4.0 and 3.9 differences.

TVRleigh · Post by **TVRleigh** » Tue Jul 15, 2008 1:49 pm

Anyone know if you can fit a 4.0 front on a 3.9

I know your need to change the camshaft, and engine brackets.

but is it possible to fit a 4.0 crank pulley on a 3.9 crank.

I have a 4.0 race spec and a 3.9

I want to use the 3.9 as a spare / Test engine, but want to try and have them as similar as possible.

I can use the old std 4.0 cam in the 3.9, and I have spare brackets and pulley's cover etc.

Just want to know if they will fit.
I think the 3.9 has a shorter crank nose, but don't know if the diameter is the same. and if it can be converted.

Thanks
Leigh

Post by **katanaman** » Tue Jul 15, 2008 2:27 pm

yes it all fits together but you will need a crank spacer, change cam, you need the 4.0 sump as the bottom of the cover is a different shape. You will also need to grind a longer keyway in the crank to accept a longer key for the oil pump drive. If your using the ECU you will also need to fit the flywheel. Thinking about it that wont work either as the older block doesn't have the mounting point for the sensor. What are you using for fuel and spark? I wouldn't have thought you would have had to change engine mounts.
There is probably more odds and ends but it can be done.

Post by **katanaman** » Tue Jul 15, 2008 2:31 pm

Is this a TVR front cover with the dizzy in it? If so some of what I said wont apply as that's not a 4.0 cover its an intermediate cover.

TVRleigh · Post by **TVRleigh** » Wed Jul 16, 2008 1:19 pm

katanaman wrote:yes it all fits together but you will need a crank spacer, change cam, you need the 4.0 sump as the bottom of the cover is a different shape. You will also need to grind a longer keyway in the crank to accept a longer key for the oil pump drive. If your using the ECU you will also need to fit the flywheel. Thinking about it that wont work either as the older block doesn't have the mounting point for the sensor. What are you using for fuel and spark? I wouldn't have thought you would have had to change engine mounts.
There is probably more odds and ends but it can be done.

It's going in a TVR but its a LR 3.9 Inty with dissy Front cover.
I meant alternator and PAS pump brackets, not engine mounts.

I have a bigger sump, and Cam and Cam sprocket.
I'll be using an emerald ECU with trigger wheel on the crank pulley.

the guy are RPi when I tried to order a crank spacer said it would not work as the are different diameter's, just wondered if this was true.

Thanks
Leigh

Post by **katanaman** » Wed Jul 16, 2008 2:43 pm

RPI are probably covering themselves and its a different spacer than they will sell anyway. They will sell the spacer to put the old front cover on the new crank. They probably wouldn't recommend doing what your doing because of the crank being shorter some bodges have to be done to get a longer key on so it can drive the oil pump. The nose of the crank is still the same diameter though.
Not sure what cam you need for the intermediate front cover to be honest as you will still need to attach a drive gear to drive the dizzy. If it is the newer cam I have thought of another job that will need doing. You will need to drill and tap the front of the block to accept the cam retaining plate. Hopefully someone will could chip in and say what cam it needs.

TVRleigh · Post by **TVRleigh** » Thu Jul 17, 2008 2:42 pm

You missed the point the the cam and cover.

I'll be using the new non dissy cover, it currently has the inty cover.

good point about drilling and tapping for the camshaft retaining plate.

should be doing it in 2 weeks so will give you an update when done.

Thanks again
Leigh

Post by **katanaman** » Thu Jul 17, 2008 2:52 pm

ok then my original applies sump and all that is needed too but no problem as you have them. Slotting the crank and tapping the block is probably the major work. I take it your going to use a toothed pulley for ecu signalling/timing?

TVRleigh · Post by **TVRleigh** » Thu Jul 17, 2008 4:57 pm

Yes I have a trigger wheel fitted to the front pulley, had it all balanced.

paul c · Post by **paul c** » Wed Jul 30, 2008 8:58 am

so is the old interim cover looking for a new home by any chance?

TVRleigh · Post by **TVRleigh** » Wed Jul 30, 2008 10:34 am

If it works,

I think I may keep the int. front cover, as they are quite rare. and sell for £75-£150 plus may want to update my 400SE.

juha_teuvonnen · Post by **juha_teuvonnen** » Thu Aug 21, 2008 2:33 am

I am more or less in the same boat.

I have a working 3.9 engine from Range Rover Classic (1992, 14CUX engine management, Ignition has distributor, old-school belt arrangement in the front).

I can buy a 1996 Land Rover Discovery I for next to nothing, but the 4.0 engine threw a rod (GEMS engine management, distributorless ignition - uses trigger wheel and sensor spark controlled by ECU, serpentine belt in the front).

I am contemplating engine swap, replace blown 4.0 with 3.9 (or may be 4.2 if I find a good stroker crank). I don't think I can swap the ECU from Classic to Disco. Reason here is legal rather than technical, 14CUX is not OBD-II so it will never pass smog in California because the car was originally equipped with GEMS which is OBD-II compliant. It's illegal to downgrade smog equipment to earlier version. I wish I could though, as it looks like it would be easier to swap complete engine and ECU.

I understand that:
- the front cover and camshaft will need to be swapped from 4.0 to 3.9
- oil pump needs to be modified
- block needs to be drilled and tapped for sensor, flywheel from 4.0 with trigger wheel will need to be installed on 3.9
- something needs to be done to crank to mount the pulleys from 4.0 onto 3.9?
- Crankshaft assembly needs to be balanced, I suppose

Anything else I am missing? Any other options I should consider for ECU? I am thinking may be I should use GM LS1-LSx ECU as it can control spark, fuel and everything else and is easily programmable to any map you want? It has OBD-II and it is legal to swap in (they started making them in 97 so it is by definition younger than GEMS circa '96).

TVRleigh · Post by **TVRleigh** » Wed Aug 27, 2008 4:34 pm

Not sure there's much point swapping from inty front cover to latest cover, unless you are lacking in spare.

If you changing from old style, and want a serp belp
then your need to
change all the ancillaries and brackets.
change the front pulley
Also it may be easier to fit a trigger wheel and sensor to the front pulley than try and come off the flywheel.

if you did use the flywheel and cam sensor method , then there is no reason why you could not use a GEMS ECU. you would need to swap the loom though.