Sleeving down a 3.9 to 3.5?

[Gasket]

An odd question - I know.

I'm currently in the process of assembling an engine for my latest project - an old Land Rover. Its an immensely well-trodden conversion - but revisiting it 25 years after it lost popularity has opened up a whole world of possibilities - 5 speed box adaptor kits (bought), ATB Diffs (bought), uprated rear halfshafts (bought), disc brake kits (bought), off the shelf V8-ready radiators (saving), distributorless ignition and far shorter timing covers/water pumps from the Serp GEMS/Thor days.

For the engine I'm trying to build the shortest, strongest motor I can.

So far I'm looking at a 4.0 GEMS V8 but rebuilt around a late 4.6 block (found a nice red-graded one, obviously the same casting as the 4.0 but the ones with the tighter tolerances were assigned to the 4.6 motors) - so already gaining cross bolted mains with big journals, 10 bolt heads, composite gasket, crank-driven oil pump and I'll be adding ARP bolts and top-hat liners. This will be dressed as far as possible to look like an early '70s 3.5. I can't do anything about the timing cover and probably the viscous fan, except for hiding this behind a shroud (unless this could be swapped for a fixed steel version?) but the rest needs to look right.

I've built half a dozen Series Land Rovers over the years and this will be the first with a non-standard engine and I want it to look like it was done in the '70s.

I'm keeping the distributorless 4.0 timing cover with serpentine belts along with its short water pump - this gives me a significant length reduction and will let me keep the engine driven fan (its a workhorse and I don't want to use electric fans).

However - what I don't need is loads of power. Frankly a stock 125bhp on carbs would be enough. A standard 4.0 isn't going to blow the doors off anything, but it isn't really needed.

Given that thicker bores can only be a good thing in my case, it dawns on me that if I simply had top hat liners with a 88.9 mm bore (stock 3.5L size) then I could use factory +0.0 pistons, would have a much thicker cylinder wall and it would be closer to what I want to achieve (taking a great, very period idea of fitting the Buick 215 into a Series Land Rover but doing it right with no engineering compromises). Plus even though I've beefed up the drivetrain, it would certainly reduce stresses and as much as I love EFI, the engine bay needs to look period so being able to use SUs with a factory Land Rover airbox would be a massive plus - a 3.9 might not run 100% on SU44s and while I don't need the power I do want it to run efficiently, with a 3.5 I could use a stock set of manifolds and carb without rejetting or finding any restrictions in trying to run them on an overly big engine.

So - can anyone imagine if this is possible? I know Turner Engineering import their tophat liners from the US where they're custom made - so they wouldn't be willing to make a custom set for me. But I am aware that some companies make their own liners and all I;d be asking from them is to remove less material in the build.

Of course I could fit a 3.5 block - but this prevents me from using the distributorless timing cover and introduces smaller journals/no cross bolting etc.

I did read in Des Hammond's book about the 3.5 Service blocks produced in 1995 that could be cross drilled - but I've never managed to find one so sleeving down a 3.9 is my next best idea. Still doesn't add any thickness to the aluminium casting between the bore and the journal but the thicker liners must help right?

[stevieturbo]

Sleeving down is doable quite easily...although I cannot see any reason to actually do it unless it was for some serious class rules.

And it would seem a bit random to get custom liners from the US when places like Westwood could supply you with whatever liner you needed here in the UK.

[garrycol]

You can put a 3.5 timing cover etc on a 4.6 with a different cam shaft so it looks like a 3.5.

As far as liners go yes - just take the liners out from a 3.9 and put in the 3.5s - not sure if this is the same for a 4.0 as technically it is a different engine - but as has been asked why would you want to go down in size - just run the engine you have.

[Gasket]

Thanks very much both - great to hear its possible and Stevie, I didn't know that the liners were available locally I had inferred from some of the builders that they were an uncommon custom made thing.

Dressing the engine is no problem - in stock I have an older mid-70s V8 so I can obviously incorporate plenty of ancilliaries to give it the older look.

Re: the obvious question of why bother?

The car is being built to recreate a factory prototype that specifically had a 3.5l engine built just at the point that the 215 licence was being acquired from GM but the result was littered with engineering compromises. The later parts-bins and aftermarket let me fix these issues in a way that simply wasn't possible at the time. The build is more about finishing a job that was started in the '60s to give a pleasant V8 than it is about power. If it was just a case of wanting a more powwerful engine then I'd just tune a standard engine or fit a cheap TDi. This basically just uses the vehicle as a picture frame for the engine. If I can get hold of a set then I'd actually love to fit a pair of Buick 215 valve covers (but no idea if they're compatable with the 4.0 heads) as the prototype had a Buick variant not a rover engine.

