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Cat exploded, motor is alive, what next

readymix

readymix

3/4 ton status
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May 30, 2004
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Murrieta, California
On the highway a few hours ago. I was running along about 80Mph, 3300 RPM, and the truck backfired very loudly, then died. I saw a huge ball of sparks in the rear-view mirror when it happened. The temp and oil pressure were both normal.

After I got it off to the shoulder, I hopped out with the flashlight and fire extinguisher to figure out what was going on and I saw that the manifolds and cat were all red hot.
What happened????

And where can I get a new motor from? I have a 305 in it now, but I would like to step up to at least a 350. The trick is sticking to the lowest budget possible. I just bought a new house and don't have the cash to deal with this right now.
 
Running way rich and went kaplooie, might be fine, sounds like your cat may have exited out the pipe.

You can probably find a running truck for pretty cheap and just swap out the motor
 
It won't start at all and barely turns over.

It is an 87 also, so I have to deal with the computer if I go with a 350
 
TBI 350! Easy enough just source an entire parts truck or make sure that the engine is COMPLETE. SUcks having to source small tedious parts for it
 
Simple to swap 305 TBI to 350. All you need is the 350 chip, injectors, knock sensor, and ESC module. All other sensors, connectors and parts are the same. Pretty much plug and play. No programming needed.
Best if you can get a complete TBI truck 350 with all the sensors and pull the chip from the donor ECM and plug it into your ECM. Just make sure it is from a truck and not a car. Unless the car ECM is a 747.
 
The other problem is that I live in the barracks and have no place to deal with a donor truck. The timing of this whole thing is horrible.
All good information though. I am going on the hunt today for an engine.
 
cut the CAt out and see if it will start. cat could be plugged up. had that problem on my 85 when i first tried starting it with a new engine installed.
 
Why do I need the knock sensor and ESC module? Aren't they the same from a 305 to a 350?
And I thought the 350 TBI unit was bigger than the 305, not just the injectors?

I am going to search the yards around here for a running 350. No quite ideal, but I am strapped for cash.
 
I just tried to start it again. It cranks fine but will not turn over.
I am going to cut the cat out in a few hours. Waiting for my buddy to get out of work.

I hope it is that simple.
 
Knock sensor and ESC are specific to the motor. I suspect it has to do with sensitivity of the sensor itself. They are indeed different.

TBI units aren't different except the 454. 305, 350 and 454 all use specific injectors.

Crank/turn over are the same thing. Crank but no start is how GM terms it.

You might want to verify that your injectors are working. Fuel pressure and injector pulse are necessary for the engine to run, regardless of the cat.
 
Just got back from messing with the truck. Here is what I found

The cat melted down and blew out through the muffler. That explains the light show I saw last night.
I also found the reason it would not start. The rotor was in 3 pieces, but the cap was fine. What would cause that?

So I replaced the rotor and cut off the exhaust before the cat, and it started. Still had god oil pressure. What should I check from here? Something had to cause all of this and I would rather not have to deal with it again.
 
Cats don't last forever, and the plastic rotor might of been loose and cracked. At least you don't need a new motor.
Tarey
 
Your timing could of been a little off with the cracked rotor and changed your timing causing glowing exhaust manifolds.
Tarey
 
I thought of that earlier, thanks for reminding me though. I need to get another timing light tomorrow after work. The other one is in So-Cal.

I have been seeing a small puff of smoke when I start the truck once in a while. Would the engine burning oil cause the cat to get clogged and run that hot?
 
Yes that could do it. I hooked a valve cover breather up to the carb wrong once and it sucked so much oil in the motor I cracked a valve.
Tarey
 
readymix said:
I have been seeing a small puff of smoke when I start the truck once in a while. Would the engine burning oil cause the cat to get clogged and run that hot?
Click to expand...


A small puff is the valve seals... Nothing I'd worry about. Many trucks will do this for a long time. Mine did and lasted over 300,000 miles.

John
 
GNERGY said:
Your timing could of been a little off with the cracked rotor and changed your timing causing glowing exhaust manifolds.
Tarey
Click to expand...
Had this same exact thing happen to me. Not on a chevy but one of my hondas. The distributor bearing wore out and caused the timing to be all screwed up. The CAT turned white HOT and was shooting sparks out the back. It melted the cat, replaced the distibutor and CAT and the car was fine.

Sounds like this may be the same isssue the OP is having. Except his root cause is the cracked rotor.
 
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