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ThreePointFive

4.0 GEMS engine swap

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I can also vouch for Hamlyns in Bogwater (much better sounding than Bridgewater!). They did a fantastic job on my series 1 engine.

If I were you I would get a 3.9 bottom end (9.35 CR), a 3.9 or 3.5 EFI cam and have that rebuilt using all your induction (assuming you have SUs) and other ancillaries and you would have a good reliable motor with a healthy grunt increase without stressing anything.

Which ever way you go, good luck.

Toby

Ugh, poor little 3.9, why do you want to go and stick those horrid things on there, when you can have a lovely EFI setup instead?

You'd probably lose 30-40 BHP sticking the carbs on compared to SUs...

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I don't understand why people favour 3.9's over 4.0's which are the same but stronger.

Carbs - ugh, but if you don't do electrics better to have clockwork cr*p you can make work than nice EFI you don't understand.

As I said to a chap the other day - the beauty of carbs is you can rebuild them in the middle of a muddy field. He was too busy rebuilding his carb in the middle of a muddy field though.

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I personnally think the small journal crank v8s are much better than the 4.0 and the 4.6 versions but that is just my opinion (never had problems with any of my 3.5, 3.9 and 4.2 motors) and as for the SUs, I to would recommend going EFI (I have hotwire EFI on my current 4.2) however for simplicity and keeping the ancillaries the same in a 90, stick with the SUs while not in EFI league they are not bad carbs and certainly the best carbs you can fit up to about 230 BHP. This is nearly 100 BHP more than a V8 90 had when it left the factory.

Depends what you want go 4.6/4.8/5.0 and fit Megasquirt or keep it simple and fit a 3.9 on SUs!

Toby

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Toby - Not sure I understand your point. You can fit MS to anything from a chainsaw to a tank (both have been done) and EFI, especially with electronic ignition, gives significant performance/economy/reliability gains over clockwork. It's also not that complex in its basic form.

In RV8 terms EFI almost steps you up a block vs carbs - a carbed 3.9 will perform about the same as a squirted 3.5. I find it a bit backwards to go up an engine size and then knobble it with carbs.

I think there's a lot of folklore around the P38 lumps, sure some of them had issues but they also featured a lot of improvements over previous ones. I never had any problems with my 3.5 or 3.9 but equally I've never had issues with my 4.6 despite abusing it quite extensively.

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Would a manual gearbox be any good with a 4.0 or 4.6? I assume that the autos are better but I don't want to go auto if I can help it, at the same time I am concerned that my LT85 is going to suffer under increased power.

I don't know if anyone even runs that set up, I haven't heard of it!

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why not the auto?
Complexity, cost, the need for oil coolers, cost, no engine braking, cost, oh and cost.

Also I'd have to move the gearbox mounts around. I do like the centre consoles you can get, but again they are rather expensive.

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+2 here for just keeping the LT85, reliability is a function of your right foot. I run an R380 behind the 4.6 and that works fine, a decent LT77/LT77S would also be fine.

Autos have some benefits but ultimately are less combat proof / fault tolerant.

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LT85, generally very reliable and strong, albeit with the tendancy to be a little noisy. I am sure it would make good friends with a 4.6.

Like FF says it all depends whether you drive like a hooligan or not. I managed to not kill a series 3 box behind the 3.5 in my 88", OVER A PERIOD OF 9 YEARS! And no, I don't drive like grandpops on a Sunday :lol:

I went to auto in my 90 because my left knee decided the LR clutch pedal was too much for it in traffic, or after a day of shunting around off road.

V8 + auto are lovely to drive.

If yours was built with a LT85 and 3.5, the ZF HP22 auto will not require any mods to the chassis mountings, it is a remarkably easy conversion, all nuts'n'bolts.

However if originality is important to you stick with the manual and carbs :)

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Thanks for the replies, it sees I am getting to the position where I know what I want, if not necessarily having found it yet.

One possibility is a P38 4.0 - what mods will be needed to make this work? The seller says it comes with the ECU and wiring for that, is that enough or is there other senders/sensors etc that will cause issues? Does it need the gearbox ECU to function? Does it need the main car loom as well?

Will it fit my gearbox or will I need another bellhousing?

Sorry to ask so many questions, I hope you can bare with me!

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Any RV8 will fit any gearbox designed for a RV8, just may need to swap flywheel/clutch to suit.

Wiring in a P38 EFI setup sounds like a bit of a task for a closed system, if you're going EFI I would say MS is the more maintainable choice.

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using an engine from a P38 should be no problem, using the EFI and ECU's could be difficult

as everything goes through the BECM.

As Fridge says, just get the lump and use MS, no problems then.

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I think an idea might be to research ms and see if it is a viable option for yourself, that way you can look at potential engine upgrades in a better light. I am only guessing but I reckon its as easy if not easier to wire ms than try a p38 brain transplant.

If it all seems too much why not stick the 3.5 straight back in and to get the rebuild going and buy a larger V8 to ms in your own time and drop it in, that keeps your 3.5 original and complete so you can go back to it if you choose, also a ms V8 is always going to be worth a good price on the open market if for some strange reason you don't like it.

