I Sherlock'd My Dead Big Block Chevy and Found Out Why It Broke!

Episode 282 of Finnegan's Garage is all about discovery how and why my all-aluminum 632ci Big Block Chevy Nitrous Motor broke during the World Finals of Drag Boat Racing last November. It was a disappointing racing weekend to say the least. We travelled from Georgia to Arizona with high hopes that we could be competitive in two different racing classes. Instead of running with the big dogs we struggled to go as fast as we had in the past when this engine was naturally aspirated. After hours of disassembling the engine, carefully measuring and staring at parts, now we know what happened. Check it out.

Want more info on the tools I used in this video? Here are some helpful links:

Moroso degree wheel

LSM Spring Removal Tools

LSM Spring Pressure Tester

Summit Racing Outside Micrometer Set

CP-Carrillo Pistons and Rods

Thanks for watching!
-Finnegan

[davelara]

Look at the ramp rates of your camshaft. If the camshaft design accelerates your valve train beyond its ability to control the valve train it will beat everything to death. If springs rockers pushrods can’t maintain contact due to acceleration they are toast. Sometimes it’s the camshaft design not the valve train.

[dustydon]

Finnegan you are a true gentleman. You never criticized, blamed or blasted the engine builder.
There’s so many things that can wrong when you’re dealing with anything mechanical. We all have bad days and make mistakes. I’ve always believed it’s how we handle our mistakes after the fact. That’s nobody’s business but yours and the other party.
Yeah, I get a lot of enjoyment watching what you do. Thanks!

[WTFvr]

Unless the rings are pinned (like a 2 stroke), the rings are constantly rotating when the engine runs. When you install them you set them at 180 degrees from each other with the gaps parallel to the wrist pin, to prevent them from gouging bore on first start before the rings are broken in.

[smckenzie]

The valves could have created their own clearance from the contact. Only way to know for sure is to check with "undamaged parts".
I love how you handled this topic and I'm glad the culprit was found.

[cabrini]

I really like it when you do this level of detailed engine teardown.

[GorhamWorks]

Mike at FSM, world class quality assurance, you build it he breaks it, and you make more power next time. Proven formula!

[freedomfox]

Your theory is pretty spot on... Engine builder overlooked some important details unfortunately and they were just so so close that it wasn't immediately noticeable on the problem or cause but that definitely answers why you kept breaking springs

[ericbrennan]

Man you are an awsome dude. Humble enough to take the human variable into account. You know that he is one hell of an engine builder. And I am glad that you are not playing the blame game. Keep up the good work.

[SteveMelissaMcAdams]

Pete's a magic man he can fix it. He's Real Good at Doin Stuff

[BCaldwell]

Awesome content man! Thanks once again for sticking with us here on YouTube, A bunch of us really appreciate

[lamarw]

It takes more work to build something from a mesed up situation than to build something new. Fixing a mess up in a hurry leads to more screw ups. Yet, we're racers and want it done now to make the race tomorrrow. It happens. Hope everyone can remain friends and we're all back racing. Yes I am speaking from experience. Granted on a lower budget.

[chennemeyer]

With so much interference, piston to basically all valves, its amazeing that it held together. I think its a testament to the very high quality parts that were used to build it.

[jerrybattisti]

That's a Bryant crankshaft for sure👌. The rocker stands threads in the heads may have been compromised from previous valvetrain issues. Seen it happen. Also on a T&D rocker arm like you have... the six digit number on the side is the date in which they were made. Can give you an idea of how old some of your parts are and the punishment they may have gone thru before you even owned the engine.

[freedomworx]

Mike, You shouldn't worry with the location of the ring gaps upon disassembly. It was likely assembled correctly, but the rings do rotate around the piston during operation. It's a common misconception that they just stay where you put them. There are several SAE Papers on the topic, and even a standard test method to determine how much they rotate in operation. A radionuclide is imbedded in the piston ring, and the rotation can be detected in operation by following the radioactive signature of each piston ring. One study I read said that 3 RPM is a good rule of thumb for the angular velocity of a ring in operation.

[jasonedwards]

Really like the technical aspects of some of your videos. Your valve clearance is technically larger than you figured because both the deck and head surface had a sealant on them. My pops always taught us stuff breaks for a reason, figure out why before you try and fix it. This video brought back some old memories w/my dad especially teaching me to read a mic. Thank you

[randr]

I've thought more on this after doing some yard work. That thing having .120" clearance even after the valve train got hammered to death tells us you need more than that on the exhaust valves given the cam timing you're running. The keepers not coming off and the valve not wanting to come out of the guide tells us the top of the valve was mushroomed. So say you had .100" clearance when it was assembled. With the trick parts made of exotic materials, they grew more than your typical engine build upon heating up, therefore more clearance needed than usual. Probably like 0.125-0.130". Valve hits, makes its own clearance, rockers loosen up. Engine runs good enough for the dyno session and a few runs, but it's just a matter of time, with bent valves, that things get interesting. I'm amazed at how long it held together and that with a valve broken clean in half that it didn't puke a rod out the side of the block.

[ericwhite]

We all have bad days and we all make mistakes...Your grace for the builder says a lot about you...

[vettekid]

Back in my younger days in the 1980's I got to work around piston engined aircraft. I wasn't a certified A&P mechanic so all I could do is help but I do remember when we would replace engines with factory remanufactured ones we would do the initial startup and run for like 10 min and then drain all the oil and cut open the filters to look for metal. If everything looked good then more ground running and checks before we actually put any air time on the engines. Also thermal expansion could alter the clearances with the engine running over checking it at room temperature.

[teknoaija]

I asked a seasoned engineer about ring end gaps and rotation and he said they filmed this in Wärtsilä engine lab and it was about 60 revs per minute.End gaps change position all the time so you have no issue there mike.

[randr]

That comment you made about trash in the new build is why I always heat cycle the engine and change the oil right away with a new filter after any internal engine work is done, and cut the run-in filter open to make sure no large chunks in it for good measure. Every single engine I've done have a little bit of fresh glitter in the filter, and I've gotten silly with cleaning on some of them. After the first time I tried that I do it on everything, including if I buy a lawnmower engine from Harbor Freight.