carb leak

[66 big block]

Ihave new 3370 holley installed and I get leak at base pas side what is the right set up for gaskets for 390hp sloted gasket is first then thin alum spacer then gasket and carb I get leak after it sits over night not when running thanks John

 

[Kid_Again]

The metal gasket should sit next to the intake manifold. It is there to protect against the hot exhaust gases flowing through the intake.

 

[JohnZ]

That's one of the manifolds with the "hot-slot" that needs to be plugged so it doesn't warp the carb baseplate - see photo below. The correct stack is carb pad, composition gasket, stainless steel baffle, then the carb; that's all the pieces. Don't torque the nuts more than 12-18 ft-lbs. or you'll crack the baseplate.

 

[Vette66AirCoupe]

John,

What is a carb pad? I have the steel baffle sandwiched between two gaskets with the carb on top on my big block. Seems to work OK that way.

 

[66 big block]

John,

What is a carb pad? I have the steel baffle sandwiched between two gaskets with the carb on top on my big block. Seems to work OK that way.

I had that set up too gaskets leaked plus I thinkI had a vac leak I just did what John said put gasket down first then ss baffle plate then carb ran car will check for leaks after I also blocked the two holes in heat passage JOhn

 

[redvett]

I had that set up too gaskets leaked plus I thinkI had a vac leak I just did what John said put gasket down first then ss baffle plate then carb ran car will check for leaks after I also blocked the two holes in heat passage JOhn

The correct way is the SS metal insulator goes on the manifold and the fiber on top. You may have a warped manifold that you can drawfile flat and also check your carburator for being flat.

 

[Kid_Again]

I'll be darned. John, you put the metal on the TOP of the stack? OK, if you say so but I thought it was the other way around to protect the soft stuff.

 

[Vette66AirCoupe]

Logically, it would seem the best way to eliminate a vacuum leak would be to sandwich the SS plate between two gaskets. Metal to metal doesn't seem like the best way to me. At any rate, manifold, gasket, SS plate, gasket, carb works for me with no leaks.

 

[Vette66AirCoupe]

I don't remember if I had plugs or not. What did you guys use to plug the holes?

 

[66 big block]

I don't remember if I had plugs or not. What did you guys use to plug the holes?

used 7/16" freeze plugs fit snug tapped in

 

[66 big block]

I had that set up too gaskets leaked plus I thinkI had a vac leak I just did what John said put gasket down first then ss baffle plate then carb ran car will check for leaks after I also blocked the two holes in heat passage JOhn

checked carb this morning still leaked after sitting over night same spot pass side at throttle plate area under secondary diaphram carb is new dont know whats causing this p.i.t.a thanks for help John

 

[Vette66AirCoupe]

The gas leak shouldn't have anything to do with the base gaskets. :confused

 

[66 big block]

The gas leak shouldn't have anything to do with the base gaskets. :confused

when I pulled Carb off gaskets where wet so I dont think end of throttleshaft is prob now I have gasket on manifold ss baffle then carb still have leak maybe bad base on new carb ???? thanks John

 

[JohnZ]

The correct way is the SS metal insulator goes on the manifold and the fiber on top. You may have a warped manifold that you can drawfile flat and also check your carburator for being flat.

May be different on C3's, but the '66-'67 L-36 (and all the other '66-'68 applications that used the "hot-slot" manifolds) assemble as I noted - gasket first, then stainless baffle, then the carb.

 

[JohnZ]

when I pulled Carb off gaskets where wet so I dont think end of throttleshaft is prob now I have gasket on manifold ss baffle then carb still have leak maybe bad base on new carb ???? thanks John

If the leak is dribbling off the end of the secondary throttle shaft, the fuel is most likely dribbling from the boosters onto the butterflies, especially if you don't see any fuel stains on the outside, above the throttle shaft; check the secondary bowl float level - it's probably too high.

 

[Drjohn]

Call tomorrow. The guys have conversations like this every day:

http://www.holley.com/TechService/

Let me know if you don't get help.

 

[Kid_Again]

As usual, JohnZ is correct about the placement of the ss baffle on the manifold. That's IF you use the correct carb gasket. Since I never used the correct lower gasket with the cutout, I stand by my recommendations.

In other words, if you want to do it incorrectly, do it incorrectly as I suggested.

Anyway, I did as suggested when I had the cast iron intake, I threaded and plugged the vents. No need for the fancy stuff.

 

[Vette66AirCoupe]

As usual, JohnZ is correct about the placement of the ss baffle on the manifold. That's IF you use the correct carb gasket. Since I never used the correct lower gasket with the cutout, I stand by my recommendations.

In other words, if you want to do it incorrectly, do it incorrectly as I suggested.

Anyway, I did as suggested when I had the cast iron intake, I threaded and plugged the vents. No need for the fancy stuff.

Sounds pretty fancy to me. Wouldn't the freeze plug method have been easier?