Rich on WOT

-
B

brasil

Well-Known Member
Joined
May 19, 2016
Messages
111
Reaction score
4
Location
Dueseldorf Germany
Need some help... I have a little problem with my 670 Streetavenger

The car runs great....but there is one thing that I want to have fixed.

First of all the carb runs good while cruising... but under hard acceleration the AFR goes down to 10 Point something SUPERRICH.

So the set up is 670 SA with 67 jets (primary ) and 69 sec. 4.5 PV AFR @ idle around 13.0
Could it be, that the PV circuit is too big ? I use the 4.5 PV because my vacuum is 9 Inches of Merc. @ Idle in Gear..
The bigger main jets are nessecary because with the 65 jets the engine is running a little lean ( 14.8-15 while cruising )

Is there a way to restrict the flow of the PV circuit ?

When I accelerate strong but not hard the AFR stays in the 12.00 Range

About the ign. 8 deg @ idle 25 advance ( very slow curve ) all in @ 4000 rpm the vacuum canister brings in 15 deg on top . I also use full mainifold vacuum to bring up the
idle... to 23 deg. ( because of the cam )

Greetings Juergen
 
Your PV sounds right. I'd try putting in a heavier vacuum secondary spring to slow down the opening rate. The paper clip trick in the video works good to see how far they are opening. I use a hairpin instead.
 
....sorry forgot to write The engine is a 340cui with 10.5 Cr x heads purplecam 71 intake hp manifold 2200 stall converter and 3.23 rear

@73Swinger18 right now I have the "stock "spring installed. I will try to use the stronger spring
but I think..the PV circuit is the problem....
 
An AFR of 14-15 at cruise is NOT too lean. I adjust for 15-16 AFR at cruise for the same engine type; lean burn engine AFR's were in the 18-20 range. So IMHO you are richening up the cruise for no good reason with the larger primary jets. If the 65 primaries put the AFR in the 13 range with the throttle opened to around 1/2 to 2/3 at 60-70 mph, that is good.

That larger primary jet may not be the whole cause of the overrich WOT but it is not helping.
 
hmmm.... so you mean that the close to 15 AFR is not too lean ? I pulled my plugs last week and the plugs were whitish... could be lean mixture..or a too hot spark . So I changed the plugs, form Autolite 65 to a colder NGK BP6ES equals a Champion N 9YC like the "old" HC engines used

Greetings Juergen
 
brasil said:
hmmm.... so you mean that the close to 15 AFR is not too lean ? I pulled my plugs last week and the plugs were whitish... could be lean mixture..or a too hot spark . So I changed the plugs, form Autolite 65 to a colder NGK BP6ES equals a Champion N 9YC like the "old" HC engines used

Greetings Juergen
Click to expand...
If you want to get a more accurate reading, install new plugs, make a high RPM/WOT run, then kill the engine. Pull over safely, pull a couple plugs, and then see what they look like.
 
brasil said:
hmmm.... so you mean that the close to 15 AFR is not too lean ? I pulled my plugs last week and the plugs were whitish... could be lean mixture..or a too hot spark . So I changed the plugs, form Autolite 65 to a colder NGK BP6ES equals a Champion N 9YC like the "old" HC engines used

Greetings Juergen
Click to expand...
It is not too lean for cruise conditions. When I say cruise, I mean a small throttle opening and running at around 100 km/h on level ground. When you open the throttle up, then the AFR should drop into the 12-13 range.

Here is a good reference: AFR+ Basic Functionality - Understand AFR Values, Wideband O2 Sensors, and Fuel Trim vs. Auto Tune Modes of our Fuel Controller.
 
I would put the 65 jet back in and run a 6.5 PV. Autolite 65 should be fine. 3.23 gear you are mainly running on the idle circuit during cruise. If it gets to rich at WOT try going bigger on the main air bleeds.
 
You must log in or register to reply here.
-

Back
Top