[DougA]

A friend of mine is building a smallblock using the phase 5 bowtie aluminum heads and was wondering what spark plugs do you use,gasketed,tapered or both?Thanks

 

[engineguy]

Doug,
Look at the spark plug holes in the heads very carefully. If they have tapered seats, you must use tapered spark plugs, conversely if the seat area is flat and machined at a 90 degree angle to the threads, then you will need to use gasketed plugs.
See if you can find a copy of the GM Performance Parts catalog - it should tell you which plugs to use. I imagine that those heads use tapered small plugs.