holley tuning questions

[Tannerm]

Holley 4160 600cfm.

Basically car stumbles off the line. Also falls on its face for a second when u goose it when cruising. Once its past the second of hesitation, the car runs like normal. It will also cruise at any rpm without a hiccup.

It has all stock parts. I had to readjust the accel. Pump arm using a .015 feeler gauge. Accel. Pump cam is a pink/orange color. Set in the "1" screw position. Accel. Pump squirter is a #31. Power valve should be a stock 6.5. Engine vacuum is a constant 15. What does a power valve do to a engine if not fully tuned (mine I guess should be a 7.5)? I also assume a bigger squirter would also help? Idle air mix screws are 1.5 turned out. I tried backing in the screws to about 3/4 turn from bottom out and its initial throttle bump would hesitate worse then before. About to try going to 1.75 to 2 turns out and see but I thought those screws were only good for idle?

I've had carbs in the past and hated it when Holley's and demons when out of tune because I suck at em. I usually fixed it by slapping an edelbrock on there but I wanna learn. I know that I get more power out of holley carbs. Thanks. I'm sitting here at work bored so I thought I'd post. Dumpycapri and I will hopefully get together Sunday to play with it. This post is really only for my knowledge in the future.

[jyro]

eliminating the dreaded Holley off idle bog
You really need to pickup a book on Holley tuning. That being said, take the Holley off and flip it over, at the butterfly bores you will find a small hole and a slot, the idle air setting on the butterfly’s should be at the beginning of the slot, not the end of it. Cams with lots of duration require more air than lots of carbs are designed to flow at idle. That's why small holes are sometimes drilled into the butterfly’s, to let in more air so you can close up the butterfly’s with the idle screw and close off some of the idle transfer slot. This slot feeds fuel to the motor when the butterfly’s open to get the motor past idle into the venturi's flowing fuel. If you have used up most of the slot just to get idle, it has nothing left to use to get the main system, (the venturi) flowing fuel. The Holley tuning book shows all of this and, for a racer is required basic knowledge.
The idle mixture screws should be adjusted to 1 1/2 turns out.
These screws add a varying amount of air to a fixed amount of fuel. The idle fuel jets are drilled into the metering block. It's hard to tell rich form lean sometimes but on a holley but this is easy because they put the accelerator pump so easy to get to, with the motor running at idle, just pump the squrter some and listen to the motor, if the idle is correct, the rpm won't change, if it's lean, it will speed up, if rich, it will try to stumble.
Sometimes, after you have drill holes in the butterfly’s, you may have to richen the idle feed jets, these are a drilled pressed in jet in the metering block, a finger miniature drill and a drill index that goes from 60 - 80 on drill sizes is perfect. You have to drill a tiny amount and test till the mixture screws are 1 1/2 out and the idle is slightly rich.
The correct fuel level on a Holley is with the fuel at the bottom of the threads of the level check screw hole, not coming out the hole. The most fuel pressure the Holley is designed for is 7.5 lbs.
Some will hold more but not reliably.
The correct setting of the accelerator pumps is done at the screw and nut with a spring on it at the end of the arm. At idle the arm should have no slack in it so that when you give the throttle gas, it makes the squrter pump gas out with no delay.
Squirter tuning is MUCH harder. It sometimes requires a plastic cam set and an assortment of Holley squrters. If you have done or checked all the above things and the carb still bogs some , then you have to fine tune the squrters. For me this is trial and error, when the motor bogs, it can be either too rich, or too lean, I change the squrter and see if the problem is better or worse, an example of this would be having a #25 squrter and a bog and going to a #30 and the bog got less, this would mean that it was too lean with a 25 and the larger 30 helped it. Keep going larger till the bog is gone. I have to change squrters for winter or summer because the air temp is so different. Colder is denser air and you may have to richen.
I hope this helps some one. let me know if you have easier ways to do all these things. Besides EFI.

[Chas_svo]

Pm me your email. I have the carb tuning instructions from the Carb Shop I can send you Tanner.

[jyro]

http://v8tvshow.com/content/view/110/28/

[Tannerm]

On your link Jyro, it says a power valve should be set 1 inch under the vacuum reading. I thoght it was suppose to be 1/2 of the vacuum reading (i.e. 15 vacuum = 7.5 power valve...)

[jyro]

whatever it takes to make it not open at idle or just above.

[Txstang1]

what size squirters do you have in it ?

also, this may help you

http://www.carcraft.com/techarticles/ccrp_0807_holley_carburetors_basics_guide/viewall.html

[Tannerm]

Contemplating a few things... One, having someone tune the carb for my fox, or buy a new:
Edelbrock 650cfm electric choke
Holley 650cfm elec. Choke
Or holley 650 double pumper...

I would assume someone tuning would obviously be grossly cheaper. Thoughts?

[Tannerm]

what size squirters do you have in it ?

also, this may help you

http://www.carcraft.com/techarticles...e/viewall.html

Sorry. Didn't see ur msg first. It has a 31 squirter. I tried adjusting the accel pump arm today to see if it just wasn't getting that initial shot quick enough. Doesn't seem to make a difference. Watching the squirter do its thing as I move the throttle seems to still not make it squirt any sooner. Oh well. The arm has a red spring if that helps?

[jyro]

do you know what the list number on your carb is?

it should be a number like in this picture location

http://www.google.com/imgres?sa=X&bi...0&tx=195&ty=70

make sure there is no screw in this slot. that was a old school way to convert a vac. secondary holley to manual. it guaranteed a bog on a vac secondary carb.

[Tannerm]

do you know what the list number on your carb is?

it should be a number like in this picture location

http://www.google.com/imgres?sa=X&bi...0&tx=195&ty=70

make sure there is no screw in this slot. that was a old school way to convert a vac. secondary holley to manual. it guaranteed a bog on a vac secondary carb.

Here ya go;



I'm assuming no screw?



Here is the accel. Pump spring



And u can vaguely see the cam color. I guess you'd am that orange?

[jyro]

the red spring is not a tuning device

[jyro]

basically, borrow a larger squirter and see if it helps or hurts then you might know if it's lean or rich

[sickpony]

Bigger squirter fo sho!

[dumpycapri85]

Bigger squirter fo sho!

Would you still say bigger squirter if you knew that when the carb was new it ran perfect on that same motor with no changes , just time ?