350 losing power on highway - Pontiac GTO Forum
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post #1 of 4 (permalink) Old 07-24-2017, 11:12 PM Thread Starter
 
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350 losing power on highway

Hey ive done some searching on my issue and have been checking off possible culprits but now i gotta ask from some experts.
My pontiac 350 bogs down on me when i hit 70mph. The car accelerates fine and gets up to 70 fine, once it hits 70 it will lose power like its starving for fuel, then will rev up again in a second then a second later lose power repeating this until i get down to around 40mph.

I replaced the fuel pump and filter and timing is set to 14 initial 36 total vacuum advance plugged
this problem initially started at 50mph but after cleaning the carb and putting in a new accelerator pump the problem starts at 70.
carb is an edelbrock 600 1406 stock set up, car runs great, starts great i just cant go over 70 and if i do i have to slow down to 40 to get my power back.
tomorrow il check fuel pressure but unsure how to check it at high speeds. and was thinking it could be metering springs since i dont know what springs are in it now and it does have a mild cam, vacuum at idle is around 12-13.
could also be the choke not being fully open which isn't allowing secondaries to open correctly but not sure why the problem would move by 20mph after just a cleaning and new accelerator pump.

Anyone else experience this issue? or have some more in-sight as to what else could be the issue
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post #2 of 4 (permalink) Old 07-24-2017, 11:42 PM
 
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my guess

time to drop the tank and check the sock

or bad gas tank fuel line .........suckin' air

maybe
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post #3 of 4 (permalink) Old 07-25-2017, 10:58 PM Thread Starter
 
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I was really hoping not to have to drop the tank again haha.
But at this point it's one of the last things to check so il have to do it.
I did notice while looking for fuel line leaks the sending unit fuel line does move a bit side to side. Is that normal or should it be held tight in the tank?
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post #4 of 4 (permalink) Old 07-27-2017, 07:37 PM
 
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Originally Posted by Mage0095 View Post
I was really hoping not to have to drop the tank again haha.
But at this point it's one of the last things to check so il have to do it.
I did notice while looking for fuel line leaks the sending unit fuel line does move a bit side to side. Is that normal or should it be held tight in the tank?
Should not move. Might be your problem right there if the line has a crack in it and is sucking air at the higher fuel demands of high speed running.
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  Pontiac GTO Forum > The 1964-1974 Pontiac Tempest, Lemans & GTO > 1964-1974 Tempest, LeMans & GTO Engine Tuning and High Performance

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