

On the subject of tunnel extensions, does anyone have a photo of one done, but from the inside of the car?

All the photos I have seen have been from underneath, or of poor quality so you couldn'r see much.

I need to have a look at the detail of how others have done it, minds eye and all that.

Liam
Liam

Liam,

Contact me and I can send you some pics of the extension. Nice thing about it is the radio consol hides it so nothing visible inside the car. I took pics with a tape measure in the shot to get perspective on how big the thing is.

Cheers
Simon
Simon Austin

Simon
Could you also send me the pictures of the tunnel?

Thanks
Graham
GLG Lavis

Sure Graham. I'll e-mail some off to you.
Simon Austin

Thanks Simon, that will be a great help.

I was out measuring the shell up for cutting yesterday and the measurements in the book for the tunnel seem to have me cutting right up through the lower part of the inboard membrane - its says cut 45mm out - that is all of it on my car!

Also having mega issues with the drivers side bulkhead - the drawings in the book just dont add up. I must be missing something, but thats a different story, I'm going to post some pics with the cutting lines marked and ask for advice here.
Liam

Liam..
Take a look at this: http://retrorides.proboards29.com/index.cgi?board=general&action=display&thread=1138467251

I think he posts on these BBSs occasionaly.
Regards
Nick
Nick Bentley

Good photos. I thought the single car garage I restored my '74 in was small.....this one has me beat!

Liam - I sent you some pics last night. Hopefully they'll help you make sense of the modifications.
Simon Austin

Simon, they arrived - thats really useful, clears a lot of things up.

You must have done your cutting from underneath, did you test fit the box in the hole without the new cover in place then make the cover to fit?

Nice work BTW.
Liam

All cutting was from the top with a plasma cutter. The guy who did the body work loves to cut things so off he went. I think I have a couple of photos of the action so will send them to you.

All we did to get the correct lines was slide the extension up to the "upright" dash support and draw an outline in the support. This was cut out, the extension slid through and another outline and further cuts were made in the inner support. Once the extension was in place, it's outline on the tunnel was made and that piece removed. MIG-welded in place and job done.

The extension was pre-fabricated from sheet steel from plans in the "How to give your MGB V8 power" book.
Simon Austin

This thread was discussed between 17/02/2006 and 22/02/2006

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