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Car keeps cutting out at higher RPM - especially when it's hot...

1971Chevelle

1971Chevelle

Veteran Member
Senior Member
I have come to the conclusion that this issue is a fuel feed problem. I run an Edelbrock Thunder AVS2 800 carburetor on my 383, which is at 500 HP. The carb is being fed with the Edelbrock dual feed line. I am, however, still running the factory 3/8" fuel line, which is supposed to only be good for up to around 350 HP.

So, I am looking at upgrading the sending unit and fuel line. RobbMc has a 1/2 sending unit, which is probably what I will use. I found a fuel line kit, but I'm not sure if I should go with the 8AN or the 10AN sizing. I want to future proof it somewhat, in case I ever decide to go with an even bigger small block. Has anyone used the PTFE line before? If so, how difficult is it to cut it - especially since this is dual braided? I will get the sending unit with the AN fitting attached to the tubes to make things easier to hook up (I will just cap the return line, though).

If anyone has used this stuff before, your input will be greatly appreciated. Thanks in advance.


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EVIL ENERGY 33FT PTFE Fuel Line Kit - 6AN 8AN 10AN E85 Fuel Hose

The EVIL ENERGY PTFE Fuel Line Kit provides a comprehensive solution for high-performance builds, featuring a 33FT PTFE fuel line kit with fittings that is engineered to withstand extreme conditions.
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I'd also check if there's an intermittent vapor lock...... had the same problem on the GTO clone with a 455, and as soon as I insulated the fuel line where it went vertical from the fuel pump to the carb, she ran like a champ at any rpm.
 
I just ran PFTE line for my Derale 9000 trans cooler with -6an fittings. Pretty easy to work with, but a simple trick for me is.
I wrap the line in masking tape wheee I make the cut, I use an air powered cutoff wheel and use the bench grinder to clean up and stay wire. I put the line in bench vise with about 3” sticking off end. The 1st fitting to go on the line I grease the fitting, push on and turn counterclockwise until line is flush with inside end of fitting. I wrap a piece of masking tape on line at the base of fitting to ensure I am not pushing line out of fitting when threading 2nd piece. . I use a tapered punch with a greased end and slide inside the line to center the opening and pre grease the inside (I use transmission assembly lube for all) and put a little grease on nipple and threads of 2nd fitting. I use 2 AN wrenches (aluminum) and thread 2nd fitting into 1st fitting on line.
I’ve assembled these lines for 35 years trying every way to make it easier and to ensure a good seal. This is what I’ve stuck to for years now. Hope it helps.
 
Running an air gap intake, so shouldn't be any need for a heat shield. If it was vapor lock, it would not resume by just letting off of the accelerator pedal for a second. When I do that, it will start pulling again as soon as I put it to the floor.
 
1971Chevelle said:
Running an air gap intake, so shouldn't be any need for a heat shield. If it was vapor lock, it would not resume by just letting off of the accelerator pedal for a second. When I do that, it will start pulling again as soon as I put it to the floor.
Click to expand...
watch this very short video and see if this is what you are experiencing.

 
If the secondary door opens too quick it will bog terribly. Don’t know if you tried to tighten the spring tension to slow the opening down. Hope this helps.
 
If this issue came on without any changes in your tuning, I'd suspect the fuel pump. And....not sure where you heard 350hp was the limits for 3/8 line, I've got 500 plus and a 3/8 line....no issues. I've always used the rule of 600hp, then up the size. I think there's others that have pushed that rule and been fine.
 
cheveslakr said:
If this issue came on without any changes in your tuning, I'd suspect the fuel pump. And....not sure where you heard 350hp was the limits for 3/8 line, I've got 500 plus and a 3/8 line....no issues. I've always used the rule of 600hp, then up the size. I think there's others that have pushed that rule and been fine.
Click to expand...
I’m running a stock (stainless steel) size metal feed line from tank to pump and an -8an line to the intake where it splits into 2 -6an feed lines to the 850 dp on a 500” big block. I’m well over 500 hp and no issues in 20 years with that setup.
 
1971Chevelle said:
Running an air gap intake, so shouldn't be any need for a heat shield. If it was vapor lock, it would not resume by just letting off of the accelerator pedal for a second. When I do that, it will start pulling again as soon as I put it to the floor.
Click to expand...
True an air gap helps but you are in Phoenix !
I had a sock collapse on my fuel pump pickup in the gas tank and it would come and go.
 
DJ’s Garage said:
If the secondary door opens too quick it will bog terribly. Don’t know if you tried to tighten the spring tension to slow the opening down. Hope this helps.
Click to expand...

There is no bog at all. It will flat out lay rubber from a dead stop. I adjusted the vacuum door about the 2nd or 3rd day after I put it on (this has been a few years ago).
 
cheveslakr said:
If this issue came on without any changes in your tuning, I'd suspect the fuel pump. And....not sure where you heard 350hp was the limits for 3/8 line, I've got 500 plus and a 3/8 line....no issues. I've always used the rule of 600hp, then up the size. I think there's others that have pushed that rule and been fine.
Click to expand...

Fuel pump is an Edelbrock 1721 110 GPH mechanical. I can't find my receipt for it, but the longest it would have been in is 5 years.
 
I've had a holley and a carter go bad in short time, less than 5 years. Sitting with ethanol can destroy them. Unless you've got an isolator and a viewable fuel pressure gauge, in the cab, I know of no way to check them. I just buy another and r/r the pump. If it's bad, you've solved the issue, if it's not bad, you've got a pump to sit on the shelf and move your suspicions elsewhere.
 
cheveslakr said:
I've had a holley and a carter go bad in short time, less than 5 years. Sitting with ethanol can destroy them. Unless you've got an isolator and a viewable fuel pressure gauge, in the cab, I know of no way to check them. I just buy another and r/r the pump. If it's bad, you've solved the issue, if it's not bad, you've got a pump to sit on the shelf and move your suspicions elsewhere.
Click to expand...

This car never sits for more than a couple of days, as it's my daily driver. I sometimes take the van when I need to pick up stuff for my mom, but I drive this all the time.
 
Car doesn't need to sit for the ethanol to destroy the diaphragm in the pump.... unless the pump was specifically made to handle ethanol it'll die a slow death anyways. Most pumps made in the past 10 years can handle ethanol though.
 
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