[Mg-mmm] MG PA spark plugs

[Lawrie Alexander]

Hi, Folks,

My rebuild of PA engine # 1038A/135P continues, following the disappointing 
failure after 118 miles when the core plug on the top of the head decided to 
pop out. I'm glad I decided to tear the engine completely apart rather than 
just draining the oil several times as numerous problems were revealed, 
largely due to, shall we say, less-than-exemplary work by the English 
specialist rebuilder.

While I had the head on the bench this morning, I noticed that the spark 
plug hole threads are quite long. The engine had been fitted with 1/2" reach 
plugs which, I noted, put the spark gap barely inside the combustion 
chamber. I tried a 3/4" plug and it appears to put the gap closer to where 
the incoming mixture leaves the intake valve. My Blower's manual references 
a KLG LK1 plug as being the one the factory fitted but I have no reference 
books which tell whether this was a 1/2" or 3/4" plug. While the car ran 
reasonably well with the 1/2" plugs, I am wondering if there is anything to 
be gained by fitting 3/4" plugs.

Any comments from our P-type owners who may have tried both?

TIA,

Lawrie