455 no power, won't go over 60mph

I have a 1971 Buick Estate Wagon with a 455. Mechanical Fuel pump. Crane XRI ignition module in stock distributor.

The car starts instantaneously, idles well. vacuum is 15 in gear at 600 rpms. At low speeds it behaves normally- slow take off from a stop and it accelerates smoothly. punch it and the car struggles. It will only accelerate with very little throttle. It went from running thermostat temp of 180 on the hwy to running 210. I have a dash mounted vacuum gauge- once vacuum drops below 10, you can hear the carb sucking air, but no increase in engine speed.

Timing is set at 6degrees. Plug gap .035. The issue occurs whether or not the vacuum advance is hooked up. I installed a brand new carter mechanical fuel pump. The quadrajet was rebuilt a year ago with guidance from Cliff Ruggles. No obvious vacuum leaks. Filter was clean when replaced. plug wires have under 5000 miles on them. No signs of break or arcing. Coil is a year old. Plugs are new. Fuel lines from metal line to pump are new. Fuel lines from tank to metal line are less than 5 years old and are ethanol rated. no signs of cracking or leaks anywhere in fuel system.

Car was running great- cruising 80mph on the expressway when it started losing power. I nursed the car home 500 miles at 55-60 mph and 8 mpg!

This happened a year ago and cleared itself up.

Your thoughts are appreciated.

 

Still sounds like fuel starvation even with the fuel line and pump replacement. This is the exact
problem I had when I first got the car on the road a few years back. My carb filter was clogged.
I removed that and put an inline filter in ahead of the fuel pump down low. No problems
since. Have you ever checked the sock in the fuel tank around the sending unit?
Maybe some junk in the tank floats around periodically clogging things up.
May also be something wrong with the floats in the carb not filling the reservoirs
up fast enough for heavy demand.

 

Let me tell you one that had me pulling my hair out with the exact same symptons!!! I checked and replaced EVERYTHING trying to repair mine on my 60 Buick.

One night I sat up in bed and thought " What about the INTERIOR (had checked exterior of it) of that little transition from fuel tank steel line to little piece of rubber then back to steel to the pump!?!"

Thing was rock hard but not leaking, finally pryed it lose and the interior of the rubber section was like jello! Mild acceleration? No problem! Step into it AT ALL and that goo closed ranks and sent my car stumbling and bucking down the road!

Hope that is all that is wrong with yours or the fuel sock mentioned earlier

 

Check for intermittent sticking distributor mechanical advance weights.

Larry

 

Sounds fuel related!
Let me guess this is the first time you have run the motor in a while?
1) dead jelled fuel in the Carb.
2) original Rubber fuel lines either falling apart and or dry rotted as hell and the pump is pulling air and not fuel.
3) fuel sock in the tank gummed up by bad fuel.
If you can drive the car somewhere that when the motor starts to cut out you can shut the motor right off and pull over, then pull the air cleaner off and work the Carbs accelerator pump and see if it pumps out a good shot of fuel, if not then , yes you have a fuel supply issue!

 

"This happened a year ago and cleared itself up." ...............What does that mean?

 

As stated this is a fuel issue more specifically a lack of it, some where your loosing it. If you have the room for s small can you can safely place in the engine bay thst will hold a few gals. Run a hose to the inlet of the pump. Thst will divided the system in half, if runs well you will know from the pump up is good and correct the problem is between tank and pump. If it runs bad you know the issue is from the pump forward.

 

Not a good idea at 80 mph to test it. Tee in a guage as suggested and put that question to rest.

 

Could also be an exhaust restriction.
Maybe the heat riser valve is sticking closed?
I have see several new cars that catalytic converters clog up on and and have same symptoms as fuel starvation.
Just another thing to consider

 

I do agree that i would do a fuel pressure check also to see if its healthy or not

 

The pressure test will tell you if there is low pressure, but if the fuel line from the pump to the carb is a hard line, teeing in requires bending or making a new one plus the cost of a gauge and fittings if he does not have one. And if pressures low you still don't know where to start looking.

By splitting the system it only cost a little in a rubber hose, and you have a direction to go cause you will eliminate half the system.

Now I assumed here, and it's a bad thing to do, that when doing this they would really secure the tank so it can't move, tape over the rest of the main opening so gas can splash out, secure the temporary lines, plug the line from the tank to pump so it can't leak. But I guess to me those are all common sense things that most ppl who work on cars would have just done without having to be told to do.

But for the couple minutes of driving needed to get the road test in I stand behind it being a valid test that cost almost nothing out of pocket and gives direction for next step, and does not bend up or require cutting of existing hard lines.

 

If you are planning on eliminating the fuel issue, ..... you can always check with your local AutoZone and rent this kit for free. Best thing is you can keep it as long as you need to and still get all your money back.

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while not very common with BBB, if you have decent fuel, your cam may be flat. It would fit your symptoms.

 

Im have same problem on my riviera 73, change carburetor from Quadrajet to Edelbrock, installed brand new Carter fuel pump. Do you find a solution of this problem?

 

I would not expect the Edelbrock carburetor to be an improvement over a PROPERLY-FUNCTIONING Q-jet. In fact, I'd expect more problems from the Edelbrock.

Look at all the usual problems:
Fuel tank venting
Fuel pickup "filter sock" inside the fuel tank plugged.
Fuel hoses at tank, and just ahead of fuel pump
Crushed fuel tubing
Failed fuel pump
Failed fuel pump eccentric on camshaft
Plugged fuel filter

Practically all of this can be verified "good" with a test of fuel pressure at high speed/heavy throttle.

 

This has been discussed in the past, and I read tons because my freshly built 462 felt like it had a governor on it, ran and drove fine but done reving or making power at around 3500rpm. I thought it was the VooDoo cam so I broke it down and replaced it with a T/A choice. It was not the cam or the lifters, same symptoms. Felt like something was holding it back, but nothing sounded weird or could be found. Believe it.....crazy I know.... it was the tranny, which I thought was 100%, shifted hard and ran great. spent $900 on rebuild and 2700 stall and BAM, ran like it was built to. SO my advice is, don't overlook this possibility.

 

Before install Edelbrock, I have same symptoms on Q-jet. I think the reason was carb, but its not carb problem 99%.