popcorn exhaust

[thinman56]

think i already know the answer, but....

i installed the FSPP dual outlet header with national parts depot's 2.1/4" dual exhaust with turbo mufflers. had the local muffler shop connect the two together, no x-pipe, ugly but functional (hard to get good custom work these days, sigh). considering the engine's still stock, it sounds pretty good. but, when i decelerate, the exhaust pops like mad. the natural assumption is a leak that sucks cold air up against the exhaust valves, but could there be another cause? there were a couple bolts on the header that needed tightening after i'd driven it 100 miles or so, could it be i ruined the gasket by not retorque-ing right away? is it possible the pipes are just too big and are sucking cold air all the way up from the tips? like to fix this before the new head goes in.....

thanks for any help

 

[MustangSix]

I would check the timing, assuming that you're not talking about a popping noise at the header flange. A little more advance might help.

Also, open your idle mixture screw half a turn and see if that helps.

 

[thinman56]

jack - i checked the initial timing, assuming the balancer hasn't slipped it was about 10 btdc with vacuum disconnected and about 14 with it connected, which i thought was about right. i'll bump it a little, the motor doesn't p9ng at all, so it can't hurt. will also try te idle screw. thanks, bud...

 

[thinman56]

jack - bumped the advance, drove it, still pops, bumped it again, drove it, now almost all gone! just some minor burbling now. also backed the idle screw out a bit, turned it in til it stumbled, then out 1.1/4 turns, it was only out about 1/2 turn. it still doesn't ping under load, at least as far as i can tell. with the exhaust it's a little hard to hear the subtle stuff. can you just keep advancing it 'til it pings when you hit it hard going uphill? it's got some more pop with the new advance setting, that's for sure.....

thanks again!

 

[MustangSix]

You can probably advance it some more. 14 degrees seems to be a good setting for most, but if you hear a rattle, back down a couple of degrees.

In exchange for all the good advice, you can feel free to donate the Norton to FSP...

 

[thinman56]

...uh, that'd be quite a donation. i am probably going to sell it to finance the mustang, tho. don't have the time/room/money for everything...