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Who changed secondaries?

Peer81

Well-known member
Joined
May 21, 2003
Messages
2,497
Location
Netherlands
Corvette
'81 Black
Hello everybody,

Now my vette is at the painter for a few months (repairing damage and putting some new nice paint on her) I'm looking deeper into the E4ME carb and the ECM.
On the net there is some info on tuning a CC Q-jet but not much. The primaries are controlled by the m/c solenoid to stay at the perfect fuel/air ratio. But at WOT the ECM will leave the carb all on its own. So this means the secondaries and the hanger could be changed to obtain the perfect power-curve. All tho I have to read two books on Q-jets and modding them I was wandering if somebody here has changed some things on there E4ME Q-jet (performance related not emissions related ;) )

The ECM is more difficult then I thought. On TBI's there are lots of mods and edits, on 81 (first) ECM's almost non. I'm going to search for a later ECM from another E4ME (305 or 350ci) car that has more options and better responses then my 81 ECM has. Maybe somebody here has already done this? I'm digging in the thirdgen archives to find some nice topics about this stuff :)

Groeten Peter.
 

gedmeyer

Well-known member
Joined
May 17, 2003
Messages
316
Location
upstate New York
Corvette
former L81 owner!
I did change my secondary rods and hanger... I did it after I rebuilt the motor to a 383. I did not do any scientific study on performance gains however. I think I went off of the recommendations in an old post.

-tim
 
Joined
Apr 29, 2001
Messages
2,141
Location
Rio Rancho, NM
Corvette
1981 HD Suspension; ZN1 Option
Gedmeyer,

I have been looking for the publication that outlines the secondary rods choices for the E4ME, but so far I have not found it. Can anyone tell me what kit part number I need and the letter code combinations and what they mean. ;shrug
 

bradfordsvettes

Well-known member
Joined
Mar 28, 2001
Messages
549
Location
Boston, MA area
Corvette
jewel blue 61.cranberry 69 t-top.black rose 92
if you google quadrajet there are many sites with jet and rod info some of them are still available from gm if you do not come up with any thing let me know and i will look through my papers that i have saved Steve
 
Joined
Apr 29, 2001
Messages
2,141
Location
Rio Rancho, NM
Corvette
1981 HD Suspension; ZN1 Option
if you google quadrajet there are many sites with jet and rod info some of them are still available from gm if you do not come up with any thing let me know and i will look through my papers that i have saved Steve

Steve,

I have done an average search in the internet (average meaning about 3 hours on the internet searching for that particular subject), and I found a site that provided moderate amount of information, but here is the problem: from what I gathered, the rod part numbers are related to the carburetor part numbers, and the rod letter codes identify the rod tip profile and diameter at which is the widest point, but from all the listings I could not discern the L81 E4ME part number related rods. For example, The L81 carb P/N I have is 17081218, so the part number for the kit with rods suitable for the L81 carb ends in 1218.

Am I understanding this correctly?;help
 

Sensei

Well-known member
Joined
Apr 5, 2004
Messages
393
Location
Jacksonville, Fl
Corvette
'81 dark blue
Here are a few mods I've made to my E4ME:
-Cut off secondary air valve stop to allow full opening.
-Perforated secondary fuel pick up tubes for faster response.
-Richer secondary rods and hanger (I have a modified engine that required this)
-Enlarged idle ports for full adjustability.
-Shortened accelerator pump rod for more pump shot.
-Very little tension on secondary air valve spring (the engine can handle it).
That's all I can think of right now but the car is pretty fast. God bless, Sensei
 
Joined
Apr 29, 2001
Messages
2,141
Location
Rio Rancho, NM
Corvette
1981 HD Suspension; ZN1 Option


Steve,

Thanks for the information. I read somewhere that short tip rods are not as widely available from GM anymore, but that one could find them in old Q-Jet carbs.

I am going to take a trip to our Junk Yard road (Broadway ave.) and see if I can start collecting some of these rods. Thanks!
 

Sensei

Well-known member
Joined
Apr 5, 2004
Messages
393
Location
Jacksonville, Fl
Corvette
'81 dark blue
Steve,
I am going to take a trip to our Junk Yard road (Broadway ave.) and see if I can start collecting some of these rods. Thanks!

The E4ME primary rods and jets have all been the same on every E4ME I have worked on, and seem to work fine with the computer for a very wide variety of engine set ups. As far as secondary rods, several are available new from Edelbrock. I think I am using "CE" rods. God bless, Sensei
 

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