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Another Thermoquad question

74RRGTX440

74RRGTX440

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Hello all, I have a 74 RR 440, all original car. The other day while driving in warmish weather, the car was running great, but, when I steeped on it to WOT is ran out fuel, I mean nothing, no popping, backfiring nothing just like I shut the engine off, let off and when the rpms dropped to about 2500, car ran perfect. So l think for some reason when the engine gets hot, I'm not getting enough fuel to feed the secondaries. but plenty for the primaries. Drove the car all summer last year, no problems. The only change I made was that I went back to the OE fuel filter. Anyone have any insight into this or experienced this problem? ANy suggestions appreciated.
 
Are you going from cruise to WOT? Sounds like accelerator pump. If you slowly roll to WOT what does it do?

I fought with an accelerator pump after a rebuild. Acted like what I think you’re describing.

I can’t image your running out of fuel supply that quickly.
 
69L48Z27 said:
Are you going from cruise to WOT? Sounds like accelerator pump. If you slowly roll to WOT what does it do?

I fought with an accelerator pump after a rebuild. Acted like what I think you’re describing.

I can’t image your running out of fuel supply that quickly.
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same thing whether I slowly go WOT or stab it. Only doe sit when weather is hot, engine running about 180 degrees
 
The new gas is really hard on accelerator pumps...you can verify that its working just by working the throttle by hand while its not running and visually watch the squirt nozzles in the top of the venture throats. If its putting out two good streams it's probably not that.
 
moparzepjr said:
The new gas is really hard on accelerator pumps...you can verify that its working just by working the throttle by hand while its not running and visually watch the squirt nozzles in the top of the venture throats. If its putting out two good streams it's probably not that.
Click to expand...
Accelerator pump can cause a bad stumble but will not cause a problem like this. The pump only provides a momentary shot of fuel to keep up with the rush of incoming air when you hit the throttle. If in fact it is running out of fuel, either the fuel pump isn't providing enough fuel to keep up or there is a restriction in the carb that won't accept or deliver fuel fast enough
 
Might be a little piece of rubber from changing the filter got stuck somewhere.
 
Rubber lines break down over time. Have had similar issues at WOT, pulls hard for a few seconds then falls off. The rubber line at the tank was soft due to "NEW" gas breaking it down from the inside out. Just something to check primarily if you have the original 5/16 hard line and a high volume fuel pump (high draw causing collapse of the rubber line).

Second thing to check is the spring that moves the step-up. If the step-up piston is stalled in the bore, it creates a transition issue and won't let enough gas (moving the step rods up) into the system.

So, rubber lines, step-up piston/spring, and accelerator pump if you have done nothing to the carb.
 
artr8 said:
Rubber lines break down over time. Have had similar issues at WOT, pulls hard for a few seconds then falls off. The rubber line at the tank was soft due to "NEW" gas breaking it down from the inside out. Just something to check primarily if you have the original 5/16 hard line and a high volume fuel pump (high draw causing collapse of the rubber line).

Second thing to check is the spring that moves the step-up. If the step-up piston is stalled in the bore, it creates a transition issue and won't let enough gas (moving the step rods up) into the system.

So, rubber lines, step-up piston/spring, and accelerator pump if you have done nothing to the carb.
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Good point, I only use fuel injection line on the rubber. It doesn't guarantee no problems but it is far better line than regular rubber fuel hose
 
Fuel slosh in the bowl. I have a thermoquad, and its very noticeable when I make hard left turn and stomp on the gas, the fuel is all on the right side of the bowl so the accelerator pump is momentarily starved for fuel and when you have a wide open carb, its more air and barely any fuel it will stumble, and I mean go completely silent, then bang, she comes back and off ya go!

Also have you checked your timing? I noticed mine has advanced 4 degrees since last summer, so I need to adjust because the car is running so lean now I get a bit of run on when I shut her down when shes hot!
 
idrivemopar said:
Fuel slosh in the bowl. I have a thermoquad, and its very noticeable when I make hard left turn and stomp on the gas, the fuel is all on the right side of the bowl so the accelerator pump is momentarily starved for fuel and when you have a wide open carb, its more air and barely any fuel it will stumble, and I mean go completely silent, then bang, she comes back and off ya go!

Also have you checked your timing? I noticed mine has advanced 4 degrees since last summer, so I need to adjust because the car is running so lean now I get a bit of run on when I shut her down when shes hot!
Click to expand...
Uhh, how did your timing advance 4 degrees?
 
Because I checked it with my timing light, and its at 18 degrees now instead of 14 when I set it beginning of last summer. For some reason my distributor seems to slip over time, its always done that, even with a new distributor.
 
I wonder sometimes if its the heat cycles of the engine that cause the distributor to move over time, because I do run a 195 thermostat and she gets pretty warm.
 
idrivemopar said:
I wonder sometimes if its the heat cycles of the engine that cause the distributor to move over time, because I do run a 195 thermostat and she gets pretty warm.
Click to expand...
New one on me. There has to be something loose or worn out somewhere, Timing doesn't change unless it's changed by someone/something. Anyway, don't want to change the context of the OPs question
 
Sounds like a problem with the springs in the secondary air valve. Maybe they’re flopping open and it’s sucking all air and no gas.
 
Maybe I can help...do you have messenger?
Carter themoquad group/ manley thermoquads on face book
 
U may have a cracked/ broken vacuum hose. The step up piston may be stuck in the bore. Distributor weights may be sticking. Fuel pump/ f p pushrod worn. Air door on the rear barrels may need more tension. Just a few thoughts. Kim
 
Rebuilt carb, new wires and plugs, and a bad dist pick up module
 
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