The reading will always jump up and down a bit , even with EFI, The important thing is to be in the ball park and not to lean or rich, Depending on weather conditions the AFR can change from 12.8 to 12.2 instantly. Having an exhaust that not leak and headers gaskets that not leak is a good start for a good reading :-)

Regards Rob

Mach173 wrote:

The reading will always jump up and down a bit , even with EFI, The important thing is to be in the ball park and not to lean or rich, Depending on weather conditions the AFR can change from 12.8 to 12.2 instantly. Having an exhaust that not leak and headers gaskets that not leak is a good start for a good reading :-)

Regards Rob

my problem is that i can not lean more than now with rods and jets in the tune kit. i can understand is rich on acceleration , but should be stoich on cruising . 

What size is your carb?  Maybe too big for the engine?

The gauge is just a point of reference. I have one in my 66.  Mine is in the glove box, angled where I can see it while driving.  I am much happier when I drive with the glove box closed!

Unlike TKO I found the AEM AFR gauge a huge help in tuning my carburetor. Since I don't have access to a dyno and the drag strip is 3000 feet lower I rely on the AFR for tuning. No data logging except with my Mark IV Eyeball and its synaptic link to the right foot. Yes the numbers jump around but I can see the average number and go from there. I'm running a Summit MO8500VS 500CFM carburetor.
Yesterdays spring test drive was fine but while on the second test drive the engine would die when the clutch was pushed in coming to a stop. A quick glance at the AFR told me it was going off-scale lean on idle. I turned the idle jets out 1/4 turn each and it would again idle but was at an AFR of 16.5 and very steady. Another 1/8 turn out and it settled down to 14.X AFR and the idle speed increased and smoothed. Try another 1/8 and the idle slowed down so I backed off the last 1/8th turn. Yes, I could have done this by feel and sound, but the AFR gauge told me the problem right off the bat.

So if you're still running rich at cruise I would lean a little more if you can. I would shoot for an AFR of 14 and call it good. My WOT AFR is too rich in the mid-range and leans out when the vacuum secondaries open. I can tell all of this because of the AFR gauge. To fix my mid-range WOT richness requires restrictors in the power valve circuit. That's not going to happen.

Getting a carb dialed in is slow and tedious work. Tweak and drive awhile and you'll notice more and more what is happening. Change one thing at a time and drive some more. Carburetors are a big compromise in all aspects, hence the reason EFI was developed.
 

Last edited by RV6 (5/04/2020 3:06 PM)

If it is a 500 Edelbrock, I would start by setting everything on the carb back to the way it came from Edelbrock.

Then, as Mach173 said, get the timing right.  It should run quite well in that configuration.  Probably too lean rather than too rich, but it should be ok.

MS wrote:

If it is a 500 Edelbrock, I would start by setting everything on the carb back to the way it came from Edelbrock.

Then, as Mach173 said, get the timing right. It should run quite well in that configuration. Probably too lean rather than too rich, but it should be ok.

Thanks MS . 
I do have the correct timing , now is setted at 14/16 btdc .
I try many times with basic edelbrock configuration but is always rich , also without afr reading . 
When went to mech shop to check afr with professional tester told me was between 13.9 and 14.7 at idle and also at differnt rpm.  The odd thing is in that attempt i was already using  lean jets and rods and result was good . 

I am trying step by step from leaner to average . More i rise in rich step , more it run bad . 
I have a video but i don't know how to post it . 

Thanks 

Mach173 wrote:

Can you reset the Carb to factory specs and take it from there. How does your plugs look like ? Edelbrock is known for being rather lean then rich if compared to Holley. Why did you change the settings that were good when you were in the shop ?
Yes mixture screws affect the idle up to a certain rpm. I dont now exact, but if the AIR/Mixture screws dont have an effect  your bypassing the idle circut or something else is wrong.

Regards Rob

maybe i explain me wrong : try carb out of the box and was not going good . i was saying in past post it was boggin , refuse to accelleration and so on . 
Buy a tune kit and try some rods and jets . 
the best configuration was to lean as much as i can . 
gone to the shop , try with professional tester and result was really good . 
Now i am trying to follow many that says " rich em up" . and car goes worst . 
float is ok , timing is ok , no leaks . 
spark plugs are fine when i use lean set up . way better than before when i was on stock edelbrock specs . 
That's all 

For everyone is using edelbrock 500 can you tell me your rods and jets size , need to compare . thanks 

TKOPerformance wrote:

If it was running good put it back to that calibration.  I don't know why anyone would advise you to richen the carb if it was running good...

yes yes and again yes ! i am happy to be right !   i am still on trial and error but today something happens ! 
i will never bet a dime that simply acting on idle screws i can see good react of gauge . Maybe i am wrong but it's affect also on riding because for first time i can see number variaton on cruising . 
Finally i can say i was right ! my car goes better when lean. 
Now i am using .086  and .068x0.52   secondaries .089  ( 8% lean)  silver spring and lower accel pump hole . 
better timing on 12  than 14  . ( at 14 i lost top end rpm ) 
car goes much better than rich, easy start , stoich at idle , regular water temp (no rise because too lean) no bogs ,no smell and good power all over range . reach  high rpm never seen before . 
now i will stop managing with carb and i will enjoy finally my new carb ! 
Thanks to everyone !  always the top notch on knowable ( ... is correct knowable ,,,, mmmm i don't know but you have understood ) ! 
very happy ! 

I'm glad to see you got it figured out and your car is running better. I'm still messing with mine but I get interrupted with other projects. I'm of the opinion that my AEM AFR gage is no good. The engine runs like crap and the AFR shows 13.5. Ocasionally now lately it will read somewhere between 15 and 17. The next day it goes back to 13.5. I installed a vacuum gage next to the AFR and I'am getting more information from that. I am still going back and forth trying to learn if my carb is to rich or to lean. So far I don't know except what I'v been told. I need to go back to when it was new and start over. EFI?

HudginJ3 wrote:

I'm glad to see you got it figured out and your car is running better. I'm still messing with mine but I get interrupted with other projects. I'm of the opinion that my AEM AFR gage is no good. The engine runs like crap and the AFR shows 13.5. Ocasionally now lately it will read somewhere between 15 and 17. The next day it goes back to 13.5. I installed a vacuum gage next to the AFR and I'am getting more information from that. I am still going back and forth trying to learn if my carb is to rich or to lean. So far I don't know except what I'v been told. I need to go back to when it was new and start over. EFI?

well i think you are right  , i have heard bad stories about aem afr gauge , and more or less the same with ours . . what shows your gauge when is on ( no crank)  ?  if shows 10  or 20 or 3 dots  the sensor is gone . That's what aem told me .