Pistons not firing 100%

[aaronng]

I was planning on stripping the head off tonight but was going to test the dizzy first.
It cant really be a sparking issue though could it? Not with the amount of smoke thats pouring out, its getting gradually worse everytime it starts so it might be a cracked piston........
Wouldnt mind forged internals but i do mind the long trip back to you! lol

Yes it can be a sparking issue. Unburnt fuel going though mixing with hot exhaust gases from the other cylinders can produce grey smoke.

You can check using those inductive current detectors that you can loop around each lead to see which ones is not firing (or is weak)

[tayl51601]

Its definately the headgasket or a cracked piston.............

Got a creamy paste in the oil cap


This is the highest reading i got on piston no.4


And this is about what i got for the other three (piston no.1-145psi no.2-150psi no.3-165psi)

[delsol9000rpms]

might be a bent valve. do a wet compression test and then pull the head off.

[tayl51601]

Defs somthing to do with the pistons, wet test on piston no.4:

[TODA AU]

Broken ring lands

[tayl51601]

Great so i need new pistons lol, is there a forged or a stronger piston with the stock compression that you would recommend adrain??

[TODA AU]

Great so i need new pistons lol, is there a forged or a stronger piston with the stock compression that you would recommend adrain??

CP Pistons PN: SC7101 - 81.50 10.5:1 C/R
Mahle Motorsport PN: ACR181199F01 - 81.25 9.2:1 C/R
Either one of these will do the job,
The Mahle piston is IMO a little nicer,
But also a bit of a pain too as you will need to narrow up the small end of the rod.
In either case, you"ll need to either have the small end (con rod)modified to accept floating pin or change to aftermarket rods.
Both run tight piston to bore clearences,
Be sure the machinist uses a dummy head for bore & hone.

Anyway...
Pull it down 1st and make sure thats wat the problem is...
Once youve found the problem, be sure to determine the cause & eliminate this from your next built...

Ring lands & head gaskets usually means 1 thing...
Detonation.
Have a real good look at the piston tops.

[tayl51601]

Could have possibly been the spark plugs that i just put in??
Because it was only about 15-20ks after i changed the plugs when it would have detonated, i know the wrong heat range in plugs can cause detonation.
The plugs i used were iriway 8's like you said so they should have been alright.

If i lower the compression of my pistons to about 9 (use the Mahle pistons) that should also help shouldnt it?

[tayl51601]

Also i found this:

Check for loss of EGR. The Exhaust Gas Recirculation (EGR) system is one of the engine's primary emission controls. Its purpose is to reduce oxides of nitrogen (NOX) pollution in the exhaust. It does this by "leaking" (recirculating) small amounts of exhaust into the intake manifold through the EGR valve. Though the gases are hot, they actually have a cooling effect on combustion temperatures by diluting the air/fuel mixture slightly. Lowering the combustion temperature reduces the formation of NOX as well as the octane requirements of the engine.
If the EGR valve is not opening, either because the valve itself is defective or because its vacuum supply is blocked (loose, plugged or misrouted vacuum hose connections, or a defective vacuum control valve or solenoid), the cooling effect is lost. The result will be higher combustion temperatures under load and an increased chance of detonation.

Could it be because i have run the pcv valve to my catch can like this:

[tayl51601]

Sorry about all the questions but what about CP Pistons PN: SC7000 - 81.00 9.0:1 C/R

They will give me a lower compression ratio and are standard size so i dont have to bore the cylinder??

[IEVAQ8]

i cant believe the engine has let go, only just after ur final tune.......

its a fukn shame.......

take ur time building it and ask heaps of questions and speak to the right people and especially ur tuner.........

it maybe possible that the gaping on the new plugs where wrong and it let go with a strong detonation, or possible just coincidence it let go after change of plugs.

let me know if u need any help

[aaronng]

Also i found this:

Check for loss of EGR. The Exhaust Gas Recirculation (EGR) system is one of the engine's primary emission controls. Its purpose is to reduce oxides of nitrogen (NOX) pollution in the exhaust. It does this by "leaking" (recirculating) small amounts of exhaust into the intake manifold through the EGR valve. Though the gases are hot, they actually have a cooling effect on combustion temperatures by diluting the air/fuel mixture slightly. Lowering the combustion temperature reduces the formation of NOX as well as the octane requirements of the engine.
If the EGR valve is not opening, either because the valve itself is defective or because its vacuum supply is blocked (loose, plugged or misrouted vacuum hose connections, or a defective vacuum control valve or solenoid), the cooling effect is lost. The result will be higher combustion temperatures under load and an increased chance of detonation.

Could it be because i have run the pcv valve to my catch can like this:
[IMG]http://img521.imageshack.us/img521/2909/le0c9ceb3e1f4450380b5c6.jpg[IMG]

That shouldn't affect it. Also, PCV is not the same as EGR.
How long were you running your car without a tune, and how long did it take to reach the final tune? Were you driving your car with spurts of acceleration during the phase where you were still tuning it?