which accelerator pump cam for holley

[77bronk]

im trying to get this holley 4bbl tuned on my 302 with long tubes and edelbrock intake. the PO had it tuned for 3500 above sea level. i rebuilt the carb and added new floats and jets and adjusted everything. but i cant get rid of this off idle bog. it idles fine and after the bog it runs ok. it has the pink cam now and ive tried all 3 hold with no luck.. im not sure which squirter size it is. gotta wait for the motor to cool down before ill be able to take a look.. anyone with a simlar set up? what color cam and what hole? when i tightened down on the accelerator pump spring/ nut the bog got little better but not much.

 

[bax]

on the pump spring / nut there should be just a bit of gap in the arm to the pump. if it is being pushed down at idle adjust it so it has just a little free play in it. go with the red cam Squirter size plays more of a roll in off the line hesitation I always go up before I go down in sizes. keep in mind a bog can be too lean or too rich. Jet stagger can also be an issue too. Only stagger the back jets by two sizes. having 74's in the front anf 90's in the back is not good.

 

[77bronk]

yea ive got about 15/14 thousandths in between. ill order some cams and a lager squirter today. only thing keeping from finally being on the road and dependable. I cant stall out at the stop light enter section..

 

[Fairlane514]

Which Holley is it?

The red or blue cam should help. 28-31 squirter

 

[77bronk]

its the 600cfm classic 80457-s and has a #31 squirter

 

[ugly74]

i rarely disagree with bax, but here goes...

i adjust my accelerator pump linkage for zero gap. you want it to start squirting fuel at the exact same instant that the throttle starts opening. any gap = hesitation/bog off idle.

 

[bax]

i rarely disagree with bax, but here goes...

i adjust my accelerator pump linkage for zero gap. you want it to start squirting fuel at the exact same instant that the throttle starts opening. any gap = hesitation/bog off idle.

I am really good with zero gap. I just dont want the pump depressed at all at idle.

 

[lowbush]

I am going thru this right now as well, I get a nasty bog right at the peddle press and after about a second or two it comes out of it. I tried adjusting the pump but it did not seem to make a difference.

 

[77bronk]

Yup same with me after the right off idle bog it's runs fine. And motors on down the road . I think this pink cam is to blame. I've adjusted the spring as much as possible from super tight to way loose and everywhere inbwteen . But it never goes away. Going to order a pump cam kit tomorrow and go from there . Will see what happens .

 

[broncnaz]

A lot depends on squirter size. You should always check the size also check the exhuast when you step on the gas does black smoke pour out? if so then you probably need a smaller squirter size. If no black smoke then a pump cam may help or you need a bigger squirter.
The yellow cam has the steepest curve so if your lean off throttle it may help eliminate the bog if it doesnt then you need a different squirter. The blue cam is the next steepest.
That pink cam is one of the slowest so something like a orange or black may help


Sometimes pump cams help but I usually find that squirter size needs to be addressed first then I fine tune with the pump cams.
Pump cams are not to pricey just slightly more than a new squirter. So you can go either route.

 

[77bronk]

That's the plan. It's running lean for sure. Has a 31 in it now . Going to order a few if them and do some test and tuning .

 

[bax]

With this carb you may want to try a slower cam for the secondaries. It;s tuning options are a bit limited due to its design, Single pump, single squirter, meetering block and vac secondaries. So your walking a fine line to get the performance you want with the limited resources this carb offers. So If you set it up for a big squirt with a quick ramping pump cam you may find that bog you have is due to too much fuel being dumped before the vac secondaries can open. this causes the bog and then the secondaries clean up the mess you made and the bog goes away. This carb is not set up with the ability to deliver large amounts of fuel. You have to use the fuel that is can deliver a little more spairingly. Go with a slower pump cam. This gives the secondaries a chance to come in and still have a little bit of fuel to go down the hole. I am saying go small on this carb. Small cam and small squirter, 6.5 power valve. jet accordingly. With a metering block you are unable to jet the secondary. The smother and longer the fuel delivery on this carb the better your drivability. We could talk about this crap all night.

 

[77bronk]

Will do and yes I replaced power valve with a 6.5 already. He had this thing way lean when I got it for altitude . Having to fix his mess and neglect .

 

[broncnaz]

31 squirter is what I usually find is needed in 600 cfm carbs. I feel the black or orange cams are a good starting point. The black will give you more intial squirt with slightly less squirt than the pink near the end. The orange again gives more intial but also a little more at the end. The secondary's on your carb should open fairly slowly so these pump cams should work fine. Of course if you like to get into the secondaries a lot then you may need something even larger.

 

[Rustytruck]

When I use to run a 600 CFM vacuum secondary holley I had to use the black cam, stock squirter, standard accelerator pump and I had to change the spring in the vacuum pod. Make sure your timing and ignition system is tuned and up to snuff before you start messing with the carb.

 

[.94 OR]

I'm playing with this issue as well.

I have two Holley's that are virtually the same so I can spread my frustration out among them. I plumbed a vacuum gauge to the cab so I can monitor what it is doing while running. I find that my 6.5 power valve comes in pretty late compared to the 16-18 inches of vacuum at idle/cruising. It takes a while to get the vacuum low enough to enrichen the circuit. I may have to jet up to see if it clears up, or go to a bigger power valve. It would look to me that a 9.5 or so would get me right in the sweet spot when the motor is wanting more juice. After watching the Holley vids on ewetube, it seems there is two ways to determine the proper PV. Divide idle vacuum (manual) in half or take idle vacuum and subtract 2. Seems like a pretty wide margin.

 

[broncnaz]

All depends on what your after and how your vehicle responds to power valve size. I like to run lower opening ones. As on the hiway at 75 I pull around 10-12in of vacuum. When I start to pull a hill thats when I want the power valve to kick in mild hills will ususally drop the vacuum to about 6-7 so thats wheere i want the extra fuel for mine.
Id see what your pulling for vacuum on a hill not a real steep one just a mild one. then pick a opening rate that falls in that range or slightly above if you wish.
Some people like the enrichment to start sooner its all up to you.

 

[77bronk]

welp i changed the the cam to the red one. got a little better with it but it still has the stutter wanting to die bog. just off idle. i also tried going up a size on the squiter. didn't change anything either. I dont have a vacuum gauge so I guess ill go buy one and see what im getting. i had one back fire. which makes me think with these crappy points its time for a new electronic distributor.

 

[ugly74]

You have points? start there...i highly recommend pertronix...and then keep new points/condenser in the glovebox for after the EMP goes off.

 

[77bronk]

yea all of old original points crap. lol.. to replace the entire distributor are the hei ones any good. i see them for sale on some of the vendors web sites for $140 im just looking for reliability nothing super crazy bad ass like the msd ones. this is just a weekend cruiser.