I'm looking at a1965 4.2 with auto trans and a 1961 3.8 4-speed/OD, bellhousing and clutch. Will they play nicely together? I've asked this on Facebook and got mixed answers.
I know:

• I'll need a flywheel, and the starter needs to match the flywheel. Will the 3.8 work? Will a 4.2 flywheel work in a 3.8 bell?
• I'll need a new pilot bushing
• Will a 4.2 clutch be better, or even possible?
• The starter is in a different location, but the location of the start should not matter, right?
• The aftermarket 5-speed conversion kits are very pricey which is why I'm considering this, but is mating a 3.8 to a 4.2 worth it, or just get the kit?

 

A 1961 manual box will be a Moss gearbox. It's very strong and efficient in terms of transmitting horse power, but has no synchromesh on first gear and is generally criticised as slow, obstructive and more suited to a pre-war truck. Since my Mk2 already has one, my present plan is to work on the change mechanism to make it function as well as possible. If it weren't already there, I'd not try to fit one. My preference would be a five-speed from a Toyota Supra or a Nissan Z car, both are very strong, quiet and smooth shifting, and kits are available for fitting to our XK engines. I realise that in the US Tremec and Borg-Warner options are also available and, in Europe, some favour Getrag.

 

What car are you trying to build? Is the present car/body a Manual or an Automatic. Tunnel sizes are different & obviously there is no change lever hole or cover on an Auto.

 

Generally you can't mix and match 3.8 and 4.2 components. So you will need either all 3.8 flywheel, starter, bellhousing and throwout bearing, or all 4.2 components. You can use either the 10" spring clutch or the 9.5" diaphragm clutch, as long as the flywheel is dual drilled for either clutch. Not all are.

 

• I'll need a flywheel, and the starter needs to match the flywheel. Will the 3.8 work? Will a 4.2 flywheel work in a 3.8 bell?
• Will a 4.2 clutch be better, or even possible?

You will need to match all three: Flywheel, Starter and Bellhousing need to be 3.8 or 4.2 specific. 3.8 or 4.2 Bellhousings are completely interchangeable to engine block.
There can be clearance problems with some large 4.2 clutches in 3.8 bellhousing.
This is why most go with proven kit by reputable firm.
Rgds
David

 

Thanks all. It's sounding more and more like the 4-speed may not a great option, although I do not plan to race it. FWIW, it's close-ratio, shaved gears with an overdrive... and much, much less than a kit.

I will be putting the 4.2 (if I can get it) into a Mk2. Modifying a trans tunnel is not terribly difficult. I'll start looking for the info needed to retrofit non-Jag parts. The kit prices are many times over what I'm willing to spend.

 

I asked the trans seller about fitting it to a 4.2 and he said "The trans is from a 1961 to 1970 XKE or a Mk 10. The trans is not original to the 1961 3.8 sedan that it was pulled from. It was originally an automatic that was converted to this 4-speed".
Serial number: EB. 12273. JS
EB. Trans is from a 1960s Jaguar Mk X 3.8, or an XKE.
E. Fitted with the Laycock DeNormanville overdrive.
J. Close ratio gears.
JS. Shaved gears.

if that's useful for decision making.

 

The all synchro Jaguar box from '65 onward with Type A compact OD is much more pleasant to use. It will take the torque of the 4.2. The Moss GB is somewhat agricultural. Beware that a BW35 will not take the torque of a 4.2 which is why a BW Model 8 was fitted to the 420.

