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6cyl SWB?


BigJ

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Does anyone have an idea of what the minimum BHP and torque an engine would need to produce in order to pull either Rangy diffs or high ratio transfer gears in a SWB on 7.50 tyres? When I say pull, I don’t just mean get the vehicle moving but allow it to drive reasonably well at motorway speeds without slowing to a crawl at the first sniff of a hill and be able to overtake fairly comfortably without being overgeared. 120 - 140bhp/ 200+ lb/ft torque? Higher/lower?

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My 3.9 was always adequate on 3.54:1 diffs + 7.50's + overdrive in the 109. When it had awful 4-barrel carbs it was probably 140 "factory" hp and on EFI they're rated about 180, but it's the torque you want in a 2-ton brick, not HP, especially from low RPM.

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I couldn't give figures, and it's so subjective anyway, but I thought 3.54s behind a Series transmission (with overdrive too) was horrible.  I run a Tdi, and found first gear far too tall as the rpm is too low for the turbo to be useful.  I think John's V8 would have coped far better.  Once it was driving, it was OK, but acceleration was less than good, much like a standard set up behind a 2.25 diesel.  I could engage the overdrive on the motorway, but it was overgeared like that.  But 3.54s and overdrive together are going to kill your gear box eventually if you use it in high range in any gear other than 4th - as long as you use the overdrive purely as a fifth gear, though, it should be OK.  A few of us on here have learned that the hard way, including Ed and me (both of us had exactly the same; 2 stripped teeth on the main shaft 3rd gear wheel).  I went back to 4.71s, which give me a noisier but otherwise far better drive with the OD.  I do plan on 4.1:1 diffs, though, if I can persuade Nige to part with one or both of the second hand gear sets he has!

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I doubt I’d go down the road of high ratio transfer gears and 3.54 diffs but either or.

I know most V8s will pull that gearing without much bother but for the smaller engines, I think a standard 2.25 petrol for instance @73 bhp and 120 lb.ft of torque isn’t really up to the job especially on any sort of incline. I’m thinking then that torque outputs over 160 lb.ft would be required to maintain a decent speed with that sort of gearing and tyre size.

I’m just looking at alternative engine choices and upgrades if I can’t get the six pot idea to work and I’m leaning towards a 2.5 petrol with head and cam upgrades just for simplicity.

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I would want 200lbft, and an rpm limit of at least 5000, for example a 3.9 V8.

As Snagger says, TDIs aren't boosting below ~1800rpm and will be horrid to drive off the line, a Rover V8 has almost all its torque available at 1400rpm, pulling away engine speed...

With the noises from government and the greens, I wouldn't be putting a diesel in unless I knew I wasn't going to go near cities and had a huge mileage to do as well - diesels do cost more to maintain compared to petrol, if you aren't doing mega mileage just go with a petrol engine.

what engine have you now found? ;)

 

 

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48 minutes ago, Bowie69 said:

You will burn money putting together a tuned 2.5, and then burn as much fuel as a V8 once running...

If I use as much fuel as a V8 I’ll be a happy bunny 😀

Actually, one thing I was looking at was fitting the Weslake head and cam maybe off this 3.0 to a standard 2.6 LR block. I’m told it’s a straight swap and these heads were fitted as standard to the North American 6 cylinder engines. As I understand it, the head is where most of the gains were made with this engine and using a 2.6 block would eliminate all the problems of trying to match the flywheel to the crank. I may even be able to bore out the 2.6 slightly, skim the head etc to increase power output further. I’m not sure the extra 400cc of the 3.0, although nice to have, would make a huge difference to the overall performance of the vehicle.

 

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Get on Ashcroft's website and look at the standard gearing ratios for the various Defenders / Rage Rovers and see how they compare to your plans in terms of which engine they fitted with which overall gearing. That should tell you a lot.

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Tak Soren, that looks much more like it 👍I reckon the 3.0 manual crank will be the same and therefore the 2.25 petrol flywheel will fit straight on. Now I just need to either get hold of a 3.0 manual crank or a 2.6 engine. 🤞

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1 hour ago, Bigj66 said:

If I use as much fuel as a V8 I’ll be a happy bunny 😀

Actually, one thing I was looking at was fitting the Weslake head and cam maybe off this 3.0 to a standard 2.6 LR block. I’m told it’s a straight swap and these heads were fitted as standard to the North American 6 cylinder engines. As I understand it, the head is where most of the gains were made with this engine and using a 2.6 block would eliminate all the problems of trying to match the flywheel to the crank. I may even be able to bore out the 2.6 slightly, skim the head etc to increase power output further. I’m not sure the extra 400cc of the 3.0, although nice to have, would make a huge difference to the overall performance of the vehicle.

