never higher than 197 for me.

 

Mine does hit 215 when im sitting dead still. Never when im driving does it go over 190

 

This could be the "reason" why #4 blows. But, all of the cylinders may go lean for a moment and all of the cylinders except for #4 can take it because they have a better cooling situation.

 

I will interject my comments and finding into this thread against my better judgement. This quoted post hits the mark. A cast piston has microscopic holes in it. These holes create edges that allow heat to become contained and build up. The pistons are failing in the same spot from photos I've seen and the ones I have replaced. If looking at the engine from the front of the car, failer originates at the 4 o'clock position. Why? This is the hottest spot. All factors are leading up to this. Cast pistons,(not very heat resistent), high boost pressure, (pressure creates heat), furthest point from inlet or outlet of cooling system,(high coolant temps do to coolant flow design around the jackets), next to intake valve,(fresh 02 excellerates temperature rise), small exhaust post, (retain some residual heat by not allowing enough flow), plus a few others. All this heat is creating a glowing spot on the piston; (this has been know from thermal imaging and therfore the piston sprayers were added and directed at a specific spot). Once this glowing spot is present, preignition will take place and erode at the metal, displace it to the sleeve and exhaust valves. If you say you detected no knock, well this entire process is so fast that if you do, the damage is already done. The theory on #4 running too lean do to fuel starvation, thow it away until you get cylinder temps under control.

 

The intake valve side would actually be cooler, not hotter. The fresh O2 does nothing to increase heat, just the opposite. But the rest of your stuff fits.

 

well im confirming this friday what happend to my engine, but i was running a 2.7 at 19 psi with a cobra h/e and it blew...

 

However, fuel starvation and lean conditions would cause even higher cylinder temps which would reinforce all that you just said.

 

what tune were u running? make sure u post up the info!

 

Example= A Blast Furnace. The fresh air should cool that area, but the 02 feeds the already burning metal and therefore excellerates the temperature.

 

2 seperate pumps on 2 seperate lines into each side of the fuel rail wouldn't be the way to go I think. The pumps would be tough to flow match.

I think the 2nd pump being inline then have a split in the fuel line before the rail and entering into the fuel rail on each side with a return in the center would be the best option to fix this problem. I still stick to the theory that running 60 lb injectors starves the #4 cylinder because even with the constant fuel pressure that our pump puts out, the first 3 injectors suck almost every little bit of fuel out of the rail before 4 has a chance to get any.

 

Your example is flawed. The fresh air on the intake side of an engine is not exposed to flame, or any fuel source at a flash point. For the oxygen to promote combustion, the combustion must already exist (like in your furnace). In an engine, the oxygen doesn't burn until ignition, completely contained within the cylinder. On the outside of the intake valve, the fresh air coming in is in fact cooling. Absolutely not heating. Engines would explode. In fact the very theory of reciprocating engines depends on the intake charge air to help in the internal cooling process.

I'm not just making this up. The exhaust side of the cylinder is and always has been the hotter side of every piston engine ever.

 

Halfcent, that's my point. I am fully aware the exhaust side retains the hottest temps and in fact the incoming fresh air charge will help cool the combustion chamber. That is why we have sodium exhaust valves. But, my point is the that the piston is reaching such a high temp, that a glowing ember may form. If this happens, you now have your ignition source which would only be fed by the incomeing 02. This would cause preignition, (lighting off the fuel mixture before the spark event). It can take only one preignition event to break the ringland, which may go undetected as "knock".
Look, I'm only trying to add insight to this problem. I feel the solution will be found by controling internal cylinder temps and swapping out the stock pistons. The theory of #4 going lean just does not seem possible. Fluid dynamics would prove that all injectors would see the same drop of pressure and volume if fuel starvation was evident. Not, a progressive decline as you traveled down the rail. I see the problem is the cast piston, the first upgrade make in all GM literature for building up an Ecotec. I have read nothing of upgradeing the fuel system, pump, rail or lines ect. on any buildup of anything under 400 hp.

 

Alright, now you are adding the fact that the piston has already developed a hot spot and hence a source of preignition. That is a problem by itself, and still has nothing to do with the intake charge. Once the problem exists, now I agree, the intake charge becomes the enemy. But only because other factors already caused a problem.

Anyway, I think we have figured out that cooling is the key here. Does anybody have any data on the coolant circulation patterns of this engine? I gotta believe GM has a picture of the heat distribution.

 

I actually found an animated gif the other day that shows coolant flowing through the engine using arrows of different colors. I cannot for the life of me find it now. Maybe somebody else will stumble upon it.