Upper Intake Manifold Exploded and Started on Fire

Wish I had seen this earlier but if your engine is back together and running then you are probably fine. GM has a tech bulletin for severe engine damage.
00-06-01-026G: Intake Manifold Inspection/Replacement After Severe Internal Engine Damage - (Aug 4, 2015)

Kind of sad that we need a tech bulletin for this isn't it ????????

However its good info. While I cant post the tech bulletin, it's about common sense. They state you should not reuse certain lower or upper intake manifolds after severe engine boom boom due to the difficulty of completely inspecting the internals of certain manifolds. They show pictures of small tinnie tiny debris, along with big debris inside them. If that gets sucked into your engine them more damage and possible boom boom happen again.

Fortunately the 3800 NA upper and lower are very wide open and easy to inspect, but there can also be debris in the intake valve so I hope nothing was in there and it seems you didnt' have any. They go as far as to say replace the manifolds you can't 100% visually inspect. I'd have to agree, better that than to wreck your engine again.

There is another tech bulletin for the FPR, that a generator like noise or whine can be heard and this is due to the FPR o-rings or other inners going bad, you can get a kit to change out FPR internals and keep the external casing:

ACDelco 17113393 GM Original Equipment Fuel Injection Pressure Regulator O-Ring Kit

Contains all 4 internal pcs plus a new external snap ring all for the cheap, non UIM blown up price of 23$, which is about 1/3 the cost of a new GM OE FPR. I heard the wine....errr whine and replaced my FPR guts, that fixed it. I would recommend it to everyone for preventive BOOM BOOM maintenance as I have heard and seen videos of many of this UIM explosions as well.

See this video of an Impala UIM exploding. Rather much think your's looked like this.

After watching, order the kit and make the change. One more thing you can do as a very easy check, is to pull the vacuum tube from your FPR and smell it, if you smell fuel, it needs a fixin', if not smell again another day,

I ended up buying a whole new FPR. Got a Borg Warner brand one for 35 bucks which i thought was a pretty damn good deal. Made in USA and came with all new o-rings. Did have to re-use the filter screen and c-clip from my old one but I don't think that would be what caused the explosion.

As far as checking the LIM I didn't even think to check for cracks in it, but I did have to take a vacuum and an air gun to clean all the debris out of the runners in the manifolds/heads. Spent about an hour trying to clean out all the fire extinguisher dust. Still didn't get all that out but I was able to get all the UIM debris out and I figured eh..... a little sandy fire extinguisher dust never hurt anything. Probably scuff up the cylinders and help re-seat my piston rings. Haha.

Well Im glad you and your car survived the explosion, it really spooks me out. I also read that problems with the CatConv can cause explosions up into the exhaust ports of the engine, something due to it's chemicals melting and being exposed to some other chemical and boom. Seemed like a long chain of events.

I didn't mean for this post to sound like the sky was falling. Its really for very complecated manifolds, long curvy internal tubes that can not be viewed, unlike our nice 3800 short ones.

I'm about to put in my rebuild components for the FPR, god this snap ring must take 10 thousand lbs force to bend, du you recall yours being that hard...or am I getting of topic here.

Anyway gals you sfe and hope the post and your experience to help others to do a good inspection and clean out such as your.
-Don