 

I neglected to say with half the power!

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2 hours ago, Bowie69 said:

I would want 200lbft, and an rpm limit of at least 5000, for example a 3.9 V8.

As Snagger says, TDIs aren't boosting below ~1800rpm and will be horrid to drive off the line, a Rover V8 has almost all its torque available at 1400rpm, pulling away engine speed...

With the noises from government and the greens, I wouldn't be putting a diesel in unless I knew I wasn't going to go near cities and had a huge mileage to do as well - diesels do cost more to maintain compared to petrol, if you aren't doing mega mileage just go with a petrol engine.

what engine have you now found? ;)

 

 

That's why I brought up that magazine article and some comments about the ACR tuning options for the 4-cyls.  Not cheap, but better value than a diesel you can't take anywhere, if that's how things go.  At least those 4-pots would be very simple to install, though.

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8 hours ago, Snagger said:

That's why I brought up that magazine article and some comments about the ACR tuning options for the 4-cyls.  Not cheap, but better value than a diesel you can't take anywhere, if that's how things go.  At least those 4-pots would be very simple to install, though.

It was the possibility of upgrading a 2.5 that prompted the question about the torque and bhp figures required for the higher gearing. That said even the top 2.8 package will only produce 117 bhp/177lb.ft torque and is very expensive.

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The gasket face of the Rover IoE 4 and 6 cylinder engine is flat - the combustion chamber being in the partial hemisphere over the exhaust (side) valve and the adjacent side of the pointed piston.

the Weslake head/manifold gets round Rover's inlet manifold cast in the head.  Its a longitudinal tube with branches for each cylinder (bit like the manifold used on the 4 cylinder S1 engines).  There's one carb for the 6 cylinders - I don't know if the end ones do much.  Its claimed to produce more power than the Rover head.

The compression ratio is controlled by the piston shape.

 

 

 

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Things have moved along a bit since I last posted but not necessarily for the better.

I’ve decided not to proceed with the Rover 3.0 as I’m struggling to get anywhere with finding a crankshaft from a manual vehicle and furthermore I’ve realised how unsupported that engine is which makes me nervous about a longer term investment in one. That said it been a very interesting discussion and thanks to everyone who has contributed to it.

I’ve been stalling for a while now with choosing whether to throw money at the Series or my RRC Softdash. I can’t justify a full restoration of both as I also have a Capri which I did a shell up rebuild on and which needs to get used more than it does. Whilst looking at the options for the Series 3, I’ve also been planning to assess how much work the RRC needs if I chose to restore that leaving  the Series as is to be used as a sunny day fun car.

Today in preparation for a visit to the body shop to have the work assessed and costed up, I decided to make the job a bit easier by removing some of the rear carpets so the guy in the garage can get a closer looksee. I already know from the P.O. that work had been done on the boot floor which “cost thousands” 🙄 and that the two front inner wings would need to be replaced but I’d not looked any further than that until this afternoon. Pics tell their own story.

0_D5_E6444-1_A4_E-4_AD5-_A3_CF-753_E3_DC

1_E70_A75_A-_E463-4_CE4-9825-56_C6_F9_EE

45_E8952_F-_CF16-4_E3_F-_A30_A-1_FBECBB5

4_D6_C294_D-27_AE-49_B1-_B459-6159239_AE

4_F205053-_F25_B-4_DD7-8_C30-2744_A98_F2

5585_DE42-_FDBA-4_E15-_B972-_C19_DD0_B73

6_A3_E3987-_CB6_E-452_A-_B508-_F48_C9_E6

95_D0_AE39-64_B8-48_FA-9220-_B00642_AE53

B372778_D-_BFD7-4_C21-91_D7-3_C6_D46_FAC

C4_A00386-_ABE6-4_F1_E-83_B4-97_E472_BDC

EE20_D4_E3-3_C0_A-4_E27-_BF21-1_A57512_F

Seen worse but still that’s just the visible stuff and the chassis also needs work.

Looking around on the various websites I can see that some repair panels are still available but even so (and without lifting up the saturated front carpets) it’s clear that there will also need to be a fair bit of fabrication work required for those areas such as the floor and rear seat base where panels are not available. I’m not a big fan of this to be honest as I don’t thing these repairs are ever as good as fitting brand new panels and the costs can easily spiral out of control  (ask me how I know) 🤬. If I was restoring the RRC it would be for it to be a keeps car or another 20-30 years or so out of it at least and it would need to be done right as my standards are very high, all of which comes at a price.

