The million dollar question.. What did this?? (PICS!)

[white-rhyno]

What would have caused this?? I pulled this quadrajet off a customers 87 dolphin motor home with a BBC 454. The only guess we had at the shop was because the heat riser valve was a bit rusty and stayed close while he was pulling a hill. This would cause a tremendous amount of heat to travel through the intake manifold. Any other thoughts?? We did get it running again with the 850cfm q-jet off my truck. Ran great actually.

 

[az-k5]

Well with ths scorched base, and blued butterflies, I would agree with the heat thing. It came from outside causing the baffles to bend into the intake. That kinda damage should need a whole lot of heat though. Glad it wasn't me drivin or following the guy.

 

[BlazerGuy]

DAMN! I assume the pieces didn't do much damage????

 

[white-rhyno]

Guess not, we pulled only a couple chunks out of the intake. They were stuck to it actually. Didnt make any noise when we fired it up. We are still puzzled.

 

[rjfguitar]

holy crap! /forums/images/graemlins/yikes.gif

 

[leadfoot067]

i wonder if it backfired at one time and dude didnt try to restart it?? otherwise....good one brad /forums/images/graemlins/waytogo.gif /forums/images/graemlins/yikes.gif

 

[ntaj*ep]

I think your right on with a high load scenario, although I would guess a number of issues. High manifold temp. and the throttle not opening fully. I would use some sort of heat isolating spacer under the carb. and make sure the throttle linkage is moving the butterflies to the wide open position. I would also make sure the intake air is coming from outside of the hood.
Just my take on your pictures, Hope you nail it.
/forums/images/graemlins/thumb.gif

 

[tRustyK5]

Aluminum melts at ~1200 degrees F to give you some idea of how much heat the butterfly's saw. I'd concur with your theory...

Rene

 

[Tweetysuarus]

Well I see nobody has answered the $1,000,000.00 question yet! /forums/images/graemlins/histerical.gif HINT: Something that has failed on every Chevy that is equipped with it on the left side of the motor........Hmmmmmmmm????????
/forums/images/graemlins/whistling.gif /forums/images/graemlins/thinking.gif /forums/images/graemlins/whistling.gif /forums/images/graemlins/thinking.gif
Bill

 

[uglychevyZZ4]

[ QUOTE ]
Well I see nobody has answered the $1,000,000.00 question yet! /forums/images/graemlins/histerical.gif HINT: /forums/images/graemlins/grin.gif Something that has failed on every Chevy that is equipped with it on the left side of the motor........Hmmmmmmmm????????
/forums/images/graemlins/whistling.gif /forums/images/graemlins/thinking.gif /forums/images/graemlins/whistling.gif /forums/images/graemlins/thinking.gif
Bill

[/ QUOTE ]you mean the heat riser he already mentioned Bil /forums/images/graemlins/whistling.gif/forums/images/graemlins/grin.gif Last time I saw that all the melted pieces were laying on the driver side bank in the head since that was the only way exhaust was flowing, towing with a rag sucked in the intake will do that too /forums/images/graemlins/histerical.gif /forums/images/graemlins/histerical.gif

 

[chevyjeff]

I have seen a nitros backfire cause that sort of damage to a holley. I bet the carb flooded and kept pouring gas down the intake and caught fire. The air cleaner kept the rest of the motor from burning but it probably had enough air to keep burning for a while.

 

[unclematty]

Ive seen something similar a long time ago, caused by a backfire that caught the carb on fire and was never put out, cause the guy working on it never lifted the hood till he saw smoke. too late! just glad it wasn't me /forums/images/graemlins/eek.gif /forums/images/graemlins/eek.gif

 

[BAJA_BLAZER]

It’s interesting that the damage was only to the secondary barrels and the primaries look unscathed. It looks like the secondaries were not open when it happened by the way both sides of the throttle plate are melted downward. Perhaps the secondaries were not opening when fuel was being dumped in to them and the fuel was left burning in the barrels. By the discoloration and carbon in the barrels it looks to be a “rich” condition and not “lean.” I would also not be surprised if the valve in the exhaust was involved.

 

[K5MONSTERCHEV]

WOW!! /forums/images/graemlins/eek.gif Thats no good.

 

[sled_dog]

[ QUOTE ]
I have seen a nitros backfire cause that sort of damage to a holley. I bet the carb flooded and kept pouring gas down the intake and caught fire. The air cleaner kept the rest of the motor from burning but it probably had enough air to keep burning for a while.

[/ QUOTE ] I'd almost agree, could be the reasoning for the secondaries getting all of it, burned at the back of the manifold maybe and did its damage to the secondaries. Hows the manifold? clean? dirtier than you would expect?

 

[realsquash]

A blocked heat-riser wouldn't do that. If the engine got hot enough to to melt aluminum in the carb it would have done a LOT more damage to the pistons, etc. Maybe it did and you just don't know it yet :P I bet fuel accumulated on disfunctional secondaries and lit somehow, softening the butterflies enough to *fall* in.

I think this happened when the engine was off....

Andy

 

[white-rhyno]

[ QUOTE ]
A blocked heat-riser wouldn't do that. If the engine got hot enough to to melt aluminum in the carb it would have done a LOT more damage to the pistons, etc. Maybe it did and you just don't know it yet :P I bet fuel accumulated on disfunctional secondaries and lit somehow, softening the butterflies enough to *fall* in.

I think this happened when the engine was off....

Andy

[/ QUOTE ]

Well the customer said he was halfway home and started to pull a hill then all of a sudden it was a dog.... The intake looked normal. And it ran fine with the new carb. Did have a little miss at an idle. But the plug wires look a little old. Hard to tell. Pulled like a raped ape going up the hills when we test drove it. Real easy to tune a carb when your stitting right above it. Man, the 4barrels out LOUD when they open with no air clean on top. Love to watch that fuel pour in. /forums/images/graemlins/eek.gif

 

[unclematty]

come on guys use your heads. this was caused by an actual fire. think about it, any residual heat , thats that hot would have melted more than just thos butterflies. I'd bet money that the air filter housing is probably scorched also /forums/images/graemlins/thinking.gif /forums/images/graemlins/hack.gif /forums/images/graemlins/waytogo.gif /forums/images/graemlins/weld.gif /forums/images/graemlins/waytogo.gif /forums/images/graemlins/grind.gif

 

[white-rhyno]

[ QUOTE ]
come on guys use your heads. this was caused by an actual fire. think about it, any residual heat , thats that hot would have melted more than just thos butterflies. I'd bet money that the air filter housing is probably scorched also /forums/images/graemlins/thinking.gif /forums/images/graemlins/hack.gif /forums/images/graemlins/waytogo.gif /forums/images/graemlins/weld.gif /forums/images/graemlins/waytogo.gif /forums/images/graemlins/grind.gif

[/ QUOTE ]

Naaa, the housing is fine.....

 

[1-ton]

One guess I can make at it is: maybe one or more exhaust valves is not opening on one or more of the back cylinders, and hot exhaust gas is be pushed back up the intake manifold, on the exhaust stroke, instead of out the exhaust manifolds. This would indicate the cam lobes have been flattened, and the metal from it is now in the engine. Try pulling the valve covers off, and see if the valves are opening and closing completely.