How to: Blow up a 3500

[Jonpro03]

Friday night I was out tuning. Went into 3rd WOT. Built 8psi then BOOM. Smoke everywhere. Out from under the hood, out of the exhaust. It filled the cabin in no time.
The engine died, I pulled over and smoke was still pouring out of the louvers. On the ground behind me, a long trail of fluid. I assumed the worse. I figured a gasket in the engine let go or worse, I blew a chunk of engine block out somewhere. It looked like there was only coolant on the ground and no oil. The datalog showed 13.3AFR, 11.5* advance and about 8.2psi boost when it blew.
I called a friend who lived down the road and we went to his house to grab a pressure tester and some water. We filled the radiator and hooked up the pressure tester. It didn't take long to find out what happened. Right in front of the turbo the radiator split open about 3".
I found another TGP radiator in Indianapolis I hope to pick up on Wednesday.

So I towed the car home and started the motor to try and clear out any coolant that got sucked in. It wouldn't run right:

So I tore into it:








Can you see it?

[jmgtp]

That sux. If you werent at WOT when the radiator popped I bet the head gasket would have survived.

Were they the stock headgaskets? I considered changing mine before putting the LX9 in the car but everyone told me I was crazy so I just did the LIM gaskets and called it a day. Then again my motor is stock and staying that way.

[Jonpro03]

Yep, I never had the heads off of this motor. What I'm trying to decided is if it was detonation.

[jmgtp]

The radiator is the wildcard though. Temps in the heads could have spiked when the radiator let go and that could be the cause of the headgasket failure. Otherwise its a coincidence for both failures to happen at the same time. Wouldn't your datalog also show knock counts if it was detonation?

[Jonpro03]

I don't have the knock sensor wired into the megasquirt. I have it wired into an indicator light inside the car. The light never went off.

I think that when the gasket went, it put 8psi of boost into the coolant system and the 21yo radiator couldn't handle the added pressure.

[HOYS]

This looks like the same failure Aaron had.

[robertisaar]

I don't have the knock sensor wired into the megasquirt. I have it wired into an indicator light inside the car. The light never went off.

Jon, you really should fix that, is there any reason it can't be hooked up to the MS?

[pocket-rocket]

Cometic time.

[Jonpro03]

Jon, you really should fix that, is there any reason it can't be hooked up to the MS?

The reason it's not hooked up to the megasquirt is that I haven't hooked it up to the megasquirt.

[Jonpro03]

I went back over Aarons thread and it looks like we had the same problem.

I have a knock problem I need to take care of. For now, I'll just add a lot of fuel up top and retard timing. I need to figure out why my knock sensor module isn't working.

[robertisaar]

describe your module....

or a link?

[Jonpro03]

http://www.msextra.com/doc/ms2extra/MS2-Extra_Hardware.htm#knock

I have that exact same module. I don't remember what I got it off of, a camaro I think.

[robertisaar]

"they were used all virtually all GM vehicles from the mid-1980s to the late 1990s"

LIES!

i've only ever seen them on the 85-89 TPI motors and EARLY V6 applications... most OBD1 applications simply used just the sensor itself and the filter that's integrated into the MEMCAL. and i have to doubt GM going back to using them for OBD2.

but i'm assuming they perform the same function as the knock filters in the MEMCALs, in which case, you might need to find something else, since they are setup to filter knock based on the bore of whatever engine they're intended for. a 5.7 is a 4" and a 5.0 is like ~3.7" IIRC. and the 3500 is right at 3.7" so if you use one of these modules, be sure it's for a 305.

[Jonpro03]

Long story short, is this LT1 module I have going to work?

[robertisaar]

well, a LT1 has a 4" bore, which makes it's natural knock frequency ~5642Hz, compared to the ~6100Hz the 3500 should create...

can't use the knock filter that gets installed into an OBD2 PCM? or did that get phased out?