The 1966 judging manual (pg 69) calls for black phosphate hex head "M" Intake Manifold bolts while I see many suppliers listing Zinc coated - Noland Adams (pg 355) black and white pictures of original L72's seem to show zinc. Can you clarify correct scenario ?
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Re: 66 L72 Manifold Bolts
I own two L72's and both have "silver" intake bolts (originals - neither engine has been rebuilt, and one is a Bowtie car). I don't know if the silver is zinc, but if I recall correctly, big block intakes did not get silver paint like small block aluminum intakes, so the silver is not paint. -
Re: 66 L72 Manifold Bolts
Thanks for your comments - What's confusing is that you confirm (original Bowtie car has zinc or silver appearence - not black) what I suspect and that is L72's had zinc plated intake bolts as stated in my previous post - yet the NCRS judging manual states known observed originals to have black phosphate bolts. I am curious as to how many cars are observed to set a standard? Obviously if full points are desired then one needs to install what the manual suggests - however - I can not help but wonder what reality was on the line was.Comment
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Re: 66 L72 Manifold Bolts
Peter-----
I think that this is likely a case in which a "one-size-fits-all" approach doesn't work. I suspect that BOTH bolt finishes were originally used in PRODUCTION. As far as which predominated, I could not say, for sure. However, I suspect that the zinc plated were the pre-dominant variety. The engine plant may have used the phosphate bolts for to-be-painted manifolds and the zinc variety for aluminum manifolds. But, I'll bet they weren't too careful about this and, if the zinc variety ran out, they wouldn't stop building engines for the lack of them. Plus, the assembly line folks might not have been too careful about which was used, even if they had both available.
If it were me, I'd assume that my engine came with the zinc bolts; they look better on an aluminum manifold. That's why they were used in the first place.In Appreciation of John HinckleyComment
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Judging Guide
Has anyone EVER seen black phosphate bolts on ANY big block with an aluminum intake (regardless of the year)? I never have, and I look closely at every big block I encounter - Regionals and Nationals included. I have owned two Bowtie big blocks and neither had black phosphate intake bolts. In addition, my '65 396 also has zinc bolts, and it is an unrestored car with the exception of body paint. I think it is likely there was some sort of "cut and paste" error in the Judging Guide whereby the data for small blocks or non-aluminum intakes was inadvertently included for aluminum intake big blocks. I know a fellow who is working on Judging Guide edits and I will take the question to him.Comment
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