Engine/Transmission (1994 - 1998) Number 6 meltdown, pics inside.

[Bobcat698]

Our tow rig motor finally gave out at 296k. . We were pulling the black truck to the drag strip the weekend before Houston and everything was fine, then all of a sudden the truck ran rough for 10-15 seconds and died.



Engine would crank but would not fire, sounded like it had no compression.



Rewind a bit. A few days before we left for the Shelbyville KY pull we took the 160 pump off and put the (tuned) 215 pump back on.

It was supposed to be pin-timed at 20 degrees, I found out on the trip that it was much higher (26. 5 degrees) and we didn't have time to re time it.

On the way there it was blowing a LOT of oil, presumably blow-by, but some was also from the front crank seal leaking (again). Then it seemed like the timing slipped and the blow by decreased along with power coming on closer to 2000 rpm rather than 2500.



Truck has a 64/14/71 turbo with stage 3 injectors and a ported head.

Has a NV4500 RPM with 4. 10 gears so most of the pulling is done at 2300-2500 RPM. Head and block are cut for fire rings.





#ad


#ad


I hope this valve job can be saved. . We'll see next week.



#ad


Notice how all the other pistons have crap in them from #6? Even number one had them!



#ad


#ad


#ad


#ad


Have to get that one straightened, does anyone have a pushrod straightener I can borrow? LOL



#ad


I am surprised how the aluminum managed to spread itself to the other pistons. . Not quite sure how that works. . Maybe someone can offer some insight. .



#ad


The right valve pictured is the intake valve, notice the buildup of aluminum shavings.

 

[Bobcat698]

#ad


#ad


#ad


#ad


#ad


#ad


#ad


#ad


#ad


Should buff right out, I'll just take some sandpaper to the cylinder wall and chip the extra pieces off the piston so they don't get caught in the valves. :hehe:



What do you think guys, will 20 over be enough to clean up #6?



This engine had 296k miles on it. All over the other cylinder walls were perfect, all still have visible cross-hatching present.



I'm blaming this meltdown on Pyrometer failure/inaccuracy, since we NEVER had this truck above 1200 degrees for any period of time.

 

[Jim Fulmer]

That sh__ will buff out!



Jim

 

[Bobcat698]

That sh__ will buff out!



Jim

Thats what I figured, what do you think about the pushrod though, is it salvageable?:-laf

 

[BILLUA]

Thats what I figured, what do you think about the pushrod though, is it salvageable?:-laf

Just put it in a piece of angle iron and keep beating on it till she's straight!:-laf



Cheers, Bill



Thanks for the pics...

 

[DCreed]

did you have a bad piston oiler or stuck injector??

 

[Bobcat698]

did you have a bad piston oiler or stuck injector??

Stuck injector is negative.



Piston oiler, not sure, engine is still together.

 

[FATCAT]

Can I ask a stupid question here ... if aluminum melts at a lower temp then iron and steel, why are the pistons not made of iron or steel? Why are these engines not sleeved and use steel pistons so these melt downs won't happen?

 

[MDULLEY]

Kind of reminds of Chris Strickland's 94 meltdown. His number six did something close to the same. If I remember right, it was suspect washer or something like that.



Good luck on the rebuild!!

 

[Vaughn MacKenzie]

Can I ask a stupid question here ... if aluminum melts at a lower temp then iron and steel, why are the pistons not made of iron or steel? Why are these engines not sleeved and use steel pistons so these melt downs won't happen?

Because with a 4. 72" stroke they would be WAY too heavy. . . wouldn't want to run much past about 2000 RPM. Compound (steel/aluminum) pistons are best of both worlds, but very pricey.

 

[rjrkihap]

Vaughn;



Maybe you can answer this question. I worked as a consultant way back in Grad School for a Titanium manufacturing company. They were making parts to replace traditional steel and aluminum such as bike cranks, sprockets, horse shoes, and a few auto parts (can't remember which ones). However, my questions is why are we not using other metals or alloys to achieve higher strengths and temperatures. I know that the Titanium parts were not that much more expensive than aluminum and I remember Titanium being stronger and lighter than steel.



Just a thought?



Ron

 

[FATCAT]

Because with a 4. 72" stroke they would be WAY too heavy. . . wouldn't want to run much past about 2000 RPM. Compound (steel/aluminum) pistons are best of both worlds, but very pricey.

OK, now I get it. Thanks. I didn't think that small amount of additional weight would cause such a big difference.



Ron's idea of Titanium pistons sounds good though.

 

[Vaughn MacKenzie]

Not sure about that Ron. I don't know how abundant titanium is, how good of wear characteristics it has, thermal expansion rate, etc. but the melting point is higher than Al.



Fatcat, if this makes ya feel better I do own a car with cast iron pistons . . . a 1950 Chevy with the 216 six



Vaughn

 

[Mokerz]

***OUCH*** that hurts just looking at it and it's not even one of mine!!! Let us know if you find a culprit.

 

[RyanB]

looks like quite the damage! We had a push rod look very similar to that a month ago on my brothers truck... we fixed it right up... pulled it out, turned it over and revered'er up to 4500rpm... straighted it right out:-laf JK.



On a serious note though... I have pulled these 5. 9's apart with 300,000 on them and there are still tons of cross-hatch marks... pull a gasser down with 100,000 and there is tones of wear and you can see where the rings made it up to on the cylinder... any idea why the 5. 9's are like that?



RyanB

 

[abdiver]

"I'm blaming this meltdown on Pyrometer failure/inaccuracy, since we NEVER

had this truck above 1200 degrees for any period of time. "



Bobcat698, Where did you have the Pyro probe mounted before or after the Turbo ?????



Bill

 

[CSnyder]

Im gonna venture to guess its a failed piston nozzle because of an EXACT failure a friend of mine had coming back from TN 3 monthes ago. Guess what! He was never over 1200 degrees either on his pyro. I wouldnt gamble on using that block over.



I hope you have a speedy recovery!

 

[ToolManTimTaylor]

Why are these engines not sleeved and use steel pistons so these melt downs won't happen?

Because they would become Navistar engines then.



I am thinking overtimed along with duration did it. #6 will show the heat from overtime first because of it's placement alone I would imagine.

 

[JGheen]

Bobcat698, Where did you have the Pyro probe mounted before or after the Turbo ?????



Bill

I am sure Garrett had it pre-turbo.

I would venture to say a combo of possible pyrometer failure and too much timing & fuel. And not surprised to see it being #6 since that one is typically the hottest of the bunch.



Joe