Which spark plug for twin plug

[quint22cp]

Situation;

3.2L Euro with nickies to give 3.5L 10.5:1 CR
Present spark plugs (6) are Bosch WR4CC

I want to twin plug and I'm going to do the machining myself.


What option do I have and which way do you think I should go ?

Looking through old threads I can see that the following have been used; NGK R5671-8, NGK 6EkUB, BR8EIX, but now I'm more confused to which plug I should use.

Help...........

[cgarr]

NGK DCPR7E this is the 12mm plug which left more meat on the head when I did mine. Otherwise mine sounds much like your engine setup.

[tadd]

Use the 12mm plug. An inch endmill works out real close the edge of the heads and even with wax it is hard to keep from breaking the first three.

The key is the wax. I used canning wax (gulf, IIRC). Just make sure the head is really clean so the wax can grip and then beat the wax into the fins in nickle sized pieces with a plastic mallet.

I've done three sets so far and broke only one fin cause I got lazy and didn't clean them well (the chips push the wax out).


tadd