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Discussion Starter #1
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Kinda confused on this one. this happened twice back to back. #3 piston smoked the first time. Upon rebuild I used new pistons, cylinders, head with fresh valve job. timing on this motor is set at 4 degrees total when using both systems. pulled another 3 degrees out of this hole. Changed injector also..... system a/f was 12.8/1. I don't have all the cam #'s in front of me but the lobe centers ended up in the range of 114 intake 120 exhaust. Other 3 cylinders are fine just issue with this hole for some reason.......
 

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Just wondering what brand of piston it was? Pretty sure my friend had "issues" with Ross pistons melting, on the unit..
Gary G.
 

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Discussion Starter #4
That is actually an MTC piston. We run these in pro mods all the time. I used CP pistons the second time with the same result
 

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looks like not enough fuel.. I had a piston looked exactly like that, I forgot to turn on the nitrous specific fuel pump..
 

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Discussion Starter #6
yea that sucks. I know that the timing was dead on and its an EFI dominator fuel system so as far as the fuel numbers being accurate I am confident they are as far as the ECM goes. I guess it's time to start looking at the injectors and flow testing them so see if the culprit is there. Just didn't think that would happen a 1 degree of timing in that cylinder.....
 

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A buddy of mine has a turbo sbc that has a number 8 piston that looks like that. His injector dumped on him. Went DEAD lean.
 

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Whats the thickness at the valve pocket to top ring?

It looks really bad but that is just the result of the problem that started there.

Hows the wrist pin bores look?
 

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Discussion Starter #10
wrist pin bores look okay. the pins came out fine. they were not tight or a cracked or anything. the rim of the piston to the top of the first ring is .300
 

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For anyone wanting to take a swing at this one...
Just should know that #3 crank throw also
Holds the crank/clutch drive gear.

I'm not making an assessment here.. Just giving info.

J
 

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I think Steve asked the 10,000 dollar question. Since he opened the safe.. I am keeping my paws out till he has a chance to respond.
 

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Discussion Starter #17
fast house is correct about the #3 cylinder so im assuming that it would be more timing and fuel sensitive....but which caused the problem????
 

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Kinda confused on this one. this happened twice back to back. #3 piston smoked the first time. Upon rebuild I used new pistons, cylinders, head with fresh valve job. timing on this motor is set at 4 degrees total when using both systems. pulled another 3 degrees out of this hole. Changed injector also..... system a/f was 12.8/1. I don't have all the cam #'s in front of me but the lobe centers ended up in the range of 114 intake 120 exhaust. Other 3 cylinders are fine just issue with this hole for some reason.......
Is the only tune related change from first meltdown till now the timing in this cylinder. What is tune in each system. What is system configuration. What is last tune you made repeated passes on with success. Do you have an A/F in each cylinder or just the collector.

Many think that pulling ICT is the best fix. In many cases it's at best a patch. In most bike #3 is a problem. So in most cases it will require a different set up then the other 3 cylinders to live. SJ
 

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Discussion Starter #20
Both systems are dry. We run the Holley Dominator EFI. I only have the 1 O2 sensor in the collector. The first system has a .030 jet with a 12/1 N/F ratio Pulling 14 degrees timing from a base of 34. 2ND system is a .040 jet same 12/1 N/F ratio pulling an additional 16 degrees for 4 degrees total timing across the board. However I pulled down to 1 degree total timing and added 5% fuel to the #3 cylinder.
 
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