Race motor *major* Hand-Grenade - doing forensics & need help.

[snowman]

Looking at all the picutres again, I still say COOL, cause, what else are you going to say?

How about the WP end of the rod? Does the rod have an oil hole at the top? The color of the wp looks like it got hot, is the picture showing the color accurately? If so this might indicate an oiling problem at the rod ends. What I am thinking about is a rod failure, leading to the rest.

Did the valve put any holes in the piston?

[CamB]

Holy sheit that is broken. Bummer

Here is a head I was shown - matched to Mahle 95mm RSR p&c - victim of an overrev or dropped valve (can't remember). It doesn't just happen to JE. Mind you - this had nothing to do with the piston (which didn't look too flash either).

[snowman]

Yes I agree, at first look it is most likely a valve train problem, ie dropped valve, valve hit piston, whatever. But just to be sure, what about the rod end? Theres a LOT of force trying to suck the piston off the rod at high revs. If it did the results may look similar.

[jeffstev]

Just like a car wreck, I keep going back into the garage and looking (staring for hours) at the mess. I've discovered a few additional things:

- a few of the oil squirters were incorrect installed in the case. they are recessed about 3/4" and "stuck".

- the rod bearing of the "exploded" piston was quite worn. The others weren't nearly as bad. the rods were Pauters, brand new w/ the ARP rod bolts that come with them. The rod "felt" fine on the crank in terms of play, etc. It felt the same as all the others.

- the color in the pics is correct although I didn't see too much friction wear on the wrist pin.

- all of the pads on the rockers were pitted. indications of an oiling problem.

- a couple of the pistons had "shadows" of where the exhaust valve came extremely close to the piston. Not actually touching but close enough that the exhaust gas created a pocket around the valve head and imprinted a faint carbon outline of the valve. Too much damage on the exploded cylinder to see what was happening there.

- I keep coming back to the chain ramp. The tensioners were installed in REVERSE (Left in the right side and vice versa) - refer to the the pic of the ramp. I'm wondering if this created an oiling problem, etc. The bottom of the oil scavenge pump was almost completely plugged with chain ramp debris which could have caused an oil starvation problem coupled w/ the oil squirter problem and caused the pitted rockers, worn rod bearing, etc...

And yes, those are ARP head studs - and they took a severe beating and didnt breat

Jeff

[Wayne 962]

Hmm, I'd have to agree with you - sounds plausible on the oil starvation issue. It's often tough to figure out what went wrong first...

-Wayne

[ErVikingo]

For what its worth, I use Cosworths, no problems (yet!). Your situation sucks, not looking forward to it at all

[David]

Sorry to hear about the motor, what a mess!

I would suggest tearing down the motor and looking for indications of a pending failure on other cylinders. You could dye penetrant check the pistons and mag partical check the rods. This would also allow you to check the as built dimensions.

Is there any undamaged fracture surface on the connecting rod? If so, a metallurgist could try to determine if the small end of the rod failed first.

[rcwaldo]

First let me say that sucks and I feel for ya! Luckily it didnt put you into the wall there at Fontana (not sure where on track you were when it let go)

I am kinda curious to your deck height (before explosion).

Our Cosworth track support guy told me while back about their F1 engines were experiencing about one full mm of rod/piston stretch at full RPM, therefore decreasing deck clearances almost .040"! Yes this is at a much higher RPM. But piston inertia is a function of piston speed and weight, so even though yours was at (only) 8k RPM, piston weight is much higher than the F1 example.

Maybe we all have this amount of stretch, but not the technology (ala F1) to identify this anomaly?

Maybe I tend to 'read into' things too much?

Let us know more as you find more...

Chris

[dickster]

wow, thats bad.

chris,

i believe that is normal at higher rpm. on sportsbikes it is recommended to open 'em up to high rpm now and then (if you dont regularly!) to "stretch" the rods - if you dont you run the risk of breaking rings on the wear ridge (which would be too low).