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Popping on Overrun
Macbeast - 27/5/12 at 04:58 PM

1.6 Pinto with Weber 2V carb. Searching suggests popping is due to mixture too weak. Presumably this would be the idle setting ?
Do you enrich the idle mixture by screwing the idle adjustment screw IN ? or OUT ?

jacko - 27/5/12 at 05:02 PM

It can be caused by a air leak in the exhaust too
Jacko

owelly - 27/5/12 at 06:49 PM

I would check for air leaks as suggested, but also check the inlet manifold. If its letting air get in, it could cause popping.

ash_hammond - 27/5/12 at 07:33 PM

What is a good way to spot air leaks in an exhaust and inlet system?

jacko - 27/5/12 at 09:04 PM

quote:
Originally posted by ash_hammond
What is a good way to spot air leaks in an exhaust and inlet system?

look for soot marks on joints

austin man - 27/5/12 at 09:20 PM

WD 40 is a good test for air leaks on the induction side spray on manifold and see if tickover / revs increase

coozer - 27/5/12 at 09:39 PM

I want mine to pop and bang on the over run.. going down the hills brrrrrrrrrrrrrrrrrrrrrrrrrrrrrrrrrrrrrrrrrr.. a few bangs, pop would be better

steve m - 27/5/12 at 10:13 PM

My old xflow does all the popping and banging i need,
So what you "new boys want" is real engine with carbs and proper ignition

none of this fancy "pc/eco" shite

hahaha

steve

Macbeast - 28/5/12 at 12:30 AM

So again the specific question - Do you enrich the idle mixture by screwing the idle adjustment screw IN ? or OUT ? (on a Weber 2V )

greavesy7 - 28/5/12 at 05:20 AM

i would say you screw it out but theres no harm in marking the current posission and then trying both as long as you can put it back to wear it was.

popping is usually due to over fueling or air leaks if the mixture is too weak they tend to spit out the carbs

Macbeast - 28/5/12 at 06:32 AM

I also wondered if it could be too much ignition advance - take your foot off accelerator and vacuum advances timing too much ?

cliftyhanger - 28/5/12 at 06:44 AM

I thought popping on overrun is almost normal.

Having had a few "old cars" with SU carbs, they can be great at popping/banging, and later versions introduced a naff little valve in the carb butterfly to enable air to be sucked through on overrun. These often get soldered up.

It is because when the butterfly is shut, there is a bigger vacuum over the jet, sucks more fuel, but much less air. Unburnt fuel enters hot exhaust, and burns there instead. Bang. Same sort of reason you can get flames out he exhaust if you try

If the car is running correctly everywhere else, I would leave it. Otherwise you need to fit some sort of overrun valve.

mad-butcher - 28/5/12 at 08:14 AM

mine pops, burbles and flames out the exhaust when you take your foot off the throttle from 10500 just can't be arsed looking for the air leak, sounds magic pulling off the M53 at 2am on my way to work.

Macbeast - 28/5/12 at 11:26 AM

OK I'll leave it. Thanks all for replies.

Dingz - 28/5/12 at 01:04 PM

In to richen I believe, the screw increases the amount of air to mix with the fuel from the idle jet.