Using a 3.5 means that there is less strain in the drivetrain and less power for the leaf springs and relay-steering to handle. it also means that the period correct inlet manifolds/carbs/airbox choices and block-hugging (car sourced) cast iron exhaust manifilds are nicely matched to the engine size rather than lightly strangling a larger capacity motor.

But all that is moot - of course if I was faced with the options of fitting a 3.9l engine as-found vs going to a load of extra work to reduce the capacity then it would of course be a bit silly. However, my engine stock currently consists of:

A fully-dressed Mid '70s 3.5 Range Rover V8 engine, a complete 4.0 GEMS V8 from a 2000-ish Discovery II manual and a known good bare, red-graded block from a late P38 Range Rover 4.6.

In whatever case, I'm going to be stripping the two complete engines and sending a load of parts off to be machined and for top-hat liners to be fitted to the red-grade 4.6 block. So if it is feasible to simply have liners with thicker walls and an 88.9mm bore fitted then its just a case of sending a slightly different mix of parts to the machine shop and assembling it as a 3.5 instead of a 4.0. So no more work and likely a minimal difference in price.

Its (hopefully) a no-cost, no-extra work choice between a 3.5 and a 3.9/4.0. The 3.5 is more than enough and lets me make use of a load of period parts I already have - but I get the peace of mind of knowing I'm taking advantage of the hidden improvements made to address some of the shortcomings present in the original iteration of the engine.

I really do appreciate your help here - and any advice on parts choices etc would be very welcome.

I'm a good few months away from sending the parts off (I have to move workshops first) but it would likely be worth me reaching out to an engine builder at this stage just to get the wheels in motion so that I can strip my donors to have the parts ready to send out.

[ChrisJC]

Your spec will indeed give you a nice short engine. I have a Thor 4.6 in my Series Landie, and I went for the distributorless combination for the same reason. In fact my engine is far enough forward to clear the footwells, and still have a viscous fan, and the headlights in the radiator grille.

The one part I don't think you've got covered is ignition. There is no distributor provision on the shorter timing cover, so you will need coil packs and some trickery to make them work. You will need a flywheel with a pickup ring and a crank position sensor. You can do it with MegaJolt Lite (I did something similar a few years ago - 2" SU's and Thor coil packs).

It is worth checking out smaller-bore liners, but in reality I think as long as they are top-hat liners, it doesn't matter. If you have 1.75" SU's, you'll strangle a larger engine at the top end anyway, so it won't go mad for power.

Chris.

[Gasket]

Chris - sounds like a brilliant build and that’s incredibly reassuring to hear that it will fit.

Being able to fit it while retaining a viscous fan is one of my main aims, but I didn’t think for a second I might be able to get away without trimming the footwells.

May as well let you know the full spec.

Engine as discussed.

For ignition I’m looking at either EDIS or a CoilNearPlug setup (like the LS/VW) run off megasquirt.

Gearbox is a R380 suffix K/L - this will be sent to ashcrofts with some other parts to build the box to spec (the donor box I’ve got is from a defender td5 and is a suffix k but it will be rebuilt as a L)

I have two options for the bellhousing - I already have a complete stumpy R380 conversion kit and am just buying back my milner v8 conversion ring, but I’m also picking up a LT77 2WD V8 bellhousing. The LT77 bellhousing is 1” longer than the stumpy + milner ring… but it’s much neater. Ratio is 050A, which is exactly the same as the series box plus overdrive in 5th.

I already have an ashcroft R380 to series transfer box adaptor kit and I’ve been redesigning the shifter linkage in cad to put the gearstick in the factory location. I’ll get this machined in one piece at work on the CNC

The new chassis will come with a 2nd set of bolt up crossmember brackets - fitted 102mm (IIRC) further back, which would put the front of the stumpy bellhousing in exactly the same position as the factory bellhousing.

However if I find like you, that I have room for the viscous fan and can still clear the footwells then I could probably use the longer LT77 2WD bellhousing and possibly keep the transfer box in a closer to factory position.

Would you be willing to share some photos at all either here or by email? Key things that would be really helpful are the fan clearance/rad position, the clearance at the footwells and the sump clearance.

As i’m ordering the chassis new and galvanised, I need to be sure of the positioning before it is made.

[ChrisJC]

Sounds similar to my setup. I got an R380 from Ashcrofts with the V8 5th gear. I also got an LT230 with the 1.003:1 high ratio, and am running 3.54:1 diffs. But my engine is chucking out around 300BHP, so can easily pull those ratios, and is only doing about 2000rpm at 70MPH.

