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1275 Head Identification

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Blueghost

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Gathering parts for rotisserie rebuild of Bug Eye (floor replaced nicely and moving on). Regarding cylinder heads, "Tuning The A-Series Engine" 3rd edition, Chapter 9 Cylinder Heads, page 167, gives a good identification of heads. I have what is closest to Group D. 1 5/16" intake valve; 1 5/32" exhaust valve. Vizard (I understand he is THE authority) gives casting Number as 12G 940. Notes say "Good ports in standard condition." My casting number (under valve cover between cyl 2 and 3) is 12G 1316 - not 12G 940. My Intake and Exhaust valve size match Vizard dimensions. Head came off of a 1275, but of unknown history. As you read thru Vizard's description, and look at pictures, it is not the head on page 170 (sculpted by thermostat outlet); it looks like the head on page 169 - therefore not a turbocharged head.

Also Vizard gives a lot of detail about flow rate / capability with regard to intake and exhaust guide casting support area. Without measurements, mine appear to be better than the "bad" examples, but not as good as the "good" examples. This will not be a race engine, but I would like to get as much out of this head as economically practical.

Therefore, if head casting number 12G 1316 (as compared to 12G 940) is a good candidate for spending a little more money for significantly better performance, I'm in. If it is already a very good (later) casting and only needs standard valve job, I'll save money. If I have a lemon head, I'll look for another head. All informed advice greatly appreciated. Blueghost (particularly significant on Veterans Day).
 
Casting number 12G 1316/12G 940 = same head. 940 is an early head before SMOG requirements. 1316 has SMOG air injection ports. They can simply be plugged with a 7/16-20 bolt or better yet, a socket head set screw.
 
Any Spridget head, any casting number is good candidate for porting and making better. I offer both street porting, and full port and polish, street porting is half the price of full porting, On street porting I basically concentrate on the areas that give the most gain, bowl sizing, short radius,and a some port throat porting. If I can help give me a shout.
 
There are two variants of the 12G1316. Those with an 'X' over the center exhaust port just inside the valve cover area and those without the 'X'. The ones without the 'X' are better in the exhaust port valve guide boss area. Less material around the guide itself. Provides a better flowing exhaust port in stock conditions. The non-'X' 12G1316 and the 12G940 are very much alike sans the air injection ports on the 12G1316. Both varieties can still be ported to the same extent. For all out racing purposes, core shift characteristics come into play. Not much of a concern for street use and up to moderate performance applications.

HTH
Mike Miller
 
Thanks guys. Grey hair is great when it comes with actual experience. Mike, I do not have an "X" (better). (been married 33 years and don't want an Ex, OK bad joke) Also only looking for moderate performance. Gerard, yes it has SMOG ports. Does that mean it more likely have hardened seats? Again, money savings if OK. Hap, I did HP small-block Chevy machining in the late '60s and understand how important it is to port properly (helicopters since). Likely be in touch down the road. Again, thanks to all.
 
I've got a good bit more gray hair than "young" Hap. Probably more hair on top as well:friendly_wink:.

No hardened seats in any of these heads that I've been able to discern in 35+ years of racing these things. The exhausts usually get beatup and burned up after many miles on unleaded fuels. Odds are about 50/50 on needing exhaust inserts when I'm tearing down heads. Intakes are usually usable except for engines that have done a lot of miles.
 
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