P76 into RangeRover  >
See how I did it below, the picture sequence is shown first.
Out with the old. The tired old 3.5 motor is removed.
The block needs the extra hole for the engine mount drilled and tapped. You might also have to grind back the casting to align things properly.
The new inlet manifold is prepared. Here I've chosen to mate the original Rover triangular mount onto the P76 one. You can also see the adaptor plate made to carry the Rover throttle linkage.
The re-drilled flywheel together with the new spigot bearing. Note that the spigot bush stands proud of the flywheel by about 12mm.
The engine is nearly ready. Here the new alternator mounting positions the alternator just about where it used to be. Certainly, the old fan belt fits easily enough.
The engine mounts need minor modifications to the top bracket. The original is on the left.
And the other mount. Again, the original is on the left.
The engine completed, ready for installation. The crank, pistons, con rods, flywheel and front pulley have all been balanced, just to make things more exciting. An alternate view of the redrilled flywheel bolts and the Rover starter motor fitted with an adaptor ring.
The finished article. Note the recycled Luminition unit on the front wing just to get things running reliably. The bonnet is a tight fit, but it just closes with the dashpots embedded in the insulation material.
(Since taking this sequence of photos, the Luminition system tragically died, but has been replaced with a Chevrolet HEI distributor instead - it makes quite a difference and is inherently waterproof to boot !)
How I did it ! What to do with a tired old Range Rover when the engine is well past its sell-by date?
For those who came up with some derogatory retort without even thinking, well, even despite government cut-backs, the psychiatric services can still offer excellent counselling and rehabilitation services.
For the more well-balanced amongst us, the choice is simple, it needs a new motor. But what? Now is the ideal time to look at the available options, bearing in mind that I don't have unlimited wads of cash lying around the place.
I could simply rebuild what's already there, yet a little more power wouldn't go amiss. How about looking at mods to the standard V8 (such as large bore, stroking kits etc.), or more naturally, go for what seems the purpose built P76 unit. More or less a straight “bolt-in” replacement based on the same Buick block as the Rover, the P76 offering gives a significantly more powerful 4.4 litres of alloy engine.
Although straight-forward, there are one or two smaller points to take into account:
The engine is slightly taller by around 20mms The P76 front cover moves the fan too far, so the old cover must be retained. This includes keeping the front pulley as well The mounting points for throttle and alternator are simply not there, so replacements need to be manufactured The taller block means the Rover engine mounts don't quite fit and need minor modification The starter motor is generally larger on the P76 yet some mods are needed to retain the old one The flywheel bolt pattern is different, so the Rover flywheel needs re-drilling The spigot pilot bearing will have to be re-engineered.
Armed now with the list of all the smaller differences, the first thing is to check out the new power plant. An elderly Bedford truck is strangely enough the donor vehicle. Used everyday with its adopted P76 unit, now a WoF failure, the Bedford unit is known…..yet…….?
Opening up the unit reveals well-worn bottom end bearings, so first call is to remove the crank for re-grinding. Now what of the bores? Inspection from below shows some quite serious scoring, so the heads come off and reveal a very disappointing state of affairs. Seven P76 pistons and one Rover piston show clearly that someone's been playing here already.
Oh well, only one thing for it. The block is stripped to despatch for rebore.
Now whilst P76 pistons are almost impossible to acquire these days, Rover V8 ones are almost a straight swap. I say “almost”, since the Rover pistons will raise the compression ratio somewhat. Best guess is that the 8.5:1 Rover pistons will deliver around 10 to 10.5:1 in the P76.
With everything back from the reconditioners, it's almost time to begin the reassembly, but one or two things need attention first.
Whilst the engine is on the bench, the P76 block must be drilled and tapped to provide the 3 bolts for the engine mount. For some reason, the P76 exists with only two bolts holding the engine mount, yet the casting includes provision of the blank for the third. You might also have to check to see how `proud' the blank actually is, on this block it was around 2mm, so a quick lick with a grinder brought it into line.
Anything else requiring attention should be dealt with now. A new timing chain proves a must, as does a service kit for the oil pump. The heads aren't too bad, but had I the cash, they'd certainly be in for attention - maybe later. I've also decided to retain the Rover sump with it's larger capacity, so I'll also need the pick-up to match.
Now it was also at this time, that I decided on something radical. The P76 carburettor is not very well set up for rough off-road use. On a sidling or steep hill-climb, petrol starvation can occur. For that reason, I chose to retain the Rover Strombergs. Although this may strangle the motor a bit at high revs, it will allow the excellent off-road manners of the dual Strombergs to be retained. Later, I'll look to installing twin 2” SUs, but that's another project.
In any case, to retain the Strombergs requires some kind of adaptor. In this case, I chose to sacrifice the old Rover manifold by removing the triangular carburettor mount with a grinder, and getting a local aluminium welding shop to graft it onto the P76 manifold. As you can see in the pictures, it's not too bad a fit.
Once the flywheel is re-drilled, and a spigot bearing manufactured, it's off to the balance shop for the fine tuning. All the pistons and con rods have already been matched to each other, simply to keep the cost down.
A torquier cam is acquired, although the Rover one is probably pretty good as long as it's not too worn. The whole unit is now reassembled ready for transplant. One tip though, do remember to pack the oil-pump with grease or petroleum jelly otherwise you have no hope of getting oil to flow - P76 and Rover both are renowned for such problems. You can manually prime the oil with a long screwdriver simply by inserting it down the distributor shaft and turning the oil-pump drive by hand (turn it clockwise!).
New brackets for the alternator and throttle cable are fabricated and installed. If power steering or air-conditioning are required then they will need new mountings as well.
Add the spigot bearing into the end of the crank, and it's ready to be popped back into the Rangie.
It's probably at this time that I should admit to having more than a little help. My very good friends at Howat Engineering Services in Lower Hutt did all modification and remanufacturing for me. Brian Howat's consummate engineering skills and love for all things 4WD helped with the spigot bearing, alternator and engine mounts and the throttle linkage, not to mention re-drilling the flywheel and much servicing of the heads.
When dropping the engine in to place, most things bolt directly into place. With only a little gentle persuasion, the exhaust manifolds were lifted the little extra to make them reach. If you have headers, you may find that some re-engineering is needed on them to make them fit and squeeze past the larger P76 starter motor.
Don't be tempted to simply bolt a Rover starter motor onto the P76, the Rover location flange (the big hole in the block through which the starter fits) is some 5 or 6mm smaller and the P76 needs an adaptor ring to take the Rover starter. Again thanks to Howat Engineering for the adaptor ring for mine!
Now with everything finally in place, it's time for the moment of truth. Wow! What a difference. The mixture needed to be a little richer, and the cam is a little lumpy at tick-over, but torque is pretty incredible.
This is one conversion I can recommend for all petrol heads, but initial readings show fuel consumption around 15 to 16 mpg (whatever that is in metric terms) compared to the 19 mpg I was getting from the old Rover motor. Not a very economical transplant, but absolutely heaps of fun!
Anyone interested in doing something similar would do well to talk to the experts. I have no hesitation whatsoever in recommending the excellent services of Howat Engineering on 04 566 6078.
Andy
PS YES! the vehicle has been certified by an approved LVVTA inspector - contact Ken McAdam at Wellington Vehicle Compliance on 04 570 6039
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