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Discussion Starter · #1 ·
welp i finally had time this weekend to take apart my car to find out the source of the oil burning that started at the track on my last trip.
up until this time we believed it to be 1 of 2 things. either a valve stem seal going completely and allowing oil to seep from the rocker valley into the cylinder, or 2 a piston ring had given up the ghost...

well it turns out it was niether,
for reasons still not known i had a hole burned strait thru #7 piston.
and the peices that broke off and burned up had FUZED themself to the combustion chamber of the heads!!! :eek:

so making a long story short, I am done for the season while i save up for a new shortblock.

now enter the portion were this becomes a tech question thread...

the cause of this failure is not jumping right up and showing itself. infact it is really confusing...
heres what we DO know.


1. the damage is without a dought the result of detonation, the way it burned up it is something i have seen several times..

2. the motor was tuned to run FAT, because we did not have time for a solid dyno session, my tuner (chad) and i set the fuel to run alittle on the rich side.

3. the fact that we were running rich was evident in the other cylinders as NONE of them show any signs of running lean at all...

4. the hole is not in the center of the piston, it is on the outermost portion of it.

so now comes the problem. why??? why did this one cylinder detonate?

we have it down to 2 possable troubles...

1. injector failure, i am going to try to prove or disprove this ASAP. these are brand new racetronic disk style 42lbs injectors, there is no reaon it should have failed but it must be tested to know for sure.

2. some unseen trouble with the afr head caused a hot spot. basically some trouble in the cooling passages in the head like a blockage or even a bad cast causing the combustion chamber of #7 to develop a hotspot, once getting hot enough it would cause predetonation, also backed up by the fact that the metal off the piston fuzed itself to the head in the same spot it burned from.

these are the only 2 reasons i can think of... if you have any ideas i am totally open for them...

i will not place the blame on ANYONE or anypart until i know 100% what the cause is, the reeasons listed above of only theory until we have had chance to know for sure... once the trouble is found, if it turns out to be one of the 2 listed above, being that the parts were installed new only 1500 miles or so ago i will keep you informed as to how said vendor responds and/or makes right...

it really sucks , but i am not going to cry over spilled milk, next year i will be back with a new shortblock and faster then ever... :thumbsup:
 

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That really sucks.........sorry to hear that. Hopefully you can figure it out.

Do you know what the next motor will be exactly?
 

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Discussion Starter · #3 ·
408... :D
 

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Was this the stock bottom end?
 

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this was on his stock bottom end.....

Mike i did some thinking last night. as we saw going from cyl 1-7 on the driver bank as we went form cyl 1 to 7 each cyl went a little more lean. My theory is that you are not getting enough fuel pressure in the rail on that bank. if you think about it those are 42 # injectors on a stock fuel pump. now i dont know what pulse rate they are set at but if they are throwing out more fuel than the rail is getting each cyl as it goes back to that portion of the rail is getting less and less fuel.


just my take. i spent 3 hours in the car on the way home from your house thinking about this.
 

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im thinking its not supplying enough pressure in the rail and what little those injectors are getting they are spitting out but its not enough to run right with his tune. hence why it is leaning out.
 

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#7 is the weak link on the LS1 and it tends to run lean, on one of our cars we had a detonation problem on number #7 that blew a chunk out of the piston and damaged the wrist pin so much the piston barely move on the rod, also cracked the cylinder wall.
 

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Discussion Starter · #10 ·
i have also heard that #7 could be the weak link, but at our mph and running a fat tune i dont see why it would be running low on fuel.
i was pretty sure the stock fuel pump was ok for most H/C cars, and at 115 mph it not like we were making rediculouse power...
 

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think about it tho, if the injectors are spitting out more fuel especially at higher RPM's the fuel pump isnt able to keep the pressure in the lines. While most head and cam cars are running stock pumps.... they also havent gone with 42# injectors like you have. plus you also have to think at what rate they are going at with each 500 RPM. i think the pump just isnt able to keep the pressure up in the rail and not supplying enough fuel to the cyl. as the RPM's raise
 

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Discussion Starter · #12 ·
also thinking more about it, if this was something that would have killed the motor like this, there should have been SOME kind of tell tale...

we logged several hours while we were street tuning this set up... there was absolutly 0 Knock retard... if there was not enough fuel getting to #7 then sould there not have been at least alittle KR ?

it just seams odd that it out of the blue BAM loses it, but showed no signs before hand...
its not like we had any kind of max set up... 205 afr's comp 224 xe-r cam and bolt ons... i just dont see were that was enough to be too much for the fuel pump...
 

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Discussion Starter · #13 ·
Raven02Ta said:
think about it tho, if the injectors are spitting out more fuel especially at higher RPM's the fuel pump isnt able to keep the pressure in the lines. While most head and cam cars are running stock pumps.... they also havent gone with 42# injectors like you have. plus you also have to think at what rate they are going at with each 500 RPM. i think the pump just isnt able to keep the pressure up in the rail and not supplying enough fuel to the cyl. as the RPM's raise
i'm tracking were your going with this, but the injectors are RATED at 42lbs, they are only going to pump as much as our tune scaled them to flow...
you can put 160 lb injectors on a stock car... but only have them flow what you need to run the stock motor...
 

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What brand injectors are you running? You might want to take them out and have them flowed. The Accel stuff is not the best for keeping all the numbers close to each other. Looking at your mph and times I'm guessing you are making about 475hp and even at a conservative .55 BSFC at 44psi the 42# injectors should have you covered at 80% duty cycle.

Put this link on your favorites to look up injector size really easily. http://www.iroczone.com/calcs/injectorsize.htm
 

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Discussion Starter · #15 ·
revolutionary said:
What brand injectors are you running? You might want to take them out and have them flowed. The Accel stuff is not the best for keeping all the numbers close to each other. Looking at your mph and times I'm guessing you are making about 475hp and even at a conservative .55 BSFC at 44psi the 42# injectors should have you covered at 80% duty cycle.

Put this link on your favorites to look up injector size really easily. http://www.iroczone.com/calcs/injectorsize.htm

racetronics disc style injectors
 

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revolutionary said:
What brand injectors are you running? You might want to take them out and have them flowed. The Accel stuff is not the best for keeping all the numbers close to each other. Looking at your mph and times I'm guessing you are making about 475hp and even at a conservative .55 BSFC at 44psi the 42# injectors should have you covered at 80% duty cycle.

Put this link on your favorites to look up injector size really easily. http://www.iroczone.com/calcs/injectorsize.htm

how do you know what HP he has just by judging his MP and times.... i have seen cars with only 380 hp go faster and have more MPH in the 1/4 than he does. no offense but hp really dont mean too much at the track. :poke:
 

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Discussion Starter · #17 ·
i was wondering the samething since my MPH is WAY low for the power i am making....

when i was 400 RWHP i was trapping 116 mph, now i am probably around 450 rwhp but trapping 115... we just never got this thing dialed in...
 

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did you find out what happend w/#7 ?
 

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If the LS engines are tempermental on #7 put a 45lb. injector into that hole, and of course run a fuel pressure gage at full bore on the dyno to see if it drops off . RON
 

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#7 piston has a hole in it in the top right hand corner. ran lean somehow......
 
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