I baught a 340 out of a wreck 71 4spd Cuda should it have X or J heads?

J

Right, most would have J heads although it's possible it might have some with another letter. The "593" X-heads were being phased out in early 1970 and replaced with the "915" heads, some 593 heads made it onto 70 model year cars as well as a multitude of other letters cast into the same "915" heads; U,O,Z,J, etc. In fact some cars came with two different letters on the same engine, example one X head and one J head.

By the time 1971 production began it was a pretty safe bet that you would get "915" with the J heads.

What's the partial VIN# & is it orange or blue??

Most likely j's with 2.02 intake size, April 2'nd build on my car orange, with 2.02 j's.

And not only that:

Did the engine originate from the Windsor Plant (GW on the front of the block) or Mound Road Plant (GM on the front of the block)?

Bill Rolik

A body, Hamtramck. Bill this engine has all kinds of odd markings on the front drive side, When your free some time i'd like to give you a call to talk to you about it. Was their a strike at a plant making the 340's in 71? Mike

ademon,

I think he's lokking for the info contained in this stamping on the front of the block, drivers side just under the head deck surface.

Thanks for talking with me Bill, Your right after pulling the engine out under my bench it does have a very faint W after the G so it does read
GW340P33980351 X maltise cross and then a A4 under it just like in Scotts pic, i measured all the bores with a telesopic gauge and then measured it with my calipers and they all look standard at 4.04 definatly not .020 or bigger on the bores could be .005 as using calipers not as acurate. here are some pic's don't think the closeup will show with my camera. Thanks Mike
P.S. So mistery is why 11/16/70 assy in a 4/2/71 Demon 340 still continues?

another

another pic

Should the engine parts like intake and carb , dist, be 30-90 days before the engine asy date or the car build date?

BTW, the block I posted as an example has a 9-24-1970 casting date.

Funny, my block (assembled on October 16th) is my dads birthday, and your block (assembled November 16th) is my birthday.

last one

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Should the engine parts like intake and carb , dist, be 30-90 days before the engine asy date or the car build date?

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Generally speaking- the engine assembly date