Jim,
Timing didn't correct the lean condition. I installed a new Tstat and
the
engine gets up to 195deg max. I drive the T/A regularly and the gas is
fresh. This fresh engine (still dialing in the carb & spark curve), oddly
enough, doesn't ping when it leans out; the power just drops until it
sputters.
I threw in the idle mixture problem in case it's indicative of
something.
I can turn in the idle mixture screws a 1/2 turn or more until it makes a
difference and the revs drop off hard.
Thanks for the reply,
Drink
"jim" <"sjedgingN0sp"@[EMAIL PROTECTED]
> wrote in message
news:1171758084_1859@[EMAIL PROTECTED]
>
>
> James Drinkwater wrote:
>>
>> Floats are correct and have fiddled with 'em up and down to no avail.
>> Revs don't drop upon hard braking (like I think you'd see with low
>> floats).
>> I have clear sight plugs and it looks good.
>
> The lean problem with very light acceleration still sounds like low
> float level or late timing. Although bad thermostat (engine too cold) or
> bad gas could be a part of the problem. How old is the gas in the gas
> tank.
>
>> I tried timing from 6-8 at idle and tried total timing and it came
back
>> to
>> roughly the same idle time. Today I used the vacuum gauge and best
>> vacuum
>> gave 20+ idle timing. When I ran it up the road, surprise... ping!
Just
>> backed off down to 15deg. We'll see how that fares without the vacuum
>> advance connected (and work from there).
>
>
> Did advancing the timing help or was it still lean? If its still lean
> that could be the cause of the ping. You may have to live with some ping
> given the nature of modern gasoline. You need to get the timing right
> before you mess with the carb. Don't assume timing marks on vibration
> damper are correct.
>
>> Still, idle mixture screws are fairly unresponsive. I wonder if the
>> secondaries are open too far. But, if that were the case, wouldn't
>> closing
>> them a bit be an erred solution to different problem?
>
> The idle mixture shouldn't have much to do with the problem you
> described. Is it getting too much gas at idle or not enough?
>
> -jim
>
>> Drink
>> "jim" <"sjedgingN0sp"@[EMAIL PROTECTED]
> wrote in message
>> news:1171738743_1661@[EMAIL PROTECTED]
>> >
>> >
>> > James Drinkwater wrote:
>> >>
>> >> Hi Guys,
>> >> Got a Holley 650 double-pumper on "Dad's hotrod" with some probs
>> >> tuning.
>> >> Upon depression of the throttle, my fuel/air ratio gauge shows that
>> >> the
>> >> mixture goes way lean and the engine goes into lean misfire and
>> >> dropped
>> >> power. Eventually it richens back up as the RPMs slowly increase.
>> >> Not
>> >> talking about the accelerator pump, just giving it a little more gas
>> >> while
>> >> driving.
>> >> Bought the carb from my machinist in the original box in like-new
>> >> (visually) condition. Here's what's new and ruled out: high-volume
>> >> fuel
>> >> pump, fuel filter, fuel regulator and pressure gauge, float needles
&
>> >> seats,
>> >> jets (just to be sure), 6.5" power valve (like the original). both
>> >> squirters appear to pump fine but the problem occurs when you slowly
>> >> roll
>> >> into the throttle and it happens really quick (very throttle
>> >> sensitive).
>> >> It's a moderate, street performance SB Chevy that makes about
10.5"
>> >> vacuum
>> >> at idle. I know the PV should move up to 8.5" but rolling into
heavy
>> >> acceleration (vacuum below PV opening point) doesn't overcome the
lean
>> >> condition either.
>> >> Two last things are that idle mixture is pretty un-responsive to
>> >> idle
>> >> mixture screws, even when idle speed is as low as the engine will
>> >> reliably
>> >> rev. Second, main jets were very, very rich at stock 67's (primary)
>> >> and
>> >> still a tad on the rich side with 65's.
>> >> Dirty passage somewhere? Higher vacuum power valve needed and
drill
>> >> the
>> >> PVCR's? I'm a little stumped.
>> >
>> > You didn't say anything about float adjustment. A low float level
would
>> > match the description of the problem. Late ignition timing would also
>> > contribute to the problem.
>> >
>> > -jim
>> >
>> >> Best Regards,
>> >> Drink
>> >>
>> >> '87 TransAm (No computer controls)
>> >> Holley 650cfm double-pumper
>> >> Victor Jr. single plane
>> >> 186 heads, fully ****ted with 2.02 valves
>> >> 218/228 roller cam
>> >> 1.6 magnum rockers
>> >> 10:1 KB pistons
>> >> Mallory Comp9000 distributor
>> >> Hooker SuperComp headers
>> >> 3.73 gears
>> >
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