Thread: 3.5 carb V8 to 4.6 block into 101" FC

What about the D1 accessories such as PS pump, aircon, alternator? Do you have them?
If not you would probably have to use the timing case of the 3.5 to have the mounts in the correct place for your 3.5 bits. If you hve the accessories then you could use the whole 4.6 shebang AFAIK. You probably don't have aircon but you could use the aircon compressor as an air compressor.

I would go with a standard manifold and you could fit 2 inch SUs from a Jag if you can find any. Otherwise standard carbs.

Regards Philip A

Firstly it's not my 101 but I am the vendor of the 4.6.

The 101 does not have PAS nor does it have A/c, but 101Ron uses the A/c compressor as a compressed air source on his 101, so my friend with the 101 may choose to also. However neither the a/c pump nor alternator are present.

The 101 is currently running with its 3.5 and I have a both a Stage 1 3.5 V8 and 91 Defender 3.5 V8 which we could donor the parts to save down time during the conversion.

So the questions remain, the 101 is staying a carby V8, so which bits can we keep from the Disco and which bits need to be swapped and still have the 4.6 fit neatly into the 101?

As some of you may know I am sitting on a 4.6 motor as a spare for when my 3.5 dies.
If the original 3.5 is running strong I would tend to leave things be, as usually dropping another motor in a 101 will create extra unseen work.
In the research on the subject I have come up with the following..
1/ decide if you want EFI or carby or LPG only.
If EFI there are 2 systems used on the 4.6 and what ever one you use you are going to need extensive information about the wiring for the EFI and 101 wiring with EFI fuel pump, fuel return lines( the carbs dont have this.) and then there is the plumbing for the 101 air cleaner to sort out , to the EFI manifold.
Locating the computor is another problem and the 101 engine tends to get very wet fording creeks etc as there is no front end on the vehicle.
Extensive work if you go EFI because the vehicle was not designed for it in any way.
Is the 101 24 or 12 volts???????????????
The EFI allows better breathing and fuel burn as the standard 4.6 heads and manifold can be used.
EFI Manifold needs reworking of gear shift relay pipe and accelerator linkage.
The 4.6 engine front end stuff like fan, water pump,oil pump, belts , altenator etc will not work in the 101 well without extensive mods.
I believe a Vee belt type and seperpentine belt front ends were used on the 4.6

The option I am looking at is the use of the standard or similar carbies.
You must decide if you are going for a standard twin carb set up or a Holly/carter/weber down draft set up on a non standard manifold.
The single down draft carby set up will give better performance than the 101s standard set up, but you will run into the accelerator/ gear shift problems again.

You can interchange the 4.6 and 3.5 heads, and the 4.6 has bigger valves etc, but the fuel injection ports will have to be blocked up.

I will be using the standard manifold, but this kills power at the top end and the standard CD strombergs will not breathe well with the 4.6 and require rejetting...tuning etc.
SU carbies will more or less bolt on if you can find the correct size and you will have to rejet to suit the 4.6.
SUs are advailible in bigger bore sizes than the CD strombergs.

It is best the bolt the front end engine components from the 3.5 striaght onto the 4.6 as every thing will line up to suit the 101 .
The 4.6 crank is 20mm longer and a simple spacer needs to be made for the 101 crankshaft pulley.
The 3.5 oil pump is smaller than the standard 4.6, but this should not matter too much.
The 101 has the early type distributor drive and there was one model of range rover for a year or 2 before the change over to the later type dist drive that had a bigger oil pump than the 101, but fits straight on to the 101.
You must remember the 101 has a special oil cooler/ oil pump/ filter set up.
The 4.6 set up could be used with a remote oil filter set up.
The 4.6 I have ....... because of the EFI has no dist drive at all.
I think every thing changes over, but the 101s flywheel needs a extra dowel or 2 to fit the 4.6 crank.
The 101 standard exhaust system kills the 3.5s top end power and the 4.6 will notice this more.
The LHS exhaust system is EXTREMELY close the chassis making the fitting of any other exhaust system extremely difficult.
The 4.6 will kill a over drive if fitted.
4.6 to one diff ratios would be a good option.
Transfercase ratios by themselves will not be enough.

The 3.5 is strong in the 101 and the 4.6 without top hat seleeve mods doesnt have the same rep.
The cam shaft being for EFI in the 4.6 should be changed for the 101 and you would be looking for torque as the 4.6 is not going to rev in the 101 because of the exhaust manifold problem.
I think I have covered it.
Some else can pick up any thing I have missed.
Ron

You can interchange the 4.6 and 3.5 heads, and the 4.6 has bigger valves etc, but the fuel injection ports will have to be blocked up.

The injector holes are in teh MANIFOLD. the head sare the same except for a little notch for the injector spray pattern and valve size.

The 4.6 I have ....... because of the EFI has no dist drive at all.

.
This comes with the timing case, but a 3.5/3.9 cam has to be used as it has provision for the dizzy skew drive , which also indirectly drives the 3.5 oil pump.

I think every thing changes over, but the 101s flywheel needs a extra dowel or 2 to fit the 4.6 crank.

Most people just grind the dowel off the crank. The rear LH flange of teh motor will also have a hole for the crank sensor that a cover must be made for.

Look I only answered this generally, as I thought that regular posters know that all RV8 blocks are backward compatable, ie all earler timing cases etc will fit the later block. Just treat it as if it is a 3.5 block except for the spacer on the crank and the extra dowel.

Regards Philip A

I second what Ron has said - if you take the 101 carbies etc off and put on the 4.6 then the change should be pretty straight forward. EFI then there are a whole lot of issues - the gear lever needs to be bent to fit around the plenium.

Exhaust manifolds will need to come off the 101 but be careful as they are as rare as hens teeth - if you modify the exhaust you might be able to use the disco manifolds - however there is discussion on the 101 club forum that indicates the P38A drivers side exhaust manifold will fit straight on and the passenger side if you weld in a dent in the chassis to provide clearance - these gets around the rarity aspects and the poor higher end performance of the 101 manifolds.

Also check oil filter clearances of the 4.6 filter as the 101 position is unique.

Garry

The 4.6 will kill a over drive if fitted.

It's it really that bad ? I'm planing upgrade to 4.6 and I have an od, if only used with 4th gear, and all heavy use/off road with od off, any changes of survival, or is the od weak?

Tito

Hi
I only use the overdrive in top gear too .
The facts are
The fairey OD is a good one and reliable for what they were designed to do 30 odd years ago for the early range rover with the 3.5 motor.
The problem is they all have seen many miles in those 30 years .
The 4.6 litre motor has a great increase in torque over the standard 3.5 litre motor.
With out reffering to output specs I think the torque increase is in order of 30% or more.
The 4.6 has a longer stroke crank which makes it a torquer motor too.
Parts or the fairey OD on the bits that wear out are very hard to find.
With a 4.6 fitted you would tend to go up hills in top gear with the OD enguaged using the extra torque.........it would be hard not too, if the gunt is there.
The 101 is a big brick and above 50 mph/80 kph air drag starts to play a big part in fuel burn and and motor and transmission loading.
With a 4.6 you should be able to cruise with the correct gearing at 110 kph/70 mph .
Sooner or later the OD will give out.
Due to the design of the OD it will fail with little warning and leave you stranded unless you carry a standard transfercase gear to replace the od and a special set of circlip piers.
Using higher ratio diffs should spread the gear ratios better suited to the 4.6 and give a stronger drive line.
My 101 had higher ratio diffs fitted many years ago and it was changed back to standard again has the 3.5 didnt have the torque.
it did show the going this way was perfect for a more powerful motor.