clueless on Holley 3247 for my 66 427/425

[Donald A.]

Happy 4th


I've been around Carter carbs all my life but Holley's are completely foreign to me.


With My recent purchase of a 66 427/425hp I find myself in the dark regarding how to fine tune and property set the auto choke/ high idle.


After searching I can't seem to find a manual that explains this stuff.


Can anyone point me in the right direction?


Thanks much

[Robert D.]

Re: clueless on Holley 3247 for my 66 427/425

Don,
with the engine cold when you give the car gas, on the passenger side of the carb there is the fast idle lever.when you give the car gas there is a plastic piece which will engage the fast idle lever. on most cars ive seen the plastic piece is green. when the engine is cold the plastic piece will engage the lever and slightly hold the idle up. when the gas is struck again the high idle will disengage. to adjust this you bend the tang so it engages the green plastic piece at apoint that you get the desired rpm for cold high idle.

[Joe L.]

Re: clueless on Holley 3247 for my 66 427/425

Happy 4th


I've been around Carter carbs all my life but Holley's are completely foreign to me.


With My recent purchase of a 66 427/425hp I find myself in the dark regarding how to fine tune and property set the auto choke/ high idle.


After searching I can't seem to find a manual that explains this stuff.


Can anyone point me in the right direction?


Thanks much

Don-------


Many sources of specs and adjustment information on this:

1) Chevrolet Service Manual

2) Haynes Holley Carburetor Manual

3) Holley Carburetor Manual by HP Books/Mike Urich

[Steve G.]

Re: clueless on Holley 3247 for my 66 427/425

Don't be intimidated. If you understand the principles on one you can fix any of them. Carbs are carbs.

As Joe said, you need a manual. There is an adjustment for the relationship of the fast idle cam to the choke plate. It is generally checked by holding the screw against a specified step on the cam then adjusting the rod so that the clearance between the lower edge of the choke plate and throat are to spec. The manual will tell you which step and what that dimension is.

Once the relationship between the cam and the plate is established rpm is adjusted by the screw, again according to a spec as to which step it is to be sitting on when the adjustment is made.

Choke pull-off and unloader are typical,and again, the manual will provide the spec.

Is there a specific adjustment you are having trouble with or a driveability issue?

Remember that with a divorced choke, a properly working heat riser and unobstructed ex crossover is critical.

Steve

[Steve G.]

Re: clueless on Holley 3247 for my 66 427/425

Don't be intimidated. If you understand the principles on one you can fix any of them. Carbs are carbs.

As Joe said, you need a manual. There is an adjustment for the relationship of the fast idle cam to the choke plate. It is generally checked by holding the screw against a specified step on the cam then adjusting the rod so that the clearance between the lower edge of the choke plate and throat are to spec. The manual will tell you which step and what that dimension is.

Once the relationship between the cam and the plate is established rpm is adjusted by the screw, again according to a spec as to which step it is to be sitting on when the adjustment is made.

Choke pull-off and unloader are typical,and again, the manual will provide the spec.

Is there a specific adjustment you are having trouble with or a driveability issue?

Remember that with a divorced choke, a properly working heat riser and unobstructed ex crossover is critical.

Steve

Small correction. As Bob points out, there is no fast idle screw. Once the relationship between choke plate and cam has been established you adjust idle speed (on the correct step) by bending the tang on the arm fastened to the end of the throttle shaft.

Steve

[John H.]

Re: clueless on Holley 3247 for my 66 427/425

Don -

Here's a tech column I wrote on the late Holley choke fast idle adjustment.


Fast_Idle_Tech.pdf

[Bob M.]

Re: clueless on Holley 3247 for my 66 427/425

What makes my Holley 3810 weep just a little after turning the motor off. It isn't much, it is on the passenger side of the carb. Do I have the floats set to high?

Bob

[Steve G.]

Re: clueless on Holley 3247 for my 66 427/425

What makes my Holley 3810 weep just a little after turning the motor off. It isn't much, it is on the passenger side of the carb. Do I have the floats set to high?

