Melted piston.

You might have been playing with them since they were IDI but that doesn't mean your right.

My egt's go down when I build rpm's and boost. I don't know what your's do. Case in point, 55mph in 3rd gear unloaded I see 5psi of boost and 600* egt's at 2000rpm, 55mph in OD unloaded I see 0psi of boost and 800* egt's at 1600rpm. Do you know why that is? To much fuel, not enough air. Add in more air and egt's and cylinder temps drop. EGT's might not measure cylinder temps but they do correspond with them, meaning that high cylinder temps equal high egt's and low cylinder temps equal low egt's.

And if you want to use your a+b=c theory, what happens when b is greater than a? If your burning all of your fuel then adding in more air won't do jack. It would be like pushing 30psi on a stock truck. It won't hurt anything, might help lower egt's a little, but that's about it. Your not going to melt a cylinder down from having to much air. It's just not going to happen.
 
same reason, a cam lowers egts, or even better intake lowers it a little even. More oxygen in cylinder pure given fuel rate, = lower egt.
 
i would have to guess its a injector issue. wether its stuck, broke, or dirty as hell it was def dumping unatomised fuel onto the piston one way or another. like whoever said it in an earlier post for it to melt that much in that way there was fuel burning right on the piston. i couldnt imagine a piston cooling nozzle doing that kind of damage for the sole reason that unlike some of the newer engines the oil doesnt get nearly as close to the crown in these engines. also this is considering i just took the crank rods and pistons out my engine and the #1 cooling nozzle has broke off completely and disapeared and my piston is unaffected.

thats pretty much my .02
 
Burnt the #6 piston in my old first gen just like that about 6 years ago. Mine was due to my oversight to check the antifreeze content. Previous owners had filled it with water and we had a cold week that I never drove the truck for about 4 days, so it was basically frozen. by the time I realized it had overheated, (didn't know the temp gauge didn't work and the radio was up way too loud. so my first indication was the smell of burnt oil:doh:) I tried to pull off but my last bit of throttle to get to the offramp netted a big bang and the motor shut down. After which I opened the hood to find coolant spraying out the side of the block between the head and block. When I pulled the head I found much the same as you did. #6 being the worst, progressively getting less damage near the front. But ALL of the pistons had what appeared to be ballpeen hammer dimples all over them. Quite catastrophic. Taught me to pay more attention to things after I buy a new truck. And incidently I got to learn how to rebuild a 6bt. As a testiment to these motors' strength though, the head nor block had cracked, and it only took a mild shave to get the head flat again.
 
too bad im too stupid to realise that the 1st cyinders cooling nozzle is cast into the block so i guess it didnt disapear ha
 
it's not cast into the block..... the casting surrounds the nozzle, but there's still one in there...
 
Is it necessary to saw for some new cooling nozzels or use the factory ones??? Kinda thought they might be getting brittle over time.
 
Really?! your telling me that at idle when my egts are at 350* that 4inches away from my pyrometer probe the temps are 700*? please tell me it uses a spark plug too!

a amoubt of fuel + b amount of oxygen= c amout of heat
Click to expand...

so 500cc of fuel+1000cfm=1500cc/cfm? :umno:
 
i do agree with you tho on the post count. just because someone isnt at compd all the time doesnt mean they dont know what they are talking about, but when someone spits crap out that he may have heard from someone else or is making it up the creditability goes down.


i have seen the same exact thing happen to a 96 that was low on water temp and wasnt watching the water temp. the # 5 let go.
 
This truck has never been hot (engine temp.) The egts have been warm but nothing major. Water level has always stayed fine also. So guess it was just an injector hung open. And I cant spell on that last post that was supposed to be swap instead of saw.
 
XTrEmE9156 said:
it's not cast into the block..... the casting surrounds the nozzle, but there's still one in there...
Click to expand...

no your right i noticed that after i took a closer look at it, my bad. you guys can disregard the breaking off of the cooling nozzle and whatnot cause that obviously didnt happen ha.

if you have the means of doing so try pop testing that injector from that cylinder and see if its letting loose early or maybe leaking or clogged. then you could rule out a few differnent things. it could be the culprit
 
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EGT is just that -- EXHAUST temperature (not cylinder temperature).

A pyrometer probe will NOT give you an accurate indication of when a piston is in danger of melting.

example -- You add a bunch of timing, exhaust gas temperatures decrease, but cylinder pressure and temperature increase. More heat is being contained in the cylinder and left on the piston for a greater amount of time.

Throw your egt gauges in the trash and get something worthwhile like a mechanical oil pressure gauge.
 
How s the mechanical oil pressure guage gonna help in a hot situation until its too late???
 
ok sir.... so since or EGT gauges are completely useless to us.... what do you suppose we should use to get a rough idea of how close we are to the danger zone eh?

come on ? do you really believe that ?


the closest we can egt is havin 6 probes in the manifold on each runner.


unless this j@ckass can provide sumthin better.
 
Kronic_187 said:
ok sir.... so since or EGT gauges are completely useless to us.... what do you suppose we should use to get a rough idea of how close we are to the danger zone eh?

come on ? do you really believe that ?


the closest we can egt is havin 6 probes in the manifold on each runner.


unless this j@ckass can provide sumthin better.
Click to expand...


Keep a close eye on that EGT gauge if it makes you feel better. Let me ask you this -- What is the maximum EGT you would consider safe?
 
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