3.5 motor into a 1994 discovery

[Oil leaks]

hello People I hope some one can help me with some questions.

I have a 1994 serpentine belt 3.9 Discovery, I have cooked the motor and need to get it back on the road as cheaply as possible while I save up for a replacment 3.9.
I have a high compression 3.5 (1983?) motor and was wondering if I can just drop that in with the 3.9 fuel injection, front cover and accessorys.
Im a bit confused on the front cover as my research here suggests that the early 3.5 crank shaft nose will not be long enough to mount the oil pump drive gear, however, other posts talk of mounting the serpentine cover onto the P76 4.4 which i assume is the same as the 3.5, can anybody tell me if I can use the serpentine cover on the 3.5 motor?

If no can i use the 3.9 crank in the 3.5 to mount the oil pump drive?

Will the 1994 torqe converter flex plate mate up to the early crank sharft?

What about the the fuel injection are there any issues there? I assume that it will run a little rich but it only ever gets used when I run out of gas.
(I will use the 3.9's crow cam)

Sorry about all the questions but it would be good to find these things out before it becomes a pile of bits

any comments would be appreciated
Thanks

[peter r]

G`day Oil leaks ,

the difference in the two is that the 3.9 has a longer keyway and key on/in the crank nose .

Unlike the 4.0 and 4.6 the 3.9 crank nose is the same length as the 3.5 .

The 3.9 crank can be fitted to the 3.5 to fit the serpy cover or the keyway can be lengthened on the 3.5 crank .

The other end of the crank is the same on both and any combination can and will work . If the 3.5 doesn`t look right it may have an adapter from the torque flite auto of its era , the zf adaptor from the 3.9 will bolt onto the 3.5.

If it runs too rich on petrol and you use it at all you could probably find an ECU from a EFI 3.5 disco , to my knowledge the ECU is the only real difference between the Discovery 3.5 and 3.9 EFI

Cheers

[Oil leaks]

thanks a lot Peter,
I will give it a go, It seems to be a cheap way to get back on the road, even if it is a lot of buggering around. I pulled the 3.5 down yesterday and it looks ok, rings and bearings and it should be a runner.
Does any one know / had experence with the Vic RTA's attitude in-regards to the "old" engine number?
David

[Philip A]

Just be aware that if it still has the emissions cam from the early 80s that this was the worst cam used in a 3.5 and should be changed to an injection cam. You could swap over cam and followers from the 3.9 , though not the best thing to do, with at the least a new timing chain and sprockets.


Regards Philip A

[Oil leaks]

Thanks Philip, I will use the Crow 771 that i was running on the 3.9, the 3.5's cam had the old missing lobe on number 5 inlet syndrome any way.

[peter r]

G`day David

You`ll find on the right side of the 3.5 at the rear of the block in the valley a pipe for the crankcase vent system that the 3.9 system doesn`t use .

It just needs to be blocked or tapped/pulled out and the hole plugged or similar .

Some of the bolts in the fronts of the heads on the 3.5 are smaller in dia than what the 3.9 uses but sure you`ll work that .

If you use the 3.5 heads it may be an idea to make a bit of room in the inlet ports for the injectors , when you look in the 3.9 inlet ports it will explain itself . Also with the 3.5 heads if they don`t already you`ll need to make up some plugs for the air injection holes into the exhaust ports , something like cut of bolts with some sealer work ok .

If you use the 3.9 heads you are able to raise the compression ratio by using 3.5 tin gaskets because of the smaller combustion chambers in the 3.9 heads or if you want near the 9.35:1 of the 3.5 use Felpro composite gaskets . The lpg will like this extra but petrol would have to be used with care

In either case i`d suggest using just 10 bolts in each head and use the ones from the 3.5 don`t reuse the 3.9 ones unless there`s no other option .
The head gaskets will be to suit the bottom so if a 3.5 use the gaskets for a 3.5 not a 3.9 .


Also if you don`t have one buy an impact socket to undo the head bolts on the 3.9 normal sockets if poor or a bit used will not be up to it always .

I guess you know to be sure of keeping the lifters and push rods in mates with the cam lobes if you reuse what you have and also checking the lifter preload when putting it together will normal prevent any rattles when it`s up and running .

Cheers

[Oil leaks]

Just to update the post, the 3.5 is in no problems, all the issues where covered here, the motor turned out to be a early low compression motor dressed as the hi comp one, I used the 3.9 heads with tin gaskets and the only issue was the rocked cover sits on the inlet manifold and isn't sealing with the gaskets im using, thicker rocker cover gaskets or an attack with the angle grinder im thinking. I used the 3.9 crank.
Runs ok on gas and petrol, I really haven't noticed a lot of differnce in performance (but the old motor wasn't well), may be a little less on a long hill.
thanks to all those that helped.



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