Will.

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I have not intentionally ignored Fridgefreezer, truth be known, I have only just noticed your post in response to mine! Blame it on trying to organise a work trip to Russia and having an 8 week old.

I agree with you entirely regarding fitting EFI/MS gives you more economy/grunt and power (after all thats why I fitted it to my 90). True also that EFI is not rocket science, however I am an Engineer which probably helps, but not everyone is and I still understand why people want carbs (most are just scared of the EFI!)

The next point is that (and may be I am wrong!), I got the impression that this was going to be a simple rebuild using existing ancillaries and induction and I think the point was already made, that it is pointless rebuilding a 3.5 when you can get a 3.9 and bolt everything to unit with no changes other than carb needles or perhaps some subtle changes (such as camshaft and matching the ports etc)that will produce a nice grunty engine even when fitted with SUs compared to an original factory 3.5. Adding MS/EFI will add it even more. As regards 3.5/3.9/4.2 verses 4.0/4.6, much of this comes down to personal choice, but plenty of people seem to slag the older engines when I do not think there is anything wrong with them. My 4.2 has covered 300,000 miles (third vehicle) now with nothing more than a cam change and that was because it was too peaky (Kent 218) and not because it was worn out (although I would not put it back in any engine of mine)

Toby

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I think an idea might be to research ms and see if it is a viable option for yourself, that way you can look at potential engine upgrades in a better light. I am only guessing but I reckon its as easy if not easier to wire ms than try a p38 brain transplant.

If it all seems too much why not stick the 3.5 straight back in and to get the rebuild going and buy a larger V8 to ms in your own time and drop it in, that keeps your 3.5 original and complete so you can go back to it if you choose, also a ms V8 is always going to be worth a good price on the open market if for some strange reason you don't like it.

Will.

It sounds like a P38 engine is not the way to go then, as I am only creating more complexity. I have nothing against MS, I just can't afford to pay out £700+ for the kits so that rules it out pretty much straight away.

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To be honest i think carbs are the way for you to go right now. This means that you can use ANY rover v8 engine as long as you use a carb inlet manifold.

Now i know your going to get lots of people (including me) saying how rubbish carbs are compared to MS, but at the end of the day they are simple AND cheap.

Yes MS is better in every respect, but it will cost you money that you dont have right now.

Id fit a larger capacity engine in with carbs with the intention of investing in MS for the future

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To sum up my current understanding -

I should avoid the 4.0 P38 engine due to the complexity of trying to make it work on EFI without the rest of the vehicle attached. I could MS it but only if I want to spend the cost of the engine twice over.

A 4.6 would work with carbs - but the problem is finding one where I don't need to buy everything else with it, front cover, dizzy, starter motor, etc etc. This doubles the cost of the engine.

A 3.9 would work, but most are old now and going to need work anyway.

A rebuild of my 3.5 will cost more than my whole car cost me to buy in the first place - I've had 4 quotes and all were around the same figure - £3500.

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I wouldnt knock the 4.0 engine. Just dont use all the efi gubbins that comes with it as standard. Dont worry about the serpentine front end. You could always put your pre-serp front cover on it..

To be quite honest with you though, unless you can do a basic engine refresh yourself your gonna be spending money. Shouldnt be anything like £3500 though! The Rover V8 is pretty much agricultural. A fun engine to learn on... Plenty of good books on the rover.

Do some reading/research and get stuck in. You will get a great feeling of achievement when you hear it running.

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TPF

To use the argument that a rebuild will cost more than the original purchase cost is daft. Following your threads on various forums on the net you have a new chassis, galvy bulkhead, rebuilt axles etc etc. Why have you gone to that extent, they cost more than the original purchase cost. If you are going to do a full rebuild which it looks like you are doing, why scrimp on the engine rebuild. If you do scrimp you will regret in time to come.

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You can't put dizzy and V-belt front covers on a 4.0, without changing the cam and therefore tappets, there's no drive gear on the end of it for the dizzy.

If you go 4.0, go with EFI.

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With that mileage it sounds like hes having to replace cam and tappets anyway so he could put pre-serp front cover and dizzy on at same time without trouble.

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before going to all these great lengths of engine swaps and stuff - wouldnt it be easier if the OP just did a compression test on his current engine to see what its health is like?

if compression is good and even across all cylinders, then just swapping in a new 3.9 crank + lifters, new timing chain and giving the heads a clean and possible skim would suffice and probably give him reliable performance for another 100k miles.

This would be easily the cheapest way forward, and the fastest and leaving things the most unmolested/original. After all, he hasnt complained the 3.5 isnt pokey enough or he is unhappy with the current set up.

and yes, efi would give him more power - but he`s using a manual, so he probably has the same usable power as a 3.9 efi auto. Slush boxes sap loads of bhp, so sticking with a manual and carbs is ok in my book as thats what he currently has and simplicity+cheapness is the goal from his initial comments.

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