I used the stumpy bellhousing and adaptor ring. I used a 9.5" clutch, but used a motorsport one to take the torque (which it just about does!)

I set everything to put the gearstick in the right place, and worked from there. The only slightly undesirable aspect was that I had to lift the front of the engine to clear the axle, and drop the back of the gearbox to get it all under the Series transmission tunnel (which I widened by rivetting two together!)

Because I modified the front end considerably internally (but it still looks normal Series Landie outside), I got a motorsport radiator made up which just fits between the back of the headlamps and the viscous fan. I just duplicated the Range Rover P38 cooling system layout, and have no issues with overheating.

Depending on your exhausts, you might have to make a tiny adjustment to the drivers footwell, Thinking about it, I had to do that, but you can't tell unless you really know what to look for.

I built mine up on a rolling chassis before committing to having it all galvanised and painted!

I'll dig out some photos.

Chris.

[ChrisJC]

If you are anywhere near Peterborough, you can come and have a look!

Chris.

[ChrisJC]

Pics:

You can see that I went to a fair bit of effort to keep the Series gear sticks but use an LT230 transmission. Not an issue you'll have if you keep the Series transfer box.

Chris.

[Gasket]

That is very, very neat. Thank you for sharing!

I think the best course of action for me is to pick up a scrap chassis (I only need the seatbox crossmember - steering relay crossmember section) and to mock up the various drivetrain options using the bare V8 block, the timing covers and an empty R380 casing with my bellhousing options and figure it out. Then I can give Richards Chassis exact measurements for the build.

Going back to the original query re: sleeving down the block, after getting the feasibility green light from the forum I've just had a chat with the guys at V8 Developments - never dealt with them before but what a lovely group of lads. They couldn't have been more helpful and understood exactly what I was trying to achieve. There are basically two options:

1) sleeve down a 3.9 interim block with top hats down to 88.9mm bores, add the crossbolting and build it up with 3.5 internals. This gives me a nice strong 3.5 block. Albeit with the smaller journals.

2) Stick with 3.9/4.0 - gaining the larger journals (apparently the 4.0 P38A crank wouldn't support building with 3.5 parts - there was a reason, but I can't remember why) and giving a slightly stronger option. But in this case they can port the cast manifolds out to match the head gaskets which will make them more appropriate for the larger capacity. Then the HIF44s can be rejetted to suit (if I stick with carbs).

They were also able to offer plenty of pointers re: the minor tweaks needed for manifold compatibility.

Really impressed with their knowledge and customer service - makes a nice change from some of the sucking through teeth I've had when working with builders in the past.

[ChrisJC]

Great - keep us posted with progress!

I used V8 Dev for a lot of my engine bits - heads, cam for a start. Very helpful.

Chris.

[SuperV8]

That is very, very neat. Thank you for sharing!

I think the best course of action for me is to pick up a scrap chassis (I only need the seatbox crossmember - steering relay crossmember section) and to mock up the various drivetrain options using the bare V8 block, the timing covers and an empty R380 casing with my bellhousing options and figure it out. Then I can give Richards Chassis exact measurements for the build.

Going back to the original query re: sleeving down the block, after getting the feasibility green light from the forum I've just had a chat with the guys at V8 Developments - never dealt with them before but what a lovely group of lads. They couldn't have been more helpful and understood exactly what I was trying to achieve. There are basically two options:

1) sleeve down a 3.9 interim block with top hats down to 88.9mm bores, add the crossbolting and build it up with 3.5 internals. This gives me a nice strong 3.5 block. Albeit with the smaller journals.

2) Stick with 3.9/4.0 - gaining the larger journals (apparently the 4.0 P38A crank wouldn't support building with 3.5 parts - there was a reason, but I can't remember why) and giving a slightly stronger option. But in this case they can port the cast manifolds out to match the head gaskets which will make them more appropriate for the larger capacity. Then the HIF44s can be rejetted to suit (if I stick with carbs).

They were also able to offer plenty of pointers re: the minor tweaks needed for manifold compatibility.

Really impressed with their knowledge and customer service - makes a nice change from some of the sucking through teeth I've had when working with builders in the past.

Some one said - there ain't no replacement for displacement
If you're adding top hat liners then what ever base engine you choose will be bomb proof.
I wouldn't go 4.6 for more power, as you say your inlet will strangle that anyway - but I would go 4.6 as it will give you much more stump pulling & off idle torque, great for a landie in my humble.
Also I believe the later 4.0 & 4.6 engines had better pistons and much better stock balancing.

[paul c]

I have just removed a 3.9 interim motor from my 110 which I had been running with solex carbs, cd 175s, I am replacing it with a 4.6 with HIF6 carbs.