Well, after fitting a 123 ignition, I went to change the spark plugs and put in a new set.
Currently have Bosch WR7DC and wanted to change to NGK6BPES.
All well until I came to no 3 plug.. Came out alright but just couldn't get the new plug to take the thread. Went on to do 4,5&6 and came back to no 3, but Still no joy.
Head scratching and muttering, I looked at the head thread and it seemed ok with little or no damage.
Took out no 4 plug and compared head threads...ah there seemed to be a little different. So to the dustbin to retrieve the old plugs to have a look see.
Found one plug of the six had a "double thread". The top half of the thread was much larger than the bottom half!
It was the only plug that would fit in that cylinder...
Is this normal for these cars? or do I have a head thread problem...
If so, is this a special type of OEM plug from Bosch... (done a Google but find nothing)
Anyone got any suggestions please.
TIA
Lazz