 | Home > V8 > Upgrade tired 3.5 or put something (better) in? |
 
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| TexasRover Member Since: 24 Nov 2022 Location: Paris Posts: 969   
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People rave about the rover V8, I had a 3.5 carb and now a V8 4.6 EFI but I find them fragile and certainly not efficient.
You can't beat originality though and if you don't drive too much for the sake of future value it might be worth retaining the V8. Parts are easy to get and not too expensive. If you plan to swap, 300tdi probably the easiest swap. |
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30th Jun 2024 5:45pm |
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| Chicken Drumstick Member Since: 17 Aug 2020 Location: Near MK Posts: 672 
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Personally would not go Tdi. They are nice engines and offered good performance back in the day, but are very unrefined lumps. The RV8 is a great motor. Shouldn’t really be fragile or unreliable, they have been used in tens of thousands of different vehicles. Think of all the p38 Range Rovers and Discoveries that have clocked up hundreds of thousands of miles as daily drivers. The RV8 is no power house though. It’s an old engine design, but they are a cheap way to get 200-250hp. Which is way beyond what a Tdi can offer. Revamping a 3.5 is certainly doable. Pretty simple engines, but it is a low CR lump in a 90/110 so lacking performance. Buying a 3.9/4.0 or 4.6 is probably the most cost effective way. With some mods the bigger displacement doesn’t make masses more Peak power. I used to have a cammed 3.5 in a Triumph that made 230hp and 219ft-lb on the dyno. The real difference is the under the curve grunt the bigger displacement gives you, ie when you put your foot down at 2500rpm type of thing. Also remember the RV8 is a naturally aspirated engine. It has bigger displacement than most period 4 banger engines. But they aren’t torque monsters like the press sometimes makes out. They will still do their best work at mid to high rpm. Indeed the late 4.6 “Thor” engines make Peak power at the red line. So you have to drive them hard to get the best from them. Cheapest option has to be a used 4.6 and slap a better cam in it. Add a good exhaust (long tube headers) and some good induction and you should have 250-260hp and a whole world of difference from how it goes now. If it is a bit tired a low CR 3.5 is probably only putting out 115-120hp. Other options would be to look at a Td5 swap, but you’ll need to change the gearbox. Not a bad swap though and a few mods and remap and the Td5 can make an honest and healthy 150-180hp and plenty of torque. |
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30th Jun 2024 9:28pm |
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| London_Landy Member Since: 06 Dec 2022 Location: London Posts: 12 
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Thanks for the reply and suggestion.
Fortunately I have access to a number of defenders so I strictly want to keep my petrol and preferably V8 though I do like the look of the m57. However, because of ulez etc I do not want to jeopardise classic car status which I will obtain in 4 or so years. At the moment my exhaust manifolds leak and my su's are shot. Also mpg is imo abnormally high for a 3.5. So mainly wanting v8 noise and thrill but trying to get the best mpg possible for the circumstances. I did read that replacing the v8 with another landrover derived one would not jeopardise classic car status. I'm just asking for opinions on spending 5k plus on revamping the original with a new exhaust/carbs and cam is better or as you say possible dropping in a later v8 would be a better alternative. my 110 unfortunately does not have the original chassis as it was too heavily corroded, but it would be nice to keep it as original as possible. |
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30th Jun 2024 10:04pm |
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| Chicken Drumstick Member Since: 17 Aug 2020 Location: Near MK Posts: 672
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Tis up to you. But I’d personally not spank £5k on refurbing the 3.5. That would seem a waste of money to me. If you believe the engine will make the vehicle worth more in 20-30 years time (I have my doubts tbh). Just chuck it in the corner with a sheet over it.
