I have a looking for advice on the best spark plug for this engine. I have read about 100 threads on this subject but have not found any that were using a setup like mine. Here is what I have.
489 BBC stroker, fully balanced with all forged parts
Large Oval GM 820 heads fully ported 2.19, 1.88 valves
Cam with 540,550 lift / 230,235 duration
Aftermarket Holley MPI
EMI exhaust
9.2 to 1 compression
Aftermarket computer controlled ignition
always use 91-93 octane fuel

I am using currently using Bosch Platinum +4. I recently read an article in Hotboat that stated the +4 design could actual drop HP? Any input would be appreciated.
Thanks,
Jeff

Your combo is not that extreme. No need to run Platinum plugs. They are probably too hot anyway. I would just run some AC Rapid Fire #1's.
They are the equivalent heat range of an AC 43.

My engine is kinda similar. 489 ci, Merlin heads, 10.1 to 1 compression, .612" roller.
I run NGK plugs. I don`t have # in front of me, but is equivalent to R43TS AC Delco. Always had good service from NGK plugs.
Pull those Bosch plugs and throw them as far as you can ! Total crap...

Thanks for the reply's Guys, it seems as though most people are using the NGK or AC Rapit fire's. Anyone know the best part numbers?

What is the difference between the NGK bpr6es and the br6fs?

Thanks,
Jeff

600hp 9.4-1 BBC 509ci iron head, taper seat plugs.
NGK R5674-9 v-power racing stock number 6468

this plug has worked well in all my BBC's (iron head) with msd almost never fouls. And even then will clean out under power.

Last time I check Bosch Platinum +4 where never tested and aproved for BBC. Where you getting a listing from?

Indexed traditional plugs will get best result from what I have read. 1-2% max gain if done properly.

I don't know what the part #'s are the boat is in storage. I bought them at Advanced. I think I had them look up the part number for the 2500 454 pickup .

I have heard about this recently and will probably try the NGK plugs BR6FS, using the indexed method.
Thanks

I just installed my new plugs and used the indexing method. This was kind of a trick getting them all in the right position. I spent a little time moving the spark plugs around the different cylinders. I got them all pretty close but only a couple were right on. Anyone else have any input on how they have done plug indexing?