How to modify your Holley Power Valve Circuit

[Gunner]

Any tips or rule of thumb on determining a starting size for the new jet? I ass/u/me you want to start some significant size smaller than stock and increase one drill size at a time.

Should the inserts be removed from the metering block for redrilling?

[trularin]

Great Tip!!!

If you use the 8-32 screws, you can have a wider range of sizes.

I would recommend a small amount of loctite blue if the set screws are easy to turn.

Thanks for the tip!

[Tom Kirkham]

Originally Posted by trularin

Great Tip!!!

If you use the 8-32 screws, you can have a wider range of sizes.

I would recommend a small amount of loctite blue if the set screws are easy to turn.

Thanks for the tip!

Typically we do not tap the entire length of the hole. This way we can bottom out the jet and Locktite is not needed. However if you tap all the way through you will need Locktite to keep the jet from falling through...

[Tom Kirkham]

Originally Posted by Gunner

Any tips or rule of thumb on determining a starting size for the new jet? I ass/u/me you want to start some significant size smaller than stock and increase one drill size at a time.

Should the inserts be removed from the metering block for redrilling?

Every carb is different. You will need a wide band O2 sensor to get to the right size hole. It is safer to start with bigger. A quick way to see if this is what you need to do is insert a piece of wire in the PVCR to make the effective hole smaller.

In the stock Holley metering block I am not aware of any inserts in the PVCR. Of course in the idle circuit their typically is a brass insert.

[Gunner]

Originally Posted by Tom Kirkham

In the stock Holley metering block I am not aware of any inserts in the PVCR.

Sorry, I wasn't clear. If you need to drill out these plugs you've added a step or two, is it safe to do so in the block or should they be removed?

[Tom Kirkham]

Originally Posted by Gunner

Sorry, I wasn't clear. If you need to drill out these plugs you've added a step or two, is it safe to do so in the block or should they be removed?

Sorry I am still confused as to what you are asking. All Holley carbs that have PV all ready have metering holes in them. Now if the metering block does not have a PV then their are no holes. Do you have a Holley or do you have a copy? A lot of the Holley copies have billet metering blocks with this mod all ready done. If this does not answer your question, could you post a picture?

Thanks,

[zrayr]

Originally Posted by Tom Kirkham

Every carb is different. You will need a wide band O2 sensor to get to the right size hole. It is safer to start with bigger. A quick way to see if this is what you need to do is insert a piece of wire in the PVCR to make the effective hole smaller.

In the stock Holley metering block I am not aware of any inserts in the PVCR. Of course in the idle circuit their typically is a brass insert.

Tom,

can you envision just using the air bleed jets instead of a brass set screw ? Is there enough material in the metering block to set the bleed jets in deep enough to clear the power valve ?

Z. Ray

[Tom Kirkham]

Originally Posted by zrayr

Tom,

can you envision just using the air bleed jets instead of a brass set screw ? Is there enough material in the metering block to set the bleed jets in deep enough to clear the power valve ?

Z. Ray

I believe you will need to counter sink for the head to clear the PV. Besides they are expensive...

[zrayr]

Originally Posted by Tom Kirkham

I believe you will need to counter sink for the head to clear the PV. Besides they are expensive...

I know that ! I have a set of them & am trying to think of "other" uses for them.

Z. Ray

[Mus408]

I recently added the PVCR jets,to a Holley metering block. I measured the O.D.of the jet head,added .010 for extra clearance,and counterbored with that size drill,about .065 deep. Worked out really well,but can get close to the edge of the power valve threads,dependeing on the actual hole location.