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MG MGA - How to tune up a MGA

OK this is a little embarressing question to ask....a little like "How do you kiss a girl".

But I've never had to tune up an engine before.

So what is the program for tuning up a MGA.

Thanks,

TM
Tysen

Hi Tysen. Do a wet/dry compression test first, to ensure compression is good and fairly equal on all cylinders. If compression is good, continue. If not, fix the compression problems. Then: change spark plugs, points, and condensor in the distributor. Oil the distributor in the places required. Wipe a tiny bit of white grease or distributor lube on the distributor lobes. Check that the mechanical and vacuum advances are free and working. Check the distributor cap and rotor for post contact corrosion, wear and /or cracks. Check ignition cables for wear, chafing, electrical continuity, high voltage leakage, and proper resistance. Replace any that are defective. Check and adjust all engine valves. Set ignition timing. Remove, wash, and reoil Vokes air filters, or maintain/replace non stock air filters. Check and Adjust carburettors. Remove and clean the carb dashpots and pistons. Reinstall them. Fill the dashpots with clean carb damper oil. Check that the jets are properly centered. Check fuel air mixture, carb synchronization, and choke adjustment/operation. Install air cleaners. Reset and finetune ignition timing. Additional (non tuneup but important options): change motor oil and filter. Check/change transmission fluid. ditto rear axle fluid, and brake fluid. Grease the front suspension and handbrake. Oil the steering rack. oil rear generator bearing. Clean out and vacuum the car interior. Wash, polish and wax the car body. Polish all chrome. Go have a cold beer then a snooze! Hope this helps. Glenn PS. You will find that your repair manual explains how to do most, if not all of the above operations.
Glenn

The things you do in order are:
Adjust valves per spec, see svs manual for spec and procedure.
Pull plugs, don't reinstall yet.
I pull the distributor to replace points and condenser clean point lube off dist cam. Once points are in set them on the bench to spec. Point gap can be set by eye if you are to use a dwell meter for final setup.
Reinstall distributor. turn crank so marks line up, notch on pulley to proper pointer. With out a timing light you can use a test light, or ohmmeter, to set initial timing. Turn dist slowly until points open and turn on light or show open on ohmmeter. Tighten distributor hold down, Loose if timing light avail.
With dwell meter, crank engine and set points, cranks easier without plugs, as close to 50 degrees without going under. After dwell is set install plugs and start engine. Verify dwell reading you want the dwell to be at 50 while running. Sometimes due to dist wear cranking and running dwell could be different so you go back and forth until you have running dwell of 50. The spec if 50-55 but because as the points wear the gap gets smaller and the dwell number gets larger set to the lower dwell number. once running set the high speed balance on the carbs at about 2500 RPM, let it run at 2500 until fully warm. During this time the DRY points are burning in. The plastic will get hot and harden up if ran without lube. After running in the points lube points at this time, use no more lube than the size of head of a paper match, lube goes on the dist cam not the point face. Recheck dwell. with dwell set and points lubed set the distributor timing with a timing light or if no light is available recheck initial timing as previously described. Timing is always set after dwell, or point gap, because point gap changes timing but timing does not change point gap.
Check oil in carbs. Once running again set carbs. I always set high speed balance first. I then set low speed balance then mixture. Going back and forth between balance and mix until both are right. Carb set up is a whole other procedure if you have never done it get someone to show you how. For a first timer it is difficult to learn without being shown how.
R J Brown

Glenn mentioned a few good checks. Compression is always first because you can't tune an engine without good even compression. Check mechanical and vacuum advance while off car. Check cap rotor and wires. DO NOT lube points until burned in, this makes point rubbing block last MUCH longer and keep the dwell setting more consistent. Clean and oil air cleaners before reinstalling. Air filters are off the whole time. Do the final mixture check after air filters are on, air filters tend to enrich the mixture slightly so compensate while setting. The order of the work is important.
Good luck Randy
R J Brown

Glen and Randy,

Thanks for posting these tips !
I learned a couple things that I had wondered about for some time.

Here's another question:
I used to use the hand crank to set things up for ignition timing. I recently installed a Judson supercharger which requires removal of the crankshaft nut, so I no longer have the crank option.

I got a remote starter switch, but haven't figured out how to get it to actually engage the starter. I've connected it to ground and the hot side of the starter switch, but all it does is spin the starter motor. What am I missing ?

Thanks,
Chuck
Chuck Mosher

I've not had much luck in using the starter to set the valve tappets. The engine seems to want to stop in one of two positions.

What I do instead is take the valve cover off, Remove all 4 spark plugs. Then put the car in second gear and slowly push it backwards, till the valves are just where I want them. Then adjust and repeat. Just be sure you don't push the car out of the garage!

