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Discussion Starter · #1 ·
chevy 350 stock
625 road demon carburetor (new)
car backfires out the intake when cold
runs rich on drivers side of engine
adjustment on the passenger side does very,little to tune the car....the drivers side front does more of the tuning.

any thoughts on why this is
 

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10,722 Posts
Take the carb off and rebuilt it, clean it very very good, check all the passages. Demon`s often come from the factory with CNC shavings in the passages. that or you have a rather large vacuum leak on one side.
 

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Discussion Starter · #3 ·
i have a vac gauge just for diagnostic work...if i had a leak the vac gauge should tell me right. i was pulling 21 when i put it on...what would the gauge be doing now if i have leak
 

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My pipes are my music
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If you have a leak, the gauge needle will be shaking back and forth like crazy when hooked up to full vacuum on the carb base. I think with your engine, you would have been happier with a 4106 600cfm holley. :D
 

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Dan The Man
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24 Posts
I had the same problem when i was running my 600 holley. it was brand new only a few weeks old. it turned out to be that the passages on the drivers side of the carb were clogged with metal shavings that the very thorough holley guys left in there for me :rolleyes: . After rinsing the carb in carb cleaner and blowing out the passages with the air compressor, the carburetor ran great. So my advice would be to take the carb completely apart and clean it very thoroughly.
 

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Technical Support Barry Grant
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1,500 Posts
glhx said:
chevy 350 stock
625 road demon carburetor (new)
car backfires out the intake when cold
runs rich on drivers side of engine
adjustment on the passenger side does very,little to tune the car....the drivers side front does more of the tuning.

any thoughts on why this is
How much timing does the motor have in it at idle?
 

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Technical Support Barry Grant
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1,500 Posts
DoubleVision said:
Take the carb off and rebuilt it, clean it very very good, check all the passages. Demon`s often come from the factory with CNC shavings in the passages. that or you have a rather large vacuum leak on one side.
Haven't had this issue in quite some time so if it is a new carburetor it should not be a concern. Also the Road Demons have cast blocks and baseplates.
 

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Technical Support Barry Grant
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1,500 Posts
chevroletman223 said:
Tech, the timing would effect all cylinders, not just one side of the engine
If the base timing was too low it can cause what he is seeing as one side could have more adjustment then the other. Generally when only one side is the problem we have found it to be an intake gasket issue as opposed to the carburetor but one has to start somewhere to diagnose it which is why we always start with base timing.
 
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