Paul's Daimler Diary, tuning Strombergs.

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Stromberg Page 1 - Go to page one two three four five Of course, tuning the carbs is only part of the story... The ignition needs to be spot on also, and the old Lucas OPUS ignition is useless. Here's a new product that I installed and it's great. Click on the logo to check it out. Tuning Strombergs There's been some queries on Strombergs on various forums recently, so I have put this article together. I used a Gunson Carbalancer air-flow meter when finally setting up the carb's. I don't know if they are still available. The text below refers to a Unisyn air-flow meter (similar to Gunson Carbalancer) which I have no experience with. On the subject of balancing the carb's, there is a note from Roger Bywater, of AJ6 Engineering that I have pasted into the article. If the carbs are all off the car, this is the way to go when synchronising, and forget the air-flow meters. A great improvement was found after I sorted the carbs, but the most beneficial improvement was when I combined the carb work with changing the V12 vacuum retard system to a vacuum advance similar to the later XJ-S. I found the articles below on the internet. I must credit this information to Steve Sutton. Although the owner has a two carb Triumph Stag, and I have a four carb V12 Daimler the instructions were very useful to me. The difference in driveability after sorting the by-pass valves and the temp compensators was superb on my car. Makes me wonder if SU's or fuel injection are that much better compared to properly set-up Strommies. My fuel consumption is virtually on a par with an HE V12 and with some distributor mods I have done, possibly better than some, although final drive ratios and model weight come into the equation. The last section is about tuning with a Gunson’s Colour-tune plug which I have and added just in case you have one. The whole set of articles with some stuff relevant to V12's is available as a downloadable "Word" document on my "Downloads" page. However, it's worth reading through the following pages as there are valuable extra contributions from Roger Bywater (AJ6 Engineering) and a few more bits from me that may help. Adjusting Your Carburettors *Extracted from earlier articles by :* *Scott Fisher, Roger Garnett, Ken Streeter, Steve Sutton,* *and other contributors.* 1. Basic Adjustment Strategy The trick to tuning Skinners Union (SU) or Zenith Stromberg (ZS) carb's is to understand that there are two things you need to get right: the air flow, and the fuel mixture. While they are interconnected, they are also independent, and need to be measured and adjusted independently. SU carb's were used on the early Triumphs, while ZS carb's were used on the later ones. Either type of carb can be found on TR4s. The design of each is quite similar; thus adjustment is performed in the same manner for either type. If you would like to read more detailed information about how your SU or ZS carb's work, there are excellent Haynes manuals for each of these carburettors. *Special Tools* · You will probably need to arrange to buy or borrow a Unisyn flow meter. The Unisyn is the usual gauge for getting the air flow balanced between the two carb's. This costs about $20 and is simple to use. It consists of an adjustable opening (same size circumference, but with a disc on a threaded rod that you can screw tighter or looser) that you use to set the level of a little float that rises or falls in a glass tube at the side of the gauge. · For the fuel mixture, one helpful device is called the Gunson ColorTune (maybe ColourTune, as it's a British Co.). This is a spark plug with a crystal pressure- and heat-resistant window in it that lets you see into the combustion chamber while the motor is running. The colour of the flame indicates the mixture richness. It costs about $40, and while it's not absolutely essential, it makes life so much easier that it's worth the cost. If you don't have a Gunson, the standard directions are included here for determining correct mixture (step 4 of the Adjusting Mixture procedure). · For some ZS carbs, you will need a special mixture adjusting tool. This is a special two-part wrench that is inserted through the top of the carburettor to adjust the metering needle while preventing the air valve from rotating within the carburetor. 1. To tune SU or ZS carb's, first locate the following components: · Throttle linkage nuts. These are the things that connect the throttle linkage (the bar connected to your foot through whatever means your car uses, cables or rods) to the carburetors' throttle levers. · Throttle stop screws. These set the idle speed for each carb, and are located typically behind the dashpot, near the connection of the throttle linkage. · Mixture adjusting nut. On early SU carb's, this is the lower of the two nuts at the very bottom of the carburettor. Later SU carburettors of the HIF type have integral float chambers, on which the mixture is adjusted by turning a screw. Some ZS carb's do not have adjustable mixture. ZS carb's that do allow mixture adjustment either You'll need to experiment (and I explain how) to see which way makes this richer and which way makes it leaner. · Lifting pins. (SU carb's only) These are little wobbly metal pins under the dashpot. When you push up on the pin, it raises the piston in the dashpot. Find these; they're crucial if you don't have a Colortune. If you don't have them, can't find them, or have a ZS carb, you can raise the piston with a flat-bladed screwdriver pushed down the throat of the carb and twisted or levered to lift the piston. · The bridge. This is the part inside the carburettor, where the gas jet opens into the airstream. You'll see a needle inside the jet, and the jet itself should be a few fractions of an inch down from the bridge itself. The jet is the brass tube that sits in the centre of the bridge, with a tapered needle poking down into it. · The choke linkage nuts. Comparable to the throttle linkage nuts (and usually the same size), but on the linkage that goes between the choke cable and the mixture adjustment mechanism. They make sure that both carb's are enriched when you pull on the choke. Your car may have no choke linkage, but a split choke cable which connects to each carb, in which you can forget about these... Stromberg Page 1 - Go to page one two three four five This site is for the benefit of enthusiasts. Much of the content is my own to use as you wish. However, some I have collected from various (forgotten) sources in the public domain. If you are the owner of any material used and wish it to be removed or so accredited, please contact me. Web Site © Double Six Design

Stromberg Page 1 - Go to page one two three four five

Of course, tuning the carbs is only part of the story... The ignition needs to be spot on also, and the old Lucas OPUS ignition is useless. Here's a new product that I installed and it's great. Click on the logo to check it out.

