carb question

jgra1 · Unread post by **jgra1** » 08 Mar 2008, 16:38

chaps, what can cause an internal carb fire ? mine has a melted float, and worse, melted areas around the jets... it's a V8 4-barrel single carb...

the only ignition is the plugs... I guess arcing at the distributor cap, or between leads in the most likely.. (in which case this problem would be prevalent on all older cars with carbs?)

My engine has LPG fitted, single point.. I do recall an LPG website noting that if you have plastic manifolds you can't have a multipoint manifold system (die to backfiring).. Is there an inherant risk of backfiring with LPG?

thanks as always
John

MikeT · Unread post by **MikeT** » 08 Mar 2008, 22:23

jgra1 wrote:chaps, what can cause an internal carb fire ?

Oh dear, sorry to hear that.
An interesting question! What has burnt inide the carb?

jgra1 wrote: mine has a melted float, and worse, melted areas around the jets...

Though melting doesn't necessarily imply a flame. Any chance of some pictures?

jgra1 wrote:the only ignition is the plugs... I guess arcing at the distributor cap, or between leads in the most likely.. (in which case this problem would be prevalent on all older cars with carbs?)

Any electrical connection is a potential spark. An engine can detonate without any spark. Friction also creates heat.

jgra1 wrote:My engine has LPG fitted, single point.. I do recall an LPG website noting that if you have plastic manifolds you can't have a multipoint manifold system (die to backfiring).. Is there an inherant risk of backfiring with LPG?

My knowledge of LPG is barely greater than zero but I think it's the old single point systems that are re-knowned for backfires.

jgra1 · Unread post by **jgra1** » 09 Mar 2008, 09:19

thanks Mike..

I have some pics but no webspace to link to

Unread post by **CitroJim** » 09 Mar 2008, 09:21

jgra1 wrote:thanks Mike..

I have some pics but no webspace to link to

Hi John,

Send them to me by e-mail and I'll be happy to host them for you...

Unread post by **myglaren** » 09 Mar 2008, 11:33

jgra1 wrote:thanks Mike..

I have some pics but no webspace to link to

Try Photobucket, ImageShack, TinyPic or PicasaWeb - the last is particularly usefullif you have a Gmail account.
Also Flickr, which is being absorbed by Yahoo, so if you have a Yahoo/BTYahoo account it will eventually be integrated with it although it is taking longer than the predicted.

jgra1 · Unread post by **jgra1** » 10 Mar 2008, 11:19

Jim thanks

myglaren thanks, dooh! I had a bucket account

http://s51.photobucket.com/albums/f364/ ... Rochester/

anyone know anyone with an old 4brl rochester from a boat or chevy van ?

Unread post by **RichardW** » 10 Mar 2008, 12:23

That's pretty impressive damage!!

Only thing I can think of is that for some reason part of the combustion has been taking place in the inlet manifold and heat from this has damaged the venturis and soaked through and melted the float. Not sure why the fire should be in the manifold though - maybe the valve timing is wrong?

Clogzz · Unread post by **Clogzz** » 10 Mar 2008, 12:45

Had that in the Solex carburettor of a Renault R4.
Backfire at start, then carburettor fire and plastic float sunk.
It was caused by retarded ignition timing because of a broken advance diaphragm.
If the ignition timing is late, the engine will also be difficult to start, and be sluggish and thirsty.

jgra1 · Unread post by **jgra1** » 10 Mar 2008, 18:11

chaps thanks

since posting, a few others have commented on these engines spiting back a bit.
but to cause this - more likely a fire burning for a while after shutdown...

when running, the draw of air would be unlikely to allow a raging inferno..
although this clip from a couple of, how do I say, interesting lads disproves this

http://www.youtube.com/watch?v=IWk5r7V9Vok

think I have found a suitable carb in US.. closes on ebay in a few hours

J

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