MG Car Repair: Clutch slipping, mgb roadster, clutch pack

Question
QUESTION: Hi Howard,

I have completed an extensive updating of my 1974 MGB Roadster. The car has 93,000 miles with original clutch and transmission. I am experiencing slight clutch slippage sometimes, primarily in 4th gear.

Three questions
1) Is this condition apt to deteriorate without warning and leave me on the side of the road?
2) Is there anything short of a major clutch plate replacement that I can do to help the situation?
3) Is istallation of a new clutch something a moderately skilled yet non professional can do?

Thanks,

Allen

ANSWER: Hi Allen,
1.Yes, if the clutch is slipping it will continue to get worse, but there is no way I can tell you when that will happen.
2.The only thing you can look at as a outside cause is to have someone pump the clutch pedal and release it and you check to see if the short rod coming out of the slave cylinder is very tight thus holding the clutch partially disengaged. If it is fix the master and/or slave cylinder, if it is not you will need to pull the engine to put a new clutch "Pack" in. (clutch, pressure plate & release bearing).
3. Yes, do it yourself people do it all the time if you have tools and a way to lift the engine out and in. Tool rental companies rent them.
Good luck if you do it. I can walk you through it if you want.
Howard

---------- FOLLOW-UP ----------

QUESTION: Hi Howard,

I need your advice on another problem. I have something going on with the valves to the No.1 cylinder. I have adjusted the clearances, however the engine has a miss. When I remove the plug wire for that cylinder there is little change compared to a significant miss when I remove the other wires. I am getting fire to that cylinder and I have confirmed the plug is good. I suspect a valve problem. I see references to "burnt valves" what does that mean? What do you think is going on and how do I fix it?

Thanks,

Allen

Answer
Hi Allen,
First thing to do is purchase a compression gauge, their not expensive.(You can even find them at Wall Mart) As long as you have any gas engines it will be needed. All piston engines only require 3 items to run. (including each cylinder)
1. Compression--(in your case, 125 PSI up to 180 PSI)
2. Fire--(A thick blue spark at the plug at about the correct time)
3. Fuel--(A combustible fuel, available to the combustion chamber)
In your case you did the preliminary test called a "Cylinder Kill test" and "Spark to that Plug". That was good, you are ahead of most people.
Now you need to do a compression test "dry" and then "wet".
The dry test is just put the compression gauge into #1 plug hole and hold the throttle wide open and spin the starter at least 4 or 5 revolutions. On your engine, you need to see at least 125 PSI for it to run. 150 or 160 would be expected on a good cylinder. When compression gets down around 100 PSI or below that cylinder will just about not run at all.
It is advisable to do all 4 cylinders and write down the results. The "Wet" test is done after the "Dry" test by putting about a teaspoon of engine oil in the plug hole and do another compression test (throttle open). If the wet test results is more than 10% to 15% higher than the dry test, the problem is most likely a ring problem. If the low cylinder is low by itself meaning there is not a low cylinder right next to it then it is most likely a valve problem. If two cylinders next to each other are low it can be a valve problem or a head gasket problem.
These test are considered about 90% + correct.
But the last thing before committing to removing the head and doing a "valve job" check one more thing. Remove the valve cover and with a feeler gauge check the valve clearance on the low cylinder.
A burnt valve means (usually the exhaust valve) the valve burns part of it's seat contact area away and compression is lost. Intake valves can burn but that is less likely.

There is a 100% test used on engines that require a lot of expensive work to remove a head like Jaguar etc. In this test you need compressed air and a fitting to adapt an air hose to a spark plug hole. In this test you would put the tested piston at exactly TDC (top dead center)and put the car in high gear and hand brake on hard (or have someone hold the foot brake) then apply the air hose to the fitting. (air at about 150 PSI) then you open the throttle and listen for a hiss. Even a slight hiss is an indication of a burnt intake valve. Then you go listen at the exhaust pipe and again even a slight hiss is unacceptable. Other tests can be used at this time by opening the radiator cap to see if the coolant level raises any or bubbles appear. This is a 100% exact test of a head gasket leak. Then you can listen with the oil filler cap off and here even a good engine will hiss into the crankcase. We checked known good new engines and compared the hiss to that of a known bad ring engine to tell the difference. Without that experience it would be difficult to determine what is a bad ring hiss and a good ring hiss as they all hiss. The "Wet/Dry" test is a better ring test.
I hope this helps, let me know.
Howard