How to: Blow up a 3500

[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.

[Jonpro03]

[Mach 5]

I have yet to read all the posts but dayum!! That sux!

-Jarek

[Jonpro03]

yeah, this is the reason bxx is getting the TGP.

[Mach 5]

yeah that really sux too bad the car has to go I love that body style soo much. Im sure his wifey will enjoy another project.. well at least you still got the other GP.

[Joseph Upson]

Others have said that the LX9 KS should work with the OBD I ecm but it was my experience that it will not.

How did you have it connected as I've heard the stock crank position sensor should work with the OBD I ignition system though I have not gotten around to trying it yet and I know of one inidividual that succeeded in getting the new style one piece ignition coil pack to work with the OBD I module. Both the late design crank position sensor and knock sensor are powered by 5 or either 12 volts so perhaps that's where the problem was.

If they can be made to work especially the knock sensor that would be the way to go since it's designed with the proper frequency. Another important fact is that the knock sensor is located closer to the cylinder head on the newer motors with a flat contact surface instead of screwed in near the bottom of the block like the OBD I sensor we're using.

Once I recover from being burned out from all the necessary work on the swap I'm going to try to get around to testing both since the stock knock sensor is already on the block and when the turbo goes back on I'll be in the vicinity of both sensor locations. I have to confirm the voltage requirement through the wiring diagram.

[Jonpro03]

Yeah....

[Jonpro03]

12V

[Mach 5]

man Im sorry to Bob but dang you should just rebuild that thing. get another motor swap cometics maybe je pistons slight bore resize for the new pistons throw in some new bearing and call it a day. but thats just me. I feel that if it didnt work out you gotta try it again.. Im still reading the posts Im gonna message you on fb

[Schmieder]

I think I know what happened.........The radiator bursted and all pressure in the cooling system dissappeared rapidly (less then 1 second). This caused a portion of the coolant in the heads to spontaneously boil over. The amount of force is insane, just like a bomb going off in your heads. The intense pressure found the first point of failure, right where you head gaskets busted. As the insane pressure warped the heads pushing them up and away from the block. SInce the heads cooling system had passages, the center piston region was augmented by both side piston regions, providing the greatest pressure at cylinders 3 and 4. Cylinders 1 and 2, along with 5 and 6 had a coolant passage to vent pressure away.

The flash boiled coolant ruptured from the heads into the valley of the oil return from the rockers and probably blew out the RTV seal between the LIM center or the PCV lines.

Just a guess, did you pin point the source of the problem yet? I be curious.....

[95SleeperAcheiva]

By the look of your gasket failure.....

Looks to me that your center slugs maybe a bit lean, got over hot, head warped, ate the gasket, then all your boost shot through the coolant system. When you get her back together, I would suggest either a slug by slug pyrometer gauges (6 of them) and see how they compare or the easy old fashioned way.... Blow down the 1/4 mile and kill the motor at the finish line, then push her to the pits, pull all your plugs and read them.

[Joseph Upson]

By the look of your gasket failure.....

Looks to me that your center slugs maybe a bit lean, got over hot, head warped, ate the gasket, then all your boost shot through the coolant system. When you get her back together, I would suggest either a slug by slug pyrometer gauges (6 of them) and see how they compare or the easy old fashioned way.... Blow down the 1/4 mile and kill the motor at the finish line, then push her to the pits, pull all your plugs and read them.

I think that's a bit much for a non race dedicated motor. I'd say the best thing to do is take it to a machine shop and make sure the deck and head surfaces are well within specs, then if the problem occurs again you'll know it's related to tune or builder error. Not sure about the 3500 but the 3900 uses torque to yield head bolts which should not be reused. I would also move the injectors to different locations on the fuel rail just incase one is not providing sufficient fuel.

As for the radiator failure theory leading to instantaneous coolant boil over in the heads, I can't imagine heat transfer traveling through metal that thick with the kind of speed necessary for that to happen. Chances are the engine was already hot leading to the radiator failure. If the coolant was well above 212 deg F at the time of failure the coolant especially if it was mostly water would boil instantly anyway once the pressure was relieved.

A nagging problem I've had with the 3900 is that if I allow a significant amount of coolant to escape from the engine; installing the thermostat, for example, despite the high level filler neck, the engine will nearly run hot before it burps (~270 deg last incident).

If this motor was run without a knock sensor I would stop right there in my search. My first turbo motor which I burned the rings up in immediately after it was built after a spirited run with the wastegates disconnected from the manifold didn't blow the head gasket but nearly did. When I disassembled it I found an area on the fire ring of the gasket that looked like somone had tried to pry the folded and flattened edges of it up away from the gasket material with a screwdriver and this motor had a knock sensor.

If he kills the motor at the end of the quarter run there's a good chance he'll shorten the life of the turbo bearings.

[95SleeperAcheiva]

What? No one reads plugs any more? :P

I know on the 3100's they didn't fire the low coolant fans till, iirc, 242 deg. I'm having a hard time remembering the exact number, But I DO recall I was rather shocked that it was a high number and just for low fans. Is the 3900's still a wacky high temp like that?

[robertisaar]

just to let you guys know, Jon sold the TGP to a W-body member...

[Joseph Upson]

What? No one reads plugs any more? :P

I know on the 3100's they didn't fire the low coolant fans till, iirc, 242 deg. I'm having a hard time remembering the exact number, But I DO recall I was rather shocked that it was a high number and just for low fans. Is the 3900's still a wacky high temp like that?

Not the plug reading, an EGT sensor for each cylinder, those things are expensive, not to mention setting up access for each cylinder.

I'm not sure what the max safe coolant temp is but the tstat is 185 deg, the engine runs at a constant 196 on a cool day. 240 deg coolant temps have been common with GM since the
80s.