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Possible to tell if this 340 has ever been rebuilt?


FBBO Gold Member
FBBO Gold Member
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10:02 AM
Oct 3, 2012
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I bought a driveway find 73 RR that sat for 10 years last year. I had lots of help from members while I was evaluating the car. The car was stopped mid restoration in 2010 and I have really no idea after that.
Today I decided to make sure that the 340 motor could turn two full rotations. I am months from trying to start it since the wiring is toast.
I removed the valve covers, put some oil on and let it sit. I then removed a few spark plugs and I was able to get it to make it two full rotations.
So, I’m pretty encouraged that the motor is in decent shape but I was wondering if anyone can tell based on stamps on the rocker arms if this motor looks untouched. It’s got a thermoquad on it so I’m thinking it’s never been rebuilt. Comments or help is welcome!

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If you remove the heads you can see if it has the original
mopar head gasket on it. It would not have been reused and that
is most reliable indicator!
If the engine is not overbored it "might" be original but no guarantee
on that.
From that picture, all I can say is it looks fairly clean. The 383 that I'm building right now, had never been rebuilt and still retained color on the valve springs. I'm not sure that a 73 340 would have had color on the valve springs or not. Mine is a 67 HP 383.
I have been buying and taking motors apart for years. Trust me, the motor needs to come apart. Sitting for all these years plus the fact it’s 50 years old, means rings are gunked up and the valves seals are in pieces. Most bearings on an original motor are down to the copper. At least pull the pan and a rod cap. You’ll find out very quickly what you need to do. If it has been rebuilt, the bearings will have dates on them.
If you fire it up, and hear lifter ticking and rod knocking, and if it smokes worse then Cheech and Chong, chances are it’s never been rebuilt
It's pretty common on budget rebuilds to re-use rocker arms and carbs, so those will tell you nothing. I would oil it, do a compression test, take the carb apart and clean it out, hook it up to a gas can and fire it up. You need minimum car wiring to start and run and engine. No need to wait.
Thanks again everyone!
My 70 has taken precedence due to final shakedown issues. Hoping to get back to the 73 soon! But, anyone that shows up with 15k can have all parts I’ve bought and the 73! Started a new job and barely get a chance to drive them anymore.
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