CorvetteForum - Chevrolet Corvette Forum Discussion

C3 Tech/Performance V8 Technical Info, Internal Engine, External Engine, Basic Tech and Maintenance for the C3 Corvette
Sponsored by:
Sponsored by:

4175 Holley fuel leak.

Thread Tools
 
Search this Thread
 
Old Jul 20, 2021 | 10:33 AM
Share
  #1  
kodpkd's Avatar
kodpkd
Thread Starter
Le Mans Master
Active Streak: 30 Days
Community Builder
Community Influencer
Top Answer: 1
 
Joined: Jun 2019
Posts: 5,501
Likes: 2,201
From: Loveland
Default 4175 Holley fuel leak.
I am getting a few drops of fuel leaking from the driver side throttle shaft on to the intake manifold. New, needle and seat,,, power valve,,, float,,, seals,,, and throttle shaft bushings. Float adjusted properly. Original fuel pump. Fuel filter and return line original. Engine starts and runs well.
WHY?
Reply
0
Old Jul 20, 2021 | 11:17 AM
Share
  #2  
MelWff's Avatar
MelWff
Race Director
20 Year Member
Liked
Loved
Community Favorite
 
Joined: May 2006
Posts: 18,755
Likes: 2,589
Default
After the engine has been thoroughly warmed up and shut off, have you looked down the carburetor throat to see if gasoline is dripping ?
Reply
0
Old Jul 20, 2021 | 11:49 AM
Share
  #3  
kodpkd's Avatar
kodpkd
Thread Starter
Le Mans Master
Active Streak: 30 Days
Community Builder
Community Influencer
Top Answer: 1
 
Joined: Jun 2019
Posts: 5,501
Likes: 2,201
From: Loveland
Default
I'll check today thx. I know when the engine is running there should be suctions/negative pressure at the shaft.
Reply
0
Old Jul 20, 2021 | 12:08 PM
Share
  #4  
Jebbysan's Avatar
Jebbysan
Dr. Detroit
Supporting Member
10 Year Member
Liked
Loved
Community Favorite
 
Joined: Mar 2012
Posts: 10,097
Likes: 4,027
From: New Braunfels Texas
Default
Originally Posted by kodpkd
I'll check today thx. I know when the engine is running there should be suctions/negative pressure at the shaft.
Not on the top half of it there is not......above the throttle blade there is no vacuum at all......
Fuel dripping from the throttle shaft is always excess dripping from the booster and puddling on top of the blade...then out through the shaft.....
Start the engine and look down the throttle bore at idle......is there fuel dripping from the boosters? If so.....then you need a primary metering gasket. No fuel should come through the booster during idle, and there is no other constant source of fuel in the venturi other than the booster.

Jebby
Reply
0
Old Jul 20, 2021 | 12:43 PM
Share
  #5  
kodpkd's Avatar
kodpkd
Thread Starter
Le Mans Master
Active Streak: 30 Days
Community Builder
Community Influencer
Top Answer: 1
 
Joined: Jun 2019
Posts: 5,501
Likes: 2,201
From: Loveland
Default
I ordered new metering gaskets already. By shaft I mean the throttle shaft where fuel is leaking,,, isn't there suction there?
Reply
0
Old Jul 20, 2021 | 12:56 PM
Share
  #6  
Jebbysan's Avatar
Jebbysan
Dr. Detroit
Supporting Member
10 Year Member
Liked
Loved
Community Favorite
 
Joined: Mar 2012
Posts: 10,097
Likes: 4,027
From: New Braunfels Texas
Default
Originally Posted by kodpkd
I ordered new metering gaskets already. By shaft I mean the throttle shaft where fuel is leaking,,, isn't there suction there?
I know what you meant. Think about the throttle shaft and the plates......one half is above and one below. Only the part of the shaft below the plates can have vacuum.

Jebby
Reply
0
Old Jul 20, 2021 | 02:43 PM
Share
  #7  
kodpkd's Avatar
kodpkd
Thread Starter
Le Mans Master
Active Streak: 30 Days
Community Builder
Community Influencer
Top Answer: 1
 
Joined: Jun 2019
Posts: 5,501
Likes: 2,201
From: Loveland
Default
So if there is higher pressure than atmospheric pressure on top of the throttle shaft you will get air and fuel being pushed out of the shaft bushing gap while running?
Reply
0
Old Jul 22, 2021 | 02:46 PM
Share
  #8  
kodpkd's Avatar
kodpkd
Thread Starter
Le Mans Master
Active Streak: 30 Days
Community Builder
Community Influencer
Top Answer: 1
 
Joined: Jun 2019
Posts: 5,501
Likes: 2,201
From: Loveland
Default
Is there a chance if the base gasket isn't sealed, fuel could leak from there? I'm pretty sure with the engine acting like a huge 327 inch vacuum, sucking air through the carb, the only pressure in the card bore is suction.
Reply
0
Corvette Stories

The Best of Corvette for Corvette Enthusiasts

story-0

5 Best & 5 Most Overrated Corvette Track Packages of All Time!

 Joe Kucinski
story-1

Every 2027 Corvette Engine Explained

 Joe Kucinski
story-2

Designer Imagines A Corvette That Looks More Like a Corvette Than the Corvette

 Verdad Gallardo
story-3

10 Ugly Corvettes That We Still Kinda Love

 Joe Kucinski
story-4

Top 10 Most Expensive Corvettes Ever Sold on Bring A Trailer

 Brett Foote
story-5

10 Things Every Corvette Owner Needs (2026 Edition)

 Michael S. Palmer
story-6

8 Most "Only Corvette Owners Understand" Quirks and Problems

 Pouria Savadkouei
story-7

10 Reasons the C6 Z06 is Still A Performance Benchmark After 20 Years

 Joe Kucinski
story-8

How Much Horsepower Every Corvette Engine "LOST" in 1972

 Joe Kucinski
story-9

Top 10 DOs and DON'Ts for Protecting Your Convertible Top!

