Have three engines, two 555s and a 540. 3/3 have cracked pistons recently but I was able to save 2/3 from blowing up. All three have Racetec pistons. Two engines had about 600 runs on the pistons, one had 440.

The first 555” started making a very slight tapping noise that I was able to hear at idle. After not being able to identify the noise, I pulled the engine out and put my spare in. Disassembled it and found that a wrist pin boss cracked on one side, the wrist pin had walked to one side and we were moments from completely breaking the piston. Upon inspection of other pistons, several other showed cracks in the pin “bridge” area (pictures below).

The spare 555” that I installed catastrophically blew up about 100’ into a run with zero warning about 30 runs after installing it. The pin completely ripped out of the bottom of the piston starting a chain reaction of calamity that claimed my block, rods, probably cam and a head needs to be fixed. Upon disassembly, other pistons were also cracked in the same area as the first one.

The 540” had 380 runs on the pistons at the beginning of last season. At that time we installed a baby blower on it and thicker head gaskets to lower the compression along with thicker wall pins. We put 60 runs on that car last year and just pulled the engine for inspection and found three pistons cracked all in the same area.

We’ve been talking with Racetec and sent them some pictures. They haven’t had much to say yet other than mentioning maybe the pin was flexing. To that end, we were running their standard .187 wall pins. The Racetec pins are shorter and thicker than for example a Wiseco pin, the theory is so they flex less. When we put the baby blower on it we went to .280 wall pins. This doesn’t confirm nor deny the pin flexing theory because the engine had been run with standard pins and it’s possible the cracks started at that time.

I don’t believe this to be a tuneup issue because we’ve been running this combo since 2013 and it’s always been reliable and consistent; bearings have always looked beautiful at disassembly. This also isn’t a “bad batch” as each set that has failed was made different years.

Maybe it’s as simple as we just need to cycle them out more often. But under 450 runs? Any thoughts would be appreciated.

Here are some pictures, click them to see larger. The first one is where the cracks form:



The next two are what happens when the crack isn’t caught in time:

This message has been edited. Last edited by: 183N,

I have never used RacTech's Big Block pistons, but on the small block stuff I have not had much luck!

Only two pistons I've ever used was JE and Gibtec. No issues with either other than finish quality on JE.

On my SB2 I used CP Carrillo, I was considering the Ractech pistons.

That is very concerning as all of the pistons now are designed very lightweight. With crank, rods and pistons we are looking for lightest we can and still be strong enough and it is a fine line.

Sometimes pin flex, always go big on pin thickness. Has a lot to do with the clover design around the pin load to piston as was explained to me by Dave Calvert CP.
Depending on power , 300 runs with good power is pushing parts limits especially now. My opinion.
Hope you get it sorted out.

The thing about aluminum is no matter how much load you put on it at some point it will fail. Only thing that changes is the number of cycles. Obivously you've reached the limit on the number of cycles on those pistons in all 3 cases. Pin flex could cause pre-mature failure and limit the number of cycles till failure even more.

My thoughts here are:
Swap piston manufacturers, do some research on which piston you decide to go with by working with different piston manufacturers. Let them know what your plans are and how many runs you are targeting before a piston swap.

If you stay with current piston design, proactive replacement at 250-300 runs blower or not. The pistons will live a shorter life in the 250 blower motor due to increased loading, its making more power so there's more load on the pistons.

Good luck that's a nasty engine failure.