Carburetor jets

Hi guys,
I have seen somewhere before that it is possible to change the jets in the carburetor to smaller ones, to reduce the amount of fuel being used in the engine, which will increase the fuel economy of the car. So I was wondering if this would be possible to do with my 1982, 88 inch, series 3, 2.25 petrol? and if so, where I could get these new jets from?
Many thanks,
Gareth.

You could change the jets and yes it would restrict the fuel somewhat. You'd lose power though and probably end up using your right foot even more = no better fuel economy. I wouldn't bother personally.

Economy on a 2.25 petrol is sh*te and there isn't anything you can really do to make it a hell of a lot better. Free-wheeling hubs help, some say a Weber 34ich helps, round tyres help or not having massive mud terrains on it when all you do is drive to the shops and back If you drive long distances an overdrive will help. You can swop the engine for something else but don't go putting a diesel engine in it, put a V8 in instead. It'll probably do as much to the gallon but will be much better value for money

Main thing is just make sure the carb is set up right and the engines well tuned (valve lash, timing, and all that stuff). Even then it will feel like your wiping your ar*e with tenners.

As above but with the addition that random jet changes may end up with you running so lean that it ends up burning out exhaust valves.

Hi,

It depends on what carburettor you have. I've got a wideband Lambda sensor to help set them up - a couple of hundred quid but I can swap it between motors and its paid for itself already.

The Weber 34ICH was pretty under-jetted and quite small to start with and runs quite lean so not much to be had there other than making sure its not leaking and its set up right.

However, I bought a new 32/34DMTL and after a lot of road testing found it to be running pretty consistently rich. I went down one idle jet size on primary and a half main jet size on primary and it now runs at about 14 on idle and up to three quarter throttle 11-12 on WOT and 15-16 on overrun. Which isn't bad. Fiddling with jets has given an extra 2-3 mpg and not affected full power. It needs a bit more choke in the cold though. I could probably improve mpg still more but not had the time or inclination.

I've no idea why it was so over-rich, maybe Land Rover did it deliberately, maybe they got it close enough or maybe the high-torque cam/skimmed, ported head has affacted set up...hard to tell.

For SUs, Zeniths, Solexes and the rest I understand they all run quite rich - not played with these yet though...but the LWB has a Solex on and if I keep the petrol engine will be playing with that too.

There's loads of Weber and SU tuning books around that will assist but without a Lambda sensor it would take a lot longer to work out. Not so much information for Zenith/Solex but I think there are still jets available.

How does your lamda sensor work Dominic? Is it fitted to the car at all times?

I have read that at least the 2.25 (not sure about the 2.5) was designed to run rich from the get go, so stock carbs would probably be jetted to suit.

Interestingly there is an SU conversion on ebay at present, could help out the OP.

I've tried several carbs on my 2.25 and have ended up with the 34ich Weber. I know it gets a lot of bad press but I just can't hack knackered old Zeniths or badly made new versions. A brand new Weber is a quality carb at least and in my experience, gives the best performance overall between the two. I can't be arsed with throttle cables (and I've spent enough money on carbs now!) and so on to fit an SU or the twin choke Weber, although I would love to try one on a 2.25 if given the chance.

I also forgot to mention that removing the stock cooling fan will take a decent load off the engine. I've read up to 5% of its effort is lost pushing the air around. A leccy fan from a Chavalier/Vectra etc... fitted to push through the rad from the front is a good replacement by all accounts.

I got one of these: AEM Wideband UEGO 6-in-1 gauge (30-4100) - EFI-Parts.co.uk: Connectors, Sensors, Trigger wheels, Wideband, Adaptronic, Zeitronix, AEM and welded a boss into my exhaust. I've left it in for the past 6 months or so but really ought to either fit it properly or remove it now. It's not a bad thing to have when driving along with a vacuum guage and rev counter to make you aware of your right foot.

Yes, fan is something I want to do - not only the fact that its wasting power and wasting more the more it's revved but it also means it takes longer to warm up and so spend more time on the choke which wastes a lot when you tend to do lots of short trips. Plus would be nice to be able to switch it off when wading etc...

I've been impressed with the DMTL - in the end it only took an hour or so to fabricate a cable from the linkage to the carb and the twin-choke design gives both power and economy without having to compromise too much.

Probably next upgrade would be a free-flow exhaust...

Cool gadget! Love a gauge, would have one for everything if I could.

Leccy fan is on the list, long list tho......

Thanks for the advice guy's, great help, and Dominic, my series 3 is just fitted with the stock carburetor

Which one - there are a couple of different ones...Land Rover Carburettors - by Glencoyne 4x4 (Thetford)

D

I'm not 100% sure, but I think it is the Zenith 36IV