Popping exhaust causes?

A leak in your new exhaust system.

Dave

Or.........it's running too lean with the headers.

Dave

That IS a sign of a vaccum leak or too lean condition...

OR you're running Bosch plugs?

As said elsewhere by our resident idiot... that popping is caused unburnt fuel being ignited in the exhaust. It is unburnt because it wasnt ignited in the chamber. While it's possible for an exhaust leak to cause this popping to be heard, by the induction (siphoning) of air into the exhaust stream, it isnt the CAUSE of the fuel being unburnt, just an element aiding its ignition.

It is caused by the fuel air mixture NOT igniting in the cylinder under no-load conditions.. in YOUR case and others like it, usually because the mixture is too lean or the plug too 'cold'.

Remember a lean mixture causes the exhaust temperatures to increase. If your headers have welding flash protruding into the exhaust stream at one of the joints it might act like a 'glow plug'.

So... a combination of that and all or some of: low compression, lower back-pressure, an air leak in the intake side, timing, spark plug heat range, etc might contribute.

Which is why I asked if you were running Bosch Platinum plugs.... they are notorious for misfiring under no-load, in Ford engines at least.

To test this theory just unhook one of your small vacuum lines and see if it doesnt become much more pronounced.

hey thats what I said

psssst it would read as a RICH mixture since fuel is in exhaust FOCTARD

so this is irrelevant rick mixture makes the pop

thats your best guess LMFAO

please show your proof

pssssst denounced RETARD h u r c

BIT!!!

Bwahahahahahah.. you f##$king idiot!

I did further searches on this and found it's common in high-flow, low back-pressure exhaust systems.. which verifies my experience as a dumb youth when running open exhausts.

Only found one other idiot, besides HURC, who claimed it was because the mixture was too rich.

Summary of possible fixes:

Increase heat range of plugs one range, and/or take out Bosch Plats and put in Autolite or Motorcraft PN specified... or one step hotter

Adjust idle mixture screws out 1/2 to one turn to enrich mixture.

Make sure you have no intake/vacuum leaks.

pssssst hack he HAS an exhaust

cant pop whats not there can you light air on fire? more air more pop good one lets make bullets with more air less powder lets get a bigger pop

LMFAO

dont deviate to a hotter plug FOCTARD lets put a hole in your piston

pssssst thats not how ya tune a carb better get a gas analizer or a propane bottle

h u r c

I can't find any vacuum leaks and I have adjusted the mixture many times with no change. I am not running Bosch plugs but I will try to go up one heat range to see if that helps. I have Edelbrock Performer RPM heads so I am not running the stock plugs. I went with the suggestion of my mechanic friend for the plugs and am currently running Champion 4071 truck plugs that the parts store had in stock. If you have a suggestion of another plug and gap that I should be running I would appreciate it.

Thanks,

Mike

The only real reason to step up in heat range is to avoid plug fouling... hotter plugs can induce pinging (and it's associated engine damage). Exhaust leaks (fairly common with headers) will give popping in the exhaust, particularly on decelleration.... With the throttle closed and engine rpm elevated, the vacuum signal at the idle and transfer ports is very high... drawing excess fuel into the cylinders.... much of this fuel remains unreacted and enters the exhaust system where it can "light off"... even to the point of destroying a muffler....

Spark plug gap will be decided, largely, by the capabilities of the ignition system... for a stock DuraSpark system, I would stick with the 0.045" to

0.050" range. If you have an MSD or similar ignition system, spark plug heat range can remain colder (the multispark at low rpms helps keep the plugs clean) and the CD ignition driver can force feed a decent coil good enough to support a plug gap of 0.060 or bigger.... of course we assume that the rest of the system can insulate high KV requirements effectively.

Rereading your post, I would also suggest looking closely at the wires... especially the spark plug boots. Stock and bargain bin wires can't withstand the heat and the insulation can break down causing all manner of abnormal symptoms. Wires should be routed away from the tubes and wires for #7 and #8 should not be routed parallel to one another to avoid the chance of inductance.... If this can't be done, 7 and 8 should cross each other at as close to 90 degrees as practical... Naturally, if mutual inductance does become a concern, something will have to change....

snipped-for-privacy@hotmail.com wrote: {garbage}

Says that one range hotter plug might burn a hole in the piston... either because of predetonation{?} or igniting too lean a mixture {?} ... so which is it?

But back to the subject... it's only empirical but most on here dont like the effects of using either Champion or Bosch. I have to wonder what's wrong with Motorcraft or Autolite?

And I was assuming that the "popping" was severe enough to be worrisome, i.e.; close to rifle or shotgun sounds... the least objectionble range of the effect is 'burbling' and mebbe that's what is the fact.

I wouldnt even be bothering to post on this if it werent for the OP saying it now happened at cruise throttle... so the question is: Do you notice any slight jerking or hesitation feeling while you are at that cruise throttle position? This is what I see after several thousand miles of Bosch plats.

When you 'tip-in', does the engine respond smoothly?

Yes there is jerking at cruise throttle and it is verry sluggish off the line when cold and not as much when warmed up. The only time it runs really well is when I am accelerating like a bat out of hell and then it seems perfect. As for the popping volume, it's not that loud now with the Edelbrock carb but when I was running the Demon it would sometimes sound like gunfire. I will try a Motorcraft plug. They seem to be difficult to find at the local parts stores though.

Do you realize that is pretty damn important in relation to the original complaint? Since you didnt mention any other problems, the assumption was the car ran fine, otherwise.

I think you'd better have that car gone through thoroughly... esp the timing.

I have adjusted the timing and it doesn't seem to make any difference to the things I have mentioned. None of the local mechanics are any help either. I had one of them rebuild the Demon carb and it started and idled better but had less power and my mileage went from 15 to 10. With the Edelbrock I get more power but it idles worse and I'm still getting only 10 mpg. I did find very slight exhaust leaks between the end of the headers and the pipes but it isn't much.

Here's my point...

1. Cylinder Compression
2. Timing chain wear/slop...
3. Distributor wear

- This can manifest in several ways.

All of these can influence another symptom and mask the true problem. \ FIRST thing to look for is the timing bouncing around at various rpm's

Ok, sorry I didn't disclose all the relevant info up front. The compression is good. There shouldn't be enough miles on the motor for a timing chain problem already, but the distributor is old. I attempted to replace it Sunday but I couldn't get the old one out. The engine was still warm so I will try again when it is cold in case that was the cause. I will also check the timing at different rpm's. Thanks for the suggestions.

Mike