James Drinkwater wrote:
> Thanks for the reply, Steve. But, I considered the accelerator shot
and
> that can't be it. Let me describe the situation better. Interstate
cruise
> is the most obvious.
> So, there I am on the interstate cruising along at about 60mph. The
> engine's revving and the mixture's doin' alright. If I press a little
on
> the accelerator smoothly to get up to 65 or 70, it goes way lean and
holds
> in a lean condition until I get up to the desired speed and ease out of
the
> throttle a tad to hold it.
> I'm not "kickin' it" to need the pump shot or so heavy that the vacuum
> drops enough that I'd need the Power Valve; just a little more throttle.
If
> I do continue to roll into the throttle for heavier acceleration, it
don't
> see the PV overcome the lean condition.
> Perplexing, huh?
> Drink
> "Steve Austin" <saustin4@[EMAIL PROTECTED]
> wrote in message
> news:45d79695$0$28119$4c368faf@[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.
>>> 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
>>
>>Maybe you aren't talking about the accelerator pump, but you should be
>>looking at it.
>
>
>
Holleys are pretty simple and lack transition circuits. They make up
for a lot of it with pump shot. Check the pump cam to see if anybody
has messed with it (stock and in stock locatation). Make sure the check
ball is still there (under the pump nozzles). Make sure it has the 50cc
pump. I like the actuating arm to be on the cam when throttle closed
(as long as you still get full travel).
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