[Bosco2]

On the way back from the OMC picnic I noticed that on the freeway at 5500 rpm I would lose power...as if i had a rev limiter. The engine runs and idles fine at all other times. Before I left for Los Angeles I put in some carb cleaner and all worked fine....even past 5500 rpm....but now something's changed.

Apparently I'm suffering from fuel starvation but I wanted to be sure of all the things to check....I'll probably start with the filter and then maybe get something that allows me to check fuel pressures. I have heard about that gas tank sock thing too. Plus maybe this is a good time to put in an electric fuel pump.

Any other things that might be causing this? Thanks,
Mike

 

[kwilford]

Any other things that might be causing this? Thanks,
Mike

Fuel seems like a good place to start. Is it only in third gear (I presume you weren't doing 5500 rpm in 4th, as that would be SPEEDING at 110 mph!)? Will it rev to 6000 rpm in first and second? Fuel starvation usually is most noticeable at full power, at higher rpm. Might be a blocked filter, or plugged filter sock, or weak fuel pump.

If it revs fine in the lower gears, then it is probably not an ignition problem, although a weak coil or a carbon arc in the distributor cap or rotor or even a bad plug can sometimes only show up at the highest load...

Or (gasp!) it might also be engine related. My first thought would be a worn cam lobe. Or a sticking valve (but you should hear that). Or..?

Start with the fuel filter, then the pump and sock (if you are going to install an electric pump, remove the sock, install a metal filter right at the tank outlet, and then put the pump at the back of the car).

HTH

 

[Bosco2]

Thanks Keith,

Thats the kind of answer I was looking for. Actually it was 4th gear...I had been trailing a 911 at about 105 for awhile and he took off......when I stepped on it I got to about 5500 to 5800 rpm and it did this.

It does have a valve that taps louder from time to time (solid lifters)...but then quiets down......not sure if this could be the sticking valve...but it made that noise even when it used to rev over 6000.

A question about the electric fuel pump....can it be used with the fuel return line found in the 1973s?

Thanks for your answer...
Mike

PS ...good to talk to you at OMC.

 

[kwilford]

A question about the electric fuel pump....can it be used with the fuel return line found in the 1973s?
PS ...good to talk to you at OMC.

I would think so, although I have never had a '73 GT. Isn't the return line on the fuel filter, downstream of the mechanical pump? If so, you should be able to just remove the mechanical pump, block the opening with a plate (OGTS has them), bypass the mech pump, and install the electric pump and inlet filter at the rear of the car. You might need a pressure regulator, which probably could go where the old pump was.

Good to talk to you as well, Mike. It sure makes it more enjoyable to have actually met the folks that are on this site, not to mention having seen their cars first hand.

 

[Turbo X]

sounds like a valve out of adjustment, sticking or floating,,you are getting to the limits of the valve train at that substained Rpm. any little hicup in the lifter will show up in the power out put. before I put in a electric fuel pump ,, install a pressure gauge and do the same run.

 

[N61WP]

I had something similar happen to me a few years ago when I was using the 38 DGAS. I would hit a wall in 3rd at about 5500 and would have to shift to 4th to gain speed. Turned out I was emptying the fuel bowl, even with 3/8" fuel line and high volume fuel pump. Changing to the SSD Weber ended that problem. It has a larger bowl.

Jc

 

[Bosco2]

I'm beginning to think this is an ignition problem.....ie. possibly a weak coil. I am running a Crane 700 ignition system and wondered if anyone has used one of Crane's coils. In one of my Z-car catalogs they show Crane PS-20, PS-40, PS-60 and PS-91 coils. Has anyone used these or know about them. Currently I'm running an older Bosch red labeled coil.

Thanks.
Mike

 

[Bosco2]

figured it out....embarrassing

Well, in my case the total loss of top-end was due ONLY to a (fairly) loose top cover on the carb (dgv). I thought SURE I'd tightened that down the last time I was messing with it. So I guess I don't need fuel pumps and coils, etc.

 

[tekenaar]

Red coil

I'm beginning to think this is an ignition problem.....ie. possibly a weak coil. I am running a Crane 700 ignition system and wondered if anyone has used one of Crane's coils. In one of my Z-car catalogs they show Crane PS-20, PS-40, PS-60 and PS-91 coils. Has anyone used these or know about them. Currently I'm running an older Bosch red labeled coil.

Thanks.
Mike

What do you mean by "red labeled" . . . Bosch red (body color) coil with label that says it requires a 1.6Ω resistance in +12V side? If so, hope you either kept the stock GT + coil wiring with the stock resistance wire or provided the required resistance for the coil in "run" mode.