 Michael S. Palmer
Old Jul 22, 2021 | 02:50 PM
Share
  #9  
Jebbysan's Avatar
Jebbysan
Dr. Detroit
Supporting Member
10 Year Member
Liked
Loved
Community Favorite
 
Joined: Mar 2012
Posts: 10,097
Likes: 4,027
From: New Braunfels Texas
Default
Originally Posted by kodpkd
So if there is higher pressure than atmospheric pressure on top of the throttle shaft you will get air and fuel being pushed out of the shaft bushing gap while running?
No, but if fuel is puddling on top of the throttle plate when it is shut then it will seep out the sides. The pressure outside the carb is the same as inside the venturi with the blades shut.

Jebby
Reply
0
Old Jul 22, 2021 | 02:51 PM
Share
  #10  
Jebbysan's Avatar
Jebbysan
Dr. Detroit
Supporting Member
10 Year Member
Liked
Loved
Community Favorite
 
Joined: Mar 2012
Posts: 10,097
Likes: 4,027
From: New Braunfels Texas
Default
Originally Posted by kodpkd
Is there a chance if the base gasket isn't sealed, fuel could leak from there? I'm pretty sure with the engine acting like a huge 327 inch vacuum, sucking air through the carb, the only pressure in the card bore is suction.
No, the base gasket has no way to leak fuel. if it is coming out of the throttle shaft then it is dripping out of the boosters like I said. No other place the fuel can come from constantly.

Jebby
Reply
0
Old Jul 22, 2021 | 06:06 PM
Share
  #11  
kodpkd's Avatar
kodpkd
Thread Starter
Le Mans Master
Active Streak: 30 Days
Community Builder
Community Influencer
Top Answer: 1
 
Joined: Jun 2019
Posts: 5,501
Likes: 2,201
From: Loveland
Default
Originally Posted by Jebbysan
No, the base gasket has no way to leak fuel. if it is coming out of the throttle shaft then it is dripping out of the boosters like I said. No other place the fuel can come from constantly.

Jebby
I'm not 100% sure it coming from the shaft. The shaft and the gasket are 1/4 inch apart.
Reply
0

Get notified of new replies

To 4175 Holley fuel leak.

Back to Subforum
C3 Tech/Performance
View Next Unread
305 heads on 350




Click for Advanced Search
Reply Closed Thread Share
Forum Jump
Trending Topics

All times are GMT -4. The time now is 01:34 PM.

story-0
5 Best & 5 Most Overrated Corvette Track Packages of All Time!

Slideshow: The 5 best and 5 most overrated Corvette track packages ever.

By Joe Kucinski | 2026-06-09 12:46:45


VIEW MORE
story-1
Every 2027 Corvette Engine Explained

Slideshow: Every 2027 Corvette engine explained

By Joe Kucinski | 2026-06-09 12:16:31


VIEW MORE
story-2
Designer Imagines A Corvette That Looks More Like a Corvette Than the Corvette

Slideshow: A Jaguar designer's personal project imagines what a modern front-engined Corvette might look like if Chevrolet revisited the golden age of the Stingray.

By Verdad Gallardo | 2026-06-08 19:53:43


VIEW MORE
story-3
10 Ugly Corvettes That We Still Kinda Love

Slideshow: 10 ugly Corvettes that we still kinda love.

By Joe Kucinski | 2026-06-03 10:34:17


VIEW MORE
story-4
Top 10 Most Expensive Corvettes Ever Sold on Bring A Trailer

A lot of money has changed hands at the online auction house over the years.

By Brett Foote | 2026-06-03 10:21:50


VIEW MORE
story-5
10 Things Every Corvette Owner Needs (2026 Edition)

Slideshow: 10 great gifts Corvette enthusiasts actually want for Father's Day!

By Michael S. Palmer | 2026-06-03 15:43:40


VIEW MORE
story-6
8 Most "Only Corvette Owners Understand" Quirks and Problems

Slideshow: These are the quirks, annoyances, and oddly lovable problems that every Corvette owner eventually learns to live with.

By Pouria Savadkouei | 2026-05-28 09:31:39


VIEW MORE
story-7
10 Reasons the C6 Z06 is Still A Performance Benchmark After 20 Years

Slideshow: 10 reasons why the C6 Z06 is still a performance benchmark after 20 years.

By Joe Kucinski | 2026-05-27 17:20:09


VIEW MORE
story-8
How Much Horsepower Every Corvette Engine "LOST" in 1972

Slideshow: How much horsepower every Corvette engine lost in 1972.

By Joe Kucinski | 2026-05-27 16:54:53


VIEW MORE
story-9
Top 10 DOs and DON'Ts for Protecting Your Convertible Top!

Slideshow: How to Protect A Convertible Top: 10 DOs & DON'Ts

By Michael S. Palmer | 2026-04-03 00:00:00


VIEW MORE