Re: Air-Fuel Ratio Tuning Questions

[Dave Casey <dcasey@xxxxxxxxxxxxx>]

14.7:1 is stoich for old fuels. Now that just about everything has 8-10% 
ethanol, you should be shooting for closer to 14.1-14.2 at cruise.
Thus it is my opinion that you could lean it out a little on the primaries. 
When you get close to too lean, you'll feel it surging ever so slightly as 
you cruise (my brother's 340 6-pak does this).
Jet for cruise, not idle. You can change the idle AFR with the air 
bleeds/holes in the butterflies.
I'd try a 66 or 67 in the primaries and see what you get.

Dave Casey

Sent from my PC
----- Original Message ----- 
From: "Dennis C." <dennis.2914@xxxxxxxxx>
To: <1962to1965mopars@xxxxxxxxxx>
Sent: Monday, April 20, 2009 3:50 PM
Subject: Air-Fuel Ratio Tuning Questions



Hello,

I am using an Innovate LC-1 Air-Fuel Ratio meter to jet my carburetor.
I would appreciate comments from anyone who has used an instrument like
this or has had experience jetting by Air-Fuel Ratio.

I have not found good information on what Air-Fuel Ratio (AFR) I should
be shooting for.  I have seen information ranging from people who are
shooting for the ideal AFR of 14.7:1 to those who feel that a "Safe"
range is between 12.8:1 to around 13.4:1.

I have a Holley Street Avenger 670 on my 383.  I now know that it was
probably not the best choice for a carburetor however when I got it I
was looking for just street performance on a driver.  I am now a
follower of Don Dulmage.s messages and learning more with each new
message he posts about tuning and carburetors.

The carburetor was running very lean out of the box with 65 Primary jets
and 68 Secondary jets.

At 68 Primary jets I am running 14.0:1 at idle and 13.8:1 to 14.0:1
cruising level ground 65 to 75 mph.

At 70 Primary jets I am running 13:0:1 at idle and 13.0:1 to 13.5:1
cruising level ground 65 to 75 mph.

To me it looks like #69 jets may be what I need.

I have some data on WOT with 70 Primary and 74 Secondary jets however I
want to get the Primary circuit set first.  It is interesting that on a
4th gear pull on the road from 2000 to 3500 rpm it first drops to around
12.0:1 then around 3000 rpm it drops again to under 11.0:1 and was still
dropping when I let up on the gas.

Again if anyone has experience in this areas comments would be
appreciated.

Dennis C.


1996 Dodge Ram 3500 Van Conversion
1964 Plymouth Belvedere 318 Auto
1963 Plymouth Sport Fury 383 4-speed
1949 Dodge Pickup 289/C4 soon to be changed
1998 Honda Valkyrie Standard


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----
Please address private mail -- mail of interest to only one person -- directly to that person.  I.e., send parts/car transactions and negotiations as well as other personal messages only to the intended recipient, not to the Clubhouse public address. This practice will protect your privacy, reduce the total volume of mail and fine tune the content signal to Mopar topic.  Thanks!

'62 to '65 Mopar Clubhouse Discussion Guidelines:
http://www.1962to1965mopar.ornocar.org/mletiq.html.