Swapping in a 4.6 would be easy, require no real mods or alterations and be completely reversible. I would say don’t hold out hopes on mpg though. My mildy modded 4.6 p38 does 13-14mpg running about. On a good steady run it’ll do 19-20mpg. But that is about as good as it gets. Pre mods and no lift and road tyres I managed 21.6mpg on a commute home. |
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30th Jun 2024 10:39pm |
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| Organised Chaos Member Since: 20 Dec 2008 Location: Chesterfield Posts: 56 
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I am in the process of finishing off my series 2a fitted with a 3.5 engine and all being well should have it on the road in the next 2 weeks. I will keep it short , when I rebuilt the engine I fitted 9.75 pistons, 3.9 heads and cam as you only really need bottom to mid range torque, and a John eales serpentine conversion. I did originally fit the edelbrock rpm dual plane inlet manifold and edelbrock/weber carb but was not that impressed with it, so took the carb off and fitted the fitech 4 barrel fuel injection throttle body and put a lambda sensor in the exhaust. Its a self learning closed loop system so all being well should give good MPG. You get a handheld controller with it to input the engine specs and also for fine tuning.
 Click image to enlarge |
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30th Jun 2024 10:44pm |
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| Chicken Drumstick Member Since: 17 Aug 2020 Location: Near MK Posts: 672
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Where did you get the throttle body injection unit from? I’ve seen them on TV a number of times but not ran one. I have a Weber/Edlebrock 500 on my 3.9 which has mostly been fine. But it was originally setup for a cammed 3.5 and isn’t 100% on the 3.9. Biggest issue is finding people who can tune carbs these days. I reckon it needs rejetting. But have been toying with maybe going the SPI route instead.
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1st Jul 2024 12:09am |
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| Organised Chaos Member Since: 20 Dec 2008 Location: Chesterfield Posts: 56
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I bought it from https://www.serckmotorsport.co.uk/shop/spe...-n-50015/, it looks like they are on offer at moment but they are not showing the price on the site, they were out of stock when I ordered it and they where just waiting for stock coming from the US but got it within a week. You can just order the throttle body if you have a EFI fuel pump to hand , which I didn't so ordered the throttle body and in tank pump kit No. 36203.
Another company that does the fitech products is https://www.vitesse-ltd.com/collections/fi...=grid-view |
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1st Jul 2024 3:51am |
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| Ranger 6 Member Since: 17 Jan 2019 Location: Yorkshireman trapped in a Surrey postcode Posts: 196 
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I'm nearly finished on my quest to do exactly the same as you.
I've got a 1988 90 V8 CSW - when purchased the engine was completely stock and quite tired. If yours is on 80k miles I'd suggest you have three options: 1. Disco/RRC twin port exhaust manifolds and system(a TD5 system is much bigger bore), new cam (3.9) and BBW needles in the carbs 2. Fit another Rover V8 - as mentioned, a bigger capacity & higher compression engine - up to you if you rebuild it 3. Fit something else - V8, M57 or otherwise My reasoning would suggest that those options will give you; 1. a budget solution - keeps the originality but brings the engine to life. I did the exhausts and needles on mine and it made a massive difference to drivability and economy. Using mostly second hand parts I did this for under £500 2. this will improve it even more and keep the look of originality - I'm putting a rebuilt 3.9 into mine which will hopefully give even more grunt and still look original as I'm still using carbs. The machining and new pistons etc came in at just under £2k 3. Loads of performance, but will need considerable budget. I'd love to put an EFI system on mine, but with everything else it's just a but much. Maybe that'll be next in a few years time, so I'll be watching with interest. 90 V8 CSW - 1988 |
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24th Jul 2024 4:36pm |
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| Chicken Drumstick Member Since: 17 Aug 2020 Location: Near MK Posts: 672
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If you can do the work yourself, swapping in a later RV8 is the best bang per buck.
I bought a sweet running p38 for just over £400 in January. It is the 182bhp 4.0 litre. If you did nothing else and swapped it in to replace the 3.5 it would give a massive performance boost. The low CR only made circa 130hp when brand new. Tired you are probably somewhere nearer to 100-120hp. Even a refreshed low CR 3.5 with slightly better exhaust is still going to be best part of 50ho shy of a 3.9 or 4.0. And that’s just Peak output. The under the curve performance, say at 1800rpm will be even more significant. There really is no replacement for displacement in this kind of scenario. |
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24th Jul 2024 7:08pm |
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