Knock/rattle at lowish rpm. 455 *teardown/rebuild pg5*

The cam bearings look pretty chewed up.
That main bearing shell showing copper doesn't look good either.
Somethings up with the oil system, either delivery, or you have dirt in it.
I would at least check rod/main clearances with plastigage.

 

The crankshaft has fingernail catching scoring on the rod and main journals, so off it goes to the machine shop tomorrow

 

Good idea
Keep us posted!

 

Grind your crank last, after everything else is mocked up and near ready, or you will have trouble setting clearances.

 

Took the shortblock plus heads to the shop today. He will disassemble the heads, hot tank/magnaflux and inspect what is there, and call.

He says nothing looks damaged much, aside from obvious bearing wear.

 

Other than the bearings, found one piston "collapsed" according to the shop, says it was a few thousandths in diameter smaller than the others.
All new bearings, gaskets, TA stock sized valves, stg1 springs, a set of Speed Pro forged pistons, and a B4B intake later...she's been back on the road for about 3 weeks now. All is right in the world, except that pesky open differential

 

Was there ever a cause determined or was the damage considered the result of 'someone slamming this together' carelessly?
What changes were made from the last version, aside from the parts?
Tuning, blueprint clearances, plug heat range, etc.?
Any theories on why detonation was or wasn't an issue?
I know detonation was never really concluded with discussion, other than the visual indicators like bearing 'wear' with patterns suggesting more than just a grit problem , collapsed piston skirt, and a description of 'I heard a slight hammer or knock like bearing/s' at a low rpm...

 

Never got a specific "this one thing was wrong" that was making the noise, but there were obviously issues. Guessing it was just a quic backyard rebuild. I did the oil mods, cleaned up some flashing in the lifter valley, triple checked the distributor and put everything back together with fresh ARP hardware. I dont have clearances at hand but bearings and pistons were checked once it came home, should be a good healthy motor for a while

 

Where are you using the fresh ARP fasteners? If connecting rods, were they resized with the new fasteners? Also if you install main studs, you will need an aligh hone with them too.

 

X2

 

When people are suggesting looking at more than what would be encompassed within a sloppy backyard build based on seeing these failures on a daily basis and how they occur...it might be prudent to put some more thought into it, even after getting it running.

I'm definitely not trying to shake some of the enjoyment of your vehicle, as it does seem like you went through it thoroughly after the failure.
I hate to see a situation like a shop saying, "yup, it's all fixed now..." and running into further problems that lead to blame to the shop or the brand as so often happens.
There's often more going on than one singular cause, especially with the general carelessness that goes with sloppy builds.
I'd hate to see this impressive piece of machinery fall victim to further damage from something that slips by so many like detonation or pre-ignition as result of improper tuning.
The piston could have been installed that way, became damaged from det., etc.
It very well could have been the cause of your light rattle at low rpm, but maybe not...I've seen .010-.013" skirt to bore clearance NOT make noise except a very slight cold rattle for 3 seconds at startup and I highly doubt yours were installed that loose.

The point of being overly vigilant about detonation is that IF it was det. you were hearing, even briefly...keep in mind that it's already at a magnitude of 10 on a 12 scale, with any magnitude below 10 being inaudible still extremely dangerous to the engine.

It's always a good idea to inspect the plugs closely from any failed engine, as well as everything else, so that the same issues don't follow the new build.
It's also imperative to dress down or deburr the newly created sharp edges left from fresh machining on the head deck so as to eliminate a new source of det. trouble as well as be cognizant of other hot spots such as valve jobs with an interference angle or otherwise narrow contact keeping the exhaust valve too hot.
I second the need to resize things after installing better bolts.

 

Head bolts and Rod bolts from ARP. The rods were resized. Stock mains, I read that for my relatively mild uses that the ARP's were overkill.

The heads were not decked, but did get a valve job. I'm not quite sure how to check for detonation that I can't hear? It's currently on the conservative side of the "power tune" recommendations, with AC Delco R45TS plugs, and the TBI EFI controlling air/fuel. 91 Octane Chevron is all that I have run for fuel. Too bad there is not a "knock sensor" I could read like a modern car, but my understanding is that they are tuned to a specific frequency for each engine.

One other odd thing, the stamped valve covers were flaking chrome off on the inside, I grabbed some TA ones to rid yet another issue during the rebuild

Thanks for all of your continued input

 

45 plugs are hot for anything more than 8.5 comp. That combined with some or all of the following:
a hot day or hot running and only 91 octane....throw in a lean TBI/possible vacuum leak and too much advance (I see it was at 38 deg at one point), cam timing off and it will kill itself. Once damage is done resetting things isn't going to save it.....
Just sayin......

 

It's great that you found the flaking valve covers, that's a huge problem...despite any allegations of a sloppy build.
That could have been much of what you were seeing right there (except for the collapsing piston)

ANY timing curve modifications for performance should be watched closely for detonation.
The vehicle owner/tuner is far from blameless saying they simply followed a guideline, and as suggested...all it takes are the right circumstances to push it over the edge when it's close to the line.
Since you can't hear 90% of destruction before it's too late, it's imperative to look closely at plugs for signs of det. and heat range/timing indications easily left on the plugs.
The engine does not tolerate the same things all around the nation, nor do heat range cross charts ensure 100% reliability.
You'll have to google plug reading or look them up here, there's more too it than rich or lean.

The last thing I'm trying to do is make you feel bad
When the thread is titled what it is, it bears mentioning and follow up.
Your heads could have been surfaced by the guy before you and still have sharps.

 

Using the ARP rod bolts isn't overkill in this case.
It forced the honing of the rods to ensure roundness after a destructive event or build.
If the engine was run hard at any time in it's life, they were likely out of round anyways and that could have contributed to the bearing/crank contact witness marks seen in your one pic.
Piston skirt subject to same things, including the fact that the previous simply reinstalled them that way.
I'm surprised to see the bores not cleaned up with new pistons/rings installed.

With plugs, start a heat range or two colder and note what happens.
The mild builds are more sensitive to low speed det. issues because of the smallish cams having a strong low end cylinder pressure curve coupled with low stall converters, mild gears and heavy curb weight.

Nice looking ride!