4.6 Rover V8 Swap

R

rob0r

New Member
Hi all,

I've recently bought a mk1 P6 3500 auto and I'm looking to swap in a 4.6. I understand the block should bolt in, but how difficult is the neccessary wiring. I did try searching "4.6" but the search didn't like such a small term. Any advice will be greatly appreciated.

Cheers,

Rob
 
Do you plan on keeping a distributor based ignition and carbs or are you planning to go with the distributorless EFI system from the 4.6?

If you're sticking with the original design then you won't need to do much in the wiring department but do consider fitting electronic ignition. If you keep the SUs you'll also need to set up new needles to cope with the increased demand for fuel, or you mght want to consider a Weber set up.

The EFI option will mean major changes as you'll need to bring over the ECU and harness from the donor as well as finding somewhere to attach the kickdown cable - you are probably going to find some clearance issues under the bonnet as well.

Oh and please do be careful with the BW automatic if you fit a 4.6 - treated gently it should be OK, but it wasn't designed to cope with the extra oomph of the bigger engine and a heavy right welly could shorten it's life dramatically
 
It's been done before, I was once a passenger in a particularly quick red Series 1 that had received a 4.6 transplant. The owner was using the original differential too, which amazed me, having already stripped a diff myself by driving my 170bhp (give or take a few!) 3.5 P6 a little too zealously.
I've seen SD1 EFi into P6 transplants where the ECU was stashed in the passenger glovebox, but I haven't carried out such a swap (yet!) myself so I'm afraid I can't answer your question. You'll probably want the whole loom from your donor vehicle to make your life simpler. Do let us know how you get on, I'm hoping to do the same thing myself in '09.
I've got a rare-as-hen's-teeth raised lettering Callaway Range Rover EFi injection manifold and plenum with a much larger throttle butterfly waiting in my parts stash, it certtainly looks great and ought to help me make a potent motor. I'm currently negotiating with the owner of a very rusty (sadly unsalvageable) long-wheelbase Rangey to take his low-milage 4.2 lump off him, we shall see, must admit I'd rather get a 4.6.
Sorry, didn't mean to hijack your thread. Our esteemed friend from Sydney, Oz should be along soon with some answewrs for you, although he's running modified SUs...
 
Are you in the UK? Have done a swap putting in a complete SD1 Twin Plenum V8 ... loom the lot. Was told it could not be done, as twin plenum fouls bonnet, too narrow in P6 etc.... but bare in mind you are putting a V8 in the place of a V8 (whats the problem!!) You will need different manifolds though, apart from that just flop it in, onto P6 egine mounts and find somewhere for all ancilleries. I had to move washer bottle to accept air flow metre and use a tiny pancake air filter, fule filter bolted to heater and so on and so on. Have put ECU into n/s footwell, cut into that fibregallsy thing that sits under carpet. It can be done.

If you need manifolds simply call FlowTech on 0208 586 1717.
 
Hello Rob,

I can tell you from first hand experience that a 4.6 will totally transform your P6B, making it a considerably more enjoyable car to drive.

Are you planning on running carburettors or fuel injection? With or without a distributor? Clearance issues will most likely dictate the selection with use of a distributor and an appropriate timing case your only choice.

What ever you decide to do, the following you will need to do in order for the engine to fit.

You must use your original P6B sump and oil pickup. With a series one P6B, you will need to acquire the latter type starter motor, else there will be clearance problems with the early larger starter motor running foul of the cross bolts.

The crankshaft has a longer "nose", so you will need to acquire a spacer to be used with your crankshaft damper assembly.

The engine block itself will fit without problems.

A larger 3 row radiator is strongly advised.

It is also a very good idea to have flange liners fitted throughout. If it is a brand new block, then provided you keep coolant temperatures to a maximum of 80 degrees C under all conditions and all circumstances you won't have problems.

I am quite happy to assist further once I know how you wish to set up your motor.

Ron.
 
Hi Rob

Well the first important change you need to do is fit the front cover and oil pump housing etc from an SD1 V8. The "serpentine" front cover on the P38 Range Rover and contemporaries is too long for the P6 engine bay. The Sd1 front cover is superior to the P6 in a number of respects. Obviously you'd fit a high capacity oil pump and duplex and vernier timing gear while you were about it. And that implies changing the cam and followers which you were of course going to do anyway.... This front cover then gives you the choice as to whether to go for a distributorless ignition system with 8 separate coils or a conventional P6 type system. If the latter there are a number of recommended upgrades, the most conventional is the Mallory distributor available in either twin contact breaker or electronic form. But there are a number of clever trevor equivalents - search in this forum or come back for more info.

If you wanted to stay with carbs you'd most likely fit a Weber 500 which is a copy of the standard american 4 barrel downdraught. But remember to get a lowline manifold so it fits under the bonnet. If you stick with the injection, consensus is to use a hot wire system. But to make sure everything has a nice lot of space under the bonnet use early series 1 engine mounts (i think from memory these are common with P5, but don't quote me on that!) which set the engine lower in the engine bay.

