Power cutoff at high RPM - HELP!

[Ploplis]

I am having another major mechanical problem with my '70 GT. The power more or less cuts out at around 3000 rpm in 4th gear When warmed up this happens in 3rd gear also (load related?). I have a webber 32/36 installed that has 2 fuel ports but I have one of them pluged. I have corrected some of the vacume problems already still encounter hesitation when accelerating. I have just finished puting in a electronic ingitor and a new coil, runs better but still have the cutout problem. Does this sound like a fuel system problem. The webber was working okay but it has not been rebuilt. Also, could the drive train be 'slipping' out. I have another trnny to put in but haven't got to it yet. Thanks in advance for the Help...
Bill

[kwilford]

First, a couple of questions:

1) Will it rev fully at lower load, such as in neutral, or even 1st or 2nd gear, and does it seem to have "power" throughout that part of acceleration?
2) Have you changed the spark plugs or plug leads?
3) Is the fuel tank vented properly, so that the vent line from the tank is open? Or has someone (blame a Previous Owner) plugged off the charcoal cannister and vent system believing, if it is related to "pollution controls", it must be reducing the performance? This will cause the tank to be pulled into a vacuum, and starve the pump.
4) Any idea how old the fuel pump is? Can you check outlet pressure? It should be approximately 3.5 psi.
5) Can you check the float level in the carb. This can be done with out "rebuilding" the carb.

Without hearing all the answers, it does sound like fuel starvation, which often shows up as "load related" hesitation. Easiest thing to fix is the lack of tank venting, which is often a problem. Or it could be a worn fuel pump. Or a sticky carb float or needle valve. Or....?

I doubt that what you describe is related to the tranny, so leave that until way down the list.

HTH and let us know some of the answers.

[kwilford]

A little birdie (with the initials RB) suggested another solution:

Keith, the other possibility is the owner hooked the fuel hose to the wrong carb 'inlet'. He mentioned there were two fittings on the carb, this type of 'smog' Weber carb used one as an inlet, the other as a return. The return side is *tiny*, and will supply enough fuel volume for cruising, but not much else. Food for thought....

If that is that the type of carb you have, (of which I am unfamilar with) you might try switching the connections.

And I guess I am now the medium for wisdom from beyond. Kind of like a seance! I FEEL A PRESENCE!!!

[N61WP]

What Keith's "little Birdie" is telling about happened to me when I first got my GT on the road. I had sent the 32/36 off for a professional rebuild. They did a great job, it started right up and ran great, until I got a load on it. It then ran out of gas. I changed to an electric fuel pump, drained and flushed the tank, replaced new filters, and pulled out lots of hair. It was so hard to find because when I pulled the carb top off, it was always full. I then ran it until it died and pulled the top off right there on the road side. It was almost dry. Further inspection of the carb inlets showed what Keith was talking about. One has a very small hole. I swaped the lines and it ran great.
Good Luck,
James

[wiseflock]

If you JUST installed the electronic ignitor and the problem developed... Let me share what happened to me with the Pertronix 1847V, just solved it today.

The instructions said to leave out the dust cap that previously covered the points. The engine started fine but had a miss about 3000 RPM. New plugs and wires didn't help, finally put the dust cap back in and the miss is gone...

-John

[Ploplis]

Guys, Thanks for the input! I'll be taking a look at the carb tonight. Another funny thing is that the loss of power under load started right after I corrected some of the vacume leaks. I've had the webber on for a year or so and never had this problem before. I will check the inlets first thing! Iv'e been avoiding the tank vents but will give them a look too. The last owner removed the canister from upfront long ago.

James - Did your dual inlet webber also have 2 idle set screws (one on each side)? I've alway just set the outboard side and left the inboard side seated. Also, did you connect the retun port or just just cap it?

John - What dust cover for the points are you referring too? I don't think their was a cover on mine.

I'll let you know how it goes. Thanks again.

Bill

[wiseflock]

here's an exploded view of the disributor (FSM 1974 1.9L), the dust cap is a soft plastic cap shown below the rotor.

[kwilford]

Originally Posted by Ploplis I'll let you know how it goes. Thanks again. Bill

Anyone (or Bill) know how this ended up?