will d

my idle rpms are significantly lower after i drop the throttle from w.o.t. as compared to a part throttle to an idle. maybe 200 to 300 lower. stalls when i drop it under a load. maybe its the fuel return idk. but i have a feeling the power valve is the wrong size. anybody help please. if it is. does it need a bigger or smaller one?

Barfly

Hey Will, check out this thread, some of the guys gave me some good info on power valve sizing.

Joe.

440roadrunner

I would guess your problem is more related to sticky butterflies or worn throttle shafts, etc.

64dodgedart

do u have a double throttle return spring?

rickyr

Hi,
the way to size your power valve is take a vacuum reading @ idle ( in gear if auto trans)
and divide that # by 2 this will = the size of power valve you need
example if you have 11" of vacuum you need a 5.5 PV
or 7" of vacuum = a 3.5 PV and so on like that
The problem you have does sound more like a throttle plate issue
but this is the way to size your power valve
If the power valve is too large for you vac. reading it will be rich @ idle
Thanks

will d

yeah i originally had a double throttle return spring, then went to one and a half ( spring hooked to the other spring half way) took the other one off the night i realized it was doing it. seems like it still does it though. i vacum tested it, its pulling 19 psi. im looking though my carb manual. do edelbrocks even have power valves cuz it doesnt say **** about power valves?

will d

ok im the idiot of the month. they don't have power valves. looks like i need to set this carb book by the *******

rickyr

When you ask about power valves
I assumed you had a Holley
Edelbrocks have metering rods and springs
I dont know much about tuning them
thanks

hcharles

Go to this site and it will help you size your metering rods and springs
http://www.edelbrock.com/automotive_...ers_manual.pdf
HTH

440roadrunner

I still say your symptoms are not power valve/ metering valve type symptoms. Is it possible the carb is loose on the manifold, do you run a spacer, any chance of a vacuum leak, or worn, sticking linkage or butterlfies? How about a loose butterfly?

will d

yeah its got a 1/16th inch thick plate under the carb cuz the guy at jegs had me thinking i had a vacum leak when i first figure out the carb had a bolt loose. i left it on. it jus simulates a square bore. the intake bor is like two upper case "b's" back to back. i found me my fuel line was touching on of the levers that comes out of the opposite side of the carb that the throttle lever but barely. and i dont think the action was being affected. ill look for loose bolts on the carb. its a year and a half old. hopefully not an intake gasket.

tell me how a pcv works exactly cause i feel it rattle hard when i rev it up does the old starter fluid shot in the valve cover imply a vacum leak internally?

Archer

will -

The PVC (Positive Crankcase Ventilation) valve uses vacuum from the carb/intake to draw crankcase gases due to piston blow-by back into the cylinders. The are supposed to rattle when shook.

Not sure what you mean by starter fluid on the valve cover to check for a vacuum leak.

Archer

will d

somebody told me to see if you have an internal vac leak if it revs up when you spray in the valve cover by what i know about pcvs now it is insufficient. i leaned out the idle mixture a bit, it seemed to help the idle rpm change when dropped from wot, maybe im exagerating the rpm difference maybe its more like 100 different its been below 10 degrees for so long maybe its the cold. thanks everybody

rickyr

there is no such thing as an internal vacuum leak
a carb is an internal vacuum leak
if you take a drinking straw and put a hole in the side of it and suck on it
that is an external vacuum leak
How would you make an internal leak?
so whatever is going on it is not an internal vacuum leak
It very well might be an external vacuum leak
to check for that have it running and spray around where the carb mounts to the intake and where the intake bolts to the heads and with carb cleaner if the RPM goes up or down this will show a vacuum leak
Thanks

will d

intake gasket sucking air out of the crankcase. internal vacum leak

rickyr

what I am talking about is, people try to say the carb has an internal vacuum leak
and that can not happen.

440roadrunner

I don't know why you say that. Carbs are really just cheap castings, and can have cracks or flaws just like any other engine. If there was an inernal body crack, let's just say the crack connected either outside air (crack ending outside the body or in the top of a throat) OR that it terminated down low near a connective point with the manifold, and that the OTHER end of that crack connected with some passage in the carb --you have a problem.

Years ago I thought I was pretty tricky with Holleys. I'd overhauled as many as a hundred for myself and friends, and was WELL AWARE of Holley's power valve leakage problems--and found some leaky power valves right out of a name brand kit, including Blue Streak and Holley.

I well remember ONE body I had, that became an "it or me" thing. I'd been experimenting with plugging the power valve, and could NOT get that carb to run. I ended up changing everything EXCEPT the body itself, and could NOT get it to idle "clean." After hours and days of playing and changing parts, the ONLY CONCLUSION I made was that body had some sort of INTERNAL CRACK which stopped it from working at idle.

rickyr

(a carb is an internal vacuum leak
if you take a drinking straw and put a hole in the side of it and suck on it
that is an external vacuum leak
How would you make an internal leak?)
This along with my training from Holley
Call anyone @ Holley Tech service and ask them
if a carb can have an internal vacuum leak there 8 techs. and all will tell you the same thing (866-464-6553 )
I am not trying to start a war just trying to help with Holley ???
But I do know what I am talking about on this one
A casting could have cracks on the inside and this could make it not run right by pulling fuel and so on
But the only it can be a vacuum leak is exturnal
Thanks

440roadrunner

What you are doing here is playing with words. From my point of view, if a carb has an INTERNAL CRACK, --that leaks--then it's an "internal leak"

That's because it's leaking --from a leak-- internally

Aren't the throats "internal?" They certainly aren't "outside" the body.

The fuel bowl is vented EXTERNALLY, but if the crack extends to the mounting face of the metering plate, and interconnects from there to the vent system, isn't the termination of the crack still "internal?" the mounting face for the metering plate certainly is "inside" (internal to) the assembled carburetor.

Holley engineers can call it whatever they want to

rickyr

It cannot leak vacuum unless the crack is all the way through to the outside
Yes a crack inside can make a leak,( a fuel leak)
I did not say there can not be an intrunal leak
I said there cannot be an internal VACUUM leak
and there can not
Holley has been around since 1903 I think they know what they are talking about
A vacuum leak will make the A/F mixture lean, from too much air
If the crack is not all the way through to the out side Where will it get that air?
I know this to be a fact
so I will not reply to this any more.
Like I said I am just trying to help others with my and Holley's knowlage
Thanks