On a lot of 64 dated 461 heads, I notice a 64 separate from the date, above and at an angle. Thought it was to designate the 1964 casting year but then I swore I saw it on a set of early 1965 casting date heads. Not all 1964 461" heads have the "64". Does this 64 have some other significance to these heads, other than having anything to do with the date? Thanks in advance!
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John,
Take a look at this webpage and read the posting by AZCamino.
Gary -
So I guess a more direct question would be if the heads with the "64" on them would be for 1964 and early 1965 solid lifter Corvette application? Or were the heads without the "64" also used for solid lifter applications.Comment
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461X heads were introduced in 1961 and installed on the both 275 and 315 HP engines, and ONLY these two small block configurations. That's how they got the name "fuel injection heads".
Their use continued in 1962 for 300, 340, and 360 HP engines, so at this point they were no longer exclusive to FI engines and were ONLY processed for the 1.94/1.5" valve set. The have a small quench zone on the spark plug side of the chamber, and port volume is supposedly in the 170-172 cc range with chamber volume about 60 cc. There use continued through the 1963 model year.
461 (non-X)heads were introduced for 64 and were machined for both the 1.94/1.5" valve size for 300 HP engines and 2.02/1.6" for 365/375 HP engines. Inlet port volume is alleged to be 160-165 cc, less that the previous 461X. Chamber volume is about 60 cc for the standard valve size and 64 cc for the larger valve set due to the chamber relieve machined on the inlet valve side by a 2.40" or 2.34" circular cutter centered on the inlet valve guide. The small quench are on the spark plug side remains.
462 castings were introduced for '67. The primary change was elimination of the small quench area on the spark plug side. I believe the spark plug may have been raised slightly, too. Port volume remains the same as 461, but due to elimination of the small quench zone on the spark plug side, chamber volume increased to 62 cc for the standard valve set and 66 cc for the larger valve set.
As far as the original question is concerned, it doesn't appear typical of a tooling number set, so I don't know what it means.
DukeComment
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Duke,
Regarding the use of 462 heads in model year ‘67 vs ‘66, the untouched motor in my July ‘66 built L79 has 462 heads on both sides. The date codes are E116 (LH); E126 (RH). I’ve read reports from other owners of mid-to-late ‘66s with 462 heads that the owners believe to be original to the car. I know of another ‘66 L79 with a March 8, ‘66 dated 462 head. David Luikkonen said the earliest 462 head he’s seen has a C 1 (March 1) 1966 date. That’s a long time for heads to sit around if only first used in the ‘67 model year.
Gary
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Thanks for the correction. I actually know that 462 heads could be on "late" '66 engines, but forgot to mention. However, I had no ideal they could have been on '66 engines as early as March '66.
Another interesting "anomaly" is the advertised compression ratios (all data from AMA specs). For the 327/300 from 1962 to '65 it is 10.5:1. For '66 it dropped to 10.25, which was more realistic, and could have been a little less than 10 with typical high decks. The advertised ratio was dropped to 10:1 for '67, which makes sense to account for the extra 2 cc of chamber volume of the 462 heads. This advertised ratio also carried over to '68 and AFAIK the '68 291 heads have the same head chamber volume as 462 heads.
Bottom line is that the advertised CRs of that era are way optimistic as were the power ratings, and actual as-built CRs could be as much as half a point lower than nominal dimensions, especially due to high decks because of broach tool wear, which was the greatest variable. I recall some years ago running nominal dimensions for the 10.5 engines through a CR calculator and the actual was not high enough to justify that advertised ratio.
DukeComment
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