Engine failure question

[Moparteacher]

The piston-to-head contact can be a result of the failed bearing.

A misfire or abnormal combustion puts an extraordinary load on the bearing. A misfire can load up the cylinder with fuel resulting in a hydraulic cylinder and that crushes the bearing causing the bearing shell to lose it's crush and allowing the bearing to spin.

Detonation and/or preignition will crush a bearing also, resulting in a spun bearing and piston-to-head contact.

Piston-to-head contact is usually a result of a spun bearing and not the other way around, unless of course the builder is incompetent and fails to check clearance.

As already posted, resolve of the missfire is priority to making a run. If the run was made with knowledge of the missfire then the engine builder has no liability and the owner bears all.

Gary Weaver
College of Southern Nevada

[Chevy454]

Ok, stopped by my buddy's garage and saw the destruction, so let's jump right in...I apologize for the length!

In the cylinder that came completely apart, rod bolts broke, rod broke, wrist pin just about broken out of piston, cylinder split, etc, etc...usual destruction stuff. But, EVERY piston had been hitting the head, in the exact same spot, and looked exactly the same...so much the same, that it looks like someone had an assembly line set up! Anyway, the piston was hitting the head at the point in the combustion chamber where the valve reliefs come together (if that makes any sense)...every piston/combustion chamber had the exact same marks...like someone had taken a punch and repeatedly beat the aluminum head in this exact same spot...had to have knocked the point down close to 1/8 inch. As for the tie bar on the lifter, the lifter looks amazing considering it rocked sideways and lived through everything else...some slight scuff marks here and there, but it still rolls perfect...nothing like the solids I've had that had quit rotating. Now, to answer some questions...

1) It could, but I would expect the piston to take a bunch of damage before hurting the bearings, and the bearing damage should show up on the upper bearing only. If there is signs of heat and the whole bearing is torn, it isn't because of the piston to head contact.

The engine won't turn over a lick, but I had him pull another piston...you could tell on the upper bearing where it had been in a bind and had worn that way...no blueing or grooving, just odd wear marks.

Oh, and the obvious question, if there was a severe miss, why did he run/race the engine? That is just asking for destruction, and despite what was causing the miss, the operator assumes responsibility of damage if he chooses to run the engine that way.

Touche, but it was down to nut-cutting time, as the guy played the old "it'll be ready next Thursday, nope, we'll try for next week, nope, for sure by Tuesday, nope..."...it was basically down to the wire to get the engine in before the first pull of the season. But, here's something I only found out last night, when my buddy first fired it, it had a bad miss, so they pull a valve cover, and one of the rockers was mega loose, like it had never been tightened (he's running a girdle)...so he ran the valves, and fixed the miss @ idle...but under the heavy load of the sled, it still had a miss. Remember, this is a pulling truck, and with the gearing/setup, the only way to "test" it is to "hook" it...his first 2 hooks he didn't even complete because the truck wouldn't get out of it's own way, so he swapped ignitions and carbs I believe and on the 3rd hook the engine let go...

The piston-to-head contact can be a result of the failed bearing.

A misfire or abnormal combustion puts an extraordinary load on the bearing. A misfire can load up the cylinder with fuel resulting in a hydraulic cylinder and that crushes the bearing causing the bearing shell to lose it's crush and allowing the bearing to spin.

Detonation and/or preignition will crush a bearing also, resulting in a spun bearing and piston-to-head contact.

Piston-to-head contact is usually a result of a spun bearing and not the other way around, unless of course the builder is incompetent and fails to check clearance.

Exactly...but it would show up in the bearings, right? It was #3 that spit it's guts out, so I had him pull a piston *ahead* of that cylinder and check the bearings, as my assumption was the bearings should look worse furthest from the pump, right? Anyway, as mentioned above, they looked good considering the amount of junk in the engine, except for the funny mark on the top bearing. The pin was locked up also, and I'm gonna guess every other hole will be the same, seeing as the thing can't be turned over.

