Jeting the 670 Holley

[Snake]

Looking for you thoughts.I have this 670 HOLLEY,it comes with 65 jets up front way to lean me thinks,it like 69 front in my old Holley,600, so that is the first thing i did on the new Holley, but the rear are 69 still sounds too lean to me on the new Holley, the old 600 had the plate in the rear but don't know off hand what it was jeted at ran great,.,so what are your thoughts on jet change in the secondary's leave it at 69 or 70,72.

 

[straightlinespeed]

I swapped the stock set out in the primary's for 68's. The car likes it a lot better! Sadly I have not been able to play with the secondarys so they are still factory jets. I was thinking of going to 70's if anything...

Did you change your secondary spring? If so what did you go to?

 

[krazykuda]

keep in mind that you most likely will have the power valve open when you are into the secondaries.


The best way to determine if you need to change them is to run the car in the range where the secondary main jets are going to be active. Make a pass and shut it down and coast to a stop, then remove the spark plugs and see what they read. If you idle down before reading the plugs, it may affect the readings, that's why you have to do a "spurt" and then shut it down with the trans in neutral and stop the car to read the plugs like at a drag strip or deserted road.

 

[Snake]

I swapped the stock set out in the primary's for 68's. The car likes it a lot better! Sadly I have not been able to play with the secondarys so they are still factory jets. I was thinking of going to 70's if anything...

Did you change your secondary spring? If so what did you go to?

Ihave change to the lighter yellow spring have not had a chance to try this carb out bet soon.

 

[Snake]

keep in mind that you most likely will have the power valve open when you are into the secondaries.


The best way to determine if you need to change them is to run the car in the range where the secondary main jets are going to be active. Make a pass and shut it down and coast to a stop, then remove the spark plugs and see what they read. If you idle down before reading the plugs, it may affect the readings, that's why you have to do a "spurt" and then shut it down with the trans in neutral and stop the car to read the plugs like at a drag strip or deserted road.

Thanks Karl for the reminder will do.