As to which engine to use, some people say bad things about the 4.6 and prefer the 3.9/4.2/5.0 (I've got a 4.6 but it is a new one so I've not inherited any previous abuse!). Depends how deep the wallet is really. Only really key thing is to make sure the engine you use is late enough to have a crossbolted block (which the SD1 hasn't).

We haven't mentioned the gearbox yet! You wont be using a 4 speed manual or a Borg Warner cos they won't take the strain, so you are likely to fit a LT77/R380 5 speed manual or a ZF HP22/HP24 4 speed auto.

Hope that gets the thought process started! Good further reading is the PPi web site(but note there are other V8 builders!) http://www.v8engines.com/.

Chris
 
Hello Chris,

chrisyork said:
We haven't mentioned the gearbox yet! You wont be using a 4 speed manual or a Borg Warner cos they won't take the strain, so you are likely to fit a LT77/R380 5 speed manual or a ZF HP22/HP24 4 speed auto
Click to expand...

So far after 12,000 miles of use I have not "touch wood" had any problems at all in using the 4.6 with my BW-35 transmission. Being serviced just in the last few weeks, the serviceman said..."the transmission is in perfect condition".

Maybe it has to do with components ( as pointed out by harveyP6 ) which are available for these transmissions in Australia, making the complete unit considerably more robust than their U.K cousins.

Either way, I don't plant the foot from a standing start nor do I use kickdown. In both cases, I don't need to!

Of course, if I had fitted a stronger ZF transmission, the "weakness" in the driveline then shows up in the differential drive axles, which will snap like dry twiggs if a person drives in a vigorous manner that the 4.6 can truly deliver.

Ron.
 
Agreed, the actual diff itself is not a problem but the long input shaft and the stub output shafts both have a reputation for failing in twist. Clearly treating the car with respect away from the line helps enormously. With mine the input shaft is an upgraded material and I have a stock of new output shafts. When those are gone there are no more (at least in the UK!) so we will then tackle remanufacturing in improved material (no doubt moving the problem on to the next weakest component.....). We haven't done so to date as the output shaft comprises a turned shaft welded to a disc hub and we didn't want to tackle getting the welded joint right, nor did I fancy the huge amount of waste involved in turning from the solid.

Other factors that play a part in these failures are if you have allowed the diff mounting to become loose or deteriorated, this generates a clonk in taking up drive which puts a shock load on the diff, also I suspect spinning, or rather stopping spinning, the rear wheels does the same. To that end we have an LSD in the original casing.

Chris
 
Hello Rob,

Something else that you may like to consider. The series one Rover 3500 differed from the later series two 3500 along with the 3500S in that a number of modifications were made to both the suspension, final drive unit, rear axle flanges, drive shafts and propeller shafts. Apart from any increase in component durbility, all were balanced to a higher degree.

Therefore, you might be disappointed in the outcome of running a 4.6 in a series one 3500. However, you can swap all the relevant parts, off the top of my head I think there are 27 of them, to the later series two specification, and then you will have no problems.

The 4.6 is a much smoother engine than the original 3.5. Rover did an excellent job on the degree of balance that they afforded the engine components. As an example, the standard Rover 4.6 crankshaft can happily spin to 7000 rpm or more in a racing engine without any problems. The maximum engine rpm however is 5800rpm, which is the safe limit for the standard rocker assemblies. Exceeding this limit could very well result in top end failure.

Ron.
 
Was having a discusion with a pal in trade yesterday, a very experienced mechanic, transplanter, modifier etc. He states be v. careful of the 4.6 as they are not a good egine to be with ... get hot! 3.9 is best in his opinion. I am not opening a debate here, nor wish to get involved in discourse ... just ;etting you know what i've been told so that you can make additional enquiries. Cheers Jim
 
I think that the 4.6s gained their bad reputation from the Range Rovers P38A. They were notorious for liners dropping and blocks cracking. So perhaps you might have problems just by buying randomly a used 4.6 and dropping it straight in.
You 'd better do your homework addressing any weak points of this engine.
 
Ther 4.6 litre engines actually fare the best out of all the 94.04mm bore engines, which also covers the 3.9, 4.0 and 4.2.

Approx 25% of 3.9 and 4.2 litre engines, 80% of 4.0 litre engines and 15% of 4.6 litre engines develop cracks in the engine block behind the liners, which then leads to a continual coolant loss problem.
There have been a number of suggested reasons from insufficient metal between adjacent liners, lean fuel mixtures and excessive (96 degree C thermostat in the case of the 4.0 and 4.6) operating temperatures.

In all cases if not buying a new block, the permanent solution is to fit flanged liners. With a new block, keeping the coolant temperature to a maximum of 80 degrees under all conditions will minimise the possibility of problems.

Ron.
 
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