I know many of you, including our sponsors, and team members wanted to know what happen to our race motor at the last RTA in Carolina Motorsports Park during the second practice session. Well I can now tell you that it was not an issue with our built block, ecu, tuning, wiring, fuel injectors, or fuel pump. After disassembling the motor today, we have come to a conclusion that it was not detonation that destroyed the motor, but instead the intake valve seats on cylinder #1 decided to drop and destroyed the cylinder head. Luckily the spec-A short block is intake, manley rods, cranks, etc. We'll know for sure if these components can be salvaged once we've had a chance to check the specs on the components.

A little background. If you've been following our post with the ptuning tC, we had a coolant leakage issue at the RTA in IL that cause the motor to overheat and blow a head gasket. Our plan for the race after that in Tennessee was to have a fresh built motor, built cylinder head, and high lift cams, billet cam followers, etc. etc. We'll the night before the race, we had some issue with valve clearance and was unable to obtain the necessary valve shims in time to install the built cylinder head onto the new spec-A race block. A last minute decision was made to run the built cylinder head from the overheated motor with the new short block. The decision allow us to take another win at RTA in TN, but it destroyed the motor at CMP.


So what happened. When a cylinder overheats, especially being aluminum with hardened steel valve seats, the overheating cause the aluminum cylinder and steel valve seats to expand at a different rate and much more than it would normally expand. Since the valve seats are interference fit onto the valve seat pocket in the cylinder head, with the cylinder head overheating an possibly warping the cylinder head and reducing the interference fit of the vavle seats, causing the seats to drop into the combustion camber. But since the vavles are in the way of the seats from fully dropping, this cause the valves to break and destroy the cylinder head. The shrapnel from the distintegrated valve seats, valve, etc. was blown back into the intake manifold and then sucked back into the other cylinders--hence the reason all the other piston crown are pitted.

So what have we learned here. DO NOT Reused a cylinder head from a motor that overheated--unless you're trying to make a race and have nothing else to use


Here's some pictures of the carnage:










MrC

 

ouchh

 

Damn!

That is well chewed.

Good luck on being able to use some of what's left.

Tom

 

Cylinder 1 looks like someone took a jackhammer to it! owwww. Keep us posted on the progress of the car MrC.

 

dayum

 

Wow... thats simply horrible!

 

RIP!!

 

Where are the pics?

 

Preface: My comments are based on my observations and experiences in the engine building realm. These are not jabs or anything of the sort so please do not take them as such.

Interesting that the intake valve seats were the ones to let go and on top of that only on the number one cylinder which is furthest from the throttle body and would have the tendency to be the leanest cylinder.

What EGTs were you seeing going around the track? I would think that the exhaust seats would be the ones to pop out as they are subjected to more concentrated heat than the Intakes and do not have fuel cooling them. Do you really think that over heating was the root cause? I'm not there to see it but I'm not so sure I would agree. How hot did the engine get when it overheated last? If you were to see a problem with seats losing their interference fit I would think that it would have been then and not during your run. Interesting.

 

from the pics, looks as though the block is salvageable. Not so much could be said for the head because of the extent of the damage to cylinder #1

 

Individual EGTs were not in placed and/or logged during the race. AFRs were they needed to be, fuel pressure correct, injectors were all reflowed and perfect, fuel pump works, timing and all other parameters that were logged during the race all showed up correct. Same fuel, no changes to tune between 1st practice session and 2nd practice session when it happened.

Our first speculation was detonation, but our driver didn't hear any pinging and car was in low boost in third when it happened. All the rings and ring lands on all the 4 pistons are perfect and wrist pins are straight. Initiallly we were speculating that the timing chain tensioner back out cause the timing chain to skip a tooth and made the valves dance on the piston, but timing mark on both cams are were it needs to be in relation to the TDC.

At this point this is all we speculate on and it's time to build another motor. if it's not breaking a hub, axle, tranny, motor, it's something else--if it doesn't break, race it and it will.

MrC

 

It should be, we just need to check all components to make sure they're still in spec. The sleeves on the spec-a block will have to be overbored to 60 over to clean out the deep grooves in the #1 cylinder from the shrapnel.

The head can be used for a paper weight.

MrC

 

nice carnage...when you guys do something you do it big....lol