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MG MGB GT V8 Factory Originals Technical - Landrover 4.6 HSE auto -> manual conversion.


We have the possibility get our hands on a 4.6L Land Rover Discovery HSE engine with an automatic transmission fitted.
Will the SD1 manual transmission fit the 4.6 if we replace the automatic bellhousing with a one from a the 3.5L engine ?
The idea is to replace the 3.5 with the 4.6 and at the same time use the fuel injection system from the 4.6.
This car (MGC conversion) already has a older Holley
system fitted together with an Offenhauser manifold.

/// Jhonny
Jhonny Sokura

Jhonny,
My understanding is that the bellhousings are fully interchangeable, as the 4.6 is just a bored and stroked 3.5. I'm using a 1962 B/O/P 215 bellhousing on my 1996 4.0 Discovery engine with a Borg Warner T-5 in my B, and it bolted right up, with no modifications necessary.

jimt
jimt

jim: I would be interested to know what flywheel did you use. Will a SD1 fit the newer crank.
Ozzie

The SD1 flywheel, clutch and gearbox will mate up to the 4.6. You should just have to replace the spigot bush with the SD1 item.

I believe the 4.0 manual flywheel can be used with the SD1 set-up, but the larger 10.5 inch clutch may foul the SD1 bell housing. I am looking into this at the moment.

I am after a later type alloy sump and serpentine alternator if anyone has one for sale.

Nick

Nick
Nick Smallwood

Nick : thanks for your answer. That helps me with my decission for a flywheel.

On the 4.6 the automatic uses the flex plate and an electrical picku-up to monitor crank position.
Would it be easier to switch to an aftermarket crank trigger or switch over to a distributor.
Any advice would be appreciated.
Ozzie

Ozzie
The pickup off the auto flywheel should unbolt and you can then have the SD1 flywheel tapped to accept it. Then use the standard Land Rover pickup. If you have the direct ignition mems system the ECU will not like any modifications to air filters and cam etc. I have the distributorless 4 coil ignition set-up and am looking in to an after-market management system to drive it.

This is all theory at the moment as I have not actually done this myself, but have taken advice from people who have.

Nick
Nick Smallwood


Unfortunately the engine was subject to fire so
all the cabling for the EFI stuff was gone.
It seemed to be to much work to get that engine running
again so no deal this time.

/// Jhonny
Jhonny Sokura

Depending on the years involved you may not be able to use the crank trigger. I'm rebuilding a '98 4.6 w/access to all the components from a '99 4.0 FI setup. The '99 auto trans flexplate uses a 60 tooth timing pattern for it's Bosch EFI. I bought a '94 4.0 Discovery manual trans flywheel but it has a 36 tooth pattern. The '94 was the only year to use a manual trans in the US w/crank sensor groove. I haven't settled on an injection unit yet(looking at Accell)but will probably use an aftermarket crank trigger. D & D Fabrications has several flywheels available that will fit.

Joe
Joe Collins

Hi again,

My father in law decided to with 4.6 despite of the fire. The engine block seems to usable for a conversion job.
To keep the engine bay look I believe a front plate from a P6B engine will be needed. Am I right in that the front plate is needed for the oil & water pump and the distributor ?
The crank trigger will be discarded in the favour for the good old Mallory distrbutor.

/// Jhonny
Jhonny Sokura

A P6B or any earlier Rover (pre concentric oil pump)or Buick timing cover should fit. Early Rover timing covers are similar to Buick, later versions use a different oil pump/distributor drive. Just about any Buick small V8, rear drive V6 timing cover will work. You will also need a different oil pan, I've just begun looking at those. The 4.6 pan is longer in front, Buick 215 pan doesn't have clearance for 4.6 crank's counterweights. I suspect there are Rover pans that will work. A new camshaft will also be needed, the 4.6 is shorter with no provision for a distributor gear. Watch valve to piston clearance with your new cam, I am currently in the process of cuting valve reliefs in my pistons.

Joe
Joe Collins


Hmm, we didn't know that the camshaft is too short for distributor gear on a 4.6. We have to check that out.
Does the Buick 3.8 timing cover fit perhaps ?

This a MGC conversion and the crossmember gives somewhat more clearance to the oilpan than the MGB equivalent. We will look into that more closely too.

A possible problem area is the exhaust manifolds.
Fitting the RV8 manifolds into an MGC with the crossmember running up on the sides of the engine bay might give us some problems.

/// Jhonny


Jhonny Sokura

A Buick 3.8 timing cover from a rear drive application will fit, it may be necessary to enlarge the two dowel pin holes. I'm not sure about front drive applications. The oil pan problem is not related to the crossmember but to the shallower timing cover. The late Rover concentric oil pump cover (some of which are available with provision for distributor) is longer. It may be possible to use this cover in a conversion, I believe Jim Stuart's web site shows his conversion with this cover. It looked as if the oil filter would interfere w/ "B" crossmember. The Buick 215 oil pan which I had on hand would not work because it was not deep enough at the front, it struck (barely) the 4.6 crank's counterweights. There is still several inches above the "B" crossmember for additional depth. Besides the cam, another consideration is the crank, which is longer. It's not really a problem but will require a spacer in order to tighten the crank pulley.

Joe
Joe Collins

Ozzie,
Sorry for the delay, been busy with my other baby (now 6 mos old ;).
My answer to Jhonny was just about the bellhousing, as I am in mid conversion. As my engine has the GEMS eng management system, it looks like I'll be using a Rover Disco flywheel with the pickups for the distributorless ignition system. As far as fitting the clutch, the archive has some info on using a 1992 MercedesBenz 190E clutch & pressure plate, it is 9.5 inches and has the correct 26 splines to mate to the T-5. The input shaft is a bit too long, 1/4-1/2" or so, and I haven't decided which of the 3 methods for clearing this issue should be:
1 cut off the necessary length from the input shaft
2 bore into the crank to accomodate the extra length, or
3 buy a spacer which fits between the bellhousing and the T-5, available from D&D Fab in MI for around $30.
Can anybody give me some pros and cons of any/all of these?

muchas gracias,
jimt
jimt

I am going to be using D&D's bellhousing spacer. It is a very simple affair about 3/16" thick, made in 2 pieces to conserve stock. I would have preferred a spacer between trans & bellhousing but this looks like it will work fine & the price was right.

Joe
Joe Collins


We will propably use the flywheel from the 3.5 becacause it's already lightened.
If we go for a distributorless ignition system and modify the flywheel to accept the pickup can we in that case keep the 4.6 timing cover or do we run into other problems ?

Jhonny

Jhonny Sokura

This thread was discussed between 24/03/2001 and 12/04/2001

MG MGB GT V8 Factory Originals Technical index

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