Thread: deciphering the carnage in my small block

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I posted yesterday that my truck was DOA on the freeway and that I took my spare block to the machinist. Today I removed the cadaver today and here is what I found. Sorry but I dont have any pics. Holes 1 and 3 have the pistons about halfway down the bore and the pistons have come apart at the wrist pins. The rods are both severed above the bearings. I found 2 studs still intact and holding pieces of the rod along with the nuts. I found one bent with the nut off of the threads and one sheared. There were 2springs in the pan that must have come from inside a couple of lifters. I haven't removed anything but the oil pan yet, but from what I can see there doesn't seem to be any grooving as if a wrist pin were rubbing the cylinder wall. I did see that the oiling holes in the crank seemed to have been elongated and one looked as if it had been hit with a punch.
The events leading up to the failure were pretty straightforward. I was on the beltway in drive and climbed right on up to somewhere around 3,000 rpm and shifted into OD. I dont have a tach but I seriously doubt that I was spinning more than 3500 tops. I have put about 5,000 miles on this motor since it was built last year. (yeah that sucks) I was running a decent piston at 9.25 on stock rods and studs. I have a very mild cam with flat tappet lifters. I dont have a lot of engine experience outside of the bike stuff, so I am wondering about the chain of events that may have caused this to happen. I will be putting together another motor this week and I would really like to avoid doing this again any time soon. Any theories and insight would be much appreciated.
Chris

Hard to say without seeing the pieces. Were the rods resized or magnafluxed prior to assembly??? Any bent pushrods or valves? Could be a rod broke and everything else is just collateral damage!!! What was the clearance on the main and rod bearings when the engine was assembled? How was the oil pressure when it was running?

oil psi up around 60 if my factory gauge is accurate. I dont know about the pushrods or valves yet, but there definitely has been damage to at least 2 lifters. What concerns me is where the rods are severed (at least 3/8" above the top bearing journal) and the one sheared stud. I am kind of leaning towards the stud letting loose and everything else just being done in the aftermath. I anticipate possible valve and pushrod damage. I really am hoping to be able to keep the cam on new lifters if I could, but if it is damaged at all its a no go.
With the new build I am using the ARP studs and the aluminum wrist pin buttons that were recently recommended to me. The crank that was in my spare is being checked out as well as the rods. If the crank is out of whack then we go 383. the block is to be align bored along with the typical decking and boring work. I am shooting for 9.8 to 10.0 with 0.040" quench and file fit rings. GM factory TBI with a chip upgrade, performer manifold and K/N intake. I am still up in the air about the cam if I need one. If there are any other suggestions as to preventative action I am listening!

the wrist pins could have frozen up that will break stuff up

Originally Posted by pat mccarthy

the wrist pins could have frozen up that will break stuff up

this time I am having the shop set the wrist pins up on a "slip" fit. They will hone the rod lightly until the pin drops down through the hole easily but doesn't just fall through in a hurry. I was really concerned about the wrist pins and made sure to check the cylinder walls for contact. I hadn't even considered that they may have just bound up. Thanks Pat.

Originally Posted by threearmsinjune

this time I am having the shop set the wrist pins up on a "slip" fit. They will hone the rod lightly until the pin drops down through the hole easily but doesn't just fall through in a hurry. I was really concerned about the wrist pins and made sure to check the cylinder walls for contact. I hadn't even considered that they may have just bound up. Thanks Pat.

KEEP THE PRESS on the rods just make sure you have a good fit i heat the rods and not press the pins in the rods this can make hard spots if done wrong . i all most all the time hone the pistons out a bit and oil the pins up good so they have oil on the pin bores on a fresh fire up

I wouldn't reuse the cam because all the metal chunks that floated in the oil, plus lifter damage. Shame about motor imploding.
Brad

#1 intake pushrod bent. multiple lifter bodies fractured, some still hanging around the pushrods. Heads appear to be ok but I will have to check them further.
Camshaft is sheared after the #1 intake.

Any ideas as to what would cause this? The shaft, lifters and springs were all a comp cams kit purchased 10/10/06.

One rod bolt bent with no nut and the other one sheared off.
Seems like maybe wrong torque on one rod bolt?

Sometimes it's the easy things: How did you set the valve lash? There's the way some people do it by spinning the pushrod of the rocker you're just setting between your fingers til you feel a slight resistance, then add half a turn.
If you use new lifters, which have no oil in them, then all that would cause the resistance is a small spring inside the lifters. That isn't always recognised as "enough resistance" and the rocker nut is screwed down til the lifter bottoms out. This way the valves will allways be held slightly open. This usually robs some power, but the engine will run. The drivetrain will fatigue very fast though and if you happened to make this mistake on a couple of cylinders then it's a sure way to wreck a lot inside an engine. Because of the fatigue of parts when one goes others which are going to go soon will go at the same time as a side effect with the added stress of vibration and metal shavings in the engine.
Post some pics and we'll possibly be able to tell you more (besides it would make an interesting pic to see anyhow...)
A Rod bolt going could break your lifters, if the crankshaft turned further and smashed the big end of the broken rod against the cam shaft. If the cam goes out you have the same effect as if your timing chain breaks: some valves are held open and the pistons smash against them from underneath, that'll almost certainly leave you no reusable parts in the whole short block, heads are most probably at least bent if not cracked, crank needs thorough inspection.
But as I say, where aiming in the dark here, it's all "could bes" and "I thinks" but no "that was a...".
Maybe this helped you none the less, but with a couple of pics there'll be more to say I guess.
GL,
Max

One theory. If you tossed a rod and it broke the camshaft, any valves back of the break wouldn't move. As the engine continue to run, you got piston-to-valve contact - which always results in bad things. Take a look and see if there are dings in the piston tops.

I soked lifters overnight in motor oil before installation.
there are two piston tops that made contact with the valve. Camshaft is sheared in at least 2 spots, the main section is now stuck in the block. It will spin but the bearing is shredded next to a shear point and holding it in for the moment. All told 4 bent,twisted or broken rods. 4 fragged pistons. 4 lifters in pieces( two of them were away from the cam fractures) 1 bent pushrod. crank rod journals are mauled. Long story short, we be buildin us another motor!

I was able to study what was left of the good pistons. There was the typical carbonization within the chamber. The skirts showed very little wear with no signs of dry start, overheating or igniton issues.
The lifter bodies showed also very little wear. my question about the lifter fatigue.......if it were a bad assembly, wouldn't the pushrods bend? Why didn't they go before the lifters fractured?

I really appreciate the MadMax's thoughts on the fatigue chain reaction. This is something I will really make sure to pay close attention to on the next build. I would love to be able to say it is 100% manufacturer defect, but I know in reality it may have baan something very little. pics soon for those interested.
Chris

By all means keep the press fit wrist pins as Pat says. To put slip fits in you will need to install bushings and drill a lube hole or holes in the small end. It will probably be more cost effective to just purchase new rods with slip fits if you are determined to have them. The only reason I could see for using them would be if you are going to be replacing pistons or rods later on.

We always used slip fits on the racers but they had aluminum rods. You use all the zippers you can when you toast a couple every pass.

[...pics soon for those interested]

Oh goody, us Carnasaurs love carnage.

man that is one major implosion, was there even 1 salvageable part?