340 X Head Value

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340sFastback said:
140k miles on my original 340 X heads unleaded gas valves never sunk? Wasn't an issue in my case. Do we have anyone reporting sunken valves with X heads, anyone?
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I agree with this. My machinist told me "If you aren't hard running it daily you'll be ok without hardened seats " But you are right it seems to be an old topic not heard much of lately and its brought up here to discount the value of the X heads. They hold their value as do the j's If they aren't worth anything they'd be cheap and people would be buying them up. There isnt 1 318 guy here that would pass on a set of them if they were cheap.
 
Dartswinger70 said:
I agree with this. My machinist told me "If you aren't hard running it daily you'll be ok without hardened seats " But you are right it seems to be an old topic not heard much of lately and its brought up here to discount the value of the X heads. They hold their value as do the j's If they aren't worth anything they'd be cheap and people would be buying them up. There isnt 1 318 guy here that would pass on a set of them if they were cheap.
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You are spot on. Dyno test show run an engine at 6000 rpm on dyno for weeks months on unleaded and valves sink. Do the same with leaded fuel or hardened seats they don't sink. So now everyone thinks hardened seats for unleaded are mandatory when 99 percent of engines aren't run full throttle non stop like that.
 
First time I heard of this was a friend's 318 challenger developed a bad missfire. Turned out to be bad exhaust valve or valves. Then a few years later a 340 with X heads I owned had been rebuilt without any attention to hardened seats. Not daily driven but seasonal driven developed a missfire and turned out to be sunken / bad exhaust valve seal. Repaired with hardened valve seats and have been happy motoring ever since. Approximately 10 years and 30 k miles ago. Just my experience yours may differ ??
 
My machinist a lifelong mopar guy said to not worry about hardened seats in my x heads that he freshened. Unless he said it's a 12 month daiy driver.
 
I just got of the phone with the machine shop, I have a set of J's with 2.02s there. i gave 200 deposit, and paid 280 shipped for the heads 2 or 3 years ago... hes saying for everything 450 so, 650 plus 280= $930 worth it ? its up to the person. Also, these days thats the price today who knows next year or 2027...:)
 
4spdragtop said:
My machinist a lifelong mopar guy said to not worry about hardened seats in my x heads that he freshened. Unless he said it's a 12 month daiy driver.
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I've heard the same...I had a set of 1.88 Js done last year. I think if someone is daily driving one of these cars there's probably a Magnum between the fender wells anyway...
 
I have a set of Js that were redone many years ago. I was asking $600.00 Canadian for them But I suspect they will be sitting on the shelf for awhile longer. Or until I build the last 340 I have. Kim
 
Dartswinger70 said:
I just got of the phone with the machine shop, I have a set of J's with 2.02s there. i gave 200 deposit, and paid 280 shipped for the heads 2 or 3 years ago... hes saying for everything 450 so, 650 plus 280= $930 worth it ? its up to the person. Also, these days thats the price today who knows next year or 2027...:)
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No, u can Speedmasters or SideWinders for nearly the same money. Kim
 
To each their own I'm just reporting what I'm spending now in my area of the East coast April 4 2024.If someone thinks I'm a fool that's ok too its what things cost ...it isn't 1991 any more. Anyone playing the old car game now is going to pay, it is what it is that's the game now. Guys that have had their cars done for years are the ones who won. This is why you see these guys on YT with junk and they are all proud of it...they are trying to change the game or play it different but junk is junk...same now as then . Truth is X and J heads are still the best factory small block heads of that era, and worth saving and rebuilding.. the price will only go up from here...the more guys who toss them for Speedmasters and take them to the scrap heap will make them more rare...:)
 
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340sFastback said:
140k miles on my original 340 X heads unleaded gas valves never sunk? Wasn't an issue in my case. Do we have anyone reporting sunken valves with X heads, anyone?
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I remember hearing about hardened valve seats in auto tech school in the early 90s, I've never seen an actual sunken valve though...I'd like to see pics.
 
I dunno... I think that if everyone tosses x and js for Speedmaster what happens if all of a sudden you cant go to wal Mart and get Chinesium any more.. ? I see an ooppotunity her for those guys who have heads... people will be saying "where are all the X and js..." "Over here rebuilt 1500 a set..." :thumbsup:
 
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