1971 340 L2316 pistons stock, modified or damaged?

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Stroked408

Stroked408

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I picked up a 1971 340 a couple of weeks ago and I was wondering about the markings/grooves on top of the pistons. I'm not a expert on building engines or pistons, but I was curious as to whether the previous owner had cut into to them or possibly installed them incorrectly. I included a picture of the same piston being sold on ebay. Either way, I plan on stripping down the block and starting from scratch. I plan on using the stock J heads with the rebuild.
Let me know what you think.

piston 1.jpg


piston 2.jpg


piston 3.jpg


piston 4.jpg


piston 5.jpg


piston 6.jpg


piston 7.jpg


L2316 piston.jpg
 
Houston we have problem here!
At some point in time valves made contact with the pistons, their are now junk.
That hard of contact can cause problems in the rotating assembly in particular with the rods.
Replace the pistons and have a reputably engine builder inspect the rest of parts before reusing any of them. My first guess would be that someone put in a cam with to much lift and/or the wrong ratio rocker arms in it. Or the pistons were installed incorrectly.
Good luck
Edit: I now see that others members have agreed that the pistons were installed incorrectly.
 
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The pistons are 180 degrees out of position with where they're supposed to be in the bore. Those are witness marks made by the valves trying to make new reliefs! Every valve in the heads are bent, and the guides are probably cracked, too.
 
Ha! someone installed the pistons upside down. I bet that hammered pretty good with some RPM. Probably bent some valves.
 
Yup.......they’re on the rods 180* out(or the rod is installed backwards. Squirt hole goes towards the cam.)

Shoulda made quite a racket.
It usually raises hell with hyd lifters too.

Those pistons are about 1/2” thick in that area.
They’re probably fine, but I’d check to make sure the skirts aren’t folded in.

If they’re still being used with bushed rods, it’s easy to flip them around on the rod so they’re installed correctly.
If you end up doing that, use new snap rings.

Very likely a bunch of bent valves...... but, even if for some reason they’re not bent...... take them out of the heads and throw them in the trash.
It’s a catastrophic failure waiting to happen.
 
Stroked408 said:
I picked up a 1971 340 a couple of weeks ago and I was wondering about the markings/grooves on top of the pistons. I'm not a expert on building engines or pistons, but I was curious as to whether the previous owner had cut into to them or possibly installed them incorrectly. I included a picture of the same piston being sold on ebay. Either way, I plan on stripping down the block and starting from scratch. I plan on using the stock J heads with the rebuild.
Let me know what you think.

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Like already stated, the pistons are upside down...

and they are not stock, especially with .030 stamped on them... They are .030" over sized because the engine has been bored .030" over...
 
How many are damaged? I have set of those in the same size if your worried about reusing them.
You could probably polish the damaged areas, make sure the rings move freely and replace the rods, or at the least have them checked. That pistons quite durable.
I also have some stock rods with arp bolts ready to go.
Valves need replaced if that was done on your engine, cam checked, pushrods.
This could get expensive.
 
Another possibility is that whomever assembled the engine installed the rods and all backwards. East to tell. Remove the oil pan and remove a rod cap. The bearing lock tangs should be pointing towards the outside of the engine, not toward the center.
 
RustyRatRod said:
Another possibility is that whomever assembled the engine installed the rods and all backwards. East to tell. Remove the oil pan and remove a rod cap. The bearing lock tangs should be pointing towards the outside of the engine, not toward the center.
Click to expand...
Oil squirt holes squirt towards the cam. Small block Mopar 101 (most engines are like that)
 
toolmanmike said:
Oil squirt holes squirt towards the cam. Small block Mopar 101 (most engines are like that)
Click to expand...

RIGHT! but "not all" have the oil squirt holes, that's why I use the bearing lock tangs as landmarks.
 
That's unfortunate, Someone wanted to be an engine builder.
But that is how you learn, or go to school, Right !
I like to see kids trying, but start with something that doesn't matter, A lot of Chevy motors out there to practice on.
 
pretty basic error there, which would make me suspicious of EVERYTHING. Tear down and check every thing. I agree with most other comments. Make sure connecting rods are not bent, too.
 
Let me guess, the guy you bought it off of said it wouldn't start.
 
Cudafever: the guy was honest about engine condition and who had built it previous to him owning it. He had it in his Duster and said it was a dog. He pulled it and ran with a 360 instead. Unlike some sellers who wouldn't take the time to let someone open up the engine, he insisted and we took off the heads to inspect. We agreed on the sale price after this was found. I didn't jump in and just lay down the cash before inspecting it. I do plan on tearing it down piece by piece. I do plan on using all new parts as well.
 
he put them in backwards to make more power with off set pins ,HAHA
 
Make sure you check the cylinder walls good. I dropped a valve once and thought I got lucky and was going to replace the head and piston. Cylinder wall looked great but was pushed out in the middle about .010 had to sleeve it.
 
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