Jet size recomendations please

[AZ59apacheguy]

Hi. I recently bought a Holley Truck Avenger 470CFM for my stock 283. The carb came with size 57 jets in both the Primary and Secondary metering blocks. Through research, I have found that 470cfm might be a little big for my engine, but should be fine if the carb is jetted correctly. I am in the middle of rebuilding the carb and don't want to button it up untill I get a good starting point on the correct jet size for my application. The person I got this from said it was on a 302 and ran great! What you all think about the 57 jet size I have now, would there be a size better suited to start with? Thanks

[geezer#99]

Bolt it on and go!
Then read your plugs.
Where do you live?

[AZ59apacheguy]

Hi, thanks for the reply. I live in the Phoenix area. Does the size of the power valve matter?

[geezer#99]

Yes!
I see by the specs it’s a 2.5.

[AZ59apacheguy]

Where do you see those numbers? I could not find that on my power valve.

[geezer#99]

Number is on the face.
Look here.

https://www.corvetteforum.com/forums...wer-valve.html

[AZ59apacheguy]

Hi. I found the numbers on the face and it is a 6.5 power valve. According to the one video I saw, you take your manifold vacuum and devide by two, since mine is a stock engine and manifold and it normally runs around 19inches, does that mean I need the 7.5? Or is the 6.5 good enough?

[AZ59apacheguy]

Actually it should be bigger than that huh? The largest valve I found a 9.5 on amazon, how's that?

[geezer#99]

Originally Posted by AZ59apacheguy

Hi. I found the numbers on the face and it is a 6.5 power valve. According to the one video I saw, you take your manifold vacuum and devide by two, since mine is a stock engine and manifold and it normally runs around 19inches, does that mean I need the 7.5? Or is the 6.5 good enough?

That’s the normal way to figure it but Holley specs that carbwith a 2.5 for some reason. Maybe it has to do with the low cfm. A higher rated valve around 6.5 might have it way over fueling.
I’d set it up too factory spec and go from there.

I see the 670 gets a 6.5. Maybe the cfm dictates the valve size.

[Hollow65]

They make a 10.5 pv. Research how they work and decide from there. Mileage may suffer if you go too high of a #.