Fingers crossed. Affecting all cylinders does seem to rule out a lot of the catastrophic problems just on the basis of probability.
Nice choice of therapy~ best wishes.

With respect to immediately preceeding, wouldn't it be more likely to loose the ring lands on the bottom of the pistons instead of holes in the pistons? Suppose that could be more gradual. But as folks said....8 psi...low compression motor, seems odd to suddenly blow a whole through all the pistons nearly at once.

Maybe the shut-down was due to a fuel pump issue, so it was lean for a while prior, and the compression is tied to cracked ring lands.

I'll be hoping not.

 

Once you blew a hole in a few cyclinders the car would either stop running or run very badly....at that point you wouldnt be able to create the power/detonation in remaing cylinders to cause any more "holes"...therefore you should be able to hold pressure on a leak down on at least a few cylinders. Sounds like it skipped timing some how.?
.
As said, DEFINITELY drain your oil for sure to see whats goign on
The fuel pump is a good call as well....youve probably increased the demand on it via boost/fueling.

 

I'll drain the oil through a strainer and see if anything turns up. The fuel pump is brand new. This is the car that had all the fuel delivery issues so every part of the fuel system has been gone through, including the fuel distributor which was rebuilt and upgraded to higher flow.

This car is pretty loud but wouldn't I have been able to hear detonation (pinging)? It was running really nice right up unitil the "end". Just like someone shut it off.

 

I wouldn't be surprised if you couldn't hear pinging over the exhaust. I will keep my fingers crossed. Look at the bright side, 4.5L motors are cheap....

 

if you were not going full throttle and keeping the rpms under 4k, i seriously doubt it could have been detonation so bad that it would grenade the entire engine.

you can run most engines at stoich at part throttle, and any leaner just reduces combustion chamber and Cylinder head temps. so, REAL lean is not usually an issue or problem.

this one is a puzzler.

im going back to broken cams as a possiblity, but that doesnt explain all holes being without pressure.

i forgot which way the rotor points, but try and rotate the engine 360 degrees and try a leak down test again. if you are leaking in all cylinders, you certainly dont need to lock the crank. just make sure you are just a tad past TDC, or the engine could spin backward. just make sure you apply the pressure slowly.

this one is a tough one to figure out!

mk

mk

 

I sort of had this same thought, so....I ran compressed air into numebr 1 cyl and then turned the crank through a couple of cycles watching the gage to see if at any point in the cycle it would hold air under pressure. It does not.

 

Have you tried listening for air come out of the coolant?

Dennis

 

Guess you won't find out unless you take the cam covers off as a first step...

 

compressed air in the cylinders will come out in the oil pan or the intake /exhaust. Put it at TDC compression for #1, compress the cylinders or run air through them if they are leaking. listen out the tail pipe for air, or in the intake entrance, and finally, the dipstick hole. that should narrow it down. very puzzling.

mk

 

Only if the head gasket is intact. If all the fire rings have shifted, you'd compress the cooling system, but then you would have also found coolant in the spark plug holes.


Here's a thought... are you sure your gauge isn't broken?

 

Correct, unless the water level was below the level of the blown gasket. In that case he would normally have seen white smoke before shut down.


+1 Especially since all 8 are giving the same low reading.

Dennis

 

///

 

Missed that one about the tester... something still doesn't add up.

 

Yes, My radiator and both hoses are out but I cannot hear any air bubbling or hissing in the water outlets.

 

Well then the HG should be intact. That leaves cams, valves, pistons, and rings. None of which are good.