How to: Blow up a 3500

[robertisaar]

you know my preference for 95-earlier Jon!

i'm looking at an 04 'Bu service procedure for the PCM and am seeing no mention of it, so i assume it went away at some point.

[Jonpro03]

You got me sir

You're the one who's supposed to know all this crap.

[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?

[Jonpro03]

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

[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]

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]

describe your module....

or a link?

[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.

[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.

[pocket-rocket]

Cometic time.

[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?

[HOYS]

This looks like the same failure Aaron had.

[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.

[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]

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