Holley Carb Set Up
Melting Slicks
Joined: Oct 2002
Posts: 2,317
Likes: 111
From: St Louis MO
Instead of starting with very early opening power valves which will probably be too rich at vacuums less than ~10" but greater than ~5", why don't you look up your carb number (it's on the air horn) and reference the Holley database:
http://www.holley.com/data/TechServi...%20Listing.pdf
I don't know your carb number, but I'm assuming it's a 4150, which has metering blocks on both ends, and you said it was an 850 vac secondary. Of the carbs shown, it appears that this size Holley uses a 6.5 PV, so why don't you start with this as your baseline?
BTW, when you step on it, you said it goes to 3" to 5" of vacuum for a few seconds. At full throttle, the vacuum should be at 1" or slightly less - you may not be getting full throttle opening.
http://www.holley.com/data/TechServi...%20Listing.pdf
I don't know your carb number, but I'm assuming it's a 4150, which has metering blocks on both ends, and you said it was an 850 vac secondary. Of the carbs shown, it appears that this size Holley uses a 6.5 PV, so why don't you start with this as your baseline?
BTW, when you step on it, you said it goes to 3" to 5" of vacuum for a few seconds. At full throttle, the vacuum should be at 1" or slightly less - you may not be getting full throttle opening.
Melting Slicks
Joined: Oct 2002
Posts: 2,317
Likes: 111
From: St Louis MO
When I mentioned carb number, I should have said part number to avoid any confusion.
The 4150 is a model number, which refers to the style of carb - 4150 and 4160 are square bores (the 4160 has a secondary metering plate); and 4165 and 4175 are spread bores.
The part number will refer to a particular carb within the model.
Hope this helps.
The 4150 is a model number, which refers to the style of carb - 4150 and 4160 are square bores (the 4160 has a secondary metering plate); and 4165 and 4175 are spread bores.
The part number will refer to a particular carb within the model.
Hope this helps.
Thread Starter
Advanced
Joined: Jun 2007
Posts: 57
Likes: 0
From: Buckhorn Ontario
The carb is model 80531, 4150, 850 CFM Holley.
It came with a 4.5"HG primary, and a 3.5"hg secondary powervalves.
I have already changed the secondary spring from a pink spring-heavy, to a long yellow spring, very light.
It came with a 4.5"HG primary, and a 3.5"hg secondary powervalves.
I have already changed the secondary spring from a pink spring-heavy, to a long yellow spring, very light.
Melting Slicks
Joined: Oct 2002
Posts: 2,317
Likes: 111
From: St Louis MO
Those power valves are correct according to the Holley spec sheet.
Based on the rather large jets stock for this carb, it appears to me that you will not have to enrich the mixture, or use PVs which open earlier (higher numbers). In fact, you may well find that decreasing the jet size will get you more power when you actually get some data from testing!
Based on the rather large jets stock for this carb, it appears to me that you will not have to enrich the mixture, or use PVs which open earlier (higher numbers). In fact, you may well find that decreasing the jet size will get you more power when you actually get some data from testing!
Racer
Joined: Apr 2008
Posts: 418
Likes: 0
From: destin fl
Those power valves are correct according to the Holley spec sheet.
Based on the rather large jets stock for this carb, it appears to me that you will not have to enrich the mixture, or use PVs which open earlier (higher numbers). In fact, you may well find that decreasing the jet size will get you more power when you actually get some data from testing!
Based on the rather large jets stock for this carb, it appears to me that you will not have to enrich the mixture, or use PVs which open earlier (higher numbers). In fact, you may well find that decreasing the jet size will get you more power when you actually get some data from testing!
SOMETHING SO SIMPLE ENDS UP BEING ROCKET 
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