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MG MGB Technical - Tune-Up Equipment

For the home garage, what tune up equipment is needed to do a competent tune up? In other words, what would I need to do a tune up that is comparable to one done at a sports car shop (timing light, dwell meter, etc...)

Thanks,
Doug
Doug Brooke (OR)

Feeler gauges
small wire brush
a couple of each screwdriver
basic set of SAE wrenches and sockets
small indicator light with aligator clips
spray type carb cleaner
points file
and as you say, timing gun and tach/dwell

That's the beauty--they're just that easy to work on!


Paul Hanley

I'd dispense with the points file as modern points don't file worth a darn and are easier and cheaper to just replace.
I'd add a decent spark plug wrench. The tube-socket and tommy-bar included in the factory tool kit is OK, but a proper socket and handle is nicer. Also, a 2-foot length of small diameter tubing or a "uni-syn" for carb balancing and an old putty knife (for scraping gasket sealant off the rocker cover).

Mike!
mike!

Well these ##$$%^&& cars got me started in 'the trade' 40 years ago, and now I've spent in the neighborhood of oh 'bout $10,000.
That's not counting the other equipment, like meters and jacks, etc.

I don't regret anything, not anything.
Dwight McCullough

Doug. I agree with Mike about deleting the points file. As to the timing light, get an adjustable one. That is the type that has a dial on the back or some other mechanism that allows you to dial back until it is flashing on the top dead center mark, then read the actual advance on the timing light. That will allow you to check out full distributor advance which is much more difficult with the only slightly less expensive "standard" timing lights.

Some dwell/tachs have a volt meter and ohm meter function, some do not. I prefer to have a seperate volt-ohm meter (VOM). Radio Shack sells an inexpensive analog unit that works well for auto use.

For the carbs, Moss, and perhaps others, sells a kit that I find much superior to the Uni-syn device. The Uni-syn device is used on one carb at a time and you have to keep switching back and forth. I used one when I first started, but then picked up a German tool kit that has two metal tubes and two wires. The tubes are inserted into the tops of the carb pistons after the dampers are removed. The wires are inserted into the two tubes and bent until they are in alignment. This makes it very easy to balance the carbs. It also allows you to make sure the carbs are synced properly. Simply open the throttle and make sure the wires rise together and to the same height. You cannot perform this test with the Uni-syn (which is also more expensive). The Moss part number for the tool I use is 386-300. Les
Les Bengtson

Hey Doug -

I'd also add a compression gauge. Without good compression all the other tuneup stuff won't help much!
Greg Smela

Great additions to the list guys. Thanks Les for the info on the German synch tool. Might have to give that one a try.

The reason I suggested Doug have a points file is not for the ignition points but for the voltage regulator if he has an early car. A points file cured a cripling issue with my car last winter and now, I never leave home without it. Not really a tune-up tool, granted.

Cheers,

Paul
Paul Hanley

Hi.

If you have electronic ignition you don't need a dwell meter.

I personally have never found an add on tach useful.

A vac gauge can be quite informative, I have one on the dash and another that I can connect up to view under the bonnet.

Don
Don

Thanks for everyone's comments. What about fuel mixture? Other than pulling plugs and looking at the color, how cah you tell if you have the air fuel mixture correct?

Thanks again,
Doug
Doug Brooke (OR)

Pull and inspect the color of the spark plugs.

Have fun !!

Edd Weninger
Edd Weninger

Doug. Mixture is a very interesting topic. Back in the old days, when performance was everything, you could buy a machine that would hook up to your tail pipe and read out the air/fuel mixture. For the last 30 years, however, emissions has been the big thing and air/fuel meters are hard to find.

Some people have found kits which allowed them to attach a probe to the exhaust pipe, near the cylinder head, and run the wiring to an air/fuel indicator mounted under the dash. There is some information on this in the archives and, from memory, one fellow included a link to a website discussing such installation.

Most of us have had to either read the spark plugs or rely on somewhat marginal test equipment. There are problems with all of these methods.

