How to Tune the Britpart Replacement Carburettor on Land Rover 2.25 Petrol Engines

Hello and welcome to the Britpart workshop. My name is Danny Hopkins and we're here in Shropshire with Paul Meyers, Britpart MD. Paul tell me what's the best thing about working here? It's a variety of vehicles that we supply parts for, a fantastic vehicle is a Land Rover Range. And we've covered the whole Range really from early to late. So every day is different, every day presents a different challenge. [Danny] - Brilliant. Today we're going to be going back in time, aren't we? Absolutely. What have we got here? [Paul] - This is a carburetor of a series three Land Rover. It's two and a quarter petrol engine. Fitted to literally hundreds of thousands of vehicles around the world and it's critical that this is set up correctly. Yes and Britpart offer a version of this don't they and another. [Paul] - Absolutely we do a version of this carburetor and we also do a Weber carburetor for the same application. [Danny] - Yeah. [Paul] - The Weber carburetor is a slight upgrade in that, it meters a fuel better. [Danny] - Okay. [Paul] - And will give a bit better performance and economy. Okay, why would you want to replace a carburetor, rather than maybe try and rebuild something that's old. A lot of the parts aren't available now for the older carburetors and also if you get wear on the spindles it will suck air into a body and you can never address them correctly after that. [Danny] - Now that makes a lot of sense, okay. Which of the screws that we have to look at? Cause we're going to be having it on the vehicle in a minute, but it's good now that it's off on the bench. This is a main adjustment screw, which is the the fuel mixture screw. And then on the other side of the carburetor we've got the idle adjustment screw to set the idle. [Danny] - Fine, brilliant stuff. Okay. So we're going to go over to our military spec 109. Right now we're going to see Martin and Steve and see if they can get it running absolutely perfectly. Right here we are with our Land Rover series three. This one's fitted with the two and a quarter petrol engine. This is the original carburetor from the engine. It's a great carb but it's difficult to get parts for these old Zeniths now. So what we've done is replace it with an equivalent unit which is supplied by Britpart. Very easy to fit this, this carb. There's a couple of small adjustments that can be made to it. One of which being the idling speed and the other is the fuel mixture at idle. Those adjustments need to be made just so that the engine runs sweetly when it's a tick over and the emissions are within specification for the MOT. Before we make any adjustments to the carb it's really important that all the ignition components are in top condition. Including your coil, HT leads, distributor points, and plugs. When you're happy that they're in good condition, make sure the timing is spot on as well before you do make any carburetor adjustments. It's easy enough to find your correct timing settings in the workshop manual for your engine. So, what we have here is a timing light which also displays the idle speed. And how it does that is it picks up, it's got an inductive sensor we've plugged onto the number one HT lead. So when Steve starts the engine this will display our idle speed. And the correct speed for this engine is between 750 and 800 RPM. So, Steve if you start her up. So that settled a little bit low we're about 650 on and off. So what we need to do is increase the idle speed and that will be a delicate balancing act between increasing the idle and still making sure the vehicles running at the correct fuel mixture. And how we are going to check that is it the other end of the vehicle, we've got a gas analyzer poked into the exhaust, which will give us a reading of the mixture and we can make the adjustments accordingly. We're almost there now, we're about 730. So a little tweak more on the idle speed screw. So we've set our idle speed. As you can see, the timing light is between 750 and 800. So now that that is set, the next stage is to adjust the idle mixture. That's done with a screw that's just inboard of the carburetor. Steve's just tweaking that now. And the reason for doing that is that for the MOT the CO mixture from the exhaust must be below 3%. At the moment we're just above three. So Steve's going to lean the mixture out slightly at idle. And that's obviously really important for the MOT, but there are many other reasons why your engine needs to be running the correct fuel mixture. Here's fuzz to explain why. Loads of people love a circus and in every great circus there ought to be a fantastic balancing act. Now, in your car's engine bay, there is another fantastic balancing act. And that is the balance between air and fuel. So air and petrol. the carburetor performs that great balancing act. If you have too much air and not enough fuel, the combustion in the combustion chamber will be hot. Hot enough to melt aluminum pistons. Not a great thing. If, however, conversely there is too little air to too much fuel, then you will get an unclean burn where you get a lot of carbon buildup. So the internals of your combustion chamber get dirty, the bowels get dirty. Everything gets covered with a layer of soot, which hardens up and chokes your vehicle. Effectively stopping it from breathing properly. The carburetors balance is vital to your engine's health. [Martin] - We've got the gas analyzer plugged in. The magic number we're looking for is 3% CO out of the exhaust. That's, that's what we need for MOT. At the moment it's a touch above 3%. So what we're going to do Steve is just going to adjust the idle mixture screw to lean it off slightly, to bring the CO down. So it's just dipping below three now and Steve's just tweaking the screw. It's mounted inboard on the carb, towards the rocker cover. As he adjusts that you can see the CO reading come down and now we're well within specification. So I'm just going to recheck the idle speed. That's still perfect. So that carburetor is now set up. For more handy tips on how to work on your Land Rover, check out the other videos in the Britpart workshop series.