MG Car Repair: Valve adjustment, wolf creek oregon, mg midgets

Question
Howard, I am familiar with adjusting valves but am a little uncertain about the spec requirements for a 1962 MGA 1622cc.  The couple of British repair manuals that I have give two adjustment numbers.  On is 0.015" (running) and the other is 0.021" (timing).  Obviously the 15 thousandths is with the motor warm & running but does the 21 thousandths mean with a cold, not ran for atleast a few hours to days?  If this is the case, why the 6 thousandth difference in adjustment?

Thanks for any help you might be able to provide me with this question.  I haven't ran the motor for over 12 hours and would hate to adjust it to the 0.021" spec and find out this is wrong.

Charley
Wolf Creek, Oregon

Answer
Hi Charley,

The 59 to 61 MGA was .015" hot intake and exhaust but the 62 MKII was .017" hot intake and exhaust.

I worked for many years in MG dealerships and often wondered about hot vs cold so I checked several MGAs, MGBs and MG midgets and even Healeys by setting to specs and then check them in the other temp and most of them were only about .001" different.

The early 3 main B was also .017" and the 5 main B went to .015" cold but we found out at the dealership that even at .015" the valves were noisy and we had many complaints from customers who would come back saying the mechanic didn't adjust the valves so we went to .012" and the valves were quiet and even ran better and we stopped all customer complaints and shortly after BLM sent a memo to all dealers to go to .013" hot.

The car manufacture does not determine the valve clearance. The engine manufacture in MGs is Austin Engines or the cam manufacture determines the clearance due to the transition ramps on the cam determine the clearance and if the clearance is too much the lifting section of the cam hits the valve off it's seat and it drops it on the seat on the way down. A cam closes the gap first before lifting the valve off it's seat and when lowering it catches the valve and eases it to it's seat thus no noise and less ware and danger of valve breakage or even spring breakage.

.021" is completely wrong and you can prove it to yourself by setting them at .021" and note the noise, it will be excessive. When you say "Running" you mean "Hot" as you can't very well set them running like some Domestic cars of that era.

Even at .017" hot, if they are noisy try .015" to see if they quiet down and then wait for the engine to get cold (half a day) and check them to see how much they changed. Most Austin engines I checked don't change much between hot and cold. Then with the two specs you can set the valves either way.

Howard