Series 3 Engine Conversion

Sorry, this is a bit of a long post…so please bear with me

I have a 1985 Series III (ex-MOD) 109 and, before I commit to any further restoration, I would like to upgrade my 5MB, 2.25L engine to see if I can get more top end speed (at lower RPM using an overdrive) without overly compromising the low end torque.

Having now read many web pages and what seems like a thousand forum threads (many of them very good), I know that there are some basic things that can (and have been) done to a 2.25L engine to this end (ie. cam change, CR increase, carburation changes, exhaust modifications, piston over-boring, etc…) and I also know that there are other numerous other engine conversions options that would get me what I am looking for and more. But, the 2.25L engine is the bird I have in hand and I would like to keep things as stock as possible, so I have decided to do what I can with it.

However, before I take the above approach, I would like to get thoughts on the idea of converting my 5MB, 2.25L engine into a 2.5L by:

1. stroking the engine by installing a 2.5L crankshaft, camshaft and pistons, and
2. possibly upgrading to 2.5L intake/exhaust manifolds and a 2 bbl carburetor (Weber 34ICH installed now)

I have looked at the specs for both the 2.25L and 2.5L engines and, although I am not a seasoned engine builder, it looks to me like it should be possible since I understand (but am not positive) that:

1. both engines use the same base block
2. both engines use the same length connecting rods
3. the 2.5L pistons are shorter from crown to gudgeon pin to, I presume, accommodate the additional throw (~5/16”) and maintain head clearance
4. the 2.5L pistons are recessed to, I presume, accommodate the additional throw (~5/16”) and maintain an 8:1 CR

Now, I’ll be the first to agree that this seems like a lot of trouble to go to to get an additional peak 6HP and 9 lbft (difference in peak power and torque for a stock 2.25L and 2.5L engine), but once done I could then apply additional performance upgrades to what would now essentially be a 2.5L engine, namely:

1. increase CR to 9:1 by milling the head/block
2. retard the stock 2.5L cam a bit or install a performance cam (source?)
3. port (and maybe polish) the head and manifolds
4. up-size and open the exhaust slightly

So, my questions are:

1. Can the proposed base 2.25L to 2.5L conversion be done and what are the primary ‘gotchas’ (either known or anticipated)?
2. Assuming the proposed base 2.25L to 2.5L conversion could be done, what else could be (or should not be done) to further improve the performance of the resulting 2.5L engine?

Thanks for reading/replying!

I now see there is an Engine/Series forum. Maybe this thread should have been posted there?

Electronic ignition will help improve power and efficiency. If you really wanted to you could do EFI but this would be very much a custom setup. Raising the compression is a good way to get an increase in efficiency and 9:1 is well within safe margins. Alternatively, leaving it a 8:1 means you could play around with turbocharging- maybe using parts from a 19J diesel.

Tuned-length exhaust manifold will help with scavenging and move the power band around- in a landy you really want a good torque figure rather than maximum power so be cautious. Don't go too mad with the big valves and hot cams as these can make the idle and low-rpm running quite erratic.

I can hear the cries of "fit a 200tdi" already but go with the petrol engine you have- long term I think this is a better option than diesel, plus is will be quieter and more refined than a clattery tdi. Should be an interesting project too as not many folks have done this sort of thing, at least not anywhen recently.

Intersting, I think there is a lot to be said for the capacity increase even though its a lot of work. The goverment policy changes make takeing a petrol out and putting a diesel in look very risky. I'm sure someone is buying upp 2.25 petrols ready to sell to all those who put TDIs in. I run a deisel but its 2historic" so its exempt all the emission zones, for an 83 I'd probably keep petrol. The goverment recently did a consultaion on fuel for classic cars, basically it boilled down to "all pertol will be very low octane" whichis fine for modern engines will full digintal control and indivdual anti-knock senors but a real pain on a dizzy / carb set up. I used to run BSA's carb and mag, and run well down to 85 octane BUT, 6.5:1 compression. I would be looking at seeing if you could fit injection and computer controlled ingnition / anti-knock - it would be a lot of work but it sounds like you want a challenge! That and mild turbo could be a good smooth engine that can take the fuel that's coming. I'm still looking at electic conversions - but realitically for a DIY conversion that would be a 20-30 mile range.

