Identify Hollet carb
Thread Starter
Racer
Joined: Apr 2011
Posts: 471
Likes: 3
Do the Holley 4175 carbs comes to defects that I could find buying an used one that I have to take care (as the wrapped horn of the Qjey)?
Race Director
Joined: May 2006
Posts: 18,729
Likes: 2,581
On the Holley make sure none of the screws are stripped particularly the bowl screws. On the Quad, why dont you pull the airhorn off and make sure you set the float correctly and that the needle is correctly installed. I believe the measurement is .250.
Thread Starter
Racer
Joined: Apr 2011
Posts: 471
Likes: 3
Could you send me a picture with the screws marked so that when I go to see the carb I can check them? Thanks!
Le Mans Master
Joined: Apr 1999
Posts: 6,134
Likes: 46
From: Raleigh North Carolina
I believe he meant the screw holes... not the screws. The accelerator pump is the most common problem but I have had to repair the main body (bowl screw threads) as well. The accelerator pump is the small rectangular device under the carb fuel bowl with a lever attached to it... 4 screw holes. These get over-tightened because they frequently come loose. The fuel bowls attach to each end of the carb (front rear) with 4 screws each. The main body threads for these 8 screws sometimes strip... again usually due to over-tightening... but more often due to sour gas. All of the screws are supposed to be torqued with an inch-pound wrench... but very few people have an inch-pound wrench...so they use the built-in torque wrench in their arm... with and error rate of 50%... or more.
Thread Starter
Racer
Joined: Apr 2011
Posts: 471
Likes: 3
I believe he meant the screw holes... not the screws. The accelerator pump is the most common problem but I have had to repair the main body (bowl screw threads) as well. The accelerator pump is the small rectangular device under the carb fuel bowl with a lever attached to it... 4 screw holes. These get over-tightened because they frequently come loose. The fuel bowls attach to each end of the carb (front rear) with 4 screws each. The main body threads for these 8 screws sometimes strip... again usually due to over-tightening... but more often due to sour gas. All of the screws are supposed to be torqued with an inch-pound wrench... but very few people have an inch-pound wrench...so they use the built-in torque wrench in their arm... with and error rate of 50%... or more.
Le Mans Master
Joined: Apr 1999
Posts: 6,134
Likes: 46
From: Raleigh North Carolina
Torque, inch pounds: -Thread- -Dry- -Lubricated- (-20%)
Fuel Bowls 12-24 25-30 20-24
Throttle Body to Main Body 12-24 30-50 24-40
Primary (Main) Jets 1/4-32 30-40 24-32
Power Valve, several small holes 1/2-28 40-50 32-40
Power Valve, two large holes 1/2-28 100 80
Discharge Nozzle (squirter) 48-52 38-42
Choke Cover 8-32 12 10
Secondary Metering Plate 8-32 12-18 10-14
Float Hinges etc 6-32 7-10 6-8
Carb Mounting 5/16-24 60-80 50-60
Fuel Inlet 9/16-24 175-200 140-160
Fuel Inlet 7/8-20 200-250 160-200
Accelerator Pump Cover 8-32 12-18 10-14
Note: Lubricated torque figures can be 10 to 25% lower than dry torque figures.
I pulled this info from an Excel spreadsheet so getting the columns to line up was a problem.
I'll let somebody else suggest a good Holley book. That's not my forte.
Fuel Bowls 12-24 25-30 20-24
Throttle Body to Main Body 12-24 30-50 24-40
Primary (Main) Jets 1/4-32 30-40 24-32
Power Valve, several small holes 1/2-28 40-50 32-40
Power Valve, two large holes 1/2-28 100 80
Discharge Nozzle (squirter) 48-52 38-42
Choke Cover 8-32 12 10
Secondary Metering Plate 8-32 12-18 10-14
Float Hinges etc 6-32 7-10 6-8
Carb Mounting 5/16-24 60-80 50-60
Fuel Inlet 9/16-24 175-200 140-160
Fuel Inlet 7/8-20 200-250 160-200
Accelerator Pump Cover 8-32 12-18 10-14
Note: Lubricated torque figures can be 10 to 25% lower than dry torque figures.
I pulled this info from an Excel spreadsheet so getting the columns to line up was a problem.
I'll let somebody else suggest a good Holley book. That's not my forte.
Corvette Stories
The Best of Corvette for Corvette Enthusiasts
Top 10 Most Expensive Corvettes Ever Sold on Bring A Trailer
Brett Foote
10 Things Every Corvette Owner Needs (2026 Edition)
Michael S. Palmer
8 Most "Only Corvette Owners Understand" Quirks and Problems
Pouria Savadkouei
10 Reasons the C6 Z06 is Still A Performance Benchmark After 20 Years
Joe Kucinski
How Much Horsepower Every Corvette Engine "LOST" in 1972
Joe Kucinski
Top 10 DOs and DON'Ts for Protecting Your Convertible Top!
Michael S. Palmer
Top 10 Most Explosive Corvettes Ever Made: Power-to-Weight Ratio Ranked!
Joe Kucinski
150 hp to 1,250 hp: Every Corvette Generation Compared by the Specs That Matter
Joe Kucinski
