Thread: Spark plugs

The engine came in both 7:1 and 8:1. To tell which you have, look on top of the head between the rocker cover and the carburetter. There should be a cast boss about 12mm square and 5mm high between the headbolts. If it is an 8:1, it will have an 8 stamped on it (may be very faint). If it is 7:1 it will be blank, have a 7, or the boss will be missing. If it is the original engine (and head) it is probably 8:1, as I think most S3s sold in Australia were. There is a possibility that it has a head originally 7:1 and reground to 8:1 without the boss being stamped, but I would consider this unlikely.

John

FWIW I dug out my old spark plug catalogues ('96/'97 editions) and the only brand that lists two different plugs is NGK

B6ES for the 7:1 engine
B5ES fro the 8:1 engine

Bosch only list the 8:1 engine
W8DC

Champion ditto
N11YX

my manual says
8:1 champion n12y or unipart gsp 131
7:1 champion n8 or unipart gsp 130
unipart is repco?

Cheers guys,

I had a look and couldn't see a boss of any kind. I guess it must be 7:1, but I know it's an original engine.

If I go for a plug that's designed for an 8:1 or one of the one-size-fits-all does it really matter in the end? In fact, my engine's running pretty rough and there's a lot of unburnt fuel passing through, so would one be better than the other?

Here's the other shot. No lug to speak of, that I could see anyway.

The small raised section in the middle of the 1st photo is what JD is talking about i think the difference between plugs is heat range so if you have unburnt fuel i would go for the hotter plug may help

G'day guys,

I went with the NGK 8:1 plugs and there was an immediate improvement.

As you can tell from the other issues I described I've got a lot more to sort out, but this is a step in the right direction.

Cheers again.

James

if you have a 2.25P thats being a bit of a snark master to get to run smoothly changing the plug can help sort that out. Run a hotter plug than specified if its messing around while its cold and a cooler one if it starts to faff around when its hot.