Have you checked fuel pressure?. You may be running out of gas on hard accell.
nruff wrote:
> Hey all!
>
> I'm back to tuning my roadster this weekend. Thanks to your last insight,
> I was able to determine one of my HUGE problems. I had ordered and
> installed rebuilt carbs from Z-therapy (nice looking carbs). After
> assembling, I was unable to get the car to idle. I followed all your
> recommnedations, setting and rechecking timing and valves, updated
> distributor to an early non-smog, replaced plugs/wires/coil. After all
> this, still the same result. Apparently either the throttle shaft bearing
> were sent without grease or my car backfired and blew out the grease (most
> likely the latter). This resulted in a huge vacuum leak, not allowing my
> car to idle or run smoothly at all. Scott at Z-therapy was great. He
> repacked the bearings and installed new seals and even expressed the carbs
> back!
>
> Now, fast forward to the future (always wanted to say that! <g>).
> These are my current symptoms and what I have checked. I'll be the first
> to admit, I am learing as I go, so I may have missed a crucial step.
>
> Problem:
> Car falls on it's face (almost like you shut off the key) under medium
> acceleration or above 2000rpm. If you keep your foot on the gas, it
> hesitates (long), pops and misses. While not under a load, it revs freely
> and idles smoothly-sounds healthy. Using a timing light, I can see that
> both my distributor advance are working.
>
> The carbs have been set with a Uni-Syn and the mixture is at 2 1/2 turns
> out. I have tried to set mixture using a vacuum gauge on the manifold.
> Vacuum or idle doesn't seem to respond to adjusting the mixture (it did when
> I had the massive vacuum leak)-am I all wet on this one?
>
> Other stats-maybe useless.
> Stock SU cam
> Manifold vacuum is at 21pounds at idle.
> Idle set at 700rpm.
> Vaccum advance starts opening at 3 pounds and is open fully at 10.
> Carbs vacuum appears to work, going as high as 15 pounds if the throttle is
> "blipped" to 3000 rpm.
> Timing set a 16BTDC (appears to advance to almost 30BTDC when both advances
> are open)
> Cylinder compression 190+ on all cylinders.
>
> What else it there? I'm sure I could hire somebody to tune it, BUT I am
> planning on driving the U20 for extended distances (like the all Datsun meet
> <g>) and want to be able to know whats going on if trouble arises on the
> road. Sorry about the length of this post. If anyone has the "miracle
> cure" or even any sage advice, I am game. Even after driving it in it's
> current condition, I'm excited about the what lay ahead. The body of the
> car is being worked along with the interior and chrome. It should all come
> together soon.
>
> Thanks in advance!
> Nathan
>
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