Bob

Bob
Where are you seeing the weeping?

Steve

[Steve G.]

Re: clueless on Holley 3247 for my 66 427/425

Don -

Here's a tech column I wrote on the late Holley choke fast idle adjustment.


[ATTACH]61979[/ATTACH]

John,

Darn fine article on adjusting the fast idle and a very handsome photo.

For future reference and perhaps to help the op of this thread if he is experiencing the same issue, your caller's problem was not his fast idle speed. The fact that he had to feather the throttle to keep it running is the dead certain indication that he has a lean condition. "Feathering" is activating the accelerator pump, dumping liquid fuel to offset the lean condition caused by the choke plate being opened too far. And in as much as the fast idle cam is indexed to choke plate opening, if the choke is open too far the fast idle is likely to be on the wrong step, too low a step. Likely nothing wrong at all with his fast idle speed setting.

Of course all adjustments should be gone through on a proper carb setup, but choke unloader is not something that comes into play in these circumstances either. Unloader is there to hold the choke well open when the throttle is wide open in order to assist in clearing a flooded engine. Or to hold the choke open on a hot engine with a divorced choke where the owner has wired the heat riser open or blocked the crossover.

Setting up chokes was part of my daily routine in the fall back in the 70's and 80's. I'd have the cars left overnight so I had an ice cold engine. Check for adequate tension and no hang up when choke sets. If choke is setting with proper tension start them up and make them pull right away. If it's stalling right away and/or you have to feather it to keep it going, you have too much pull off. If it will run and pull, but seems sluggish and the idle speed starts to slowly drop, it's too rich. Not enough pull-off.

You can get out your gauge set and manual, but in time you learn to tweak for just the right effect. Sometimes you have to deviate slightly from spec to get it perfect. But if you've done it enough, you can feel when you are bang on. Get in it and make it pull as the final test. Making an auto choke work like it's supposed to is not hard with a bit of a basic understanding.

Steve

[Bob M.]

Re: clueless on Holley 3247 for my 66 427/425

Steve,

On the passenger side under the accelerator pump and the fast idle cam. It isn't much. but it is a hazard on the hot block. I have tightened all the bolts after each time I see it, it just keep weeping.

Thanks again,

Bob

[Steve G.]

Re: clueless on Holley 3247 for my 66 427/425

Steve,

On the passenger side under the accelerator pump and the fast idle cam. It isn't much. but it is a hazard on the hot block. I have tightened all the bolts after each time I see it, it just keep weeping.

Thanks again,

Bob

If you don't see spillage high in the throat from the discharge nozzles, your seepage won't be due to a high fuel level.

You have an external connection/gasket issue. It's probably also leaking when it's running but the hot air movement around it from the fan is likely evaporating it b4 you see it.

Look closely at the line connections. A leak there will run down and drip off underneath. Blow everything dry with your air hose then shut it off. Feel around the fuel lines and see if your fingers get wet.

If you don't see it at the lines then you may as well pull the front bowl and metering block and replace all the gaskets, including the accel pump diaphram. Those are really the only places it can leak to the outside.

One of the places you can get a leak from is the metering block to body joint. And retightening the bowl screws will only make matters worse. Distorted metering blocks are not at all uncommon and are generally the result of overtightening the bowl screws or reusing old gaskets.

Most gaskets are intended to be used (compressed) once. In the case of the block to body, the gasket extends across the entire block, a fairly thick cork gasket. It is clamped against the body by the 4 bowl screws. Retightening crushes the perimeter further, but not the centre as much. This causes the block to take a concave shape. This appears to most often cause an internal leak existing low in the throat from the idle ports. Not as likely to be your external leak, however important to remember to replace all gaskets, torque to spec and leave it alone.

Steve

[Bob M.]

Re: clueless on Holley 3247 for my 66 427/425

Steve,

Thank you for your help.

Bob