SLROC Forum

I managed to get my hands on a 3.9 V8 from a 1990 Range rover for the costly sum of £61 off of ebay (including gearbox and LPG system) . my plan is to do a complete strip & rebuild, switch from the injection to carbs and then give my stage one a heart transplant.

Just looking for a bit of general advice on the rebuild if anyone has any?

Also the current 3.5 has a battery sensed 18ACR alternator, will using the later LRA 813 from the 3.9 cause any problems? Mainly in relation to the extra power it's putting out compared to the old one.

Is there any problem with using the newer 35DLM8 Distributor with the existing ballasted coil in the stage one?

Thanks,

Jack.

Hi Jack,

You need to remember that even on carbs the 3.9 will have a lot more oomph than the 3.5 you are taking out (it is a low compression unit). Brakes steering and suspension need to be top notch or you will end up with a 100mph death trap.

Lots and lots of info for your rebuild, what do you want to achieve? In the vehicle you have I would suggest you don't go far from standard spec becuase of the reasons previously stated.

For parts I suggest you go to Real Steel or LR genuine for rings and bearing shells - do not cut corners with pattern stuff it will only end up being a massive waste of money. Buy right and buy once.

You will need a new cam and followers, LR gen for the followers and something like a Piper 255 for the cam (better value than LR and it will be around the same spec as standard). Genuine for timing gears and chain. There is a strong likelihood the rockers and shafts are tired as well, again genuine ones are the only source of reliable quality for standard type engines.

If you want a nicer end product and a little power gain it is worth having the pistons, rods, crank and flywheel all balanced - much smoother and cleaner power delivery. Engine services in Rosewell are very good, they balanced my 3.5 when I had it rebuilt by Rocket Sled tuning.

Heads are probably not worth starting to play with much, 3 angle seats and minor smoothing will give quite big gains in power for relaitvely little work although to be done correctly a good machine shop will be better than amateur mechanic. If you start going to these lengths you will need disc brakes on your car.

A little more info on your aim would be good, to do a proper standard rebuild yourself I would have £1k ready to spend to avoid disapoinment.

HTH

PS Is the injection kit up for grabs with the ECU and air flow meter? I'm upgrading from carbs to efi and need all the 14CUX hotwire bits....

Thanks for the reply.

In reality I'm just looking for a bit more power over all, the 3.5 is just a bit lack luster and could really use a rebuild it's self, it's at about 100K and looks like it's had about 1 oil change in that time...

I had (still am slightly) contemplated just doing a engine swap now and then rebuilding the 3.5 with a few performance upgrades, increasing the compression ratio etc as it would be quite nice to keep the original engine in it.

So yea as to my aim, I'm looking for good low-mid range torque and enough power that I'm not working the engine quite as much when driving at 60-70 mph. It would be nice to get more than the 11mpg i'm getting at the moment as well.

Most of the stuff I've had a look at so far hasn't mentioned getting the bottom end balanced really but I'll definitely have a look in to it.

No ECU unfortunately, at least not so far, the garage I picked it up from hadn't finished stripping everything off of the car so I'm going back for a few of the LPG pipes & brackets, might be bundled in with them. Alternatively I'll have a word with my mate, I'm sure he should have at least 2 sitting about. but I think everything else is there. Does that mean you're selling your carbs?

Jack

PS Is the injection kit up for grabs with the ECU and air flow meter? I'm upgrading from carbs to efi and need all the 14CUX hotwire bits....

Steve.

If not I have all the bits.

Drew.

If the original engine is what you'd prefer to have (and for the added value to the vehicle) I would stick with it.

Stock v8's are a bit asthmatic and there is a Lot that can be done to improve them. My own 3.5 will blitz a standard 3.9 and does 22mpg cruising at 70 even with the knacked carbs that are on it (part of the reason I'm changing to efi). 

I would stick to a mild cam and get the heads lightly cleaned up, coupled to tubular manifolds and you will notice a huge improvement.

More powerful than a standard 3.9 and 22mpg would be very nice!

The 3.5 has done about 45k less than the 3.9 as well so it's starting to edge forward a bit as the engine to rebuild.

I'm not in too much of a hurry to be honest (would just give me something to do over winter) so I think a bit more research and procrastination is in order.