That's a new one, but sounds vaguely familiar. But, if your right, it
wouldn't be an issue on the interstate when the revs and vacuum are up.
Check my logic on this one. At cruise (2,500-3,000rpm) the vacuum's from
15"-20" and the PV's out of the picture. It goes lean with even a slight
increase of throttle. Heavier makes it worse.
Drink
"Gary - KQ6RT" <kq6rt(NoMoreSpam)@[EMAIL PROTECTED]
> wrote in message
news:SBIBh.6469$o61.4548@[EMAIL PROTECTED]
> Actually you need a smaller power valve. Power valves and vacuum gauges
> are rated in two different systems. I forget which is which, but one is
> inches of mercury and the other is inches of water. Divide your gauge
> reading by 2 then subtract 1 and round off. I figure you probably need a
> 5.0 power valve.
>
> Gary
>
> "James Drinkwater" <jdrinkwater@[EMAIL PROTECTED]
> wrote in message
> news:45d74c48$0$24706$4c368faf@[EMAIL PROTECTED]
>> 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.
>> 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
>>
>
>
|
