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MG MGA - ignition timing marks

I have looked in both my manuals and Barney's site. Am I the only person whose 1600 does NOT have the two timing marks at the bottom of the timing chain cover, but rather 5 timing marks welded on the cover at the TOP of the pulley, just before the 12 o-clock position?

If someone has marks like mine, what positions do they indicate? 5, 10, 15 degress BTDC?

thanks in advance!
B Phillips

Your cover is from another engine. Most likely a B. If the mark on the pulley corresponds with the cover marks it may be from something else also.
R J Brown

The B covers had a oil seal instead of felt packing. It was more oil tight. The timing marks of a B cover are on the top.
JEFF BECKER

B. As the others have noted, you have a timing chain cover from an 18V version of the B series engine. This engine was used in the MGB and other vehicles. Thus, it would be of interest to know if they fitted the later model harmonic balancer instead of the 1600 crankshaft pulley. I know that the later model parts will fit onto the earlier 5 main bearing MGB engines because my 68GT has such a set up added to it. Makes life much easier when timing the engine dynamicly.

The timing marks on your current cover have the zero degree pointer at the upper most and each of the remaining pointers is spaced five degrees apart.

Both my my 1600s had the timing marks on the underside of the cover, and, as I remember it, a crankshaft pulley made out of two pieces of formed sheet metal rivited together. Later, at some point in MGB production, a harmonic balancer was introduced which dampened some of the engine vibration. When I drove my first MGB, I was amazed at how much less vibration the engine seemed to produce.

I do not know if it is possible to fit an MGB harmonic balance to an MGA engine. Barney might know and would be worth asking.

One thing to consider is that you might have a three or five main bearing MGB motor in your car. To many people, myself included, this is a desirable modification and does not detract from the value of the car. Bad thing on a show car though.

In any event, please let us know some more about what you find. If you are running an MGA style crankshaft pulley, it would be worth checking to see if a second timing notch has been cut into it for use with the 18V cover.

Les
Les Bengtson

If you have a timing cover with the TDC pointer at the bottom and a corresponding TDC #1 (and #4) cylinder notch in the pulley, when you fit a cover with the TDC pointer at the top you do not have to cut another TDC notch in the pulley, just time the ignition on #2 or #3 cylinder.

Mick
Mick Anderson

Of course using the single pulley notch for timing requires both the fixed pointers to be 180 degrees apart on the two timing chain covers.

Mick
Mick Anderson

Some other British cars have the same engine as the MGA such as the Riley. They used the MGA engine for a few years longer then MG did. I have a spare 1500 Riley engine with the same cover. The pulley is a little larger then the standard MGA. All the internal parts are the same as the MGA.
To determine TDC on the engine just remove the #1 spark plug. Put a long rod in the spark plug hole. Turn the engine over by hand until the #1 cylinder reaches the top of the stroke. Now look at were your mark on the pulley is.
If you have the original engine tag on the side of the block you can determine if your engine is correct for your car. Check the number out in your Moss catalog.
Hope this helps.
Gary
Gary Krukoski

The balancer from B will fit an A, as a performance upgrade to a B is to fit the lighter A pulley.

The pointers of the Late B style timing cover and the A style cover are NOT 180 degrees apart, so timing is not that easy. You'll need to find TDC and make a new mark unless its already been done, or if you already have the B balancer.
Jeff
Jeff Schlemmer

Just came in from the garage and can report a few things. The engine is a 1600 - 1600 casting on the side and a "16GA" prefix on the engine id plate.

The pulley is an MGA and not MGB. But it has two, not one, notches on it, approximately 5 degrees apart from each other. Perhaps a previous owner put the second notch on the MGA pulley, so that it would mean something when used w/ the MGB timing marks on chain cover? Of course, I cannot tell which notch is original and which one was home-made. So, as Jeff S notes above, I will have to find TDC and proceed from there, unless anyone else has any ideas.
B Phillips

I just rebuilt a 1622 engine and replaced the timing chain cover with a cover from an 1800 to get the better oil seal.
I set the engine up with #1 cylinder at TDC, installed the new cover and created a new mark on the pulley.
Carefully check your pulley for another mark as I know the one I filed in was much smaller. I reused my MGA pulley for the same reason Jeff identified. Incidently, Jeff Schlemmer did a beauiful job rebuilding my MGA distributor
If this dosn't work get back to me off line and I will measure around the circumference of the pulley from the original timing mark & post the info. It is too dark & cold to fiddle around in the carport now. The original and new mark are not close togather.
Cheers
Morris
ME WADDS

B. Finding the exact top dead center is an interesting experience. To do the job properly you need to have the cylinder head off, a dial indicator (clock gauge) with a magnetic base, and a degree wheel.

You bring the number one piston up until it looks to be full up. Then, you back it off a little so that you see it has moved downwards. Install the dial indicator with the pointer in the very center of the cylinder and zero it. Move the cylinder upwards until you show the maximum reading on the dial indicator. This takes a little "playing with it" to get it exact. Then, adjust the scale to zero and back the piston down the bore. Bring the piston upwards until the dial indicator is reading .001" below the zero. Adjust the degree wheel to zero. Rotate the engine until the dial indicator has reached zero, then, passed it and is reading .001" low. Note the reading on the degree wheel, normally about 15-20 degrees, and back the piston up for one half of the degrees registered. That is the exact top dead center. Note that the piston is at the top of its travel and does not move for several degrees of crankshaft travel. This is common in all reciprocating systems. But, if you want the true top dead center, that is how you will find it. That is the method a competent machinist or mechanic would use when determining top dead center and making the new timing mark.

So, where to go from here? I would pull the rocker arm cover and put a wrench on the crankshaft pulley nut. Rotate, manually, the engine until you watch the intake valve, the second valve from the front, open, then close. At that point, you are on the compression stroke of the engine, just before the firing stroke. (The ignition actually fires near the end of the compression stroke, giving the fuel/air mixture time to ignite properly so it will be able to produce the maximum power on the firing stroke.) I would, then, see which timing notch was close to the pointer. I would paint it with a thin stripe of white paint. I would make sure the other notch was painted black. At that point, you have a useable reference for tuning.

Les
Les Bengtson

If you would like send me an email. I will lend you the pulley with the correct marking on it after the new year. It is off the engine but not at my home at this time.
Gary Krukoski AT Yahoo Dot Com
Gary Krukoski

thanks for everyone's input. The head is coming off anyway since I am going to replace it with an early B head I recently picked up. I will establish TDC and mark the A pulley accordinlgy to corroborate w/ the B timing chain cover marks.

I looked again at the A pulley and can't find any other marks on it - I have no clue how the P.O. was able to perform static timing - maybe a chalk mark that is now long gone. . . .
B Phillips

This thread was discussed between 17/12/2006 and 23/12/2006

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