 

You should be able to move the 3.8 trans. setup completely over to a 4.2 block.... Stick with the 3.8 104 tooth flywheel; matching clutch and starter that come from a 3.8 Mark 2 manual transmission from 1962-65. After tunnel work and mounting; (the trans. mount on a sedan is different than XKE, you want to set it up using 1962-1965 Mark 2 manual transmission mount system). You may have to to complete project with custom length drive shaft. ( you can get these made locally fully balanced, as well as online, if you collect all the measurement for the shop. That is a very good setup with the O.D.
Rgds
David

 

The letters indicate that it's a Moss box, which isn't as nice as the later synchro. As it has an overdrive, it's most likely from a MK X. I didn't find the Moss so bad, but it's a few decades since I used mine. There was an obstructive 'notch' in neutral on the way from 2nd to 3rd that I think I've figured how to fix. And getting into first from rest takes practice. I used to push the stick back towards 2nd, enough to give the layshaft a spin, and then forward into first. I always followed William Heynes' instructions (that the clutch is a luxury item that you dip once to ease going between gears and use minimally for starting off) and the box worked OK for me.

The upgrade kits for the Toyota and Nissan gearboxes aren't as extreme in cost as some of the Tremec/Borg Warner and they are very good gearboxes. It's possible to buy part and pick up some of the Toyota and Nissan parts second hand.

 

I am about to transplant a 1983 XJ-6 4.2 engine into my 1965 S type and I have no clue what to expect.

So I called a friend from the XJ-6 forum who lives nearby and he says he can do it. He owns XJ-S, XJ-6 and he has done other transplants.

So wish me luck. I am going to keep the DG250 transmission which is fine. I know issues will come up but once the 3.8 engine is out of the S type then I will know more.

I have to admit I am scared of this.

 

It should mostly bolt in. The 4.2 is dual drilled for the earlier front motor mounting brackets, so you'll be fine there, but you might have to swap the oil pan and oil pickup tube. Possibly the dipsitck and tube as well. Oil filter head will need to change, but this is a good time to do a spin on conversion. If you're staying with carbs you'll need to swap the heads, as the S Type manifold will not fit the 4.2 head. Or get a 4.2 style twin carb manifold. Hoses will need to change, as the 4.2 intake manifold has the thermostat in a different orientation. Actually, I consider the 4.2 thermostat an upgrade over the 3.8, head over the XJS forum for discussion about thermostats, lots of research has been done there and the Jaguar supplied ones are not correct. The 4.2 and V12 thermostats are identical. You may need to modify the oil line and feed to the rear of the cams, I'm not sure.

That's all the changes I can think of off the top of my head.

 

Thanks, if this is replying to my post, then I just decided this is too much. Particularly the 3.8 carbs manifold not working with the 4.2. I will just try to fix the 3.8

 

It was, sorry if I wasn't clear. What's wrong with the 3.8?

 

There are plenty of 4.2 two carb manifolds around

 

the 3.8 has worn crankshaft bearings, I drove it long distances. 2,900 miles one way, then 800 miles 4 times. One day I started the engine and it was making a ticking sound which turned into a clacking sound when accelerated. I drained the oil and it had golden or bronze particles mixed with the oil. I haven't started it since.
I purchased a running 4.2 planning to transplant it but with all the issues I have given up.

 

Jose if you are pulling the 3.8 out changing big end bearings is a very easy job as long as you have not damaged the crank shaft itself. I have in the past changed the big end shells on my first car, a Ford Cortina Mk1 with the engine still in the car propped up on a couple of concrete blocks on an Army parade ground. You only need to drop the sump to gain access and basic tools. The only specialist tool you would need is a torque wrench. I am sure your mate could give you a hand and you could have it done over the weekend./ Shame I am not on your side of the pond as I would willingly help out.

 

Jose. Can the DG250 take the 4.2 torque? Jaguar only used it with 3.8 engines. With 4.2's they used the BW Model 8 & the BW65.

 

Cass, thanks. That is exactly what I want to do, inspect the crankshaft (I believe it is not damaged at all) and just replace the bearings.​​​​​​Going to meet with the man tuesday and he has a hoist and a stand with radiator and starter to run an engine out of the car.
If we have to remove the crankshaft, so be it. I want to fix the 3.8.

Once engine is out I will be able to photograph the engine mounts orientation,
(no guys, I didn't forget about that, I just don't have enough light or space to photograph the mounts where the car is).