Brakes and a tuneup.

Its been a while since I posted, largely because I haven't done any work on the car - which is good!! I've driven it quite a bit in the meantime. I did replace shoes and rotors on the front brakes a while ago and today I took a look at the back brakes.

Before you get started take a look at this video by John Twist. It goes through the components and assembly nicely.


To do the back brakes, its worth taking a look at them before you buy any parts. (If you can't get the drum off - check you don't have the handbrake on!) Here is what one side looked like

 

Clearly there is plenty of life left in these shoes, although the cylinder is leaking. I checked for movement in the components by depressing the pedal and making sure everything moved it should. Then I put the wheel back on. I'll order a new cylinder and do that replacement another day.

If you have a sharp eye, you'll note that both shoes are in the same way. This is not how they are supposed to be. One should be up and one should be down - they are not supposed to be symmetric. I actually just realized this and I'll fix them next time I have the brakes apart.


I also have a pinched brake line which was probably caused by someone trying to pull the car with a rope or chain around the rear axle. I'll replace that when I do the brake cylinder as bleeding the brakes will be called for.



I also did a few other maintenance items. I had noticed a little exhaust noise from under the car, so I re-positioned and tightened the exhaust brackets.

I also did a tuneup. This involved:
1. Check spark plugs and gaps. - The plugs were all nice a clean with no bad discoloration or oil.
2. Check timing. Its where I left it at 14 BTDC.
3. Check valve clearance. This is something I haven't done before, but it is pretty easy. Check out first these two videos.

First, it helps if you can turn over then engine from under the hood. This video shows you how to do it. But basically you run a wire from the brown/white pin on the ignition starter relay to the bottom fuse of the fuse box. I also disconnected the HT lead from the top of the coil.



The second video shows you how to set the valves - basically we are adjusting the gap between the tappet and the top of the valve. The system is easy once you see it! You follow the rule of 9. There are 8 valves. When a valve is in its lowest position, its' pair (they should add to 9) is the one to adjust. So the pairing is as follows:
1 - 8
2 - 7
3 - 6
4 - 5
5 - 4
6 - 3
7 - 2
8 - 1

You get the valve in to its lowest position by just turning over the motor.

I did this with a cold engine and set the gap at 0.015. It'll be a bit narrower when warm - and the shop manual recommends 0.013 for a warm engine. I'll probably go back and check it in a few days.

You do not want to set it too tight!!!! You'll wear out the cam and you'll hurt performance. If it is set right, the valves should sound like a sewing machine!



Finally, I put a 180F stat in and took out the 195. Its been running a little warm and I want to see if this makes a difference.

Temperature and Thermostats

The car has always run pretty cool. In fact I don't think the temp gauge has ever made it more than 1/4 of the way to N, and that is the middle of the NC summer. Normally the temp gauge won't get above C. I checked the temperature sender and it was working fine. You can test it by just making a circuit with it and the temp gauge should go to H. The sender seemed fine. I pulled the thermostat, it was rated 180 F. It also worked OK when I dropped it in a pot of boiling water. I also have another one that I ordered from VB. This one is rated so 195 so I decided to experiment. First of all, the new one also worked fine. One difference was that the 180 F thermostat opened much wider than the 195, so it would provide much more rapid cooling.

OK, so I went ahead and swapped out the thermostats, and went for a long drive. First of all the temp gauge moved!! Very quickly it moved to the left of N, and pretty much stayed there all the time.

So what???
Well a few things...
First, the car reaches operating temperature much more quickly. This means that I can put the choke in more quickly. This will save gas, reduce emissions, and result in less running rich which can coke up the engine.

Second, the car is now running at a higher temp, and within reason, a hotter engine is a happier engine in that it will run more efficiently, and in fact generate more power.

The results were quite dramatic, the car drove much better and performance was better as well. Its amazing what a $5 part can do.

I am running a 195 thermostat, which I might need to replace in the summer with a lower temp rated one, but I think that the old one was opening too much and letter too much coolant flow through the engine.

For an excellent discussion of thermostats, see this site..
http://www.mgcarz.com/thermostats.html

The key point here is that a fully functioning thermostat doesn't prevent the car from overheating. As the car gets hotter the thermostat will be wide open and the radiator is working flat out. The thermostat does provide a minimum operating temp, unless of course it is sticking open, in which case the min temp is going to be too low.