It’s a shame really as it’s a very original Softdash that has everything working and.....a very sweet 3.9 V8 serpentine engine 😬. However, heart cannot rule head as we all know so a choice has to be made.

Given the shortage of good second hand Softdash spares available to buy then potentially I could keep the engine and diffs and sell the rest of the car for spares if I don’t get the work done on it. Although I didn’t want to modify the bulkhead on the S3, it could now turn out to be that using the RRC V8 may well be the best way of upgrading it to act as my new daily just for the cost of a conversion kit. 

If I did this then I would probably keep it EFi but I would also need to take it easy for the sake of the gearbox given the output of these engines. If I did fit this engine then would I need to change exhaust manifolds to an earlier version or could I keep the ones on it? I think you can still buy exhaust systems for this conversion but might need to look at an additional silencer if I could squeeze one in somewhere if it was too loud with the truck cab.

Thoughts, advice and opinions are, as always, very welcome.

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With a serpentine front end you can move the engine forward more easily, there's potential for not modifying the bulkhead at all - modify the radiator position if needed and use a pusher electric fan.

There's loads of manifold options out there, you would be bound to find set that fit, even if it is MG ones...

V8s are kinder to gearboxes as the torque delivery is another, so rest easy on that one.

Definitely keep it EFI, even hot wire stuff is better than carbs on the bigger V8s.

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14 minutes ago, Bowie69 said:

With a serpentine front end you can move the engine forward more easily, there's potential for not modifying the bulkhead at all - modify the radiator position if needed and use a pusher electric fan.

There's loads of manifold options out there, you would be bound to find set that fit, even if it is MG ones...

V8s are kinder to gearboxes as the torque delivery is another, so rest easy on that one.

Definitely keep it EFI, even hot wire stuff is better than carbs on the bigger V8s.

Cheers. Wouldn’t the engine position be dictated by the gearbox and thickness of the conversion plate though?

I’d like to keep the existing manifolds but not sure if the exhaust systems currently on offer will fit to them, will need to investigate further.

Is there a smaller serpentine belt available if I bin the aircon compressor?

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1 minute ago, Bowie69 said:

You can move the gearbox mounts ;)

Yes, I forget the part number, but I did the same on my V8 that went into my RRC.

Ok 👍. I take it I can’t fit my auto box.......? 😬 Permenant 4WD I know but...

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Of course you can!

A V8 auto series would be great, but you will need to shove the engine as far forward as you can, otherwise you end up with a rear prop that is too short.

You can get a 4x2 conversion for an LT230, if you swap one of these in for the Borg Warner transfer box.

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As Bowie says, you've quite a choice in manifolds. 

Yep, you can get a non aircon belt, but you'll need a different tensioner to suit as it's routed differently on the non aircon version. I run my serp with just water pump and alternator on a 7PK1220.

You could move the lot forward by fabricating new gearbox mount plates, custom props and modifying the tunnel a bit. I'd just bite the bullet and scallop the bulkhead a little, though. 

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Somehow, I forget the details, I re-drilled the tensioner mount and flipped it, no need to change tensioner.

But then I have a PAS pump as well, unless you go crazy, you won't need that.

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1 hour ago, lo-fi said:

As Bowie says, you've quite a choice in manifolds. 

Yep, you can get a non aircon belt, but you'll need a different tensioner to suit as it's routed differently on the non aircon version. I run my serp with just water pump and alternator on a 7PK1220.

You could move the lot forward by fabricating new gearbox mount plates, custom props and modifying the tunnel a bit. I'd just bite the bullet and scallop the bulkhead a little, though. 

So if I was able to keep my auto box then I wouldn’t need the conversion ring, flywheel, clutch etc. Would that combo then push the engine forward enough to get access to the spark plugs without needing the bulkhead mods or hitting the radiator or would I still need to move the radiator forward a bit? I’ve done a search but can’t find any posts about this particular conversion so I’ll keep digging.

Edit: I’ve emailed Ashcrofts to see what their take is on it.

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It'll be longer than the series box, for sure! As Bowie says, the serp has a short nose pump, so a pusher fan in front of the rad will probably see you right. My setup put the engine so far forward I didn't need to mod the footwells, but there's not a lot of clearance for the manifolds: about an inch or so. Enough, but tight. 

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