Mustang

Spokane County Raceway

My cousin recently purchased a Mustang GT and took it to his local track.  He sent me some pictures and an invitation to join him at the next track day.  Seemed like a great opportunity to learn a new track and visit with family.  The weather was beautiful and it was looking like a perfect day.  A few drivers warned me about some humps on the back straight so I asked a driver that I recognized from some NASA events if I could follow him for a few laps to see the line.  Spokane County Raceway is a fairly simple 2.25 mile track as it’s relatively flat and has only 10 turns.  There is a slightly blind crest on the back stretch but otherwise visibility is pretty good.  It has an interesting mix of very high speeds and some very low speed corners and I was using every gear but first.  I started off very conservatively as there was no rush in going full tilt and the runoff areas are not forgiving, plus I wanted to stay behind the M3 for a few laps until I felt confident in the line before giving it the full beans.  First lap was warming up the tires and seeing the track for the first time.  Second lap was a bit faster but still finding turn-in locations.  Started pushing a little harder on the third lap (still turning in much too early for T3) but felt a slight hesitation accelerating out of a corner.  I didn’t see any smoke and it seemed to run OK but I slowed down and noticed that the oil pressure seemed a bit low.  I coasted around the track for a lap and when I pulled off, the car died.  In the pits I pulled the plugs and #4 was black and wet.  The others looked perfect.  I figured the most likely cause was broken rings or ring lands.  In hindsight, I have been noticing a bit more blow by accumulation recently.  Not something I was going to fix at the track so I spent the rest of the day hanging out with family and did get a ride in my cousins Mustang which was super fun.  I then packed up and drove home.  It was a long 800 mile round trip for 2.5 laps!

There was an interesting mix of cars and a bunch of very friendly drivers.  I’m looking forward to making it back to Spokane.  I ran a high 1:39 on lap 2 (while coasting in several areas) and would really like to see what time I could run after learning the track and pushing it.

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I reviewed the data and found that the oil pressure started slowly dropping on lap three.  Blue trace is oil pressure from Lap 2 and Pink traces is oil pressure from Lap 3.  Knock voltage looked pretty normal until the middle of lap three where there was some very high readings.  Could be detonation due to the increased blow by gasses or it could be picking up the sound of the now-loose main bearings.  I didn’t see any significant knock prior to the failure.

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Once home, I pulled the oil pan and found a lot of bearing material.  I just had the pan off recently and there were no signs bearing material so it must have been a very fast catastrophic failure.  This explains the low oil pressure but didn’t explain the hesitation and fouled plug so I pulled the motor and removed the head.  Looks like broken rings and a very scored #4 cylinder.

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