Tuning Strombergs

There's been some queries on Strombergs on various forums recently, so I have put this article together. I used a Gunson Carbalancer air-flow meter when finally setting up the carb's. I don't know if they are still available. The text below refers to a Unisyn air-flow meter (similar to Gunson Carbalancer) which I have no experience with.

On the subject of balancing the carb's, there is a note from Roger Bywater, of AJ6 Engineering that I have pasted into the article. If the carbs are all off the car, this is the way to go when synchronising, and forget the air-flow meters.

A great improvement was found after I sorted the carbs, but the most beneficial improvement was when I combined the carb work with changing the V12 vacuum retard system to a vacuum advance similar to the later XJ-S.

I found the articles below on the internet. I must credit this information to Steve Sutton. Although the owner has a two carb Triumph Stag, and I have a four carb V12 Daimler the instructions were very useful to me. The difference in driveability after sorting the by-pass valves and the temp compensators was superb on my car. Makes me wonder if SU's or fuel injection are that much better compared to properly set-up Strommies. My fuel consumption is virtually on a par with an HE V12 and with some distributor mods I have done, possibly better than some, although final drive ratios and model weight come into the equation. The last section is about tuning with a Gunson’s Colour-tune plug which I have and added just in case you have one.

The whole set of articles with some stuff relevant to V12's is available as a downloadable "Word" document on my "Downloads" page. However, it's worth reading through the following pages as there are valuable extra contributions from Roger Bywater (AJ6 Engineering) and a few more bits from me that may help.

Adjusting Your Carburettors

Extracted from earlier articles by : Scott Fisher, Roger Garnett, Ken Streeter, Steve Sutton, and other contributors.

1. Basic Adjustment Strategy

The trick to tuning Skinners Union (SU) or Zenith Stromberg (ZS) carb's is to understand that there are two things you need to get right: the air flow, and the fuel mixture. While they are interconnected, they are also independent, and need to be measured and adjusted independently. SU carb's were used on the early Triumphs, while ZS carb's were used on the later ones. Either type of carb can be found on TR4s. The design of each is quite similar; thus adjustment is performed in the same manner for either type. If you would like to read more detailed information about how your SU or ZS carb's work, there are excellent Haynes manuals for each of these carburettors.

Special Tools

· You will probably need to arrange to buy or borrow a Unisyn flow meter. The Unisyn is the usual gauge for getting the air flow balanced between the two carb's. This costs about $20 and is simple to use. It consists of an adjustable opening (same size circumference, but with a disc on a threaded rod that you can screw tighter or looser) that you use to set the level of a little float that rises or falls in a glass tube at the side of the gauge.

· For the fuel mixture, one helpful device is called the Gunson ColorTune (maybe ColourTune, as it's a British Co.). This is a spark plug with a crystal pressure- and heat-resistant window in it that lets you see into the combustion chamber while the motor is running. The colour of the flame indicates the mixture richness. It costs about $40, and while it's not absolutely essential, it makes life so much easier that it's worth the cost.

If you don't have a Gunson, the standard directions are included here for determining correct mixture (step 4 of the Adjusting Mixture procedure).

· For some ZS carbs, you will need a special mixture adjusting tool. This is a special two-part wrench that is inserted through the top of the carburettor to adjust the metering needle while preventing the air valve from rotating within the carburetor.

1. To tune SU or ZS carb's, first locate the following components:

· Throttle linkage nuts. These are the things that connect the throttle linkage (the bar connected to your foot through whatever means your car uses, cables or rods) to the carburetors' throttle levers.

· Throttle stop screws. These set the idle speed for each carb, and are located typically behind the dashpot, near the connection of the throttle linkage.

· Mixture adjusting nut. On early SU carb's, this is the lower of the two nuts at the very bottom of the carburettor. Later SU carburettors of the HIF type have integral float chambers, on which the mixture is adjusted by turning a screw. Some ZS carb's do not have adjustable mixture. ZS carb's that do allow mixture adjustment either You'll need to experiment (and I explain how) to see which way makes this richer and which way makes it leaner.

· Lifting pins. (SU carb's only) These are little wobbly metal pins under the dashpot. When you push up on the pin, it raises the piston in the dashpot. Find these; they're crucial if you don't have a Colortune. If you don't have them, can't find them, or have a ZS carb, you can raise the piston with a flat-bladed screwdriver pushed down the throat of the carb and twisted or levered to lift the piston.

· The bridge. This is the part inside the carburettor, where the gas jet opens into the airstream. You'll see a needle inside the jet, and the jet itself should be a few fractions of an inch down from the bridge itself. The jet is the brass tube that sits in the centre of the bridge, with a tapered needle poking down into it.

· The choke linkage nuts. Comparable to the throttle linkage nuts (and usually the same size), but on the linkage that goes between the choke cable and the mixture adjustment mechanism. They make sure that both carb's are enriched when you pull on the choke. Your car may have no choke linkage, but a split choke cable which connects to each carb, in which you can forget about these...

Stromberg Page 1 - Go to page one two three four five

This site is for the benefit of enthusiasts. Much of the content is my own to use as you wish. However, some I have collected from various (forgotten) sources in the public domain. If you are the owner of any material used and wish it to be removed or so accredited, please contact me.