just been on paddocks to order some service parts for my 2 1/4 petrol series 3 and found they list 2 types of spark plug, one for 8:1 and one for 7:1 compression engines . right well i'm assuming that this is stamped on the engine somewhere but i'm buggered if i can find it. can anyone tell me where it is located please,

DETERMINING COMPRESSION RATIO OF YOUR 2.25L PETROL ENGINE:
There are multiple head castings used on the engine over the years. The two standard compression ratios used by Rover are 7:1 and 8:1.

The easiest way to determine your head's compression ratio is to look at the top surface between the valve cover and the carburetor. You will see a head bolt located there. On some heads there is a flat rectangular boss under the head bolt that extends towards the carburetor to the edge of the head.

If your head does not have this boss it is an early 7:1 compression head. If your head has the boss it is a later casting that came in both 7:1 and 8:1 versions, depending upon the country the car was originally sold in. If the boss has no stamping on the top or a big 7 it is a 7:1 head and was probably originally sold outside the United States. If the head has a large 8 stamped on the top (could look like two '0's) then it is an 8:1 head.

Enjoy
Ps
There is a Lady who answers the phone some times at Pads who knows her **** and she told me.

this mite help

The Mad Hat Man said:

this mite help

Click to expand...

Not really it's un-readable.

now look at pic2

Don't get all uptight about spark plugs.

The best by far would be a NGK BP 6 EC type of plug.

20,000 miles at least of clean trouble free running.

But what do I know?

CharlesY

found it, a big number 8 hiding under 4 layers of duck egg blue military paint. cheers guys

Thanks Clivees, found the "etchings" on two engines ths morning, both dodgy 8's (more like 0's), exactly where you said to look

BeeP