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#1
10-03-2009, 02:16 AM
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291 Head Differences
I have 2 3964291 rectangular port heads. Both are cast D 23 70. The strange thing is the heads have "HI PERF" cast into them. This may be common but I have never noticed it before. Here is a picture of what I'm talking about:
 Jason  
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#2
10-03-2009, 02:20 AM
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Re: 291 Head Differences
 
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#3
10-03-2009, 06:13 AM
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Re: 291 Head Differences
Make sure they are both machined for the same style spark plug too.
__________________
...................... John Brown This isn't rocket surgery.....
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#4
10-03-2009, 02:41 PM
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Re: 291 Head Differences
2 different styles of "HI PERF" being cast the same day is interesting.
Like John Brown said, check to see if they both take the same style spark plug.
__________________
Rick 69 Chevelle SS396 Silver L78 M21 Post Sedan (Berger Chev.) 69 Chevelle SS396 Black L78 4-speed 4.10 Post Sedan  Don't text and drive. Somebody's life may depend on it!
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#5
10-03-2009, 04:58 PM
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Re: 291 Head Differences
To my understanding, the Tonawanda foundry had multiple molds for the same head, with some having slight cosmetic differences from one to the next. I am sure some of the site members here can give a clearer answer on the subject
__________________
70 L78 Nova Fathom Blue,Bench, 4spd, F41, 3:55 71 Porsche 911 Targa
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#6
10-03-2009, 05:29 PM
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Re: 291 Head Differences
[ QUOTE ]
Make sure they are both machined for the same style spark plug too. [/ QUOTE ] Also, make sure they're cast for the same size valve seat...
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#7
10-04-2009, 03:33 AM
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Re: 291 Head Differences
They both use the same style park plugs and look to have the same size valve seats. I guess there were just different molds. Learn something everyday.
Jason
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#8
10-10-2009, 03:55 AM
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Re: 291 Head Differences
To be more precise, high-volume castings had multiple PATTERNS (made of cast iron or stainless steel); when sand was packed around the pattern, it created a sand mold. The sand mold was opened, the pattern was removed, and the mold was closed. Iron was poured in the sand mold, and the sand disintegrated on the "shake-out" table after cooling, when the raw casting was removed.
Each pattern was numbered and carried the casting number, casting date and hour clock; that appeared on each casting, and enabled internal traceability in the foundry back to the pattern in the event of a problem with a casting. The casting number, casting date, and pattern number were individual brass characters soldered to a brass plate that was pinned or screwed to a recess in the pattern; the date tag was changed every day, and the clock tag was changed every hour. Photo attached of tags from the Saginaw Foundry.
__________________
'69 Z/28 Fathom Green CRG
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