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Discussion Starter #1 (Edited)
Exhaust Popping between 3800 & 4200 RPM's **UPDATE!**

**UPDATE!** See#10

Howdy All! I am hopping you can help me diagnose this. My brothers boat seems to be popping out the exhaust between 3800 and 4200 RPM's or so. You put the pedal to the floor and it will push past the popping to cruise at 4800 RPM's (Pump Probably Getting Loose =) without as much as a hiccup. It was fine when we put it away from a day at the lake, then next time we took it out it popped. Since it started, New Cap, New Rotor, New Plugs, New Wires, New Coil. This last time it ran, past Saturday at Modesto, I re-gapped the plugs from .045 to .037/36 with no change. The plugs did look cleaner towards the back of the engine while the the ones near the front were darker. Thoughts on where I should start?

Stats: 79' Nordic Bubble Deck, Stock 454, Air Gap Intake, HEI, Vacuum Holley 750, Stock Dominator Pump, OT Headers.

Thanks!
 

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Howdy All! I am hopping you can help me diagnose this. My brothers boat seems to be bopping out the exhaust, only between 3800 and 4200 RPM's of so. You put the pedal to the floor and it will push past the popping to cruise at 4800 RPM's (Pump Probably Getting Loose =) without as much as a hiccup. It was fine when we put it away from a day at the lake, then next time we took it out it popped. Since it started, New Cap, New Rotor, New Plugs, New Wires, New Coil. This last time it ran, past Saturday at Modesto, I re-gapped the plugs from .045 to .037/36 with no change. The plugs did look cleaner towards the back of the engine while the the ones near the front were darker. Thoughts on where I should start?

Stats: 79' Nordic Bubble Deck, Stock 454, Air Gap Intake, HEI, Vacuum Holley 750, Stock Dominator Pump, OT Headers.

Thanks!
.
Magnetic Contact in the Dizzy..Had the same problem with MSD
 

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Howdy All! I am hopping you can help me diagnose this. My brothers boat seems to be bopping out the exhaust, only between 3800 and 4200 RPM's of so. You put the pedal to the floor and it will push past the popping to cruise at 4800 RPM's (Pump Probably Getting Loose =) without as much as a hiccup. It was fine when we put it away from a day at the lake, then next time we took it out it popped. Since it started, New Cap, New Rotor, New Plugs, New Wires, New Coil. This last time it ran, past Saturday at Modesto, I re-gapped the plugs from .045 to .037/36 with no change. The plugs did look cleaner towards the back of the engine while the the ones near the front were darker. Thoughts on where I should start?

Stats: 79' Nordic Bubble Deck, Stock 454, Air Gap Intake, HEI, Vacuum Holley 750, Stock Dominator Pump, OT Headers.

Thanks!
VAcuum secondary carbs tend to do that in transition to the secondaries on jets. Fatten the primaries a tad, go softer spring or mechanical secondary.
 

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Thanks Guys. I think I will do both. Go up two in Jets and probably just replace the distributor with this...

https://www.ebay.com/itm/Racing-Che...029725?hash=item283ee72d9d:g:da8AAOSwpFlaOx0K

Hopefully that will be the last of the popping :thumb:
Don't waste your money on a distributor. Jets don't want a vacuum advance and all your advance should be in by around 2000 rpm. I would put a timing light to it and increase rpm until all the advance is in to see where you're all in. You should find you are all in WELL before your issue starts. Find a known good double pumper and try it out..... I think you'll find your cause.
 

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Didn't you used to have a boat called...Heatseeker?

If you are truly popping out of the exhaust, I would recommend removing the valve covers and checking valve lash. That can be a symptom of cam lobes flattening... Better to find it early before all the lobe material gets sent through the engine.
 

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Discussion Starter #9
Howdy All!


Sorry it took so long to reply. Life in the way, so still haven't had a chance to look into it yet for an update. In regards to the flattening cam lobes, if it was doing this, would it still allow me to rev past the popping (3800 to 4200 rpm) and cruise smoothly at 4800 rpm? I was test driving a boat once that was found out later to have a flat cam, and it couldn't rev past 3500 rpm no matter what the owner tried.



Hi Heatseeker! Yup its me. Just getting back into things. How are you doing? Still doing your thing?
 

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Discussion Starter #10
Problem Solved!

And the Winner is... Gone Green!

We replaced the distributor and the popping is gone. Thanks! :)devil
 
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