1967 427 390hp (L36) - Holley Carburetor

[1stVette]

Hello,

I am new to this forum, so please excuse me if my question is worded incorrectly or if additional information is required...

I have a 1967 Corvette Coupe, 427 390HP (L36) which is believed to be a survivor (except for one repaint in the early 1980s) with approx. 42,000 miles...

The carburetor is leaking (rather spewing in a very fine -pin like- stream) from the top of the carburetor from one of the "brass plugs" on the float bowls...I have been told that this is not repairable and I need a new carburetor...can anyone confirm if this is true??

Secondly, if I need a new carburetor and wish to keep it numbers matching...

Crane Corvettes have a new reproduction Holley 3811 carburetor (which they will "date stamp" - for an additional fee, of course)...would this meet NCRS standards for "numbers matching" or do I need to source an original real date coded carburetor??

Any assistance or guidance would be greatly appreciated!!

Thanks

 

[Tom Bryant]

Welcome to the CAC

If you have a pin hole in one of the float bowls it is only held on with 4 screws and is easily replaced. No need to change out the carb. If it is a screw in plug, remove it and see if there are damaged threads or some other reason it is leaking past the plug.

Got a picture of the leak?

Tom

 

[Vettehead Mikey]

Tom is right about changing just the bowl or individual component that is leaking. No need for a complete carb.

If your car is that close to being a 'survivor' and you intend to have it judged, then make as few changes as possible.

NCRS does not use the term 'matching numbers' as there's many varied and conflicting definitions. In judging a carb, there's dozens of factors that go into the evaluation, far beyond simple numbers. It's highly unlikely that any modern reproduction piece would get very far and hardly worth paying extra for.

 

[Hib Halverson]

You say the leak is in a "float bowl".

Are you sure you don't mean "metering block" which is the rectangular, inch-thick block between the carb's center section and the float bowl.

If it's the metering block which is leaking, you can buy replacement metering blocks from Holley.

Pull the carb off, take it apart, scrap the leaker, install the new block with new metering block and bowl gaskets.

 

[Toms007]

First off, welcome to CAC. Your 1st vette is a real nice one! I'm with Tom and HIb on this. We need to find where exactly the leak is occurring. Float bowls and metering blocks can be replaced without replacing the entire carb.

Maybe post some pictures of the leak, so we can help you out a bit more.

Congrats on the 427 survivor, and post up some pictures of your ride (and the leaky carb) when you can.

 

[kpic]

I might be wrong, but didn't the 427-390 have a Rochester?

Edit
MT Q-Jet 7029204
Auto Q-Jet 7029215

As I was around back in the day; the Q-Jet to Holley was a very common conversion as people preferred the Holley. GM's habit of putting Holleys on their high performance engines probably convinced folks.

1stVette,
What does the manifold look like and is the Holley a dual feed?

 

[Tom Bryant]

!967 used the Holley 4160. R3811A or R3815A with K19 option.

Tom

 

[motorman]

Hello,

I am new to this forum, so please excuse me if my question is worded incorrectly or if additional information is required...

I have a 1967 Corvette Coupe, 427 390HP (L36) which is believed to be a survivor (except for one repaint in the early 1980s) with approx. 42,000 miles...

The carburetor is leaking (rather spewing in a very fine -pin like- stream) from the top of the carburetor from one of the "brass plugs" on the float bowls...I have been told that this is not repairable and I need a new carburetor...can anyone confirm if this is true??

Secondly, if I need a new carburetor and wish to keep it numbers matching...

Crane Corvettes have a new reproduction Holley 3811 carburetor (which they will "date stamp" - for an additional fee, of course)...would this meet NCRS standards for "numbers matching" or do I need to source an original real date coded carburetor??

Any assistance or guidance would be greatly appreciated!!

Thanks

clean the area good and seal it with clear fuel proof model airplane dope. there is a O ring under that plug that goes away after years.

 

[kpic]

!967 used the Holley 4160. R3811A or R3815A with K19 option.

Tom

You are correct, single feed Holley. 68 & 69 used the Rochester or Holley carbs; oval port were Q-Jets and rectangular ports were Holley.

