1970 Ford Thunderbird 600cfm Holley flooding.

[MrSony]

Hey all. So, story time. There I was, making my way to McDonald's for a midnight McMuffin run, when my car, affectionately named "ThunderTurd" starts sputtering and spittin somethin horrible. Next thing I know, engine is still running, but power brakes go out. The car itself has power brakes, front disc rear drum, I have full fluid in the master cylinder, but it's like they aren't even there and the pedal is SUPER hard to push while this is happening. I coast it off to a side road, and for the life of me I can't get it started. Keep in mind this has a rigged up toggle-ish type ignition under the dash and I am by myself in front of said McDonalds. And when I do get it to fire, I HAVE to keep my foot (or in this case my hand as I am lying on the floor) on it at about 1000rpm or it will sputter and die. I looked in the carb (car is off at this point) and I can see the throat of the carb is pitch black, but the blades are still shiny and clean. Comes off when rubbed with finger and I can see the vapor from the cold gas on warm carb coming out of the front two barrels. And this car has had a history with running rough and not idleing worth a damn if it's below 30F here. It's 20F as of coasting the 4500lb boat home. It sits in the driveway until tomorrow. So, I'm thinking a GOOD carb rebuild is in order at the very least. It was running fine earlier today btw. Like a top. So, after this long post, what say you guys? I know it's a Ford, but the principles for carb operation should be the same, no?

 

[HOAdrian]

I had a similar issue with a 69 Cougar I owned years ago. Suddenly started running like it had a huge vacuum leak, wouldn't idle, gas consumption doubled. I thought it was going to need a carb rebuild. It turned out the gasket under the carb had failed. The Autolite carb had a cavity between the four venturis. The gasket had been sucked up into that cavity. A $1.21 gasket (that's how long ago this was) cured the problem. Look for a vacuum hose that's off. It could also be the diaphragm in the brake booster has failed. That's easy to check - plug the line to the intake and if the engine runs normally, you've found the problem.

 

[lilbowtie]

Sounds like you haven't done anything since your back fire post.

 

[1evilregal]

do yourself a favor and go back to an original motorcraft carb... I had a holley 600 cfm on my old F100, and the rear float stuck open 1 week after rebuild, and just about caught the truck on fire... luckily I had a back-up carb I was able to run, and after I sold the truck to a buddy, he put a rebuilt motorcraft unit back on and it's never run better. It also went from 8.5 mpg(what I always got with either carb) to 16mpg. I know it's a popular carb manufacturer, but you couldn't pay me to run another holley carb on anything I own anymore, including the lawnmower...

like Adrian stated, sounds like you've got a MAJOR vacuum leak, and with all the carbon, you're def running too rich.

 

[MrSony]

Sounds like you haven't done anything since your back fire post.

I've been doing little bits here and there. Not much when you can do as a teenager who is on leave from work. No cash flow.

 

[MrSony]

It seems to be running a bit better now. BUt with 4 inches of snow here in Iowa and more on the way, can't really test drive it to make sure. Especially with little to no brakes. The electric choke was way out of wack for one, and it's still running rich. If I could afford a new carb or a rebuild kit, new brake lines, etc, I would've done it long ago. Shoestring budget.

 

[MrSony]

I had a similar issue with a 69 Cougar I owned years ago. Suddenly started running like it had a huge vacuum leak, wouldn't idle, gas consumption doubled. I thought it was going to need a carb rebuild. It turned out the gasket under the carb had failed. The Autolite carb had a cavity between the four venturis. The gasket had been sucked up into that cavity. A $1.21 gasket (that's how long ago this was) cured the problem. Look for a vacuum hose that's off. It could also be the diaphragm in the brake booster has failed. That's easy to check - plug the line to the intake and if the engine runs normally, you've found the problem.

What if I pull the line and plug going to the booster itself? would that create the same effect?

 

[RustRocket]

I had almost the exact same problem with my Gutlass. Turns out the vacuum connection on on the back of the carb(for the booster) had come un-done, just enough to kill the car, but was still connected just enough to let it somewhat run

 

[HOAdrian]

Plug the vacuum going to the booster whichever way is easiest. The point is to eliminate the booster from the system so you can determine of it is the source of the problem. There's usually a check valve on the booster to retain some vacuum.

 

[lilbowtie]

(I've been doing little bits here and there. Not much when you can do as a teenager who is on leave from work. No cash flow.)

If you are seeing vapor coming from the front barrels your leaking gas.

Set your blades to the proper transfer port settings frt & rear.
Set the idle air screws to 1 1/2 turns out
Set your float levels.
As stated above check for vacuum leaks or isolate them.
This should be a good start - No cash flow
If you can afford a midnight McDonald run- new needle & seats wouldn't hurt