Choke pull-off operation - E4ME carb

Reply Subscribe

Thread Tools

Search this Thread

Jan 27, 2009 | 05:07 AM

#21

noonie

Race Director

Joined: Mar 2006

Posts: 14,112

Likes: 28

From: Florida

Quote:

Originally Posted by Jon S

Well, I'm not going to argue with you or anyone else about the merits of disconnecting the rod. All I will say is that on my cars, iIget a surge of power when the secondaries kick in that did not happen with the rod attached. There is zero bogging - just a blast of power. I guess you have to try it when the weather gets better to appreciate it.

You can set it to react that way and keep the rod and the original orifice size.
The 81 is a smog carb. For kicks, put on an original pre 75 carb, and you will see a bigger difference.

Quote:

Originally Posted by Reggie Dunlop

The blast of power is actually a bog. It is caused by too much air too quickly and then the motor catches up all at once. A motor that is tuned right will just pull hard - no big blast - like shifting into passing gear.The purpose of the secondary choke pull-off is to keep the air flaps closed during high vacuum conditions AND to prevent them from flopping open too quickly under hard acceleration. Basically, it allows the secondary air valves to open gradually as vacuum bleeds off when going to full throttle. If you feel yours is to slow you can purchase a different one with a lager orifice for faster action. If you have yours removed and the car does not bog / hesitate, then your spring has to be set too tight to get full opening. This is just simply how the quadrajet works. If you would rather not beleive me, just read Doug Roe's book or get a copy Cliff Ruggles' new book (it covers everything q-jet). It is not my intent to be obtuse, back in 1976 my thoughts were the same as yours until I ran my car down the track. I just want to put accurate info out there.

It doesn't necessarily mean it's a bog, You can improve the original secondary opening operation, just as you can improve the passing gear shift.

Watch the real world operation of the secondary opening with the hood and air cleaner off. You can set it for a much more instant opening without a bog and still have it open all the way.

BTW, you also can have the air valve open in neutral, but not all the way.

The proper setup is to have a smooth transition to the secondaries where the only way to tell, is by the sound alone. In real world driving the only difference would probably be a little bit of gas savings.
At the track the difference would have to be timed.

Jan 27, 2009 | 09:28 AM

#22

a1sensei

Melting Slicks

Joined: Mar 2006

Posts: 2,465

Likes: 0

From: Orange Park Fl

Quote:

Originally Posted by noonie

The 81 is a smog carb. For kicks, put on an original pre 75 carb, and you will see a bigger difference.

I'm not trying to hijack this thread, but I'll put my E4ME against any other carb on a car like mine (street performance, 350-400hp). It is tuned down to a "T" and leaves no performance on the table (and I get great gas milage too!). If you know how to work with the E4ME, it is the ultimate carb, the most advanced carburetor ever made.

God bless, Sensei

Jan 27, 2009 | 09:50 AM

#23

noonie

Race Director

Joined: Mar 2006

Posts: 14,112

Likes: 28

From: Florida

I prefer the later smog carbs too.

They have several advantages. But it takes a lot more than just fine tuning, you have to start reworking the air bleeds, APT, accel pump squirter, idle tubes, secondary wells and bleeds, and the list goes on.
This gives noticeable performance and response differences and unless you have compared both on the same engine...........

These later smog carbs were designed for fuel economy and emissions, so of course your gas mileage will be good if not altered too much.

For quick reference check the books by Roe or Ruggles, but judging by the OP's question, it is probably beyond his desire or scope.

Jan 27, 2009 | 11:50 AM

#24

LannyL81

Thread Starter

Melting Slicks

Joined: Nov 2005

Posts: 3,323

Likes: 142

From: Green Valley Arizona

I have Doug Roe's book and have read about the performance mods that can be done to the E4ME...just have not done any yet as I needed a working base to start from.

Now that I have a properly setup choke...I am getting ready to try a few things.

One comment about the pull-off rod controlling the opening of the secondary air valves.....I disagree with that somewhat. If the vacuum is low so that the rod is moved, thus unlocking the air valve, its the spring tension that controls the opening of the air valve. And this tension is critical as it cannot just flop open, but it also cannot be restricted in its opening. There is a balance here. Once again, to me the pull-off rod causes a delay as it has to move, unlocking the air valve and then the spring tension controls the opening.

Whatever mods I attempt to make on this carb will be slight as I am not after a track car. The use is a street cruiser.

Jan 27, 2009 | 12:21 PM

#25

Reggie Dunlop

Drifting

Joined: Aug 2008

Posts: 1,381

Likes: 11

"The proper setup is to have a smooth transition to the secondaries where the only way to tell, is by the sound alone."
Your not serious are you?

Jan 27, 2009 | 01:35 PM

#26

Jon S

Instructor

Joined: Jun 2005

Posts: 135

Likes: 0

Considering the Carter, Holley and even the Motorcraft carburetors do not have secondary air valves, if it were up to me, I would remove them totally as I still maintain they are emission-related delay mechanisms! I like the sound of the secondaries opening instantaniously; but like the surge in power even better. I'll stick to my rod-less configuration. It has worked well for me for 26 years on this car. I believe in results.