Bought a pack of accelerator pump cams and over half of them look to have the same profile. Does anyone have a color chart showing the differences between the others? Also the stock power valve is a 6.5 and my vac at idle in gear with A/C on is 6hg I believe I need to change it to a 3.5 power valve. What are the symtoms of a power valve being to high or to low? Right now with the 6.5 valve, if I punch it it goes rich (10,1200rpm) and stumbles and then starts going lean (16,1700rpm) as the rpms build a bit then goes perfect.(13.7,2300rpm) I am going to change power valve first because I beleive its wrong, retest and likely will need to chance to shooter to a smaller one to extend to spray time which should help the rich condition and extent into my lean condition.
Any thoughts?

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67Cuda,FAST EZEFI,340cu,CR=10.25,RollerCam&Rocker (XR268HR,#20-810-9)(#1622-16)(EddyRPM#60779,#7576), (MSD6AL,#6425) A904, GearVendorsOD, 8 1/4,3.55:1, ClassicAir

If you go to the Holley site, search on the part number and it will have a file you can download with the cam colors and screw positions, curves and such.
You have a 470 on there? I didn't know the 470 could be used in a single carb arrangement.

I've got the info saved on my home computer. I'll shoot that to you tonight.

CJ

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Part of Tyrde-Browne Racing

Thanks for the chart. Well I don't have a 65 power valve. Talked to Holley tech today and the factory valve is a 25. Factory jets are 57's in the front and 57's in the back. Yes there the same front and back. I changed them a couple of weeks ago at dyno tuning. They are now 55's in the front and 58H's in the rear. Had the pink accelerator cam but ground it a bit then and the rich bog was not as bad. I believe the next step is to put a new pink cam in and also reduce the pump discharge nozzle from .035 to .028

So everyone can see the chart
http://tinyurl.com/yrk4d9

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67Cuda,FAST EZEFI,340cu,CR=10.25,RollerCam&Rocker (XR268HR,#20-810-9)(#1622-16)(EddyRPM#60779,#7576), (MSD6AL,#6425) A904, GearVendorsOD, 8 1/4,3.55:1, ClassicAir

Bought the AED cam kit which doesn't look like the colors follow the Holley chart. Anyway the PINK one seems to work the best but is not right.
From the beginning.
#1
30 CC accel pump
35 nossle
cam- gound down ORANGE one.
Symtoms- Hit gas to floor and car rolls forward and slowly takes off building with intensity.
#2
30 cc
35 nossle
Cam-PINK
Sysmtoms- Hit gas,car lifts front end for 5-7 feet and then drops nose next 10-15 ft and then builds intensity.
#3
30cc
32 nossle
Cam PINK
Sysmtoms - hit gas car hardly moves and allmost stalls.

Your thoughts please.
What effect does ignition timing have on takeoff. I have 12 inital and 27 total. Also changed the torque converter to a 3000 stall which seems to be stalling at 2400 holding the brakes and gas to the floor.
I was also told I can screw open the secondaries a bit and close down the primaries a bit to mantain idle and this would improve throttle responces some. What do you think about this?
One more thing. I was recently told that the Holley 470 Truck Advenger carb is for trucks and will not work correctly on a car. Comments please.

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67Cuda,FAST EZEFI,340cu,CR=10.25,RollerCam&Rocker (XR268HR,#20-810-9)(#1622-16)(EddyRPM#60779,#7576), (MSD6AL,#6425) A904, GearVendorsOD, 8 1/4,3.55:1, ClassicAir

What Holly carb are you using model ak 4150 and what cfm. I might be able to help you on this. Thanks Ron Parker











Jaggers Fabrication Slanted Attitude Dart

David,

If you could post the carb you're using (cfm, mech/vac sec, etc), I can probably give you some info on this, too. Below is a very brief primer on carbs (holley in particular). Please excuse me if I'm just re-iterating what you may already know.

A quick & dirty breakdown of the holley's systems (I'm going to do my best to not get boringly long-winded):

-choke circuit: Used to make cold starting easier and more pleasant
-Idle speed & mixture screws: idle circuit. It's for idling.
-Main jets: the main circuit: in use basically any time you're not idling.
-Secondary jets: secondary 'main' circuit; in use under high load situations for vacuum secondaries or staged w/ mains on mechanical secondaries
-Accelerator pump and jet (nozzle): this is used to cover up the 'holes' between the idle circuit and the main circuit. Also comes to play when throttle positions are rapidly changed. Only in the primaries on a vacuum secondary carb; one in the primaries and one in the secondaries on a mechanical secondaries carb. Cam determines volume & squirter duration. Examples: critical for off-idle behavior; also for quick tip in at speed
-Power valve: This guy comes into play at low engine speed/high load situations (mainly). It's in play whenever vacuum drops below the valve's rated opening point (higher load situations). I've always foudn it to be the most noticible in the following scenario. Example: You're cruising on the interstate at 65mph and 2200rpm. You tip in the throttle a bit to pass (not flooring it, just a gentle bit of part throttle). The accellerator pump will pump just a little, but not enough; the power valve should open to cover this 'hole' in the accelarator pump & main systems. It's a 'extra rich' switch for when the engine is in high load (low vacuum) situations

So, practically:

1) if you haven't checked fuel pressure, set the float bowl level, that sort of thing, do that now. If you haven't been reading the plugs regularly while you tune, start doing that, too. And if you can swing it, even the (relatively) cheap narrow band O2 sensors are a great boon to tuning. Removes a lot of guessing, particularly if you don't have a lot of experience or have a finicky combo.

2) The power valve (as long as it's not blown) is just about the last thing to mess with on the carb. Everything else needs to be pretty close to perfect before you start playing with this one, and you ought to drive around for a while with a vacuum gauge attached & make notes, too. If you have 6 inches of vacuum at idle, this could be tricky to get right.

3) based on what you said about changing different cams, the pink #2 sounds like the winner of the three. comes on strong, sounds like a slight rich bog immediately after. #1 sounds like rich bog; #3 sounds like lean. Real hard to tell over the internet, though. If you're using the screw hole that delivers the highest volume on the cam, try using the other hole to get less total fuel volume. Also try the next larger squirter and see if it eliminates the later power loss. If that isn't satisfactory, You can try the same things with the #1 cam, also. if you try #3 (I'm assuming it's a lean stumble, does it sound like it wants to backfire out the carb?), try using the screw position to deliver more fuel volume and a larger squirter.

Some more experimentation and specs on the carb would be in order; there may be more at work than just the accelerator pump. Unless you're just the Bach of carburation and naturally gifted, the trick is to be meticulous: Keep good notes, only change ONE thing at a time, keep reading the plugs and driving the car.

If you're running a mechanical secondary carb, 6 inch vacuum at idle cam and an automatic transmission w/ numerically low gears and plan for this to be a decently behaved street car, be prepared to spend a lot of time on this. That's not an easy combination to tune at all. I can't remember what all you're running, but that's the gist I'm getting.

As for a 'truck carb' not running right in a car; sounds bunk to me. The carb doesn't know what it's sitting on. As long as you have a bit of patience and a good selection of jets and such, you can make almost any holley run on almost any engine.