hot_post in 1969 340 4bbl with X-Heads in What's It Worth? Author Topic: 1969 340 4bbl with X-Heads  (Read 692 times)

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Re: 1969 340 4bbl with X-Heads
« Reply #15 on: October 08, 2018, 09:17:19 AM »
Maybe its me, but I struggle to understand how .040 over is considered perfectly fine but .060 over is a time bomb.  That's a difference of less than three sheets of notebook paper per side in the cylinder wall.  Doesn't jive with my (admittedly limited) understanding of strength of materials from college.
     You're seeing opinions from different experiences.
     340 was engineered to rev at higher rpm to make power.
     Thinner cylinder walls doesn't necessarily mean splitting wall or windowing the block.
     Thinner walls mean more wall deflection resulting in blow-by past the rings... I.E. loss of
     potential power.
     Any block with .100 or less wall thikness (esp. on thrust side) is a grocery-getter to me.  Do
     your self a favor and sonic test any block you want to make good power first.

Offline 340challconvert

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xx in 1969 340 4bbl with X-Heads in What's It Worth?
Re: 1969 340 4bbl with X-Heads
« Reply #16 on: October 08, 2018, 02:22:57 PM »
I passed on a 70 340 engine slightly built up w 30 over.  Ran great, went for $2500
 :wrenching:  Thought it was a fair deal
« Last Edit: October 08, 2018, 03:14:25 PM by 340challconvert »
1970 A66 Challenger convertible

Online Katfish

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Re: 1969 340 4bbl with X-Heads
« Reply #17 on: October 08, 2018, 04:32:00 PM »
Following along, I also have a 69 340 with x-heads.
Been driving the car for the last 20yrs, curious WIW also.
Putting together plan for a Gen3 swap, so the 340 will eventually go.

Was thinking ~$2k also for a complete running motor.

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xx in 1969 340 4bbl with X-Heads in What's It Worth?
Re: 1969 340 4bbl with X-Heads
« Reply #17 on: October 08, 2018, 04:32:00 PM »

Offline Fastmark

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xx in 1969 340 4bbl with X-Heads in What's It Worth?
Re: 1969 340 4bbl with X-Heads
« Reply #18 on: October 09, 2018, 05:22:58 AM »
The trouble I had with a .060 motor was a race motor that I just freshened up. We honed it about .002 because the previous builder had the forged pistons too tight. It ran about 25 passes and went .2 faster and then started putting water in the oil. Pulled it apart and found a pin hole in the cly. Had to sleeve it. It had a big hole when we bored it out for the sleeve. The inside of the cast cly walls are not smooth in the first place and you add water and they can form rust pits. A sonic test would not have caught this hole. It was a thin casting with bad core shift from the factory.

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Re: 1969 340 4bbl with X-Heads
« Reply #19 on: October 09, 2018, 06:08:56 AM »
   Holes/pin holes are pretty rare. Core shift is not. Sonic test would've caught core shift. Some times core shift is obvious by eye. Big blocks are easiest to spot this.

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xx in 1969 340 4bbl with X-Heads in What's It Worth?
Re: 1969 340 4bbl with X-Heads
« Reply #19 on: October 09, 2018, 06:08:56 AM »

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