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290 Head Castings on '67 343? Whatda?

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67 Marlin View Drop Down
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Post Options Post Options   Thanks (0) Thanks(0)   Quote 67 Marlin Quote  Post ReplyReply Direct Link To This Post Topic: 290 Head Castings on '67 343? Whatda?
    Posted: Oct/09/2015 at 9:13pm
Here's a fun one. I took the valve covers off to see if the rockers were getting too sloppy and I noticed the casting number is 3178453, a 290 casting. The valve cover ID indicates the motor was built on November 15, 1966. Has anyone heard of the factory putting 290 casting heads on the 343s they put together? Would a November motor be so early in the production run that things like this happened? The patina and old copper colored paint that still exists in some spots is the same on the heads, manifold, and block, so I think these heads came on the car and weren't swapped on at some point, that and the carb and distributor numbers match up to the '67 343.

I've listened to some Art Bell broadcasts in the 90s, so first thing I did was crawl under the car and see if there was a conspiracy brewing. Nope. Block says 343 like the last time I looked. You have to check these things; aliens would probably drive AMCs if they could, like any sophisticated race of beings would be reputed to do, and I wouldn't put it past them to abduct my Marlin while I'm sleeping and throw 290 heads on to irritate me.

I know 290s had smaller valves and slightly less compression. Don't care if I don't have 10.2 compression. Do care if it has smaller valves, because that means more $$ I spend when it comes time to rebuild. Can anyone tell in either of the photos, by the springs I guess, if these are small or big valves in the head? Also, how much lower would the compression be with these heads? My TSM says the 290 4-bbl motor had 10 to 1 compression, still pretty high IMO, would it be even lower with these heads on my 343?






Edited by 67 Marlin - Oct/09/2015 at 9:16pm
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Post Options Post Options   Thanks (1) Thanks(1)   Quote amc67rogue Quote  Post ReplyReply Direct Link To This Post Posted: Oct/10/2015 at 12:21am
Have no fear the aliens aren't here. The 67 343s have that head casting #. The valves in them are larger 2.0 in. 1.62 ex. They were rated at 10.2 comp. The 8558 castings were on 68 & 69s.
Keith Coggins 67Rogue X code
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Post Options Post Options   Thanks (1) Thanks(1)   Quote 401MATCOUPE Quote  Post ReplyReply Direct Link To This Post Posted: Oct/10/2015 at 4:36am
Keith is exactly right, that is correct head casting number, however I will warn you, they were very prone to cracking.  I "had" 4 sets of them including the one set on "george w" 67 Ambassador I just redid the engine on for him, every one was cracked and I ended up putting the 8558 heads on it since they are the same combustion chamber sizes.  Just remember AMC changed compression rations mostly by piston change, not head swaps in the same year on engine build....so no matter if your 67 was 2v or 4V it would have had that same head, a piston change would have altered the compression ratio.  If you are taking the heads off, make sure you get them magnafluxed, but if not don't stress on it just run it until you see a coolant leak.
Ross K. Peterson
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Post Options Post Options   Thanks (0) Thanks(0)   Quote 67 Marlin Quote  Post ReplyReply Direct Link To This Post Posted: Oct/10/2015 at 1:23pm
Excellent, this I like to hear. So, I've got one-year only head castings; this car gets more unique by the day. Wish they weren't "crackheads," though   
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