4.4 p76 engine into '73 P6B rover 3500

7FOUR7 · 26th February 2014, 08:19 PM

G'day everybody, name is Brad.

I'm obviously new to this forum, I'm after a bit of tech info in regards to upgrading my tired, old 3.5 in my p6b to the 4.4 from a p76.

I've found a short motor cheap as chips which I plan on fitting with some 3.5 heads, a good mid range cam, a nice manifold and carb etc..

I have a few questions for anyone in the know, probably easier if I put them up in point form.

- I understand the heads are a straight swap but will I have to change pushrods? Or are 4.4 and 3.5 the same?

- in fitting the 3.5 heads, what comp ratio would I end up with?

- does the engine mount in exact same position?

- I've read that I will have to drill the block for water pump dowels, any other mods I should be aware of?

- will the engine mount in exact same spot using rover mounts?

- being that the p76 donk has a higher deck height, will an aftermarket p76 inlet manifold still bolt up?

- I have the BW65 transmission, is this also a straight bolt up?

- I've read that the flywheel needs to be machined for a manual gearbox but how about the auto flex plate? Also, is spigot bush the same?

- and oiling issues, what do people do to rectify this with the p76?

My plans are just to have a punchy little donk to pull the old girl around town. If I'm happy with it I'll rebuild the donk and maybe strap a couple of t28 turbos to it (mounted beside the gearbox) with a blow through setup and 5500-6000 rev limit for a stump puller.

Any help muchly appreciated
Brad

**justinc** · 26th February 2014, 09:18 PM

don't do it.

a high compression 4.6 short engine will bolt straight in, will accept/ run beautifully on the twin su's and be way more reliable than the 4.4.

i just sold both my p6b 3500s manuals, 1 of which would've got the high comp 4.6 treatment...no time, no $

jc

7FOUR7 · 27th February 2014, 04:38 AM

Thanks for your input mate but I can't justify the dollars for a 4.6 short engine. If I were to spend more money if rather throw in a stock ls1 with carb and t350.
I'm looking for a fairly budget upgrade, being as this is just my daily at the moment.

**justinc** · 27th February 2014, 05:19 AM

i mentioned the don't do it as the 4.4 isn't much of an engine when compared to the rover v8, also by the time you have finished modifying things to fit etc etc you would be using a fair bit of your budget up...on a lesser engine with parts rarity.

just from my experience at modifying vehicles this is invariably how things end up, i.e. think of a figure and then double it

sometimes simple/ straightforward is best.

jc

7FOUR7 · 27th February 2014, 06:22 AM

Yeah I'm hearing you there mate, I'm not new to the modified car scene having many vl turbos ranging from 200-600hp plus a few v8s of the LS series etc so I realise how budgets can blow out haha

**justinc** · 27th February 2014, 07:35 AM

Originally Posted by 7FOUR7

Yeah I'm hearing you there mate, I'm not new to the modified car scene having many vl turbos ranging from 200-600hp plus a few v8s of the LS series etc so I realise how budgets can blow out haha

mmmmm, RB30T....

jc

**bee utey** · 27th February 2014, 08:33 AM

There are a whole bunch of minor differences between the P76 and the Rover 3.5 but basically everything is more or less in the same place. The crankshaft bolt pattern and spigot bush size are different (P76 ran a ball bearing) the block height means one of the Rover engine mount bracket tags needs to be cut off and extended.

Only P76 specific inlet manifolds can be used unless you purchase spacer plates. "Willpower" single plane 4 barrel manifolds totally suck at bottom end torque and if you constantly use peak RPM the cast crank will eventually break. A dead stock inlet manifold and a 350 Holley is as much as the engine will safely handle. Forget force feeding it, there's too little strength in the crank.

Now talking heads, the P76 engine ran pressed metal rockers with splash lubrication via hollow pushrods. Various old Range Rovers have run for years using Rover heads on a P76 block with the rockers reverse fed using the hollow P76 pushrods but its marginal lubrication at best. The P76 block is missing the drillings from the oil gallery to the head gasket face.

Then there's the overheating issue, adding 900ccs to a stock 3.5 block design gets too hot unless you have a monster radiator and an equally giant fan to drag air through it.

Summing up, either freshen your 3.5 with high comp pistons or go straight to snail power. Or a 4.6 as mentioned, a bolt in fit. The purchase price of the cheap second hand engine is usually the smallest cost in an upgrade of the type you're contemplating.

**101RRS** · 27th February 2014, 09:17 AM

747 - if you do not want this project ending in tears I would be listening to what JC and Bee Utey have to say.

Garry

**chazza** · 27th February 2014, 09:32 AM

The P6 had high compression pistons anyway.

To recondition my P6B engine cost about $2800 for a totally clapped out motor. In those days I didn't know about slipping liners, so 6 of the bores need to be re-done with top-hat liners.

Anyway; the point I am trying to make is that about $3000 for a long engine re-build, which gives heaps of power for a P6, is not a bad deal. Plus; it won't overheat; you won't have to modify anything and you will still have one of the best saloons ever made

Cheers Charlie

**POD** · 27th February 2014, 12:26 PM

About 8 years ago I put a 4.4 motor into a 1988 Rangie, using the original 3.5 heads and EFI. It ended up costing over double what I had expected, more than a straight swap with a 4.6 would have cost. No way would I do it again, there are far better options out there that will work without the stuffing around, and the 4.4 is virtually an antique motor now with parts hard to find.
A few comments though if you are absolutely dead-set on going down this path; bear in mind these relate to the Range Rover 3.5, I don't know what differences there may be with the P6b:
The original RR cooling system (in perfect condition) had no difficulty cooling the 4.4, including on a trip up the Tanami Track to Broome towing a heavily loaded camper trailer. I don't know anything at all about the P6B cooling system by comparison.
The 4.4 litre block is 3/4" taller than the 3.5, hence the pushrods are 3/4" longer. You can't use the 3.5 pushrods.
An oil gallery can be drilled into the block to feed the rocker gear.
A stock 4.4 inlet manifold will fit. A friend of mine had the top of a RR inlet manifold mated to the bottom of a Leyland inlet manifold when doing a similar conversion with carbies.
The crankshaft/flywheel bolt pattern is different, you will need an adaptor to mount the driveplate. There used to be kits available that included this adaptor, these days you would probably need to get something made by a machine shop.
The engine mount lugs are present in the casting of the 4.4 but not drilled. The top lug is in a different location to the 3.5 and the top part of the mount needs to be modified.
The engine will mount in the same position but be 3/4" taller. There was just enough room for this under the Rangie bonnet, dunno about the P6B.
I fitted the 3.5 timing cover, with water pump & oil pump. Some lugs had to be ground off the inside of the timing cover to clear the timing gear and cam.

Again, my advice would be to pass up the 4.4 short motor, even if you're offered it for free. There are much better options to spend the time and money on for a better end result.

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