FlyingPete said:

Electronic ignition will help improve power and efficiency. If you really wanted to you could do EFI but this would be very much a custom setup. Raising the compression is a good way to get an increase in efficiency and 9:1 is well within safe margins. Alternatively, leaving it a 8:1 means you could play around with turbocharging- maybe using parts from a 19J diesel.

Tuned-length exhaust manifold will help with scavenging and move the power band around- in a landy you really want a good torque figure rather than maximum power so be cautious. Don't go too mad with the big valves and hot cams as these can make the idle and low-rpm running quite erratic.

I can hear the cries of "fit a 200tdi" already but go with the petrol engine you have- long term I think this is a better option than diesel, plus is will be quieter and more refined than a clattery tdi. Should be an interesting project too as not many folks have done this sort of thing, at least not anywhen recently.

Click to expand...

you could just buy a 2.5 and add a better cam etc
it is the same block ,fits the diesels too except td unless it has oil feed and drain bung for turbo added which they all later had turbo or not
rods arent the same ie different part numbers
you skim head to get higher cr

rob1miles said:

The goverment policy changes make takeing a petrol out and putting a diesel in look very risky.

Click to expand...

What policy what risk? utter nonsense.

tynker said:

Sorry, this is a bit of a long post…so please bear with me

I have a 1985 Series III (ex-MOD) 109 and, before I commit to any further restoration, I would like to upgrade my 5MB, 2.25L engine to see if I can get more top end speed (at lower RPM using an overdrive) without overly compromising the low end torque.

Having now read many web pages and what seems like a thousand forum threads (many of them very good), I know that there are some basic things that can (and have been) done to a 2.25L engine to this end (ie. cam change, CR increase, carburation changes, exhaust modifications, piston over-boring, etc…) and I also know that there are other numerous other engine conversions options that would get me what I am looking for and more. But, the 2.25L engine is the bird I have in hand and I would like to keep things as stock as possible, so I have decided to do what I can with it.

However, before I take the above approach, I would like to get thoughts on the idea of converting my 5MB, 2.25L engine into a 2.5L by:

1. stroking the engine by installing a 2.5L crankshaft, camshaft and pistons, and
2. possibly upgrading to 2.5L intake/exhaust manifolds and a 2 bbl carburetor (Weber 34ICH installed now)

I have looked at the specs for both the 2.25L and 2.5L engines and, although I am not a seasoned engine builder, it looks to me like it should be possible since I understand (but am not positive) that:

1. both engines use the same base block
2. both engines use the same length connecting rods
3. the 2.5L pistons are shorter from crown to gudgeon pin to, I presume, accommodate the additional throw (~5/16”) and maintain head clearance
4. the 2.5L pistons are recessed to, I presume, accommodate the additional throw (~5/16”) and maintain an 8:1 CR

Now, I’ll be the first to agree that this seems like a lot of trouble to go to to get an additional peak 6HP and 9 lbft (difference in peak power and torque for a stock 2.25L and 2.5L engine), but once done I could then apply additional performance upgrades to what would now essentially be a 2.5L engine, namely:

1. increase CR to 9:1 by milling the head/block
2. retard the stock 2.5L cam a bit or install a performance cam (source?)
3. port (and maybe polish) the head and manifolds
4. up-size and open the exhaust slightly

So, my questions are:

1. Can the proposed base 2.25L to 2.5L conversion be done and what are the primary ‘gotchas’ (either known or anticipated)?
2. Assuming the proposed base 2.25L to 2.5L conversion could be done, what else could be (or should not be done) to further improve the performance of the resulting 2.5L engine?

