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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