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Engine running great but a few misfires on decel

1695 Views 8 Replies 4 Participants Last post by  Sergio 69 SS396
So I've been getting on her pretty good as of late and having fun with my MJ467 beastly motor. I have her tuned pretty good. 18 degrees base timing, 36 degrees total timing all in by 3500 if memory serves. Idles at 1000rpm and makes 15" vacuum, which is how I like it. Holly HP4150 DP 750 carb needs a fine tune and maybe some new plugs. Today I noticed a few misfires on decel when I would let off the gas pedal on the freeway. Timing or carb or a little of both? Otherwise response is great and pulls through 5500 and scares me sometime haha.

Just thought I'd ask before I start messing with stuff this weekend. Gracias :thumbsup:
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Like a pop out the exhaust on decel and no foot on the throttle? I would check to make sure all the header bolts are tight to make sure you don't have a leak. Some decel pop is normal in my opinion.
Headers are good :thumbsup:. I agree that it's not a huge deal, but I don't remember it being so apparent and noticeable.
Maybe check to see if you developed a crack in one of your mufflers. If so, could be sucking some air in which will cause popping.

What mufflers? I have Flowmasters and they decel pop a little as well.
Hey hey. Well my mufflers look good too. I have Magnaflow mufflers. Love 'em!
Had magnaflows on my truck. Same thing, no other issues (EFI and tuned) and if I got into the 2,500+ RPM range and let off it would pop on decel. Below that no popping. Freeway decel it would pop intermittently. No leaks, nothing broken, plugs / wires fine not rich or lean. Just the way it was. Had aerochambers as well and same thing.
Yea, same exact thing here! I was going to rebuild my carb anyways and maybe do some jet tuning and timing checks. If it doesn't go away, no biggy. It seems as though the consensus is that it is either normal or not an issue.
some people try hard to get that sound and you are complaining about it...
Someone is trying hard to get misfires on decel? Well have them get an MJ467, run my timing and carb, and then get my Magnaflows and voila, they'll have it, haha. ;) . I'm not complaining about it, I just thought I'd ask people their opinions on the matter. That's what this place is about imho.
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