Falls Flat after 65MPH
Thread Starter
Heel & Toe
Joined: Feb 2012
Posts: 22
Likes: 0
From: Niagara Falls New York
Falls Flat after 65MPH
Hey all having a problem that I have been banging my head off the wall to solve for the last month that I need some help on.
Car: 1978 L48
Edelbrock Intake
Holley Street Avenger 670
Headders and side pipes
New furl pump as of this spring
New coil
new hei modulator
new starter
On the highway when I get up to 65mph or 2800rpm she starts surging like it just runs out of gas. I can limp to an off ramp and let her sit for a bit and then fire up and go again but cant go over the 2500 3000rpm range.
When it is cold there isnt a problem but once you get 10mi away on the highway thats when it acts up.
Can drive around all day long on surface streets but just gets mad when she gets pushed.
Thanks all.....
Car: 1978 L48
Edelbrock Intake
Holley Street Avenger 670
Headders and side pipes
New furl pump as of this spring
New coil
new hei modulator
new starter
On the highway when I get up to 65mph or 2800rpm she starts surging like it just runs out of gas. I can limp to an off ramp and let her sit for a bit and then fire up and go again but cant go over the 2500 3000rpm range.
When it is cold there isnt a problem but once you get 10mi away on the highway thats when it acts up.
Can drive around all day long on surface streets but just gets mad when she gets pushed.
Thanks all.....
Race Director
Joined: Jan 2000
Posts: 12,399
Likes: 247
From: San Jose CA
How's the fuel filter? Any kinked lines? When was it last rebuilt?
I'd expect kinked/damaged fuel lines
Dirty fuel filter
Sunk float
There's obviously a few more things it can be.
Is it 65mph or 2500 in any gear?
I'd expect kinked/damaged fuel lines
Dirty fuel filter
Sunk float
There's obviously a few more things it can be.
Is it 65mph or 2500 in any gear?
Thread Starter
Heel & Toe
Joined: Feb 2012
Posts: 22
Likes: 0
From: Niagara Falls New York
Floats are good in the carb. Checked that
Cant locate a fuel filter in line so I guess it is in the tank
Once trouble occurs you have to go easy on it and not go over the 2500 rpm limit or she falls on her face again
and thats in any gear.
Cant locate a fuel filter in line so I guess it is in the tank
Once trouble occurs you have to go easy on it and not go over the 2500 rpm limit or she falls on her face again
and thats in any gear.
Race Director
Joined: Jan 2000
Posts: 12,399
Likes: 247
From: San Jose CA
There's a filter sock in the tank but there should be one inline. Now I'm wondering if you sucked some garbage into the carb.
I'd start with a carb rebuild and install a fuel filter inline.
Do the floats actually float?
I'd start with a carb rebuild and install a fuel filter inline.
Do the floats actually float?
Advanced
Joined: Jul 2012
Posts: 56
Likes: 0
From: San Antonio, Tx
Similar, but fixed problem
I had a similar problem - at 3k RPM it would fall flat on its face, with that surging/bucking feeling that I think you are describing. For me it was a fuel supply issue, which is now resolved. The fuel pump and fuel filter I bought are still sitting in the boxes.
In my case, it was the gas tank and sock. The gas tank had surface rust on the inside, which resulted in rust 'dust' caking on the fuel sock. The fuel sock had also 'collapsed' so it had less useable surface area - which was caked with rust.
ergo, reduced fuel flow.
Replaced the tank and sending unit, and voila - no more RPM issues.
Check the innards of your tank for rust, and see if the 'sock' is somewhat sucked up on itself.
In my case, it was the gas tank and sock. The gas tank had surface rust on the inside, which resulted in rust 'dust' caking on the fuel sock. The fuel sock had also 'collapsed' so it had less useable surface area - which was caked with rust.
ergo, reduced fuel flow.
Replaced the tank and sending unit, and voila - no more RPM issues.
Check the innards of your tank for rust, and see if the 'sock' is somewhat sucked up on itself.
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Race Director
Joined: Jan 2000
Posts: 12,399
Likes: 247
From: San Jose CA
on your car it's not too bad. Just a number of bolts. First you take the gas lid off, then the stuff underneath it. after you've done that, there'll be a few wires/lines to unhook and then a lot of bolts to get the top of the sending unit off.
(78-82, the unit can be pulled from the top)
(78-82, the unit can be pulled from the top)
Thread Starter
Heel & Toe
Joined: Feb 2012
Posts: 22
Likes: 0
From: Niagara Falls New York
Went to all the auto parts stores to get a new sock but they all didnt have anything. I've decided to install an in line fuel filter (that I can see if the element gets dirty) and run with that.
It is all installed and took her out for a ride. No problems past 65 to 70 but the real test will be tomorrow when I take it to work 30mi away all thruway driving at 70mph.
Wish me luck.......
It is all installed and took her out for a ride. No problems past 65 to 70 but the real test will be tomorrow when I take it to work 30mi away all thruway driving at 70mph.
Wish me luck.......
Race Director
Joined: Jan 2000
Posts: 12,399
Likes: 247
From: San Jose CA
Went to all the auto parts stores to get a new sock but they all didnt have anything. I've decided to install an in line fuel filter (that I can see if the element gets dirty) and run with that.
It is all installed and took her out for a ride. No problems past 65 to 70 but the real test will be tomorrow when I take it to work 30mi away all thruway driving at 70mph.
Wish me luck.......
It is all installed and took her out for a ride. No problems past 65 to 70 but the real test will be tomorrow when I take it to work 30mi away all thruway driving at 70mph.
Wish me luck.......
Advanced
Joined: Jul 2012
Posts: 56
Likes: 0
From: San Antonio, Tx
<<nub speaking what I read on other posts - Sock was a strainer to separate water from gas in the event it got in there. That you DID install an inline filter, you won't get crud in your pump (assuming it is before the pump and of good enough micron). You can get a replacement sock from most any of the online sources, worst case it would mean buying a 50 dollar sending unit (or something like that).
Race Director
Joined: Jan 2000
Posts: 12,399
Likes: 247
From: San Jose CA
<<nub speaking what I read on other posts - Sock was a strainer to separate water from gas in the event it got in there. That you DID install an inline filter, you won't get crud in your pump (assuming it is before the pump and of good enough micron). You can get a replacement sock from most any of the online sources, worst case it would mean buying a 50 dollar sending unit (or something like that).
Thread Starter
Heel & Toe
Joined: Feb 2012
Posts: 22
Likes: 0
From: Niagara Falls New York
Bryan that fuel sock was nasty. I don't think it's was from bad venting. But then again you never know. I could literally scrape off crud off the sock. I sure hope that was the problem.