ZZ4 Intake

[Stevetoxic]

Any of you guys running a Goodwrench ZZ4 (or other dual pattern Intake) in your truck ?
I just installed one in my 59 and wonder if when using a square bore Edelbrock carb do I need a spacer/plate/adapter on the intake ?

[1project2many]

You almost always need a plate to cover the larger secondary openings when putting a square bore carb on a spread bore intake.
http://www.edelbrock.com/automotive/mc/install-items/



Sometimes a simple plate like this can be used:

[mr48chev]

A simple check is to lay the Qjet to manifold gasket on the bottom side of the Square bore and see if you have all the needed areas covered. I had to use a spacer like the one he showed on my Cad 500 with a square bore carb because the linkage wouldn't clear the low profile manifold and work but can't remember if the carb would fit the manifold right otherwise. I know you need the spacer to go the other way as I have done that before using a spread bore on a square manifold.

[Stevetoxic]

Thanks for your replies, I've spent the last few months (slow worker) carrying out some jobs on the old truck. Including the engine swap - the carb was on the old 283 and ran fine.
I've had this engine running and driven it around the block.
I have a faster than normal idle speed so am thinking vacuum leak - the idle adjustment screw will not slow it down.
When I test fit the carb to the manifold there seemed very little gasket area making contact.
I downloaded GM's ZZ4 info and it just states dual pattern intake, no mention of a plate/adapter.
Got a few jobs left to get it running right, busy weekend I guess.

[Coupeguy2001]

Sometimes you can use a phenolic spacer to cut down the unwanted heat from the manifold to the carb, and the spacers come in 1/4 inch increments. My phenolic spacer is an inch thick.

Beware, it changes the fuel mixture on the carburetor under certain circumstances, and also affects the carburetor response time that your carburetor sees from the opening of the throttle to the actual carburetor response. This is due to the "compressibility" of air under a vacuum, such as in a carburetor manifold relationship. With a spacer, there is more air involved from the valves in the engine to the throttle plate.

I use a spacer with a step in it to give a venturi effect, and speed up the air past the spacer to nullify the small lag that the carb sees when it is raised another inch over the manifold. I have a ZZ4 with an Edelbrock intake.

This speeding up of the air changes the speed of the total air flow, and changes the fuel rate rawn out of the bowl: during acceleration at the end of the pump shot, steady throttle, and climbing a small hill when the vacuum signal is stronger before moving the gas pedal.
Drive your truck around with different thickness spacers, and if you can't tell much difference, the thicker one will do you the most good in keeping the fuel cooler, it won't hasten the vacuum signal through the jets, but the cooler fuel will be denser, making up for the small lag that you might otherwise feel.

[Stevetoxic]

Originally Posted by Coupeguy2001

Sometimes you can use a phenolic spacer to cut down the unwanted heat from the manifold to the carb, and the spacers come in 1/4 inch increments. My phenolic spacer is an inch thick.

Beware, it changes the fuel mixture on the carburetor under certain circumstances, and also affects the carburetor response time that your carburetor sees from the opening of the throttle to the actual carburetor response. This is due to the "compressibility" of air under a vacuum, such as in a carburetor manifold relationship. With a spacer, there is more air involved from the valves in the engine to the throttle plate.

I use a spacer with a step in it to give a venturi effect, and speed up the air past the spacer to nullify the small lag that the carb sees when it is raised another inch over the manifold. I have a ZZ4 with an Edelbrock intake.

This speeding up of the air changes the speed of the total air flow, and changes the fuel rate rawn out of the bowl: during acceleration at the end of the pump shot, steady throttle, and climbing a small hill when the vacuum signal is stronger before moving the gas pedal.
Drive your truck around with different thickness spacers, and if you can't tell much difference, the thicker one will do you the most good in keeping the fuel cooler, it won't hasten the vacuum signal through the jets, but the cooler fuel will be denser, making up for the small lag that you might otherwise feel.

Wow - great info, thanks.
As a temporary fix I'm using an old 1/2" aluminium 4 hole spacer which seals well on the manifold.
Obviously getting heat transferred though that, but has run ok on the limited miles I have covered so far.
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[Jemezcrusher]

x2 on the spacer. I have a performer manifold on my ZZ4 with a half inch spacer to insulate from excess heat

[67 chevelle]

had a zz4 in my 49 , great engine
, doubt you need a spacer as the manifold is for a square bore . I did not have one on mine , but was running a holley carb

[Coupeguy2001]

Great!