How to Blow Stuff Up 101.

[JustaRacer]

I didn't want to pollute a build thread, so I'm posting a new thread that is applicable for many kinds of engines.  It's really obvious, but what the heck.

I hurt rods and pistons as a hobby, most my friends do as well.  It's how we get our kicks.  We see lots of them.  Hundreds.  It is our badge of honor to crack our pistons and bend our rods.  In this realm, you're a wuss if you haven't hurt an engine.  My first Merit Badge: factory output was 245rwhp, and I bent my stuff at 754rwhp while dragracing.  Drove it home when it started crying Uncle.  Like taking your daily driver family car with it's stock engine and pushing it to 900HP and using the power every chance you get.

Here's what I do, ghetto failure analysis:

I number and measure the rods, wristpins, and pistons accurately prior to assembly.  0.0001" resolution or better.

When it blows up, I remeasure everything again. 

I try to destroy everything in sets.  Ever see 8 steel rods that all measure .018-.022" short?  Beautiful!  People call BS on it, so I saved that set.  I currently retire rods at are 0.0020" shorter than new.

If I saw the autopsy pics in the 'Aluminum Rod Chewed By Wolves' thread, I'd be looking really carefully at eye to eye before and after but also cylindricity of all piston wristpin bores and profile on the ring lands of all the remaining cyls.   I'd guess the ring land went first, partially seized, tore the rod apart.  Why?  If the rod was allowing the piston to hit the crank or head, it's REALLY noticeable.  It's not subtle.  He probably would have heard it way before the engine let loose.  But whatever the cause, it's very likely you'll see it to lessor degree on the other bores.

If it all checked out, I'd assume somebody screwed up on assembly, or you got a bad part from the factory.

Yes, this is common sense.  But it will save you money in the long run if you aren't doing it.

[wobblywalrus]

Good grief.  We are at the other end of the totem pole here.  An engine is a big investment of money that should, by a mature person, be spent somewhere else.  The big mantra is "whatever you do, don't blow up the motor."

[JustaRacer]

Good grief.  We are at the other end of the totem pole here.  An engine is a big investment of money that should, by a mature person, be spent somewhere else.  The big mantra is "whatever you do, don't blow up the motor."

Buying a Toyota Prius is a sign of maturity.  Hotrodding as a hobby is not.  

Our Red truck has 79,000 miles at near double the factory output on all original parts (540rwhp).  The Blue one (502rwhp) has 93,000 miles with all original parts with double the HP.

It's rare to see that kind of mileage on vehicles that have spent a lot of time on the racetrack.

Both were purchased with under 5 miles on the clock and were turned up shortly there after, and have done hundreds of passes.

How do we know where the limits are?  Well, I can tell you it wasn't by just guessing at it.  We know the rods start to bend beginning at 600rwhp.  

Why is busting stuff like a Merit Badge?  It is when you share the autopsy info and data logs.  Then the group knowledge increases.

It's not a mindset sane people can understand.  Why in the world would you turn up your engine?  That shortens engine life.  Pretty stupid if you ask me.



  

[Stainless1]

Racing motors may be a big investment but if you are running for records and pushing your engine to the limits it will occasionally disappoint you.  Ask One Run... and me... and most of the racers here.  Failure analysis may keep the same thing from happening again.

Breaking something... records or parts.... that's racing 

[GizmoQ]

Breaking something... records or parts.... that's racing 

Or both.   

[JustaRacer]

Racing motors may be a big investment but if you are running for records and pushing your engine to the limits it will occasionally disappoint you.  Ask One Run... and me... and most of the racers here.  Failure analysis may keep the same thing from happening again.

Breaking something... records or parts.... that's racing 

It would be nice to have the resources to do what the OEM's can do, which is run an engine at full target output on a dyno, then tear everything apart and analyze it.  Make corrections, then do it again.  And again.

The best you can do on a budget is to record what everything measures before and after a failure.  This keeps you from adding parts that do no good, and lets you spend your resources on items that aren't holding up.

We had a lot of drag experience on our engines.  But little was known about more than 12 seconds at WOT.  Year one, we found the cooling system wasn't.  A piston overheated, seized in the bore, and the rod tore the piston in half at the wristpin.  Then the rod punched a hole in the block the size of your fist.  The rod was actually in pretty good shape, and all the others were just a couple tenths shorter.  So we know we have the right rods.

So we improved the cooling dramatically, and went with stronger pistons.  The first ones were cast, but these were forged.  However, the cast ones have a steel insert that supports the top ring, but the forged do not.

So guess what?  We found out why that insert was there the second year.  The ring land collapsed, stuck the ring, and blew the a path down the edge of the piston.  Extreme blowby caused me to shut everything off at just over 200.  It blew the dipstick out so hard it bent it, and dented the steel hood. 

Now, I could just put Year One pistons back in, increase the cooling and hope for the best.  Not going to do it though.  For a few years we have been waiting on "super pistons" that are supposed to be available "next quarter".  Until the super pistons are ready, we can't up the HP.

LSR was a learning experience, and the reason you don't just use drag parts in a LSR engine and expect perfection.

[Frankie7799]

LSR was a learning experience, and the reason you don't just use drag parts in a LSR engine and expect perfection.

Its funny that you say that. As someone who worked in a performance store seeling engine parts for 8 years, most manufacturers ( especially piston manufacturers ) dont always differentiate between the different motorsports in their catalogs. Sure youll get camshaft and oil pan listings for street, oval, drag and such. When it comes to pistons if you look at JE, CP, Diamond etc, they dont. Other than specific pistons for supercharged, turbo, nitrous etc they just give bore, stroke, ring land widths, comp height etc. That piston has no idea if its gonna be in a bracket bomber, comp eliminator, pro stock or a NASCAR engine. Its more or less putting the best, well designed and strongest pieces together to get the right combination and hoping for the best. 

[Glen]

Yeah but justaracer has to be retrained weekly

[JustaRacer]

Yeah but justaracer has to be retrained weekly

I'm learning to blow up a whole new technology now. 

I know how to blow up 2-strokes, VW's, 4-strokes, V8's, and Diesels.

On to the future!   

[tauruck]

You left out Rotary motors.