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Hi Dave (and gang):
That's the kind of old timer advice I knew was out
there!
It does seem lean, and I do have the accel. pump in
the max stroke hole. What am I looking for with the vacuum test with
speeds at & before stumbling? What will it tell me?
I figured metering rods would be the next place to
attend to - I just wasn't sure how delicate they are, or if, carefully, I can
play around with them. Assuming that it's a 2 step metering rod,
at about what throttle position does each step come into play? In other
words, should I look to reduce diameter of a certain step? Or just reduce
diameter across the board?
I will try the slight spring stretching idea
first. Your guess is that because I have an original carb, it's just
running lean on today's gas? I've covered the other places to look
already?
Thanks again for the info,
Dan Richardson
300L Family Heirloom
----- Original Message -----
Sent: Wednesday, October 17, 2007 5:13
PM
Subject: Re: IML: '67 Carter carb flat
spot
Dan, you can probably solve your flat spot, or fumble by some metering
rod, and mostly spring modifications. A vacuum test at the speed prior to, and
when the stumble occurs, may be helpful. Two easy cures: stretch the metering
rod power en-richment springs, a 1/4-3/8" this will help to en-rich the
mixture sooner (higher vacuum). The other thing is chuck-up the metering rod
in your drill, and polish the steps to a more gradual transition. You can also
reduce the diameter of the rod, thus en-richening without a jet change. Make
sure the accelerator pump linkage is in the max stroke hole too. You can't
hurt much, and if the carb is original, it's lean by todays gas quality. Ya'll
have a nice day, Dave.
--------------
Original message --------------
From: therichardsonfamily@xxxxxxxxxxx
> Here's a question for the carb tinkerers (hi Dave):
>
> '67 Imperial 440, w/ Carter AFB - the model that went on HP engines
w/ bigger
> secondaries. Idles smoothly, idle screws adjusted. At WOT
she goes like a
> r__ed ape - rubber in 2nd gear with a 3:55
suregrip.
>
> 18 inches of vacuum at idle - gauge moves just
like it should when I rev the
> engine - as per the IML website
(which is really neat, BTW - everyone should
> look at that page!).
>
> Timed at 12 degr. BTC - new chain & gears - Mallory
dual point distributor -
> mechanical advance appears to work - if I
suck on the vacuum advance, it also
> moves timing forward. Have not
found a shop with a distributor machine yet.
> Plugs are new - wires
& cap are not (I'll get them on soon) but seem to be OK.
> Again,
she's a rocket with my foot in it.
>
> I have a flat spot from
about 1/3 to 2/3 throttle. I see no black smoke during
> this flat
spot. Carb has been rebuilt (by an amatuer - me), and seems ok.
>
Choke is open when warm - linkage adjusted correctly - accelerator pump
seems to
> work right - bowl vent closes just beyond idle - VERY low
exhaust restriction
> (i.e. 2 glass packs + small resonaters out the
sides)
>
> So... the question is - how do I fix the flat spot?
Smaller metering rods
> becuse of the open exhaust? Or is there
something else I may be missing? Throw
> some old school thoughts at
me to try and tweak it.
>
> Thanks, as always, for the help,
>
> Dan Richardson
> 300L Family Heirloom
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