Sorry this is not a Camaro, but I thought some of you GM mechanics would know.

My friend has a 98 Z-71 4WD Chevy truck with the Vortec 5.7 in it, 137,000 miles. It had trouble starting a month or two ago so he had a tuneup. Well today it had trouble starting again and on his third try the engine had a massive crankcase explosion. It split the timing chain cover, peeled up the driver's valve cover and blew the oil filler tube off. :eek: He said smoke came from the front of the engine for a few minutes afterwards. This was not just a little backfire, it was a bona fide crank case explosion.

I know the engine will have to come out to fix damage from the explosion, but do you guys have any idea what could have caused it to go "pop" like this to begin with? I smelled the oil and it had a mild gassy smell but nothing really out of the ordinary. we cranked it over afterwards and it seemed to crank fine, just didn't want to start like before (would hit a couple times but not fire).

What do you think happened?

Probably the injector unit or the fuel pressure regulator leaking, filled it up with fuel and then when it finally lit ........... :eek:

What Bill said.I saw an older engine do this when the fuel pump diaphram leaked gas into the crankcase.

The 1999~02 GM trucks with RPO-L30/L31 engine have had several problems with sticking injectors on their Sequential Central Port Fuel Injection (SCPI) systems.
Calif. only vehicles were recalled under service policy #99066G for cleaning or replacement of defective injectors.
If he was getting 'missfire' codes with his "Check Engine" light coming on, then he was probably experiencing sticking injectors (note, bulletin refers to 'sticking closed' but sticking open injectors have also been reported).
If the injector sticks open it washes the walls and causes excess fuel in the crankcase.
Have him check for scoring of the walls if he tears the engine down. This could indicate fuel washing.

I smelled the oil and it had a mild gassy smell but nothing really out of the ordinary.

What do you think happened?

Well..the big bang gobbled up all the vapors..but the oil is still contaminated.Just like Bill stated..the pressure regulator leaked raw fuel into the intake and washed down the ring seal.replace the covers and gaskets..pull the plenum and replace the regulator and change the oil and filter.The rings should survive with no more fuel wash imo.

OK, thanks guys. Spoke with my friend this morning and he doesn't want to fix it, he's frustrated with it and wants to sell as is so I might just buy it from him.

I figure it at least needs new tin, new gaskets, and probably a couple fuel injectors so with that mileage I probably ought to re-ring it while I am in there. Especially if the injector probably had been around for a while and the walls are worn or scored.

Any idea what it would cost to fix the fuel problem ??? I have a good idea about the rest, just wondering about the fuel injection stuff.

Agree with your plan. Buy a re-ring kit, change all the bearings, t/set, and injectors along with filter & regulator as a minimum. Cylinder wear would be the determinig factor. New pistons, might include a balance job.

Fuel pump may not be a bad idea either. Plus all the other nickel-dime items related to engine overhaul, belts, hoses, battery cables, etc. The list never ends. Trans maintenance same time, w/seals? Rear axle lube? Brake fluid flush? Pads/shoes?

Snowball is rolling.......

Yeah, that snowball is what I'm afraid of Everett

He wants $2k for it and the Kelley Blue Book is $6k-$7k assuming it was running good. Its a nice truck too -- Z71 package, 4wd, no rust, leather int., cd, 4 seater cab, etc. even has new tires. I might just go for it . . .

I figure I should be able to fix it for $3k worst case so I would only be into it for $5k plus my labor.

Don't know what to tell ya, Man. It is a tough decision.
Time & monies avail?
Do you have room for another vehicle?
Would the purchase work for its room?
Would you use it?
Can you afford the infrastructure expenses?