Thanks for reading/replying!

Click to expand...

Just seen you are in Canada, so my post above may not apply, thought you were in the UK.

TBH - rebuilding your 2.25 to a 2.5 seems like a lot of hard work. Are the 2.5 engines available in your part of the world? Could you import one, they are usually cheap to buy in the UK.

I believe you can take the old 4 pot out to 2.8 litres, but I hate to think of the cost of doing this. Normal n/a tuning mods will up the power and torque as with any motor, but it'll never be a power house and certainly not in a 109.

Turbo conversions will be bespoke and require plenty of R&D, but should offer more performance.

I don't know if it was available were you are, but the Rover 2.0 T-Series engine was fitted in some Discovery 1's and Defenders and will fit a Series. These were also used in many different Rover cars. They are 16v engines but make a lot more power than the old 2.25 and make more low end torque too, although being 16v they will feel more revvy. It should be a nice engine in such a vehicle though. There was also a factory turbocharged version for more oomph.

And of course if you are wanting to stick LR, have you considered a Rover V8 swap?

Thanks for all the replies thus far! Lots of good ideas and feedback.

One of the challenges here in Canada is that we do not have access to parts (particularly used parts) that you have in the UK or, for that matter, any other country that imported a lot of Land Rovers (which oddly Canada did not). Also I have found that many of the UK Ebay sellers do not sell/ship overseas which is understandable given the relative ease for them to serve, and the size of, the local UK and European markets.

So getting a 'good' used 200Tdi or 2.5L petrol is tough here. Now, the British training base here (where my LR originally came from) does sell off surplus from time-to-time but I haven't seen an auction notice in years. And compared to the UK, the trucks they have to sell still go for a pretty good penny - even after they've been beaten to death in training maneuvers on the unforgiving Alberta prairie. It is a supply/demand thing after-all.

As far as emission go, I live in the 'wild west' where we extract bitumen out of the ground from the oil sands (not 'tar sands') to produce the fossil fuel derivatives that Land Rovers love to slurp so un-quenchably. And so, while it may not be politically correct to say in some (maybe most) circles, emissions are not likely to be a concern here for me for some time.

While EI and EFI are potentially beneficial changes, I see them a bit above my pay grade (read 'skill level') and they move me away from the principle of keeping things 'as stock as possible' (read 'simple').

So my quandary has been (and remains): 1) upgrade the 2.25L and hope that I get the boost I want OR 2) do some other non-standard engine conversion (200TDi being my preferred) and definitely get the boost I want. So while the latter is the best option in terms of probability of meeting needs, given the local lack of availability of a 200Tdi (and ancillary parts) and the additional fitting/fiddling needed, it also has the highest cost and complexity. So, as a result, I have focused on what I could do with the 2.25L lump that sits in my garage to increase the probability of it meeting my needs at lower cost and (I hope) complexity.

The concept of converting my 2.25L to 2.5L is really a bit of a 'hail Mary' effort to try to effectively start with a 2.5L base engine and then make additional 'performance' upgrades from there. No doubt there is more 'hair on this dog' than I think

Anyway, while I continue to vacillate on the 2.25, 2.5, 200Tdi options, I welcome further, and thank you all for your, input!

While Chester might be a bit of a bus ride for you, check out the ACR website, they do a lot of 2.25 upgrades:

https://www.automotivecomp.com/services/land-rover-products-and-services/

I have a Stage 1 head of theirs on a 2.3 engine, and a 4 into 1 branch manifold. It restored the power I lose using LPG/

I have a 200Tdi Series. But honestly the sort of distances you have in Canada I think it would be the wrong engine. They just lack refinement and are much more noisy to be in. Massively more than a petrol 2.25

The only real reason to go Tdi is for mpg reasons. Here in the U.K. fuel is massively expensive. I’m not sure on fuel prices in Canada, but if it’s similar to the USA then the engine you want is V8.

