This story is a good reminder that checking and re checking everything , even with new parts Is needed .
I got a call from a guy a few years ago who just had his 350 rebuilt and it was making a lot of noise. He sent me video of the engine running in neutral and running down the road. he thought it was spark knock, but nothing changed the noise when he fooled with timing or fuel. it made the noise mostly under light throttle and in neutral if brought the rpm’s up and let it float, it would rap like crazy
he sent me a video of it…I told him it sounds like a wrist pin, more than one. he pulled the engine and brought it back to the builder who tore it apart..he said the builder checked everything, bearings looked perfect, the bushing in the rod was perfect, no scuffing ok skirts and clearance was good.

Cam and top end was checked, all good. put it back together and it made the same noise. he put less 1000 miles on it and it kept getting worse. he gave up and parked it,, totally disgusted. fast forward to a couple days ago and he called me asking if I was interested in buying the whole engine or parts from it …he gave up.

it had a lot of good stuff in it, 330 crank, bushed 403 rods, Diamond forged +.040 pistons, nice pan, HV pump, good cam and lifters, 7a heads worked on and a performer RPM intake. I bought most of it. while looking at the rods, I slid a pin in and it felt good. then tried the pin in the Piston and it was sloppy…checked the others and all were super sloppy…he looks at me and says WTF ? that’s your problem…he’s like Jesus Christ. It’s been 7 years fighting this thing and over $11,000 down the drain.

when I got home I measured the pin and the piston pin bores. they had .980” pins in a .984” pin bore. Looks like Diamond supplied the wrong pins . Diamond like many others use a .984” Chrysler pin in their 350 Olds piston because they are more common and there’s more pin choices.
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here’s the Piston specs from Diamond .

 

 

Do you see evidence of any induced damage on the piston bores? What a sad story.. The kind of stuff that makes people go corporate or LS.

 

Holy, that sucks.

 

That's crazy that the builder missed that when checking and assembling the pistons and rods.

 

The Mahle 350 pistons have that size as well, rods need a hone.

 

the rods were bushed and ok. Active Engines in Mississauga built this thing, it sounded like it was full of marbles

 

true..but a hack who just put some assembly lube on them without checking them dry first, would probably never have felt they were loose

 

loose pins won’t hammer the walls..it’ll eventually pound the pin bores out of the piston.

 

the 350 was in a 70 W31. he ended up selling all his Olds stuff and bought a 74 Mustang Grande🤢

 

here’s how a correct .984” pin fits..perfect

 

That's even harder to hear. Yeah, hard not be pissed. Something simple but a nightmare if they screw it up like this. A 1974 Mustang Grande, boy did he ever give up on life.

 

That's crazy, and sad!
Did this egg the pin bore of the pistons, if so could they be honed to .990, correctly?

 

I did a dial bore gauge measurement today..they’re fine. Still have the original honing cross hatch marks. being a good quality forging helps.

I doubt a cast piston would last very long. I was wrong on the mileage. I picked up the rest of the parts today and he told me he only drove it 360 miles total after the rebuild.

 

I misunderstood you. The piston pin bores are ok

 

There's a reason why I don't use Diamond for anything, a lot of people love them, but not me.

 

Where has the quality control gone?
Sad that yet another company previously thought of as "high quality" has gone low, this should've been an easy catch before shipping out.

 

They have always been sketchy...................this didn't just start lately.

 

Thanks!

 

All good. I appreciate your constructive feedback, perhaps I was not clear about my concerns. I truly hope that you all can come to a reasonable solution. Take care!
I certainly do hope that the op can come to an agreeable solution to provide some mutual benefit.😃