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Hi, I have another question, I have the 428 motor, Dyno max mufflers original exhaust half way back, H pipe, I am getting a sputtering sound coming from the driver's side muffler, passenger side sounds smooth and even, not the driver's side. The car has new exhaust manifold and gaskets on both sides. The exhaust that bends over the rear axle is not mendrel bent so the bends aren't smooth....at all. I thought the H pipe would prohibit this from happening. Thanks!
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Even with an H pipe the majority of exhaust coming out of the driver side muffler is from the driver side of the engine. Sputtering can be a number of things. Your carburetor has two mixture screws. One adjusts the passenger side and one the driver side. It's possible the driver side is not adjusted correctly. You may also have a misfire on that side caused by something else.
JohnJohn Pizzi - Squarebirds Administrator
Thunderbird Registry #36223
jopizz@squarebirds.org 856-779-9695
https://www.squarebirds.org/picture_gallery/TechnicalResourceLibrary/trl.htm -
Do a compression check on all cylinders and report your findings.Comment
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It's my belief the two sides of the carb 'serve' four cylinders each, one side of the carb does the front and rear cylinders on one side and the middle two cylinders on the the opposite side.
And the other side of the carb serves the remaining cylinders.
So I doubt an out of adjustment idle mixture would cause just one side of the motor to splutter.A Thunderbirder from the Land of the Long White Cloud.Comment
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If you don't think so turn one of your mixture screws and see how the exhaust sound on one side changes compared to the other side. There's certainly some crossover in the intake and having an H pipe rather than two separate pipes makes it more difficult to troubleshoot but from experience adjusting one side and listening to the exhaust sound is how we learned to fine tune the carburetor when we didn't have a vacuum gauge handy. You are correct in that it's not cut and dry as far as which side but that's where I would start.
JohnLast edited by jopizz; July 15, 2017, 07:27 PM.John Pizzi - Squarebirds Administrator
Thunderbird Registry #36223
jopizz@squarebirds.org 856-779-9695
https://www.squarebirds.org/picture_gallery/TechnicalResourceLibrary/trl.htmComment
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I like ALL these suggestions. I tend to suspect mechanical faults so Joe's suggestion would reveal a bad valve.
John and Tom's suggestions are probably the correct and cheapest things to check first.
There is another possibility and that is a vacuum leak, which leans the air-to-fuel ratio in the leaky cylinder. So, a vacuum check might help as well. Then, turn on an in-lit propane torch and slowly wave it around the intake gaskets. I would do this outside. If your engine speed increases, you found the leak.
If all this checks out, pull your valve cover off of the faulty cylinder and watch the pushrods and rocker arms as they cycle. You may find one that isn't right. - DaveMember, Sons of the American Revolution
CLICK HERE to see my custom hydraulic roller 390 FE build.
"We've got to pause and ask ourselves: How much clean air do we need?"
--Lee Iacocca
From: Royal Oak, MichiganComment
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This is a case where audio is worth a thousand words. A burnt valve will have a distinctive sound different from many other exhaust noises. If it has a rhythmic sound like a choo-choo train then it's most likely a burnt valve.
JohnJohn Pizzi - Squarebirds Administrator
Thunderbird Registry #36223
jopizz@squarebirds.org 856-779-9695
https://www.squarebirds.org/picture_gallery/TechnicalResourceLibrary/trl.htmComment
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CLICK HERE to see my custom hydraulic roller 390 FE build.
"We've got to pause and ask ourselves: How much clean air do we need?"
--Lee Iacocca
From: Royal Oak, MichiganComment
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Have the obvious like a bad spark-plug or disconnected plug lead or even crossed leads been checked?A Thunderbirder from the Land of the Long White Cloud.Comment
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