 

[1stVette]

First off, welcome to CAC. Your 1st vette is a real nice one! I'm with Tom and HIb on this. We need to find where exactly the leak is occurring. Float bowls and metering blocks can be replaced without replacing the entire carb.

Maybe post some pictures of the leak, so we can help you out a bit more.

Congrats on the 427 survivor, and post up some pictures of your ride (and the leaky carb) when you can.

Hello,
Wow...thanks for all of the responses!!

I will post some pictures of the carb (and the car) in the morning, to better detail the leaking issue...all of the responses are very much appreciated!!

 

[Toms007]

!967 used the Holley 4160. R3811A or R3815A with K19 option.

Tom

Tom, that's what I was remembering, that the Qjets came in on the C3 low HP BBlocks. Thanks for confirming my recollections.

 

[Hib Halverson]

clean the area good and seal it with clear fuel proof model airplane dope. there is a O ring under that plug that goes away after years.

"Model airplane dope" is likely not a good choice because of questions about its durability when subjected to underhood heat along with some of the additives which are in automotive gasoline.

If you're going to repair the carb in that manner, cleaning the area and using an epoxy product might work better.

Best is a replacement metering block.

 

[1stVette]

First off, welcome to CAC. Your 1st vette is a real nice one! I'm with Tom and HIb on this. We need to find where exactly the leak is occurring. Float bowls and metering blocks can be replaced without replacing the entire carb.

Maybe post some pictures of the leak, so we can help you out a bit more.

Congrats on the 427 survivor, and post up some pictures of your ride (and the leaky carb) when you can.

Hello,

I have attached 3 images of the Carb for your review...the leak is streaming from the "frost plug" located on top of the rear float bowl (see image #4)...the numbers on the Carb are as follows: 3906633-E0
List-3811
2159

I thought that the Date Code on the Carb was 3 digits not 4...can someone kindly confirm??

The build date of the car is March 17, 1967, not sure if this carb is correct or not??

Any assistance is greatly appreciated!!

Thanks

 

[Toms007]

Beautiful car! reminds so much of my old 64. Is that Lyndale Blue? Kind of hard to tell from the picture.

 

[1stVette]

Beautiful car! reminds so much of my old 64. Is that Lyndale Blue? Kind of hard to tell from the picture.

Thankyou!!...wrapped in its factory colour of Lynndale Blue...

 

[1stVette]

I might be wrong, but didn't the 427-390 have a Rochester?

Edit
MT Q-Jet 7029204
Auto Q-Jet 7029215

As I was around back in the day; the Q-Jet to Holley was a very common conversion as people preferred the Holley. GM's habit of putting Holleys on their high performance engines probably convinced folks.

1stVette,
What does the manifold look like and is the Holley a dual feed?

Hello,

I think the Holley 4160 #3811 is a single feed carb...please see pictures above...not sure if the carb is numbers matching to the car. As I thought the date code on the carb was 3 digits; whereas this carb appears to have 4 digits...

Any help is greatly appreciated!!

Thanks

 

[Vettehead Mikey]

I might be wrong, but didn't the 427-390 have a Rochester?

Edit
MT Q-Jet 7029204
Auto Q-Jet 7029215

The fourth digit in a Qjet part number designates the year the carb was first released, in this case 1969 for the numbers you quote. The OP has a '67 originally equipped with a Holley.

 

[65TripleBlack]

clean the area good and seal it with clear fuel proof model airplane dope. there is a O ring under that plug that goes away after years.

Correct, as usual. I have successfully sealed those with clear 2 part epoxy cement. Almost undetectable, but wouldn't amount to more than a "dot" on a judging sheet (depending on the judge, 2-3 "dots" equals a point).

 

[motorman]

"Model airplane dope" is likely not a good choice because of questions about its durability when subjected to underhood heat along with some of the additives which are in automotive gasoline.

If you're going to repair the carb in that manner, cleaning the area and using an epoxy product might work better.

Best is a replacement metering block.

if you use epoxy make sure it is ethanol safe.

 

[Hib Halverson]

Now that I see the pictures, that leak is coming from the pressure side of the float valve. That's why it sprays anytime the engine is running.

Unfortunately, Holley does not service the float bowls for the 3811.

What I'd do is contact a carb specialty vendor such as the "Carb Shop" and see if they can repair it by installing a new soft plug.