Holley 2 stage power valves

[gliderider06]

So, on a 650 Holley spreadbore carb list 7004-1, is there a benefit to running the 2 stage powervalves over the standard single stage ones? They are discontinued for one. Holley claims they aid in economy. The one in the carb is fine, I was just wondering. Holley replacement PV is a 6.5. The 2 stage is 10.5/6.5 Would it make a difference to change it out for a standard 6.5?

 

[Mattax]

So, on a 650 Holley spreadbore carb list 7004-1, is there a benefit to running the 2 stage powervalves over the standard single stage ones? They are discontinued for one. Holley claims they aid in economy. The one in the carb is fine, I was just wondering. Holley replacement PV is a 6.5. The 2 stage is 10.5/6.5 Would it make a difference to change it out for a standard 6.5?

Depends on what the engine wants. An engine that is less efficient at part throttle will need enrichment earlier (higher PV opening number).
If it really needs enrichment around 10.5, then best to use a 10.5 to 8.5 opening.
If it doesn't, then its just wasting fuel and not doing the engine any good.

 

[AJ/FormS]

I don't know, have never run one.
I run 10.5s in everything I got.
If you run a 6.5, invariably, you will run more MJ than you need to, to cover the late-to-the-party, 6.5PV.
With a spreadbore, you can run the front a tad lean, and let the back barrels even it up. Part Throttle Timing is everything, on the street.
Economy starts with your right foot. You can build a 30 mpg combo, and never get half of that, if your right foot is a rebellious sumbtch.