lemons CMP race

MikeWhitney · **Joined:** Wed Aug 20, 2003 9:15 pm **Posts:** 4724

So what happened? Root cause?

Bernie Baake · **Posted:** Mon Apr 01, 2013 8:53 am

Looks really ugly, Roger. I'm with Mike What do you think happened????

Roger McDaniels · **Posted:** Mon Apr 01, 2013 9:40 am

Piston slap from too much piston-wall clearance shattered the skirts of the stock cast pistons, which are relatively brittle. It chipped away at them until one got sideways in the cylinder and cracked the sleeve.

Right before the HPDE at CMP last October, I built a really nice new motor, new pistons, machined at a machine shop, spent hundreds of dollars. I put it in the car on Wednesday night and it ran for 6 minutes before throwing a rod out the front of the block and through the radiator, still not sure why. It completely destroyed the motor, nothing was reusable.

At that point Ricky and I had a day to get it ready for CMP, so I looked at what I had laying around the shop and built another motor from some used stock pistons and a block that had been bored .010 over. I only had stock sized rings, so my ring gap was huge (.050 or greater) and it had a lot of blowby, but it ran well enough to get us through the weekend. Later I file-fit a set of rings for it and we took it to the snow autocross at Danville and it ran very well. You could hear some clattering on startup, but it quickly quieted as the motor warmed up.

I've run big piston-wall gaps before, but only on racing motors with forged pistons that I planned on running 30 PSI of boost on. I should probably count myself lucky that it made it through an HPDE and got us almost all the way through a LeMons race.

clinehall · **Posted:** Mon Apr 01, 2013 2:08 pm

Roger McDaniels wrote:

I ain't no mechanic, but I did stay at a Holiday Inn Express during the Lemons race and I would say that is done blowed up.

George Bright · **Posted:** Mon Apr 01, 2013 6:17 pm

clinehall wrote:

I ain't no mechanic, but I did stay at a Holiday Inn Express during the Lemons race and I would say that is done blowed up.

I slept at the track and watched the mid engine Geo Metro guys swap the motor out of a driving Contour into their Metro.
:sleep2:

clinehall · **Posted:** Mon Apr 01, 2013 6:46 pm

George Bright wrote:

I slept at the track and watched the mid engine Geo Metro guys swap the motor out of a driving Contour into their Metro.
:sleep2:

I did too, it was more like swapping the chassis, the left the motor on the ground and lifted the car off of it! While I loved the airplane, that was the most interesting example of Frankengineering. I think I just made up a word.

Ryan Holton · **Posted:** Tue Apr 02, 2013 7:43 am

Be careful Cline, I don't want you to pull a muscle patting yourself on the back

steve remchak · **Posted:** Wed Apr 03, 2013 11:37 pm

Ryan Holton wrote:

Be careful Cline, I don't want you to pull a muscle patting yourself on the back

T-Rex with a chubby......... he has no choice but to pull a muscle trying to pull a ............... muscle?

Those dudes may have been awesome mechanics but I can tell you when that car was running they were damn fast and skilled. The dude I was up against broke my momentum at least five times before I figured him out.

MikeWhitney · **Joined:** Wed Aug 20, 2003 9:15 pm **Posts:** 4724

Roger McDaniels wrote:

Piston slap from too much piston-wall clearance shattered the skirts of the stock cast pistons, which are relatively brittle. It chipped away at them until one got sideways in the cylinder and cracked the sleeve.

Right before the HPDE at CMP last October, I built a really nice new motor, new pistons, machined at a machine shop, spent hundreds of dollars. I put it in the car on Wednesday night and it ran for 6 minutes before throwing a rod out the front of the block and through the radiator, still not sure why. It completely destroyed the motor, nothing was reusable.

At that point Ricky and I had a day to get it ready for CMP, so I looked at what I had laying around the shop and built another motor from some used stock pistons and a block that had been bored .010 over. I only had stock sized rings, so my ring gap was huge (.050 or greater) and it had a lot of blowby, but it ran well enough to get us through the weekend. Later I file-fit a set of rings for it and we took it to the snow autocross at Danville and it ran very well. You could hear some clattering on startup, but it quickly quieted as the motor warmed up.

I've run big piston-wall gaps before, but only on racing motors with forged pistons that I planned on running 30 PSI of boost on. I should probably count myself lucky that it made it through an HPDE and got us almost all the way through a LeMons race.

Was there a lot of obvious wear on the cylinder walls from the piston-to-wall contact, and was there noticeable oil consumption prior to blow-up?

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