The Rover V8 isn’t a bad engine. It’s light and compact and makes sufficient power for a Series Land Rover. Plus it’s a pretty easy swap and you had them for sale locally in things like the Discovery 1. Ditch the EFI and just run a 4 barrel carb.

I suspect you could end up spending loads of time and money on the 2.25. And you’ll get some gains. But it’ll always be a massively low power engine.

"... "all petrol will be very low octane" which is fine for modern engines...well down to 85 octane... I would be looking at seeing if you could fit injection and computer controlled ignition / anti-knock - it would be a lot of work but it sounds like you want a challenge!... "
If petrol went 'really low octane', the low compression Land Rover engine would be fine, just change the timing as per here:

http://www.series2club.co.uk/pages/technical/servicing.html

Yes I agree, the Land Rover engine will have been designed in the era of "pool" petrol, my fear was that if we are going that way again its not a good plan to up the compression, though I suppose you can all was take it down again with a 2nd head gasket.
I was bemused by the observations on shale oil. I work in oil and gas and recognise exaclty what you describe; I've been to seminars from Canadian shale oil companies that manage to completely avoid the words "shale" and "oil". I run a diesel and plan to for some time but I think in the UK private diesel driving will be sacrificed to meet targets without disrupting haulage and agricuture who will keep their diesels, unless of course a new health scare / bandwagon comes along first. The V8 idea has some benefits, it is after all a Buick, the other option of you are going for change is (correct me someone) the Chevy in-line 6.

jamesmartin said:

you could just buy a 2.5 and add a better cam etc
it is the same block ,fits the diesels too except td unless it has oil feed and drain bung for turbo added which they all later had turbo or not
rods arent the same ie different part numbers
you skim head to get higher cr

Click to expand...

wireman said:

While Chester might be a bit of a bus ride for you, check out the ACR website, they do a lot of 2.25 upgrades:

https://www.automotivecomp.com/services/land-rover-products-and-services/

I have a Stage 1 head of theirs on a 2.3 engine, and a 4 into 1 branch manifold. It restored the power I lose using LPG/

Click to expand...

Thanks for the reference. I had been corresponding with Roland at ACR already. He sent me a quote for Stage2 head, PP camshaft, etc... I like the idea of going this route as I have read good things generally, but it is expensive...especially when I must include shipping allowance (significant) and potential import taxes. Just the head alone would be 4-5 times more expensive for me than having similar machining/assebly done here on my own head. Tough to justify, even if what ACR provides is superior. About the same multiple for the ACR PP cam over what I can get a new OEM 2.5L cam for here. I was troubled by the fact that Roland could not provide any details on the cam (ie. no cam card or specs relative to the stock cam...just "a bit more lift and duration"). I might be better off to take a trip to the UK and bring it back in my luggage if I decide to go that route...just have to find somewhere to send the wife

rob1miles said:

Yes I agree, the Land Rover engine will have been designed in the era of "pool" petrol, my fear was that if we are going that way again its not a good plan to up the compression, though I suppose you can all was take it down again with a 2nd head gasket.
I was bemused by the observations on shale oil. I work in oil and gas and recognise exaclty what you describe; I've been to seminars from Canadian shale oil companies that manage to completely avoid the words "shale" and "oil". I run a diesel and plan to for some time but I think in the UK private diesel driving will be sacrificed to meet targets without disrupting haulage and agricuture who will keep their diesels, unless of course a new health scare / bandwagon comes along first. The V8 idea has some benefits, it is after all a Buick, the other option of you are going for change is (correct me someone) the Chevy in-line 6.

Click to expand...

