This article Copyright 2001 - Chris Kotting 

Permission to reproduce is freely granted upon request

Tuning 101:

Getting your SU's set properly.


How to get your car running the way you want, without frustration.

The biggest hassle with getting an MG (or other British car) running properly is multiple SU carbs. Not that there's anything wrong with the carbs themselves, but there's this incredible temptation to "fiddle" with them, and the range of possible adjustment is large and varied enough that you can really get things out of whack in a hurry. This tends to result in owners going prematurely bald from tearing their hair out trying to get the car running properly.

I 've been there, done that, and fortunately my scalp healed up nicely. However, in the interest of keeping other MG owners from having to wear baseball caps ALL the time to hide the missing patches, I humbly present a methodical process for making your MG run it's best.


This is just one person's experience. If you prefer to do things differently, fine. If you've had success by some other method, good for you (but stay away from my car). Also, I can't possibly cover everything that might be wrong in one article (or even six). If you've got a problem that this doesn't deal with, contact me and we'll see if I can help you figure it out.

I will assume that your carbs are in reasonable repair (not in need of new seals, not leaking gasoline, not dropped from a height of 150 feet onto a granite outcropping). We will be checking for some of the more insidious possibilities as we go along.

Tools required:

Screwdriver (flat blade)

Wrench to fit valve cover hold-downs

Wrench to fit valve adjusting lock nuts

Wrench to fit Distributor clamp

Spray Carb Cleaner or Starting Fluid

Feeler gauges

Timing light (if you need/prefer to do dynamic timing)

White-Out(for dynamic timing)

12V test lamp (if you need/prefer to do static ignition timing)

SU adjustment tools

Tools that are nice to have, if you like them:

Dwell/Tach (I use this regularly)

Gunson ColorTune (I have one and use it sometimes)

Gunson Clik-Adjust (I have one, use it regularly, and love it)

Uni-Syn or other Carb Synchronizer (I do without this. Had one, didn't like it, sold it. The fella I sold it to likes it, so different strokes...)

Vacuum gauge (one of those tools that you'll rarely need, but when you need it, you REALLYneed it).

Compression Tester (ditto)

Point file (for the truly meticulous)

Pediatric ear syringe (handy for emptying float bowls)

Parts you may need (only if you find they are messed up):

Valve Cover Gasket Spark Plugs Spark Plug Wires Distributor Cap and Rotor Points and Condenser

First Principles:

Vacuum controls everything else, therefore, get the vacuum right before pursuing anything else.

The factory had a pretty good idea what they were doing, so no matter how radical you want to get, start with the factory settings.  Ignition and Carbeuration affect each other. If one is way off, the other can be set up to compensate, but at a cost in efficiency or power.  Patience is a virtue. So is being methodical. If physicians worked on us the way we tend to work on our cars, there'd be a lot more dead people.

Okay,now to start getting into the meat of things.


Step 1: The "Cheat Sheet"

The first thing you do is sit down with the manual and write down, in big friendly letters and numbers (so you can read them in poor light, at a funny angle, with sweat running in your eyes) the following statistics.

Valve Lash (and whether it's set HOT or COLD) {If you use a Clik-Adjust, you'll want to record the number of clicks, once you calculate that.}

The most efficient order in which to set the valves (under the valve adjustment section)

Points gap

Dwell (if available)

Spark Plug Gap and Type

Timing (and whether it's set STATIC or DYNAMIC, and if Dynamic, whether it's set with the Vacuum to the distributor CONNECTED or DISCONNECTED)

Trust me, you won't remember them long enough, particularly if you work on multiple cars. I actually have one prepared for each of our cars, laminated so that it can survive multiple tune ups and not become an oily, smeared mess. I use one of those "magnet-with-a-clip" jobbies to hang it under the bonnet while I'm working.