The Autopsy Results.....OUCH!!

[Zack]

If you keep the max timing to 13 or under on a stock engine, it will live forever.
(Unless a pump or other extreme factor is to blame)

[Marauderjack]

If you want to splash the tank with a little race gas to suppress detonation there is nothing wrong with that. If you are running on the ragged edge on a pump gas tune I would suggest it. Otherwise just lower the timing down for 91 octane and motor on down the road.

It was setup for 91 Octane and lived 174K miles before this so I truly suspect a bad load of gas.......working on that with the seller!!

Shell 93 from now on.......never had a hint of trouble with Shell fuel!!

[fastblackmerc]

I was cleaning up 2 of the piston/rod assemblies for gag gifts and LOOK WHAT I FOUND.....YIKES!!

Wonder how many more are damaged??

Stay Tuned!!

A little dab of JB Weld and they are good as new!

[Marauderjack]

Closer investigation revealed another BROKEN piston so my #7 & #8 theory is shot!!

Wonder which ones the other two are since they both have 2nd lands broken while #7 has the top land broken.....ideas??

BTW.....they all seem to be broken on the "thrust" side.....right??

[Marauderjack]

A little dab of JB Weld and they are good as new!

I'll send 'em to you to JB Weld.....if you will GUARANTEE they will last forever Jim!!

[lifespeed]

Note that the fact this engine is supercharged is not a contributor, as a normally-aspirated engine would do the same thing, under the same load conditions.


One of the best written explainations I've read.
It has happened to me, and how / why is in the words above.
You have a smart engine builder

An excellent analysis, except for the comment on supercharging. It is widely recognized that supercharging increases cylinder pressures and temperatures. How else would you get more power?

An experienced engine builder will increase the ring gap to accommodate the added heat from a supercharged engine. An OEM concerned with naturally-aspirated power and efficiency will set the gap appropriately smaller. This appears to be at odds with the above statement.

I doubt that all those pistons broke during a single incident of low octane. The problem, whether it was too much timing for the fuel/boost combination, too much heat for the ring gap, or a combination of the above was, IMHO, present for some time.

[RF Overlord]

Holy Moley, 'jack...looks like you had a 5-cylinder car there for a while....

[chief455]

An excellent analysis, except for the comment on supercharging. It is widely recognized that supercharging increases cylinder pressures and temperatures. How else would you get more power?

An experienced engine builder will increase the ring gap to accommodate the added heat from a supercharged engine. An OEM concerned with naturally-aspirated power and efficiency will set the gap appropriately smaller. This appears to be at odds with the above statement.

I doubt that all those pistons broke during a single incident of low octane. The problem, whether it was too much timing for the fuel/boost combination, too much heat for the ring gap, or a combination of the above was, IMHO, present for some time.

I think his comment on supercharging was meant to keep focus on the root causes. Yes, forced induction adds heat / pressure, but the incorrect air / fuel, timing, etc root causes remain the same, n/a or forced induction.
I agree this much damage likely happened over a period, however short, of time. Maybe an entire tank run of total garbage fuel, detonating all the way
I lost 6 JE forged blower pistons, 8.5:1, conservative tune, due to fuel starvation when the in tank pump was falling off.

[justbob]

A detonation in one cylinder could easily carry into all others simply by harmonics. Besides, if it's detonating from fuel quality, it's detonating in all cylinders or at minimal the hottest ones.


Builder Of Badassery

[Zack]

All broken pistons pictured will (and would have) made close to 100% compeession

[chief455]

All broken pistons pictured will (and would have) made close to 100% compression

Thus the engine runs so strong when the damage is being done. I know mine was. It was tuned rich at WOT to keep the chamber cooler, so when the fuel starved, it went leaner, made more power and felt great! So I drove it hard
Wish I knew than what that 7 grand rebuild cost and made me understand now. Have an air/fuel gauge and watch it. Have a fuel pressure gauge reading after the injectors on return, and watch it closely for sudden drops. Have your computer sense knock (or assume it) and pull timing if it does.

[Marauderjack]

Holy Moley, 'jack...looks like you had a 5-cylinder car there for a while....

Only #7 misfired Bob......the other 2 were not even visible until cleaning resulted in the 2nd land piece just falling out!!

BTW.....when I started it to back it off the trailer it ran PERFECTLY!!

[Marauderjack]

All broken pistons pictured will (and would have) made close to 100% compeession

It ran fine after the top land debris was ejected.......almost put it back on the trailer to take it home.......NAW!!

[Marauderjack]

Thus the engine runs so strong when the damage is being done. I know mine was. It was tuned rich at WOT to keep the chamber cooler, so when the fuel starved, it went leaner, made more power and felt great! So I drove it hard
Wish I knew than what that 7 grand rebuild cost and made me understand now. Have an air/fuel gauge and watch it. Have a fuel pressure gauge reading after the injectors on return, and watch it closely for sudden drops. Have your computer sense knock (or assume it) and pull timing if it does.

During the last "hard launch" it was crazy strong.....I had to get off the throttle a little to guarantee control.....just a little but it was too late!!

I am in contact with the fuel supplier.......probably no help but we'll see??

I suspect someone dropped the wrong gas in the "93 Hole" and I was the only "lucky" one.......most people waste $$$'s running high octane thinking they get more power!!

[martyo]

The lawyer in me says that if the fuel supplier gives you anything, it will be a gift card worth $100 as a matter of good will and nothing more.

You had a stock car with 250,000+ miles on a motor admittedly exceeding rated hp levels which let go when you were romping on it.

In any event, I want you to let us know what happens here because pf my super human curiosity skills.