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Quadrajet jetting

schweng18

Well-known member
Joined
Jan 22, 2006
Messages
55
Location
Bismarck, ND
Corvette
81 Frost Biege
Does anyone know what size the original jets are in the stock '81 Quadrajet?

I removed all of the smog contol equipment and think I need to install larger jets.

Any advice?

Thanks

Dave
 

Yoda

Well-known member
Administrator
Joined
Oct 12, 2000
Messages
4,884
Location
Amarillo, TX
Corvette
1981 UL5
:w Dave,

I know nothing about this subject;shrug but... we have several L81'ers that have done some fabulous things to their engines and carbs... hand tight one will be along with some advice and suggestions..

Bud
 
Joined
Apr 29, 2001
Messages
2,141
Location
Rio Rancho, NM
Corvette
1981 HD Suspension; ZN1 Option
Does anyone know what size the original jets are in the stock '81 Quadrajet?

I removed all of the smog contol equipment and think I need to install larger jets.

Any advice?

Thanks

Dave

Dave,

I am at work right now, but tonight I could send you the E4ME maual. It is about 8 megs, so let me know if you can receive it. I also believe I have it broken-down into four parts (this would then require 4 emails at about 2 megs each).

Generally speaking, the primary jets do not need messing with, since the L81 has the closed-loop mixture control (M/C), and the computer is going to adjust that as it is needed.

The secondary jets (aka metering orifice plates) are not removable. To effect a change in the metered fuel on the secondary side, one must change the metering rods which are designed to change their relative position within the metering orifice plates.

You shouldn't have a reason to mess with these unless you have a change in the engine's compression ratio, or basic deviation from original design. Perhaps your "problem" is just a matter for adjustment of key factors (TPS, M/C).
 

schweng18

Well-known member
Joined
Jan 22, 2006
Messages
55
Location
Bismarck, ND
Corvette
81 Frost Biege
Dave,

I am at work right now, but tonight I could send you the E4ME maual. It is about 8 megs, so let me know if you can receive it. I also believe I have it broken-down into four parts (this would then require 4 emails at about 2 megs each).

Generally speaking, the primary jets do not need messing with, since the L81 has the closed-loop mixture control (M/C), and the computer is going to adjust that as it is needed.

The secondary jets (aka metering orifice plates) are not removable. To effect a change in the metered fuel on the secondary side, one must change the metering rods which are designed to change their relative position within the metering orifice plates.

You shouldn't have a reason to mess with these unless you have a change in the engine's compression ratio, or basic deviation from original design. Perhaps your "problem" is just a matter for adjustment of key factors (TPS, M/C).


Thanks Gerry

I can receive the emails.

Dave
 

schweng18

Well-known member
Joined
Jan 22, 2006
Messages
55
Location
Bismarck, ND
Corvette
81 Frost Biege
Got it fixed! With a litttle guidance from my uncle the mechanic. It wasn't the carb at all, somehow the harmonic balancer must have moved a little bit and the timing mark is off. We set the timing by ear and kept adjusting it until the hesitation was gone. What an incredible difference, it's a totally different car. Thanks for al of the information though, I really appreciate the help.

Dave
 

Peer81

Well-known member
Joined
May 21, 2003
Messages
2,497
Location
Netherlands
Corvette
'81 Black
Good to hear Dave!
But if the harmonic balancer has moved, I think it's time to replace it. You don't want that big round metal disc getting lose at 3000 rpm!

Greetings Peter.
 

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