On Fri, 14 Mar 1997, Dwade Clay Reinsch wrote:
> problem from the faded yellow days. I've got a Weber downdraft carb and
> headers and when I really punch it, it really goes! Until I shift! I let
What size Weber (cfm rating), and what type of header (primary size,
tri-Y or long centre, etc.). Stock cam??
> lag, so the RPM's are too low when I let the clutch out, your head is
> jerked forward and then the power comes back on and, boy, is your head
> jerked backwards again! :-)
This sure looks like an engine air-flow problem. If the carb cfm
rating is too large, you've got a lag in throttle response at low to
mid-range rpm. Conversely, the carb may be ok, but your headers might
be tuned for high rpm applications. The end result is the same as a
malfunctioning accelerater pump; you hit the gas and the engine sees a
lean mixture and falls on its' face until the gas catches up with
the sped up air in the manifold/intake passage.
> Any suggestions for tuning out the big lag?
1. Check your carb accellerator pump function
2. Find out the cfm rating of your Weber, and downsize to the
recommended size for your stage of tune.
3. Look at your header, and see if it's a "street", or "race" header.
Be prepared to change back to cast iron if you find that you don't
like the price of a new "street" header, then you can spend the bucks
on a Borla muffler...
4. Beg, Borrow, or Steal the latest edition of David Vizard's
"Tuning BL's A-Series Engine". 99% of the book also applies to the
"A" block's big brother, the "B" block.
The best part of the book is the EXTENSIVE use of DYNO TESTING... no
guessing, no "I think it runs much better since installing those xxx
plugs" claims.
5. "Tongue in cheek mode ON"- always run one gear LOWER than you think
you should... ie.-25 mph in second, 45 mph in third...
You'll see that when some high school kid runs an 800 cfm double
pumper Holley on a little 350, and it bogs so bad that a stock MGB
eats him at every stop light. So the kid runs around town in low
gear to keep the revs (and airflow) up, to prevent the bog.
TTUL8r, Kirk Cowen
|