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Posted (edited)

Took apart a 1.6L motor with low miles and it appears to have two of the rods slightly twisted.

The motor had 9.5:1 compression forged JE pistons. Piston #1 has a large hole in the crown the size of a quarter.

The motor also had a lightened flywheel. Some Gremlin grenaded this motor, obviously.

 

I'm going to compare these rods to others I have. I've never come across twisted / bent rods on my motors.

Have any of you come across bent / twisted rods or had such issues ?

Edited by Slavs
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  • Slavs changed the title to Twisted Rods

Never on an M10, and never happened to one of my engines, but I've seen a few bent rods out of M5x-series engines that hydrolocked. In what axis did the rods in your engine bend/twist?

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Posted (edited)

With the "Y" axis being longitudinal representing the length of the rods, two of them are slightly twisted like a pretzel, along the "X" axis. The motor must have sharply frozen, twisting the rods. I found metal chunks and flakes from the destroyed #1 piston all over the block and pan. # 1 bore is a complete disaster with huge scores in the block. 

 

Whoever built the motor has some odd ideas such as installing one of those undersize aluminum crankshaft pulleys on a motor used for the street. I've never seen the upper end, but if they applied the same philosophy to the head as they did to the block, it was a disaster in the making; probably a long duration high lift cam coupled with the undersize pulley, badly tuned sidedraft carbs and mistimed ignition timing all added up to the perfect explosive cocktail in the combustion chambers to blow a hole through a forged JE piston. The lightened flywheel was another tell-tell sign of a Gremlin at the wheel hell bent on driving the motor into the ground. I can only imagine how they abused the transmission.

 

Why in the world would someone install one of these undersize crankshaft pulleys on to a street motor in Southern California where the temps are high through most of the year ? Our cars are on the margin with respect to cooling capacity, so why exacerbate the problem by installing a small pulley which makes the water pump less efficient ?

Edited by Slavs
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No sign of coolant in the cylinders? Twisting from a seizing event means it must have locked up hard at high RPM. Maybe a missed shift (went 3-2 instead of 3-4) and overreved? Based on the build as you describe it, I doubt it saw a lot of time at lower engine speeds. Did the crank survive?

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You sure it wasn't turbocharged?

 

Sounds like it was built by a shade tree mechanic and driven by a kid with a lead foot 

 

I've never understood why anyone would run under drive pulleys on a street car. Even on a race engine they don't usually make enough of a difference to make it worth while.

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8 hours ago, Son of Marty said:

Long or short stroke 1600?

All 1600s are short 71mm stroke. It'[s the 1800cc M10 which comes in both, the long and short stroke configurations.

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On 5/5/2021 at 2:44 PM, 2002iii said:

Sounds like it was built by a shade tree mechanic and driven by a kid with a lead foot 

Your assessment is probably correct. I noticed the engine builder had left out the "C" clips on the studs at the front of the flock which hold the timing chain rail in place. The 1600 has a light flywheel , so why lighten it even more for a street engine build ?

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