Last week I did a WOT run and my laptop went for a ride into the back seat. That was kind of disconcerting so I did not watch the gauges much, just tried to keep it straight....LOL. Anyway it seemed like it made a weird noise and afterwards the idle was lumpy, like I imagine a cam might, be so I got a little paranoid about it and did a compression test today to see if I might have burnt a piston.

The plugs all looked in great condition with no wear, light brown insulators and very little carbon fouling.
Compression test results:
1 - 130 psi 2 - 133 psi
3 - 110 psi 4 - 133 psi
5 - 133 psi 6 - 130 psi
7 - 130 psi 8 - 130 psi

So everything looks great with the exception of cylinder 3 (second back - driver's side)

I also found that the hose from the passenger side valve cover to the STS PCV solenoid was split so I repaired that. That may have been the problem but I think it has been split for a while.

The engine still accelerates very smoothly. I have not done a leakdown test yet but will if I can figure out how to get #3 cylinder to TDC.

Any ideas on how bad #3 is and what I should do about it?

 

I did a leak down test today and the results are not encouraging. #3 is only maintaining 30psi/95psi and it is leaking into the crankcase.

Looks like the dreaded piston melt down for sure. It sure happened fast!

 

Ouch. So what's the plan?

 

I am going to need to replace or fix the engine. I am interested in trying heads and maybe a cam so this may be a good opportunity to step it up a notch as well. Got the bug......lol

Calling WCCH tomorrow to get the ball rolling.

 

Good and bad news. Good news is more power is on the way! That is a little different that #3 gave up for you rather than the typical #7. Do you have any more details on what happened, how much boost, how much alky, how much timing?

 

i ran mine on nitrous and burned 2 exhaust valves.if its not smokin i wouldnt think its not the piston unless it broke to top off.if its a hole it should be smokin from the oil gettin into the combustion chamber.where you spraying?mine burnt a hole in both valves that you can put your pinky through but the piston doesnt even have a scratch on it.i would pull a head before i spent any money .ok i read your sig.you run single or dual nozzel ? what size pill in the alky injection?

 

Good news first = more potential for power

Bad news last = more $$$$$$$

But I figure now is a good time to do upgrades...LOL

Well I have no idea why #3 vs #7 but I guess #3 is at risk as well.

What happened was I did not check the level in my tank. It must have been near or slightly less than 1/4 tank. It has happened before but all it did was misfire with no apparent damage. I think with the meth and lean fuel flow it was enough to burn the piston whereas without the meth it just misfired and did not get hot enough to burn a piston. I did not figure this out till the next day when I noticed my tank was empty and I had hardly gone any distance. If there was detonation I more sensed it than heard it as I was very preoccupied with just driving the truck at the time.

I was running around 12 psi boost, 17 degrees timing, and my alky kit set to initiate at 1.5 psi with a gain of 4 and a M15 nozzle. My AFR was 10.5 and went to 16 then back to 9.5 over 10 seconds.

Did it spool fast as well. I planted the brake and gave it about 50% throttle and by the time I looked at the boost gauge it was over 6 psi and about 7.5 psi by the time I got off the brake and onto the gas. Well that part was a rush

 

I run a single M15 nozzle in my alky kit. I did a leak down test and there was no sound of air escaping out the tail pipe (exhaust valve OK) or the intake (intake valve OK) but there was sound and warm air coming out of the PCV valve hole in the driver's side valve cover (leaking by the piston into crankcase). I had the TB propped open and when I plugged the PCV valve back in the air was coming out of the intake through the PCV system and there was no mistaking it. No doubt in my mind that the piston is damaged or the rings are broken.