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Discussion Starter #1
OK everyone, I ran into something new to me today that I need some help with!
The car in question is a 57 with a 402 big block, mechanical fuel pump.
I had a 650 DP on the engine until about a couple of hours ago. I have been having another, totally different, problem with that one, and instead of trying to figure it out I got lazy and threw my spare 750 DP on it.
Up until now the GM mechanical fuel pump was pushing a steady 8 PSI to the carb, a little high, I know, but no regulator. After installing the 750, it sounds much cleaner and seems to have much better throttle response in the garage. BUT, now the fuel pressure gauge bounces around faster than you can even pretend to see it! I think it is going from about 0-8 or 9 PSI!
When I rev the engine to about 2000 even the hard fuel line is pulsating against the cylinder head (almost thought I had lifter trouble!).
It seems a little too coincidental that the fuel pump would decide to retire between carb swaps.
Open to any and all suggestions at this point.

Thanks,

Clint
 

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Trifive Automotive Electrical Wiring Expert
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26,426 Posts
Could be air in the line. How much have you run it? It will probably clear itself.
 

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Discussion Starter #3
Could be air in the line. How much have you run it? It will probably clear itself.
I was thinking/hoping that too! I hope your right!
I didnt run it too long at all, just long enough so it would be safe to rev a little.
I will run it longer tomorrow and post an update.

Thanks for now.

Clint
 

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Discussion Starter #4
Could be air in the line. How much have you run it? It will probably clear itself.
Good call!! I took it out on the highway after work and made sure to "use up" the gas in the back bowl so it would push any air out, when I got back the pressure was nice and steady.

Thanks for the suggestion.

Clint
 
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