Reading the spark plugs worked well back in the days of leaded gasoline/petrol. Today's unleaded gasoline, often a blend of petroleum and either alcohol or MTBE (ether) does not give the same "readings" that the leaded gas did. The plugs remain cleaner, even with a slightly richer than required mixture. Thus, a "golden tan" plug is seldom encountered. A sooty plug is a sign of an excessively rich mixture, just as before. But, you can be a lot richer than previously, before you get signs of fouling.

The gunson's Color Tune, a form of sparking plug having a clear insert that allows you to see the mixture burn, is one piece of available test/tuning equipment. My experience is that their required "bunsen blue" does not happen with the blended fuels in my area. They are using the same pictures that they used 30 years ago and, if they are useful in the UK, where the device is made, they are not useful in my area.

The Gunson's CO meter. This is a somewhat expensive device at the hobbyist level, being over $200 from Moss, et al. I have played with one for about 6 years now. My experience is that they are somewhat fragile and very inaccurate. You set the meter reading to 2.0% CO in ambient air which is supposed to calibrate it. The air quality in my area is not the best. When the machine is set to 2.0% in ambient air and the car tuned for emissions testing, the test station measures significantly different test results than my machine indicates.

An accurate CO reading of about 5.0% is generally thought to provide the proper air/fuel ratio for best performance. With cars having an air pump, the air pump should be disconnected and the lines blocked. With the air pump connected, the tail pipe reading should be under 2.0% CO. Such testing is best performed by a professional mechanic having the more expensive test equipment (about $5,000) which will allow proper setting of the mixture. Les
Les Bengtson

Doug,

The most important piece of info yet to be disclosed is what year car and type carbs and any other significant mods. That aside, many, many MGB's have twin SU's. On the SU's are mixture checking lifting pins (see your manual--you have one, right?) At idle, lift the pin slightly. A sharp rise in rpm indicates rich, a sharp decrease=lean and a slight, momentary rise is ideal.

While we're on the subjuct of tune up equipment, add the Haynes or Bently manual.

Cheers,

Paul
Paul Hanley

Paul and Les -

Thanks for your help. I have a 67 BGT with rebuilt carbs (w/new throttle shafts). From most of the tuning information that I have read, you essentially tune the carbs at idle, using the plungers, intake flow calibration, exhaust note, what ever and trust that the carbs/needles stay in tune throughout the rev range. It's the period of time where the engine is running that I would like to check out. I believe that Les is correct when he states that this type of tuning should probable be conducted by a proffesional mechanic. Although, I would like to be able to do it myself.

Cheers,
Doug
Doug Brooke (OR)

Doug,
Tune up at idle is, in someways, only the beginning of the end of the process. As others have said, judging each carb's mixture and a carb mixture balance are best seen via a look at the spark plugs, after the car is back on the road and under real world conditions. Only then can real performance can be assessed.

The same is true, to my mind about the dynamic balance of the two carbs air flow compared to each other. At idle, you can get air flow between carbs spot on with the linkages at rest against their stops. And yet you can discover, via the tools which Les suggests, that your linkage is worn or out of kilter once the linkage rotates and the throttles move off their rest stops as the engine moves up in RPMs. It is only then that the "apparent" balance at the static idle position can be seen to disappear when you press on the accelerator pedal (IF you have a bad linkage or sticking throttle plate). Like other basic idle adjustments, that is a situation which can be pretty accurately addressed while the car sits in your driveway.

Not everyone follows the procedures in the books to the letter, but I think results are a better way of judging ultimate procedures than is absolute concern for following every jot and tittle of the shop manual. The manuals are always the best place to begin.
Bob Muenchausen

You can adjust both timing and mixture to the nth degree by proper reading of the plugs. Even with todays gasoline. If you have the proper technique. Check out this web-site:
http://www.strappe.com/plugs.html

I was doing it wrong all these years!

Mike!
mike!

Good info, Mike!
Bob Muenchausen

This thread was discussed between 13/09/2004 and 21/09/2004

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