Interesting. I did not realize that the UK was considering reduction/removal of diesel usage from private, non-commercial vehicles. Given the global intent to reduce emissions in general and all the trouble that manufacturers of new passenger diesels seem to have gotten into over falsified (questionable?) emissions testing, its not hard to imagine a future without non-commercial (private) diesels. And since the UK (and Europe, in general) are always one step ahead of us on these things...if it happens there it will eventually hit our shores too.

I'll keep my mind open on the Rover (Buick) V8 or maybe this Chevy inline 6. Definitively, as someone else posted, easier to find parts for them here.

jamesmartin said:

you could just buy a 2.5 and add a better cam etc
it is the same block ,fits the diesels too except td unless it has oil feed and drain bung for turbo added which they all later had turbo or not
rods arent the same ie different part numbers
you skim head to get higher cr

Click to expand...

Thanks James. I'll have to look into that con rod more if I continue down this path. If I do I would probably have to use 2.5L pistons, conrods and crank (as a set). Even then I would still have to deal with possible issues including: bearing size/clearance, cylinder sweep, bottom-end clearance, etc... Without doubt I have much more to learn than I know. Hell, I don't even know what I don't know!

300bhp/ton said:

I have a 200Tdi Series. But honestly the sort of distances you have in Canada I think it would be the wrong engine. They just lack refinement and are much more noisy to be in. Massively more than a petrol 2.25

The only real reason to go Tdi is for mpg reasons. Here in the U.K. fuel is massively expensive. I’m not sure on fuel prices in Canada, but if it’s similar to the USA then the engine you want is V8.

The Rover V8 isn’t a bad engine. It’s light and compact and makes sufficient power for a Series Land Rover. Plus it’s a pretty easy swap and you had them for sale locally in things like the Discovery 1. Ditch the EFI and just run a 4 barrel carb.

I suspect you could end up spending loads of time and money on the 2.25. And you’ll get some gains. But it’ll always be a massively low power engine.

Click to expand...

Hearing protection is pretty much required in my 2.25L as it is, so I can't imagine amping that noise up with a 200TDi. The truck will probably not be used for long haul driving so I'm not to fussed about mpg. Also, because I probably won't be putting massive miles on the truck it is harder to justify any extra expense to just improve mpg...so I might as well spend it on fuel (I know, that's probably not the most environmentally friendly approach, but it has to be considered). Thanks for the input. I'll reconsider that Rover V8.

wireman said:

"... "all petrol will be very low octane" which is fine for modern engines...well down to 85 octane... I would be looking at seeing if you could fit injection and computer controlled ignition / anti-knock - it would be a lot of work but it sounds like you want a challenge!... "
If petrol went 'really low octane', the low compression Land Rover engine would be fine, just change the timing as per here:

http://www.series2club.co.uk/pages/technical/servicing.html

Click to expand...

My desire for more power by upping the CR to 9:1 is countered by my desire not to have to source/buy higher octane fuel. Octane ratings seem to be based on differing standards in UK and here. UK uses the RON standard for octane rating and Canada (and US) use the AKI standard. If I want to stick to using regular unleaded fuel (the least expensive) I use 87 AKI (or 91 RON). And, although I am not sure of this, I think that during the winter what we buy as 87 octane fuel is actually only 85 octane (something to do with air density at lower temperatures). I know that ACR stipulate that 95 RON fuel be used with their Stage 2 (9:1) head which, if I used it or milled my head to this CR, would have me buying 91 AKI (premium unleaded) at about 1.1 times the cost of the 87 AKI. I guess I just have to decide if the added power at 9:1 is worth the 10% increase in fuel cost given the expected annual mileage. And around and around I go!

tynker said:

Thanks James. I'll have to look into that con rod more if I continue down this path. If I do I would probably have to use 2.5L pistons, conrods and crank (as a set). Even then I would still have to deal with possible issues including: bearing size/clearance, cylinder sweep, bottom-end clearance, etc... Without doubt I have much more to learn than I know. Hell, I don't even know what I don't know!

Click to expand...

you wont have any issues such as those as they are the same blocks