440 Six-Pack install: Woohoo! It's on! But needs adjustment... ideas?

[Grec]

I know this stuff is hard to diagnose over the Web, but here goes...

Finally got the last piece in place (3/8 pipe fitting for brake booster vaccum). Primed the carbs and checked for leaks. Fixed the leaks. :-)

Turned her over and ba-da-bing! she started right up and kicked into high-idle just like she was supposed to.

BUT... I'm getting a fair amount of popping/backfiring in the exhaust, even at idle. Not "startle the crap out of you" loud backfiring, but definitely very noticible.

Does this sound like a mixture issue? Backfiring ususlly means running lean, no?

It's pretty much just the center carb that gets the adjustments, correct?

I'm not even sure where the mixture screws are, so any help is appreciated.

 

[MEK-Dangerfield]

It sounds like you could be running lean. Check a spark plug and see if it's white-ish. To be back-firing, it will be waaay lean. I'm not familiar with the six-pack setup, but there should be an idle mixture screw on the side of the middle carb. If you are lean, going with bigger jets would be my first move.


  Mike

[Grec]

Does anyone have a pic/diagram that shows which screws adjust what on the center carb?

I'm pretty sure I just have to reduce the air in the mixture...

[moper]

The center carb has two screws set int eh block just ahead of the body, between the body and the float bowl. Turniong the screws in leans the mix out, tunring them out richens it. You should have a vaccum gage plugged into the vaccum nipple under the center carb's bowl, and set the mix for the highest steady vaccum reading. Very small adjustments. Like I go 1/8 turn at a time, and look for the gage to change. it sounds lean to me too.

[Chryco Psycho]

the outboard carbs also have mixture adjustment screws , they are located under the float bowl & usually hidden behind a steel cap , once you remove the cap the scres can be adjusted although getting at the rear ones is difficult

[Grec]

The out boards wouldn't have any effect on performance at idle though, correct?

They only come into play with mid-to-full throttle...?

Good to know that's where I would need to look at if I found I was running lean or rich at the higher RPMs.

Thanks.

[Chryco Psycho]

Actually no , the outboard idle screws work the same as the center carb & do work at idle , generally I set the rear carb at 3/4 turn from bottom before installing the rear carb