Just yesterday when I was pushing my car hard and it's under a heavy load, the car stumbles at 5 grand and above and just doesn't go anywhere. Tonight was the same.
It really only does it in third (shifting into third sometimes) and the higher gears @ high rpm... Power is still all there in first tho.

I recently hooked the fuel return line back up
(had it blocked off ever since I installed the mikuni) and I upped the fuel pressure to compisate for it; I wasen't having any problems.

COuld it be the fuel filter? I'm going to try that tommorow.

thanks,
matt

ps. got a gsl-se alternator in and the car idles smoother now and the lights are brighter. The converstion to the later alt was a snap!

 

mine does that to sometimes up high in 3rd and fourth.
i'ld say try changing the fule filter for starters cus there cheap anyways..

 

Could also be a low float level, not enough accelerator pump, insufficient idle jets or a lean idle mixture.

 

this mean the fuel pump aint filling up the floats fast enuf? or is there more to it..

 

If the condition just suddenly came on, then crap in the system is the most likely culprit. This can mean a clogged fuel filter, a chunk of rust flake stuck in the line, minute bits in the screens of your carb, ect.

It could be that you just now noticed it, and your problem is just accumulative crap in the air filter or fuel filter, the fuel pump is dying and can't keep up (or has a fleck in it), or your carb gaskets are just tired and you need a rebuild.

If the float level were set too low, you would lean out severly in the top end, yes. But you would have done that ever since the carb was worked on. That can't happen by itself- someone has to set them that way.
During idle, the fuel level should be halfway in the site glasses.

Proceed like this, and don't go further than what fixes the problem.
First troubleshoot the delivery system- see that there is a hearty fuel flow coming from the inlet hose.
No?- Fuel filter.
Still no?- Check tank breather system. ("Whooshing" sound when opening gas cap indicates problem here.)
Still no?- Fuel pump. (Be sure the relay is not the culprit first before you go buying a pump! The relay can be bypassed.)

Good fuel flow?- Then it's a carb system problem.
Are there wet fuel spots anywhere on the carb? This indicates leaky gaskets. If the carb has'nt been rebuilt, it probably needs it.
Rebuilt recently?- Try tightening things up (DON'T OVER DO IT!!!)
No?- Then it's time to get "into" it. You'll have to at least investigate the two feeder pipes, as the "banjo" plumbing fittings each have a screen.

This Is A PITA!!! Reason being, they incorporate aluminum "crush" sealing washers. It's difficult to get them back together leakproof with used washers. You should loosen (not necessary to completely un-do) the bolt that joins the inlet and return pipes together. This takes tension out of the pipe assembly, and makes for much easier reinstallation.

Treat the screens with great care as they are fragile.

 

I had the same problem last year and a new fuel filter did the trick. I think it was like $4 at napa too so you might as well get one.

 

Well I changed the fuel filter and it seemed to do the trick... I could barley even blow through the filter. I wasn't all that bright and didn't replace it when I put in the new carter pump.

Great write up sterling, This should be posted in the archives

Thanks guys for the help.
matt

 

Mine was the fuel filter. Had the same problems, replaced it today, and runs much better.
Goodluck