How to: Blow up a 3500

[Jonpro03]

You got me sir

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

[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]

Ugh... figures.

Well, what came with a 305?

[robertisaar]

looks like 1997 was the last year for a replaceable knock module, so a 3400 U-van knock module is a potential idea, though not optimal IIRC.

305?

well, if something was RWD and was made from ~1980 to ~1995, and not a corvette, it was an option like ~90% of the time. i'd go for the latest ones possible, since they will have been equipped with a roller camshaft(~1988 i think?) and POSSIBLY roller-rockers, to try and keep things the same as the 3500.

EDIT: http://en.wikipedia.org/wiki/Chevrol...ock_engine#305

[Jonpro03]

I'll try to find one from a uvan. There's a couple in a PAP close by.

Do you know where under the hood of a Uvan it'd be?

[robertisaar]

http://en.wikipedia.org/wiki/GM_LT_engine#3.736_in_bore_blocks

that may be the easiest path for you ATM.

in a 97 Trans sport, it looks to be RIGHT in front of the airbox, should you still want to go that route.

[Jonpro03]

yep, I think I'll grab the module and the sensors. MSextra recommends I keep the sensors with the modules, Megamanual says to keep the sensors with the engine.

Whatever, I'm putting 3400 knock sensors on my 3500.

[robertisaar]

3400 sensors in a 3500 block sounds like the best compromise there. i would think you'll only need 1 though...

this may help as well i believe it came from here a while ago too. i was going to use it for my OBD1 conversion.... then i found out that the 94-95 3100 A cars had MEMCALs with knock filters built in.



i would verify that it looks believable first before going at it though.

[Joseph Upson]

Since I'm about to bypass my turbo which apparently has blown in short order sharing my 5W30 in smoke form with the people around me, I'm going to try and do one or both of two things; see if the stock 3500/3900 crank position sensor will work with the pre 3500 ignition coil system despite its direct signal, and install the stock knock sensor and run the signal wire to the 730 ecm to see if it will work properly. I have a few areas of low degree ignition retard on a hot engine that I can use for comparison. Despite it's design the frequency range should be near the same as the previous engines, the signal it sends maybe the sticking point if it is different like the CPS sensor which I suspect it is since both require voltage input to work.

Knock sensor light instead of a feed to the ECM, that takes guts because you'll never be able to lift your foot quicker than the ecm can pull timing. I feel your pain though with problems shortly after a fresh build.

[bob442]

This looks like the same failure Aaron had.

X2, think i might shell out the extra $200 for cometic gaskets

[Jonpro03]

Knock sensor light instead of a feed to the ECM, that takes guts because you'll never be able to lift your foot quicker than the ecm can pull timing. I feel your pain though with problems shortly after a fresh build.

The idea was to use it only for tuning, not for driving. Ideally, tune up to a boost level with no knock. Up it two more psi and tune watching the light... repeat. I'll quit messing around and enable the knock retard function on the megasquirt and get it wired in.

About the coils... you are trying to use a 3500 CPS on a 7x wheel? I recall someone telling me that would work.

[robertisaar]

the sensor is a sensor.... it works on the same principle, so i don't see why it wouldn't.

[Jonpro03]

Actually the 3500+ sensors have logic in the sensor itself.

[Alxsmt]

do you have a part number for the 3400 knock module? I was going to go with the one form the 80s cars but not anymore lol.

[Joseph Upson]

the sensor is a sensor.... it works on the same principle, so i don't see why it wouldn't.

The concern is with the signal sent by the CPS, AC (sign) wave from the OBDI sensor vs. a DC wave sent by the 3500 sensor, the OBDI ignition module may need to see the negative wave for a proper count and the 3500 sensor doesn't produce one.