I run a 468 cu in chev twin set up at about 420 horse ea. What plugs would you recomend. Currently the book calls for an NKG br6fs. Thanks Rick G.

ngk racing plugs are shorter r5674-, ive run these with good luck . the mrt45 also.

The best plug I have found for these engines are the Champion RV15YC4 plugs gapped at .045 inches. They are available at any auto parts store.

Dennis,
What do you recommend in the Mercury 500 EFI. How about the Mercury 525 EFI.
Thanks, John B

The 500 EFI works well with this plug but I don't know about the 525 EFI. It won't work in the 496/8.1
The Champion RV15YC4 is the best bargain in the boating industry.
Sincerely
Dennis Moore

Thanks guys. Rick G.