#1  
Old 07-17-2019, 03:37 PM
allenga allenga is offline
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Default RPMs Dropping Under Moderate to Hard Acceleration

Hey Guys, appreciate your feedback on where to look next.

My car starts and runs fine under normal driving conditions and light acceleration.

Especially after its hot, the car will stumble under moderate to hard acceleration.

RPMs will drop by 1000, then come back, then drop if I hold my foot into it. Feels like the car is starving for fuel.

Not sure if this is coincidence, but I just installed a new DUI distributor. Initial timing is 12 and I have no pinging.

Thank you

  #2  
Old 07-17-2019, 03:49 PM
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Chris65LeMans Chris65LeMans is offline
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If it happened right after you installed the distributor, I’d take a look at that.

More info needed: Did you replace a points system or a different HEI?

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Old 07-17-2019, 03:54 PM
allenga allenga is offline
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I replaced an HEI with an HEI. I actually installed two different new DUI HEI distributors. No change in problem.

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Old 07-17-2019, 04:01 PM
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could be a mild case of vapor lock. Considering this happens at moderate to high throttle openings when fuel need is at it's highest and again only when the car is hot, I'd look for an issue there myself.

When I was still running a carb (1407 eCarb) I would get similar performance as the heat built up in the engine bay. Most often if you popped the hood, you could hear fuel percolating in the carb.

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Old 07-17-2019, 04:05 PM
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I'd first check the gas filter.

Then make sure the tank vent is working like it's suppose to.

Inspect all the short pieces of rubber hose where hard lines are hooked together. One at the tank, one where the hard line goes from the body to the subframe and the one at the fuel pump.

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Old 07-18-2019, 06:13 AM
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If the motor will rev cleanly out of gear to 5000 rpm when you mat the throttle open then you likely do not have a ignition problem, its fuel related!

I can't tell you how many times I have helped a guy who rebuilt his car only to have it do what yours is and at the end of checking out things it turned out the issue was the poor clamping job done on the furl line hose jumper back at the darn tank!

In each of these cases the hose was tight enough to not leak, but it would suck air and since air is far lighter then fuel that's what the fuel pump sucks, air!!!

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Old 07-18-2019, 06:22 AM
jamaca85 jamaca85 is offline
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sounds like a fuel problem or carb. does the carb have a choke? almost like the choke is closing and cutting the air flow...if its a q jet then the secondary flaps might not be openning all the way.

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Old 07-18-2019, 02:02 PM
Schurkey Schurkey is offline
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What is the fuel pressure when the engine stumbles?

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