The thing I like about this method is that I can look at the rockers as I'm moving the car/turning the engine over. But maybe people have better ideas.
Steven Loe

There already is a remote starter switch under the front it is attached to the wire from the knob with the S on it.
I prefer to set the valves with the plugs in. On each bump of the starter brings up the next 2 valves that need adjustment in order. Engines always stop in 1 of 4 locations if bumped carefully. Those locations always line up 2 open valves an intake valve and the exhaust valve of the cylinder that precedes in the firing order.
My method of choosing which valve to adjust is by adjusting the valve in the companion cylinder when its opposite valve is open. Adjust #1 in valve when #4 in valve is open. at any stopping point 1 intake and one exhaust valve are open each time you bump the starter it goes to the next pair in order.
1 and 4 are companion cylinders as are 2 and 3.
Much easier to show than to explain.
R J Brown

Just a point on R J Brown's contribution: my info says that the dwell for a MGA engine is 60 degrees + or - 3 degrees. Do different values apply?
J H Cole



Tysen

RTFM. If you don't have a workshop manual, it is worth buying one - it REALLY is worth it, and each step of setting up the engine is explained in detail.

Some tips:
1. Set the valves without spark plugs in the head - makes a much easier job. Remember the rule of 9; when a valve is fully open, 9 minus the number is the valve to adjust. Check the manual for the valve gap - too close, the performance will be poor, too wide and the engine will be noisier than necessary. Go through a number of revolutions to recheck to have done it right. The engine will not start if the valves are significantly out. A compression check before this step is pretty meaningless as valves may not be closing of the rockers are set incorrectly.
2. Set the points with the distributor held in a vice and don't overtighten the clamp when you reinstall it in the block.
3. Set the engine timing to put cylinder 1 at the degrees below TDC on the pulley indicated for your engine in the manual.
4. Then use a bulb and wire to set the points statically (bridge between the points and ground with a 12V bulb, turn on the ignitin, and rotate the distributor clockwise until the light comes on, Then rotate in the opposite direction until the light JUST goes out, which shows that the points have just opened) , and then mark that point between the distributor and the clamp with a dab of paint as a reference mark. tighten the distributor clamp so that you have still some moevement possibility, but with resistance.
5. Set the carb jets using the procedure in the workshop manual, and slacken off the linkages. If you have a B carb, a small offset in the setting is required for the front carb. See the B Board or archives for details
6. Gap your plugs and reinstall.
7. The car should start first pull, then use a timing light to check timing dynamically. Tune the carbs for balance using a piece of tube in your ear and the other end in the same place in each of the carb throats. When they are singing the same note, tighten the clamps on the connecting shaft.
8. Tighten the distributor clamp a little more
9. Refit the air filters, and fine tune the carbs using the lift pin as a guide to check mixture.


Chuck

The solution is to have a new pulley machined that has the grooves for the three different belts, but still allows the use of the Dognut from the original setup. Cost me $60 US, and means I can set the engine up easily.
dominic clancy

Tysen,
There is a complete and fully detailed article in the NAMGAR TECH TIPS BOOK. It is worth the purchase price just for the one artical but you also get all of the tech info included. A terrific book.
Gordon Harrison

The original BMC service manual, Autobooks and Scientific publication manuals all list only point gap @ .014in -.016in. No listing for dwell.
The only listing for dwell I have found is in the Moss parts book, it lists the 60 +/- 3 mentioned.
My experience is with Japanese cars and they all list 49-55 for 4 cyl engines. I have used this number with success. I looked through an old Chilton's manual and checked dwell on Audi 47-53, BMW 62, Datsun Honda Mazda Toyota Isuzu Subaru all 49-55, Fiat 52-58, Peugeot 55-59 Porsche/VW 44-50.
I have been setting MGA points to 49-55 blindly assuming it was a "universal" 4 cyl specification because all the cars I worked on with points used it. Has anyone found a definite spec, or experience that something else should be used?
57 to 63 just seems too high to use. My experience with Jap cars is once over 60 the car starts missing.
R J Brown

Hey RJ, I've never heard about running the points dry until they get hot.
Hmmm, maybe you have sumthin' there?
As a mechanic for [ever] never did that.
But I won't use points again, Pertonix is just sooo much better.

I like to pull spark plugs, shove it into 4th gear, and rock the car back and forth to adjust valves.
Way more accurate-----------than bumping with the starter.

As far as point dwell, as long as the points make and break, dwell isn't terribly important, but it affects timing. so be consistent. Or you will have to change timing dramatically.
SF
Dwight
DCM McCullough

This thread was discussed between 07/05/2006 and 09/05/2006

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