Mark...more questions

[Steven C.]

I am running headers (gasp...the "H" word on this forum!), what do you mean about incorrect spark plug sizes? Is there a particular casting number that will bolt in place, with necessary mounting holes (PS/alt)?

Thanks

[Mark #28455]

1969 vs. 1970

The 1969 heads used the gasketed spark plug with 13/16" wrench size whereas the 1970 and later used the taper seat plug with 5/8" wrench size. It is a visibly smaller spark plug (at the metal part). Then again, unless you really look, would you notice?

All BB heads have the necessary mounting bolt holes for the front mounted accessories, but some heads use 3/8" bolts while others use a mix of 3/8 and 7/16. You would have to look to be sure.

I had a set of the service replacement heads - either casting number 6272990 or 14096188 - still sold as part number 6260482 I think, on my 1969 L89 for about 20 years and they worked without a glitch. They used to sell for about $500 to $600 a head new from GM, but they may have been discontinued. You can easily find them at swap meets and on e-bay for a lot less than the correct casting number vintage heads.

Mark

[Steven C.]

Thanks, Mark! *NM*