Paxton Problems

[6S896]

Hello everyone, I'm running a Paxton SC on my 350, and every time I brake at a light the car cuts off instantly. She always fires right back and with no problem. I take off everything is great with no hesitation. I come to the next stop sign or light and she cuts off again. She doesn't stutter, she literally just cuts off. I called paradise wheels, but as usual not much they can do over the phone. I have tried to see if there is a vacuum leak, which I can't find one. I know she isn't starving for fuel, because she fires right back up and runs fine. It really only does it when I come to a sudden stop say a stop sign or light on country roads. If I'm creeping downtown from light to light its no problem...I've tried racing fuel (paradise wheels suggestion), I looked through the carb, no problems there. Manual fuel pump is working as again she always fires up....Any other suggestions?

[shelbydoug]

To me this sounds like a fuel level issue in the fuel bowls.

Likely, too low rather then too high.

When you are stopping, the fuel in the front bowl is moving away from the metering body. The front is mostly where the carb idles from. There is a little in the rears but not enough to keep the engine running by itself.


I'd also advise that particularly since you are pressurizing the carb with the blower, it would be a good idea to run the solid nitrofil floats rather then the hollow, soldered together brass floats.

[1175]

Automatic or 4 speed.  If an automatic, is there a dashpot on carb?

[6S896]

4 speed car...Thanks Shelbydoug

[TA Coupe]

Have you tried taking off the belt to the supercharger? To see what happens? You might gain a little data to work with that way.

     Roy

[tesgt350]

Since it doesn't do it when you just creep along and stop, could it be a loose or broke connection that when you do a "Sudden Stop" things shift breaking the connection shutting off the engine and when the Car settles down once stopped the connection is restored?  I have seen that happen before, I think it was in the Distributor.

[67350#1242]

Too high fuel level in rear bowl can cause the engine to die when suddenly stopping. (Fuel sloshes in). IDK if this problem may be accompanied by hard to start situation, like flooding.

[shelbydoug]

Since it doesn't do it when you just creep along and stop, could it be a loose or broke connection that when you do a "Sudden Stop" things shift breaking the connection shutting off the engine and when the Car settles down once stopped the connection is restored?  I have seen that happen before, I think it was in the Distributor.

Now that you mention the distributor, it is a very remote possibility but these cars can now show unexpected wear in places that you would normally never expect it?


One place would be in the distributor. There needs to be zero play on the points cam that the rotor mounts to.

I have had a couple of distributors that needed to have it knurled and reamed. What happens is that if there is play in it, you won't be able to maintain an accurate points setting and if there is enough play, the points will lock up.

The gravitational momentum of the car stopping is enough for that points cam to move several thousands and close up the points. That needs to be looked at and verified but it is more likely a fuel level issue.


The back level in the Holley is the most difficult to get just right,. It's a go/no go to get just right and the type of fuel you use can effect that setting.


Also, if you played with spacers under the carb to get the air box to fit right, keep in mind the angle that the carb is set at normally for a normally aspirated engine.

In cars like the Cobra and the Pantera, the engines are installed with no pitch like in the Mustang. The Pantera didn't use a carb spacer to angle the carb because it used a Ford carb,  but the 427 Cobra did with the Holley carbs and angled carb spacers were used on them. This effects the float level settings in the carb.

The carb mounting pads on Ford intake manifolds are angle cut (I think it is either 12° or 17°, I forget) but that is because the engines get installed on that angle and the carbs were intended to be mounted level.


It is more likely that it is the front level is too low. This normally doesn't even show up until a situation like yours happens. A carb with a low level will idle all day long on level ground with no issues.

[texas swede]

To me it sounds like a vacuum problem in conjunction with the power brakes.
Texas Swede

[FL SAAC]

have you attempted to contact vortech/paxton directly

[pbf777]

The carb mounting pads on Ford intake manifolds are angle cut (I think it is either 12° or 17°, I forget) but that is because the engines get installed on that angle and the carbs were intended to be mounted level.

    Just to clarify:

    With most of Ford's V8 engine installations the carburetor pad is angled up at the rear at an angle of 3 to 5 degrees from the crankshaft centerline; but there 'are' exceptions, one of Ford's most notable that comes to mind is that of the Thunderbirds. 

    But this is not really as critical as one might think, as for example, the '59,'60 "J"-code T-Birds received the 430 MEL engine which was intended for the Lincolns and presented angled carburetor pad which wasn't correct for the T-Bird, hence the carburetor is tilted forward noticeably; and then there have been plenty of hot-rodders & racers over the decades whom have mounted blowers/supercharges (rootes types particularly), these requiring parallelism of the blower's rotors to crankshaft centerline, meaning that the carbs were generally now tilted rearward the sum of the driveline angle, either of these presenting no great difficulties.    

    Scott.

[67 GT350]

Hmmm
My 67 GT350 will start up great, cold, take it for a nice ride and it will idol but then in about 10 seconds it will idol slower and slower until it stalls out, restarts no problem but then stalls again...of course the engine is fully warmed up. Do I play with idol or is there a problem? its a 715 and I am not sure how to adjust it? Is there a "how to adjust article?

[shelbydoug]

We need one of those roulette wheel popup things so we can all bet on what the discovered cause will be? It's anyone's bet now?

[6S896]

So I gave up guys, unfortunately I won't be able to take her to NC SAAC event this weekend. Fortunately I will be able to take my 66 Shelby though. Baldwin Performance Carburetors in Trinity NC is doing me a favor and letting me bring him the entire car. I'll let you know what he finds...

[Royce Peterson]

Sounds like the timing is off. What is it?