How to: Blow up a 3500

[Jonpro03]

[jmgtp]

POSSIBLY roller-rockers, to try and keep things the same as the 3500.

I don't really know much on this subject but I can say that the above is important in regards to which knock module you use.
I have an LT1 and all LT1s are factory equipped with stamped steel rockers (non roller, tip or fulcrum). I installed a set of aftermarket roller rockers and it was also necessary to install an LT4 knock module. The LT4 is factory equipped with roller rockers and the knock module is 'tuned' to be less sensitive so as to not pick up the 'sewing machine' type noises typical of roller rockers and report it as false knock.... BUT, my LX9 which does have roller rockers runs quiet as a mouse. It doesn't seem to make the sewing machine sounds that my LT1 does. The only thing slapping around is my clutch/trans when the pedal is out at idle. So it may be a moot point.
I'm thinking a 305 knock module would work since I doubt any came with roller rockers. If the LT1 didnt get them, I can't see any 305 getting them. (Plus all the stuff about the bore size and frequencies that Robert mentioned that sailed right over my head).

Also, when I had a code 43 on my LX9 swap I tried the 3500 KS and couldn't get it to work. My issue turned out to be that the OBD I KS I was using had dirty threads and was not making a proper ground. I cleaned it up with steel wool and it works correctly now. Others have said that the LX9 KS should work with the OBD I ecm but it was my experience that it will not.

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.

[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.

[Jonpro03]

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

[robertisaar]

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

[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.

[bob442]

This looks like the same failure Aaron had.

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

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.

[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.

[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]

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]

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]

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]

Ugh... figures.

Well, what came with a 305?