[alanmay0]

Hello I have a 1967 GTO with the original quadrajet carb on it. When I floor the car and run it up close to 5k RPM's it bogs down like it has run out of gas. If I shift into second gear and I try to run it up to around 5K rpm's it does the same thing. The only think I can think of is that is not getting enough gas. I have no inline fuel filter just he one where the fuel line enters the carb there is a filter.

Could anything else cause the bogging problem. The engine is stock 4 speed.

thanks in advance
alan

[steve25]

Do this.

Drive on a road such that when the issue takes place you can turn the motor off and just pull right over.

Once you have done this if the motor then restarts and idles normal then you likely do not have a fuel supply issue.

Your choke could be closing down and strangling the motor, so you wire that open to see, and also the secondary air flap on the carb might be doing the same.

Here again you wire that open to see, but you will then need to dive into full throttle a lot slower to avoid a big, but once you get to 5K rpm you should know if that was a issue or not.

[kyle_blake]

I once hooked a fuel gauge and long fuel hose so that I could run the gauge under my windshield wiper while car is running. Be safe with routing of the hoses and tape the gauge to windshield ..secure and be safe. then take it out and from standstill do your wot blast , have friend monitor the gauge, it should not drop below 5-6 psi while dropping the hammer , gotta keep the float bowls full is my understanding. When I did my test, and end of the yee haw blast in 3rd gear it dropped to zero. I replaced mine with a carter hi volume pump . re-did test and it stayed steady. check fuel filters and also the lines at fuel tank that connect (sometimes they are rubber back there connecting to main lines . can always blow lines out to with air and then reprime . anyway just some ideas

[Scott65]

Has the sock in the tank ever been replaced? They can be an issue. Sometimes they're still intact, but folded together in the middle, essentially cutting off flow.

[alanmay0]

Originally Posted by Scott65

Has the sock in the tank ever been replaced? They can be an issue. Sometimes they're still intact, but folded together in the middle, essentially cutting off flow.

yes it has a new tank and sending unit along with the copper sock

[alanmay0]

Thanks I will try these test.

[geeteeohguy]

On my '67 GTO I have had the same problem on two different occasions. The first time it was the sock in the fuel tank wadded up into a ball. The second time it was small cracks in the rubber fuel line from the tank sending unit to the steel line. Not leaking, but causing the fuel pump to pull air instead of fuel.

[JacintasHot]

Don't rule out vapor locking due to "winter blend" fuel or whatever bull**** it's called.

[Stuart]

Is the engine tired? Worn cam or valve springs? These cars weren't meant to rev a whole lot above 5,000 rpm when they were new, so if it's worn out it may just not be able to go any higher.

[steve25]

Exceeding the rpm where worn valve springs will let you go will result in back fires thru the carb and a ruff idle for a bit and many times rockers ticking.

In extreme cases the valve float will kick the out the plunger clip from the lifter and then you can never get the valvetrain quite again until you get a new lifter( s) in there or get the clip back in there.

[alanmay0]

Thanks engine was rebuilt about 3k miles ago

[mchell]

Originally Posted by alanmay0

Hello I have a 1967 GTO with the original quadrajet carb on it. When I floor the car and run it up close to 5k RPM's it bogs down like it has run out of gas. If I shift into second gear and I try to run it up to around 5K rpm's it does the same thing. The only think I can think of is that is not getting enough gas. I have no inline fuel filter just he one where the fuel line enters the carb there is a filter.

Could anything else cause the bogging problem. The engine is stock 4 speed.

thanks in advance
alan

Rig a fuel pressure gauge that you can watch and troubleshoot the issue in short order...

5k?....isn't that old Pontiac engine out of breath by then anyways?

[steve25]

Well if you want to get deep into once any motor reaches the rpm of peak torque it’s used up its breathing capacity as is put in place due to the combo of parts it’s made from.

All its parts that effect the total intake and exh flow!

Carb.
Intake.
Cam.
Heads.
Exh system.

[Koppster]

What size/type air filter? I had a similar problem on my 64 and it turned out to be insufficient air.

[jamaca85]

do you have a manual or electric fuel pump. i would start with checking the filter then pump. When the motor was rebuilt did you upgrade the cam? Did they install new springs in the heads or just check the springs?

[Schurkey]

Originally Posted by alanmay0

When I floor the car and run it up close to 5k RPM's it bogs down like it has run out of gas.

Originally Posted by JacintasHot

Don't rule out vapor locking due to "winter blend" fuel or whatever bull**** it's called.

At 5K rpm? Not likely.

A hot-restart after sitting for five minutes, sure.

[jhein]

Ignition problem??

[Formulabruce]

Time to experiment with secondary fuel jets or hangars if its not starved at the bowl and ignition is good.

[Schurkey]

Originally Posted by jhein

Ignition problem??

Maybe. I'd be checking fuel pressure when it's running poorly, first.

After that, there's lots of suspects...but fuel flow is the number one priority for me.

[lust4speed]

I've removed the brass carburetor filter and swapped to a standard Wix type in-line filter and had the problem go away. Just the slightest additional restriction of fuel flow can make a difference on a Quadrajet.