Good Timing

• Adjusted the timing

• Partially fixed misfiring problem
• Gained more engine power (timing was way off)
• Figured out how to set timing
  

Adjusting the timing is another one of those simple miracle cures that can really improve things. Just to name a few, the engine won't sound like a tractor anymore, emissions will improve, fuel economy will improve, no more misfiring, etc. It's also one of the easiest things you can do ... that is if you know what to do.

For a long time I didn't know what to do, and so kept postponing this. I finally took the plunge this weekend and figured out how to check and adjust timing. Sure enough, the timing was off (as if the misfiring hadn't told me that already).

First off, you'll need some equipment. You'll need a timing gun (see image below), a 12 V automotive source for the timing gun (car battery; from another car if you have an MGB), a 12 mm wrench, and some white-out (with a brush works best).


The 1977 MG B specs state that at idle (850 rpm) the timing mark should be at 5 degrees BTDC (before top dead centre), and for 1500 rpm at 10 degrees BTDC. This could be different on your car, so check before doing anything by reading a service manual. On my car I found the instructions on a lable under the hood (where other emissions info such as spark plug gaps etc is found).

Update: If you use a weber (like I do) you'll need to set idle to 14 BTDC. However this differs from car to car. Mine uses a free-flow Peco exhuast, so 14 is correct for me, but if you still have a catalytic converter you will probably need a lower offset.


Finding TDC is not the most obvious thing on my car. One can generally locate it as the 'odd one out' of the teeth that make up the timing alignment. Usually it's slightly bigger, however note that this differs on MGBs (based on the year they were built). The image above shows the situation on my car, the 'teeth' illustrated by #1 and the notch in the front wheel by #2. I used white-out to make them more clear. TDC is - I guessed correctly - the right most tooth. As per the specs of the car, at idle I need to be at 5 degrees BTDC (the 2nd tooth from the right), and at 1500 rpm at 10 degrees (centre tooth). All teeth have a 5 degree separation. On some MGBs these teeth are at the bottom of the engine.

What you do is simply adjust the distributor by turning it left and right till the notch on the wheel lines up with the 5 degree mark on the teeth (at idle). Do this by hooking up the timing gun to spark plug 1, the plug closest to the front of the car (the power cable on mine wasn't long enough to go the the battery, so I had to bring my other car next to it to connect it to a source), and aiming it at the teeth. To turn the distributor loosen the nut holding the sleeve of the distributor to the engine block (#3 in the image below).


And the result is... (idle, 1500 rpm, then idle again)

Note that all this should be done after driving the car around for atleast 5 minutes and everything is at running temperature. The timing marks on my car are on top of the bottom wheel (drive pulley?), but on older models it is often underneath.

Thanks to MG's great battery placement, my timing setup looks like this:
Get a friend to hold the gun.

UPDATE: I'd like to say that the top picture was a joke, but actually I was just being an idiot. A much easier timing gun setup is: connect the ground lead to a bare part of the frame (for example, that thing that sticks out of the engine where the air pump used to be), and the hot lead to the bottom fuse (ONLY TOUCH THE BOTTOM FUSE). The images below (taken with my phone... sorry) should explain.

Spark plugs: another easy way to fix serious problems

• Changed spark plugs and spark plug wires (Bosch)

Sluggish pick-up, tractor sounds, bad fuel burning, and mis-firing. These are all things possibly caused by bad spark plugs. Not surprisingly, my car featured all these exciting quirks, and as a result had a zero to sixty of about a year, and started with the reliability of an old Dell laptop (think: say nice words and it may start). After changing the spark plugs and wires, I now have slightly better performance! Also, the car starts on the first turn of the key! And best of all, the engine sounds like a car engine again!! I wanted to go on to change the timing, but had cut myself enough just changing the plugs so I left it for another time (and performance was good enough for now).

I'm not going to go into the details of how to change a spark plug here (on this car, any idiot could change them), however you should note that the bolt is not the standard spark plug size bolt. In fact, it's quite a bit larger and I had to use an adjustable wrench to get them out. Also the reader should note that I didn't have to gap the spark plug, as the spark plugs can be bought with the right gap nowadays (I wish I knew that before buying the gapping tool...).

Most notably, the mis-firing you see in an earlier blog (flames coming out of the carburetor) has now stopped entirely. This is due to the fact the old spark plugs were very oily (see image of one of my spark plugs below). Over time the spark kept reducing in size (due to crap build-up) till the spark was so small if didn't ignite the fuel anymore, resulting in excess fuel at times. At that point the slightest spark set of an enormous explosion that partially went out the carburetor. That's what I think happened, if anyone has any other suggestions please let me know as I'm just guessing here.

According to Haynes, this could be due to worn bores/piston rings, or valve guides, and sometimes occurs during the running-in period of the car (though only temporarily). Considering I recently changed the valve cover gasket (though I doubt this has anything to do with it) and don't drive very often, I'm going to be optimistic and say this is a temporary problem that has now been corrected.

So there we have a simple way of improving performance: change your spark plugs and spark plug wires. Baby steps towards getting back to (better than) factory settings.

Cold morning

This morning was rather cold, but I went out to start Bonnie regardless. After all, having spent a whole week in the cold, it was time for a little warm up. Apparently I primed the fuel pump a bit too much, letting too much gas in the carburettor prematurely. Nothing terrible, it all burned off quite quickly:

I've always known that flames and smoke came out of the carburettor when the engine is cold. This generally happens if I accelerate too hard on a cold engine. However I had never seen it in person before, so when my girlfriend jumped back the other day while I was starting the engine, and she then filmed what happened, I must say I was quite surprised. Regardless, I'm getting a new (more regular) fuel-pump as soon as possible.

Here's a freeze-frame of the large flame:

Update:
Apparently I had no idea what I was doing. The problem is mis-firing, where a not enough fuel is being ignited, and it all goes off in one go (hence the stalling). The fix: new spark plugs (actually, just changing the spark plug wires does a lot already) and adjusting the timing.