L-72 Carb Base Gasket Help

[Glenn B.]

Any one know what/where I can get the correct gasket between the carb and manifold is on this L-72 intake? I have an old three hole one, and some square open types, but the gasket thickness appears to be important because the choke pull of rod adjustment seems way too long. The gasket I purchased from Long Island Corvette supply was not even the correct inside dimensions.

It appears that the correct gasket thickness makes the choke rod adjustment easier. The choke butterfly is totally closed when cold, so it seems that the carb should be raised slightly. Any ideas would be appreciated.

Glenn

[Rich P.]

Re: L-72 Carb Base Gasket Help

Glenn,

the choke rod is supposed to be bent for each car to get proper operation. The gasket should not affect that. Unless you used insulated gasket which is a 1/4" thick or the car had a carb spacer.

I don't know who has the correct gaskets.

Rich

[John H.]

Re: L-72 Carb Base Gasket Help

Any one know what/where I can get the correct gasket between the carb and manifold is on this L-72 intake? I have an old three hole one, and some square open types, but the gasket thickness appears to be important because the choke pull of rod adjustment seems way too long. The gasket I purchased from Long Island Corvette supply was not even the correct inside dimensions.

It appears that the correct gasket thickness makes the choke rod adjustment easier. The choke butterfly is totally closed when cold, so it seems that the carb should be raised slightly. Any ideas would be appreciated.

Glenn

Glenn -

The 3-hole gasket is the one you want, and the minor difference in gasket thickness is unrelated to making the choke adjustment - that's done by bending the kink in the remote rod after the carburetor is installed.

[Joe L.]

Re: L-72 Carb Base Gasket Help

Glenn,

the choke rod is supposed to be bent for each car to get proper operation. The gasket should not affect that. Unless you used insulated gasket which is a 1/4" thick or the car had a carb spacer.

I don't know who has the correct gaskets.

Rich

Rich------


There are two choke rods on 66+ apps. One attaches to the choke butterfly valve. This is the one that is bent to adjust as required. The other is the rod that attaches to the choke thermostat. That rod is usually not bent to adjust.

[Joe L.]

Re: L-72 Carb Base Gasket Help

Any one know what/where I can get the correct gasket between the carb and manifold is on this L-72 intake? I have an old three hole one, and some square open types, but the gasket thickness appears to be important because the choke pull of rod adjustment seems way too long. The gasket I purchased from Long Island Corvette supply was not even the correct inside dimensions.

It appears that the correct gasket thickness makes the choke rod adjustment easier. The choke butterfly is totally closed when cold, so it seems that the carb should be raised slightly. Any ideas would be appreciated.

Glenn

Glenn------


You need the equivalent of a GM #3881847 or a GM #682914. Both are GM-discontinued. Dr. Rebuild usually has these carb gaskets right.

[John H.]

Re: L-72 Carb Base Gasket Help

Rich------


There are two choke rods on 66+ apps. One attaches to the choke butterfly valve. This is the one that is bent to adjust as required. The other is the rod that attaches to the choke thermostat. That rod is usually not bent to adjust.

Joe -

I've always understood that bending the upper choke rod (the one from the inboard choke lever to the choke butterfly) is done when adjusting the choke unloader (not the vacuum break, which is done by bending the diaphragm rod), and the choke adjustment is done by bending the lower choke rod (the one from the remote thermostat to the outboard choke lever).

Photo shows a '67 3810.

[Ronald L.]

Re: L-72 Carb Base Gasket Help

Bend this, bend that, sure recipe for why most of then were missing 10 years down the road.

[Glenn B.]

Re: L-72 Carb Base Gasket Help

Thank all,

The responses were helpful. After much searching, and head scratching, I found the holley instructions for "bending" and there are three items that are "bent to work" for proper cold start operation on these divorced choke carbs.

http://www.holley.com/data/Products/.../199R10013.pdf


Figure 21 Bend tag on cam positioner. (Fast idle speed?)
Figure 25 Check and bend the choke rod length. (this one will be affected if the base gasket thickness is off more than 1/16"
Figure 28 Bend the pull off link. (Cold idle mixture?)
Figure 32 Bend unloader tang. (WOT performance cold?)

Now, I just need to find the correct choke to horn clearance DIMENSIONS???

Glenn

[Rich P.]

Re: L-72 Carb Base Gasket Help

Now, I just need to find the correct choke to horn clearance DIMENSIONS???

Glenn

Glen all the settings/specs will be in the 66 Chassie Service or Overhaul Manua l.

Rich

[Joe L.]

Re: L-72 Carb Base Gasket Help

Joe -

I've always understood that bending the upper choke rod (the one from the inboard choke lever to the choke butterfly) is done when adjusting the choke unloader (not the vacuum break, which is done by bending the diaphragm rod), and the choke adjustment is done by bending the lower choke rod (the one from the remote thermostat to the outboard choke lever).

Photo shows a '67 3810.

John------


That could very well be. I just didn't recall any instruction for bending the lower choke rod but my recollection might be faulty. However, on some applications the rod is pretty much "straight" so the only thing that could be accomplished by bending would be effectively shortening it.

[Ronald L.]

Re: L-72 Carb Base Gasket Help

Is this an all new carb?

And how often do you bend these?

If these were basically set at the factory and you rebuilt an original, should you be real close?

I took mine out of the box from Eric's rebuild, bolted it on and with only running this in the summer, the choke is wide open all the time anyway.

I did not bend a thing, will check this spring, but did not note an issue last summer.

Glenn, any big box vette shop should have the 3 hole gasket, even many general autoparts stores might, color I think is the only thing that may get you.

[Rich P.]

Re: L-72 Carb Base Gasket Help

Ron the choke unloader rarley needs to be fooled with. The one that needs adjusting when removing or replacing a carb or choke is the pull off rod. This is the one that attaches to the coil on the intake and the to the carb.
I use a heat gun to adjust these when first installed. Once heated up I make sure the unloder opens the flap and the idel control drops clear of the plastic cam. Then I use high pressure air to cool the coil of to make sure it closes properly.
As per specs you want the choke to engauge when the motor is cold by depressing the accellerator once. When the car is started the high idle should be set between 1500-1800 rpm. Once the car is started you should be able to tap the gas once and the idel should drop 5-600 rpms. Then let the car warm up and hit the gas one more time and the idle should drop to specs.

Rich