My buddy talked to the engine guy last night while I was there, but as you can imagine, it was kind of tense...the guy was real quiet, and agreed that it sounded like a clearance problem and even admitted that with that head/piston combo that that part of the chamber is supposed to be taken down...but then he crawfished back around and told us basically we weren't seeig what we were seeing...the main thing that worried me, is the guy had no idea what parts were in the engine, and yet he put it together within the last month? I just called a guy about an engine in one of our cars that put the engine together 19+ years ago, and the guy told us each and every part in the thing, and how it was set up...and my local builder can tell me everything about my personal motors as well...but this guy had NO CLUE.

The scary part is, this guy not only just built my buddy's engine, but his dad's engine, and another friend's engine...and they all have a miss, and one has a serious vibration...!

And I should mention, I understand not to expect a 5&50 warranty with a race engine, but at least check things out and give it a *chance* to live...

[doug schriener]

I knew some guys that put a BB Chev together and had wrong piston/head combo and had 'em all hitting the head.Just a thought.

[rx dealer]

A very expensive lesson!!! Why in the world no one DYNO these engines...If you spend this much money on any engine it should be on a DYNO and make damn sure at least it runs. Just common sense...Luke

[Chevy454]

Why in the world no one DYNO these engines...

I'll agree with that...all of my engines see the dyno before install, and I preach it to anyone that'll listen...but few do?

They actually got the engine builder to drive over today...we let him tear the engine the rest of the way down, and then digest what he saw. He showed little concern for the piston/head contact, and said he "always checked them, but didn't check that exact spot because it never hits"...he then said the contact was from the piston rocking over, but the contact had nothing to do with anything else. Only 1 rod bearing was spun (in the hole that came apart), but 2 others were working on it, but the rest just showed the odd wear mark that *I* believe was due to contact with the head, but he disagreed. 1 or 2 of the mains were on the way out as well, and the lifter failure has him stymied...the lifter tie rod split at one of the lifters, but all of the parts stayed connected, and there is only minor scuffing on the cam/lifter itself...granted, one of the lifters had to be drove out...oil pump was fine. His synopsis is that, for whatever reason, there was an oiling problem that caused everything, so it's not his fault...my thoughts were that if it was an oiling problem, wouldn't the cam & lifters show it? When I left, my buddy was offering to meet the engine guy half way on a basic short block the guy had rebuilt, but the guy really wasn't wanting to deal...

[Bob Pagano]

Sounds like the rods were never checked to see if they were round on the big end or they were honed without cutting anything out to bring the rod back to round within the proper clearance for bearing crush.

[CPOlesen]

I am not an engine builder!!!! I had a roller motor do the same thing yours did and it was caused by the engine builder installing the cam 12 deg fast. therefore the pistons hit the valves and the rest is history.

[55 Chevy]

I think that CP Oleson might be correct. Sounds like there was too little piston to valve clearance for some reason.
If everything isn't bent or broken you might be able to mock it up using whats left & see if there ever was ever enough p/v to begin with.

[Chevy454]

And the drama continues! I've been in Florida for a week, but when I returned, I learned that another engine this guy "built" for one of my buddies bit the dirt...if you'll recall, this guy built engines for 3 of my buddies (502 for a 2wd stock truck, 454 for a 2wd modified truck, and another 454? for a 4wd modified truck). Anyway, the engine in the 4wd modified truck grenaded just like the engine that I started this thread about...came out the oil pan, but ruined the block and anything that rotates, as well as all the valvetrain stuff...if you'll remember, the guy personally told me after the piston-->head contact fiasco that wrist pins DO NOT bend, well this latest engine blowup has several wrist pins in the shape of a U! Guess I at least got *1* thing right....LOL! Also, the vibration in the 3rd engine this guy built for my buddies (the 502), come to find out he'd put a 427 flywheel on it, instead of the extrenally balanced 454/502 flywheel...so they put the right one on, replaced a couple bearings, and that engine finally seems ok, at least for now.

The engine guy offered to eat the labor on this latest engine build for the 4wd truck, and then said he's only had 2 engine *EVER* fail, and it was 2 of the 3 he built for my buddies...my gut tells me #3 will be when my other buddies engine comes apart! He also screwed up a block for the guy whom I started this thread about...block was supposed to go .030" and get rebuilt, but the guy called and said he'd screwed up and went too big on one cylinder after adding new stones, so he was gonna have to go on out to .060"...