X-flow flame thrower.....

[PACR]

Started up an X-flow equipped car (not a Seven)with downdraught weber last night for first time in a while. It wasn't happy about starting or running but the most worrying thing is that every so often as revs fell to a very low idle a stutter in the engine noise followed by a puff of fuel vapour out of the carb would occur. Not too much to worry about. However when the fuel ball turned into a ball of flame I became a little concerned..... Is there a known reason for this behaviour? Seems like blow-back through the inlet valve - I thought maybe one is sticking? I want to re-assure myself that it's just because its been sat for a while and isn't going to happen with a fuel soaked air filter in place...

 

Cheers

 

Piers

[Richard Gibson]

It sounds as a simple case of the car being slightly out of tune (timing) or most likely the Idle mixture for the carb being out of wack. If it pops at low RPM, you can raise the RPM a 100 or 200 rpm's. Again, get the car warm, check RPM, Vacuum leaks, Timing and Mixture and you should get rid of the backfire/pop syndrome. FYI This is common on a built up crossflow with sidedraft Carb's when first starting out.

 

Richard Gibson

[EFA]

Too much ignition advance.....

 

Has the disti moved??? Are the plug leads in the correct order???

 

 

 

Arnie Webb

The Fat Bloke blush.gif in a Slow Old Vauxhall wink.gif

[Roger King]

It isn't possible to be certain of the cause over the net, but is the engine standard or does it have an uprated cam?

 

The reason I ask is that modified cams rarely work satisfactorily with a downdraught carb. It's all to do with terrible mixture distribution between cylinders and the fact that the throttle butterfly has to be opened so much for idle that it passes the point where the mixture screw has any effect. The emissions under these circumstances are usually off the clock (hydrocarbon emissions that is). Bizarrely, if you fit a pair of DCOEs the problems disappear and the emissions drop drastically.

 

Of course, it is entirely possible that this is not the problem.