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MGB Help: 73 MGB w/ Weber DGV Carb - Popping Downhill?

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martyc

martyc

Jedi Hopeful
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We're loving the new (to us) MGB! One thing that bugs me is that when coasting downhill with closed throttle (i.e. engine braking) there are often "pops" that sound like they're coming from the exhaust.

It's a 1973 that has had the dual SU's replaced with a Weber DGV by a previous owner. It also looks like it has a "performance" exhaust and headers from what I can tell, so it sounds a little different than a typical B in general.

Any suggestions on what the "pops" could be? Recent work since I've owned it includes a valve job by a reputable shop, but I believe it "popped" prior to that.

Perhaps this is normal and I'm paranoid?!?!?!

Thanks, in advance, for any advice.
 
The pop is caused by extra fuel burning in the exhaust system when you let it run on compression down hill. Might be just a bit rich.
 
Re: Help: 73 MGB w/ Weber DGV Carb - Popping Downh

jlaird said:
The pop is caused by extra fuel burning in the exhaust system when you let it run on compression down hill. Might be just a bit rich.
Click to expand...
That is usually the cause. It is normal to have excess fuel during deceleration. However, there should not be enough oxygen in the exhaust system to support combustion of the unburned fuel. The popping is often caused by exhaust system air leaks which supply the additional oxygen that is needed for combustion of the excess fuel.
D
 
Re: Help: 73 MGB w/ Weber DGV Carb - Popping Downh

Is the smog pump and air injection manifold (and the rest of the emissions equipment for that matter) still in tact?

If so then you might have a Gulp Valve that isn't letting enough air into the intake manifold to burn the engine braking fuel in the combustion chamber, and the unburnt fuel is going into the exhaust and igniting with the air being injected by the smog pump.
 
Re: Help: 73 MGB w/ Weber DGV Carb - Popping Downh

You guys mean t' tell me that when I lift in a tunnel with the Elan at 6.5K and four foot FLAMES come explodin' outta the blat pipe I'm ~really~ not P.C.?!?!


...I guess I gotta apply fer them "carbon offsets" now...

RATS! /bcforum/images/%%GRAEMLIN_URL%%/devilgrin.gif
 
Re: Help: 73 MGB w/ Weber DGV Carb - Popping Downh

Or the track car lifts at turn one at 10.5K and you get two foot flames and the crowd goes ahhhhhh that it is wrong. hehe.
 
Re: Help: 73 MGB w/ Weber DGV Carb - Popping Downh

I like the popping in my car's exhaust... only thing is if it's too forceful it'll clear the catalytic converter out. hmmmmmmmmm... /bcforum/images/%%GRAEMLIN_URL%%/devilgrin.gif


no no no no ... I still have to pass emissions tests!
 
Re: Help: 73 MGB w/ Weber DGV Carb - Popping Downh

Nunyas said:
no no no no ... I still have to pass emissions tests!
Click to expand...

Rest of US > California /bcforum/images/%%GRAEMLIN_URL%%/devilgrin.gif
 
Re: Help: 73 MGB w/ Weber DGV Carb - Popping Downh

Nunyas said:
Is the smog pump and air injection manifold (and the rest of the emissions equipment for that matter) still in tact?
Click to expand...

Nope...it's de-smogged. /bcforum/images/%%GRAEMLIN_URL%%/sick.gif
 
Re: Help: 73 MGB w/ Weber DGV Carb - Popping Downh

Mine is really loud when it pops...probably because i have a straight pipe on it /bcforum/images/%%GRAEMLIN_URL%%/smile.gif
 
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