# AFR part two



## Baaad65 (Aug 29, 2019)

Ok so got the car out for a drive and watching the afr gauge it's around 12.5-13.5 at idle and cruising and of course dips way down when accelerating, rises when you let of the throttle. I couldn't film it being alone so my question is where is the afr supposed to be and and at what rpms ideally? I know the 12.5 is pretty good, I have a Youtube video on my channel @ Baaad65 of it in the garage but guessing it needs to be under load. The sensor is in the passenger down tube, this is a 461 with an Eddy Perfomer RPM w/ a 1/2" spacer and an 850 Quickfuel DP, 7.5 PV 76 jets up front 82 in the rear, 35 tube squirters in both. Thanks


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## BearGFR (Aug 25, 2008)

At wide open throttle, pulling hard, I like to see around 12.5. Cruise and idle, mid 13's to low 14's.


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## Baaad65 (Aug 29, 2019)

BearGFR said:


> At wide open throttle, pulling hard, I like to see around 12.5. Cruise and idle, mid 13's to low 14's.


Ok thanks Bear, I'll try pay attention next time out.


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## michaelfind (Dec 14, 2018)

Please pardon the butting in, but I just came home with similar questions.
So the upper 10s and 11 s I just saw at wot mean I’m way too rich on secondaries, right?

other wise I’m 13s and 14s at idle and cruise.


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## Baaad65 (Aug 29, 2019)

michaelfind said:


> Please pardon the butting in, but I just came home with similar questions.
> So the upper 10s and 11 s I just saw at wot mean I’m way too rich on secondaries, right?
> 
> other wise I’m 13s and 14s at idle and cruise.


No butting in just useful information my friend 👍


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## BearGFR (Aug 25, 2008)

michaelfind said:


> Please pardon the butting in, but I just came home with similar questions.
> So the upper 10s and 11 s I just saw at wot mean I’m way too rich on secondaries, right?
> 
> other wise I’m 13s and 14s at idle and cruise.


That's pretty rich. The concern with overly rich mixtures is fuel wash. Raw gas washing the oil off the cylinder walls, leading to ring wear. Plus, it can get into the oil and dilute it to the point where it no longer does a very good job of protecting the bearings. 
Pull the dipstick and take a good whiff. If you can smell gas, that's bad. Change the oil and filter immediately, and correct the problem.
It could be that the secondaries are too rich, and/or the power enrichment circuit is too rich. 

"Knobs" you have to lean it out at WOT:
QJet: 

Primary and secondary metering rods (less taper towards the tips)
Power piston spring (weaker)
Secondary rod hanger
Air valve spring tension (last resort only)
Holley/Holley clone 

Secondary jets
Power valve (weaker spring)
Secondary high speed air bleeds (bigger)
Power valve channel restrictors (smaller)
If it jumps rich at first but then gets better the longer you're at WOT, and if the carb is a double pumper, the problem might be the secondary pump is pushing too much fuel. The fix for that is smaller squirters on the secondary side, less aggressive pump cam, converting to the smaller pump (if it has the big 50cc pump on the secondary side)
What carb are you running?

Bear


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## michaelfind (Dec 14, 2018)

BearGFR said:


> That's pretty rich. The concern with overly rich mixtures is fuel wash. Raw gas washing the oil off the cylinder walls, leading to ring wear. Plus, it can get into the oil and dilute it to the point where it no longer does a very good job of protecting the bearings.
> Pull the dipstick and take a good whiff. If you can smell gas, that's bad. Change the oil and filter immediately, and correct the problem.
> It could be that the secondaries are too rich, and/or the power enrichment circuit is too rich.
> 
> ...


Thank you.
I'm running two Edelbrock 600CFMs on a P65 dual plane manifold.

Yesterday, I changed out the secondary jets to the smallest I had on hand, .089 in the front carb and .092 on the rear carburetor. They both had .095 in secondaries before the change. This changed my WOT AFR to 11.2, no more 10s. I see that they sell some .083 jets and I'm thinking that may be what I should try next.

I'll check the oil today for gas smell. I don't go WOT too often so I'm probably OK but have oil and filter on hand if needed.


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## BearGFR (Aug 25, 2008)

Sounds like you're headed in the right direction. I've got no hands on experience with the Edelbrock carbs so I'm out of my element with those. I did just now look at an exploded diagram and I _think_ I'm seeing a pair of metering rods on each side of the carb that are part of the power enrichment circuit. Edelbock calls them "step-up rods". Looks like under vacuum they protrude into the primary jets? If that's the case you might also try either rods that are "fatter" towards the bottom end, and/or some 'weaker' springs that don't take as much vacuum to overcome.


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## michaelfind (Dec 14, 2018)

Will do. Thanks


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## PontiacJim (Dec 29, 2012)

michaelfind said:


> Will do. Thanks


As BearGFR pointed out, there is available different tension springs that go under the step-up rods. These are based on engine vacuum. For example, if you have low engine vacuum and use the stronger springs intended for an engine with 15-17" Hg of vacuum, the spring will not be pulled down by the lower engine vacuum causing a rich condition within the carb. So you want a softer spring that will work with lower engine vacuum and pull the step-up rods down and eliminate the rich condition - then when you step on the gas and engine vacuum goes to near zero, there is enough tension in the springs to allow the piston of the step-up rod to rise and add more fuel.

Easy enough to change and I suggest you get springs from Edelbrock as I have read some bad reviews of the cheaper non-Edelbrock springs that don't work.


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## Baaad65 (Aug 29, 2019)

Here's mine parked, probably not accurate because of no load...hopefully get it out this weekend for a better test.afr


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## 67ventwindow (Mar 3, 2020)

It helped me see what was going on with Amy. You could see and hear when you gun it the the AFR gets fat 11ish when you let off that it went lean 14+. Time to get back to work on my custom ECU. I know Jim says to go by the seat of your pants. When I am grabbing gears I only look at the road, my ears are listing for the revs. My nose tells me if something is going wrong. The seat of my pants is trying to hold on to the bucket cause that lap belt aint doing much.
I remember the weekend they opened the first coaster that would do a loop back in 1976 stood in line 3 hrs. I remember climbing that first hill after that it was a blur. That is the same feeling I get when a depress a clutch its like climbing that hill waiting for the blur to start. Doesn't matter if its a car , a bike or a deuce and a half.


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## Baaad65 (Aug 29, 2019)

Ok I got her out and tried to video but it's hard by yourself, the first one is cruising in second gear then going wot to the shift light at 5700 rpms, the second is cruising in third doing the same. Seems to stay right at 12.5 so is that good?afr


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## Baaad65 (Aug 29, 2019)

Third gear to wot.afr 2


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## coyote595 (Dec 4, 2019)

That is great at WOT. Too rich at cruise.


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## Baaad65 (Aug 29, 2019)

coyote595 said:


> That is great at WOT. Too rich at cruise.


So do I change the PV, it's a 7.5? I make about 15 inches of vacuum.


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## Baaad65 (Aug 29, 2019)

coyote595 said:


> That is great at WOT. Too rich at cruise.


Cruising it was still around 12.5, it's not in the video...at idle it's right around 13.5.


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## Baaad65 (Aug 29, 2019)

So had the car out for a longer highway drive and cruising at 60mph my afr was reading 13.5 most of the time so I think it’s dialed in pretty well, I'll keep an eye on the plugs too.


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