RV8 Spark plug thread size.

[BenBaron]

Yes I know Im always asking what thread is this and what thread is that, but Im at work, its dark when i get home and i usually only come out to play at weekend.
So I need the thread size to buy a compression tester to check all is well

cheers
Ben

[craggle]

I think they are M14 x 1.25mm pitch

You can check this by measuring the outside diameter of the spark plug thread which should be 14mm or a little bit under and the pitch between the threads should be 1.25mm. If you have vernier or digital calipers you can measure this quite accurately.

Craig.

[BenBaron]

thanks again Craig

Ben

[wilf]

Many compression testers don't screw into the plug thread anyway - they just have a rubber bung that you have to press tightly into the hole.

[BenBaron]

Originally Posted by wilf

Many compression testers don't screw into the plug thread anyway - they just have a rubber bung that you have to press tightly into the hole.

mmm ok, do you turn the engine over by hand or via the starter?

[wilf]

Starter, and with the throttle wide open. Remove all plugs. Disable ignition!

Details here: Engine Compression Testing

[BenBaron]

Cheers Wilf, very helpful as per normal

[427scr]

Originally Posted by wilf

Many compression testers don't screw into the plug thread anyway - they just have a rubber bung that you have to press tightly into the hole.

They do, but they are useless if you are on your own or the plug hole is burried in the engine like on a Ford Zetec or down by the bulkhead like on my Cob. My advice is to buy a screw in one every time and make sure it has a pressure releif valve so that you can see the max pressure you are achieving.