First Drive With Wide Band

[Gear grabber]

I picked up a barely used AEM 3150. The install was pretty easy,just plug and play.
What this little gem is monitoring. 427,Quick fuel,950 black diamond on a FTI ported super vic.
Timing is 16/29,no vac. advance.

Normal temps for 2/23, 44, today was a record breaking 71.
I decided beforehand i was not going to touch anything,just observe.

Idle was 12.5,at a long light it would creep up to 12.7.
Cruise +/- a few tenths 23-2500 high 12's13, 2100/12.8, 1900/12.7, 17/1800 lower 12's.
Even at rock bottom 1600 6th,12.4 (248/[email protected]) it's happier at 1700+
WOT tests from 3500 in 3rd showed 12.2 to start and leaning out to high 12's,13.1at 6500.
A little concerned about that 13.1
For the most part,low to high 12's. The highest i saw was14.1,about half throttle.

 

[a91what]

Hmm your running fat at idle but depending on the cam it may need it to smooth out. I usually try for 13.5-14.5 but give the car what it wants.

Cruise at all RPM ranges should be between 13.9- 15.4 this is tricky with a big cam if you get a surge at cruise fatten it up a tad.

Wot- look for 12-13 most carb engines make best power at 12.5

I'm no carb expert but I do know my tuning.... carb vs efi.... carb tends to run a tad fat.

 

[Gear grabber]

Considering the out of the ordinary high temps +25* it did not feel fat at idle. With the new toy to look at,i did not pay much attention to the vac. gauge at idle. Will work with mixture screws and swap the .073 I.A.B.'s to .075 to see if it will pull 13 ish,idle and cruise.

 

[CarMichael Angelo]

The carb needs a main jet change. The idle circuit is based on mixture screws,..cruise is metered via the main jets. No need to change the boosters or the idle air bleeds until you can get the thing to idle in a respectable 13.5:1 range.
At 12: anything, nobody could stand anywhere close to it w/o smelling like exhaust.

 

[Gear grabber]

Played around with the car today. The first go round i set the idle in the 13.6-13.8 range,but it went pretty lean in in the area just before the primary jets come in to play. I saw close to 16 around 2400,by 2500 the main started flowing and it dropped back to 13.5.

Went a little richer at idle 13.3-13.5 at that point most cruise rpm's were low to mid 14's with a peak of 15.1 just before the mains came on. Now the pump cam,squirter needs a little work,tried a few things but not right yet.

Tried richer 12.9-13.1 idle,no help.

 

[CarMichael Angelo]

Played around with the car today. The first go round i set the idle in the 13.6-13.8 range,but it went pretty lean in in the area just before the primary jets come in to play. I saw close to 16 around 2400,by 2500 the main started flowing and it dropped back to 13.5.

Went a little richer at idle 13.3-13.5 at that point most cruise rpm's were low to mid 14's with a peak of 15.1 just before the mains came on. Now the pump cam,squirter needs a little work,tried a few things but not right yet.

Tried richer 12.9-13.1 idle,no help.

How are you knowing when "the mains come on"? You shouldn't be able to feel any transition in the carburetor, unless you're just talking about observing the gauge. The main jets are flowing at anything above idle. I can guarantee that,...if you look into the carburetor at 2000 RPM,..you're gonna see gas coming out of the discharge boosters, and those boosters are sucking gas out of the bowl through the primary circuit.
Your last set of figures sound perfect to me, where's the beef?
The accel circuit is dead easy to tune. typically only needs a squirter change. You should be able to watch how much fuel is being "shot" into the primaries as a result of tapping the throttle.
When I used to have a Holley,..I'd tune that so that every time I tapped the throttle back with my thumb on the throttle arm while under the hood there was no flat spot in the rev. The first part doesn't require that you buy, or change out anything:
Take the lash out of the accelerator pump actuator by loosening the screw that is wrapped by a spring. This will slightly preload the accel pump.
You should be able to snap the throttle at unloaded idle w/o a "BO..WAH" on the engine, and this part has Zero to do with AFR. I'd see what size the primary side squirter was, and buy a couple of different ones larger and maybe smaller depending on how the engine responds now.
The pump cam has everything to do w/ eliminating the off idle bog when the engine is loaded, as it can be set to change where, and when the accel pump is activated during initial acceleration,. I rarely messed w/ that,..I was more concerned w/ getting a snappy throttle response, and most of the time, a squirter change always fixed that.

 

[Gear grabber]

Yes,observing the gauge. You can see when the main circuit is the primary influence,when the gauge goes from 15.5 to 13.5

I have all the cams and several squirters. Being a heavy stick car with a tall 2.66 1st,it needs some fuel to get it moving. I was using a very aggressive blue cam 33 squirter and it worked well with the formerly richer afr's. Once leaned back,it became unhappy tipping in. After looking at the charts,this morning i put in a less aggressive orange cam,much better but not perfect. Still spiking lean on tip in,swapped the 33 for a 36 and initial indications are good. Cam,squirter,timing make all the difference in making a hot rod civil.

 

[a91what]

+1 things to remember about the WB.... the target AFR is not always what the engine wants.
If the throttle is nice and crisp with a richer afr by all means go with it..

 

[Gear grabber]

I made some interesting observations today. As noted above,the temps fri/sat,were well above normal,averaging 71* 60r/h 29.6 (1271 d/a) Today we are back to the norms,43* 36r/h 30.07 (-1340)
With a 2600 ft. swing,i was sure the afr's would go leaner. They did not...and on average,were richer.

My only guess is the atmosphere (pressure) change,was pulling more fuel through the circuits ?
Maybe this dumb carburetor,is pretty smart after all ?

While i did not have any trouble with the cam/nozzle moving away from a stop,or matting it at 3k,i did notice a lean spike,tipping in from cruise. Now that the air is back,will try the blue cam again,33/35 nozzle.

 

[a91what]

This is where datalogging is a life saver. Sometimes a lean spike on tip in can be raw fuel in the exhaust.

 

[Gear grabber]

This is where datalogging is a life saver. Sometimes a lean spike on tip in can be raw fuel in the exhaust.

It does have the ability to data log...but i know nothing about that.

I used the wallace jet calculator to figure out how much more fuel was needed with the big DA change,(+2) and because it was 13.1 i went +3 to see if it would pull it down in to the 12's wot. Put the ''winter'' springs back in the diz.(bring the timing in slower,poor mans traction control) Set idle,low 13's,added all fuel in the primary (78 to 81) hoping to pull the cruise values to low14's or richer. Only a 30 minute ride,but did seem to accomplish that,mostly 13.5-14,did see 14.5 a few times. WOT was stout,not wanting to push my luck with more 3rd gear pulls,tried 2nd,rolled it open at 4200 by 5700ish still 13. then the tires let go. Pending DA will start adding fuel in the secondary.

 

[Gear grabber]

So after playing with this thing for a month...and temps getting more normal. I have pretty much settled in at low 13's at idle. 13.5 creates drivability issues. Cruise is for the most part in the 14's,some low 15's

I fixed the wot lean spike (17 briefly) with a cam change on the secondary. Now when I hammer the throttle the afr stays steady,then drops back to low 12's and works it's way back up to high 12's.

 

[a91what]

Sounds like you have the carb pretty well dialed in. I don't think you will idle any leaner without an milder cam, overlap and fuel crossover in the ports at low velocity won't allow it.
Plus you have a great diagnostic tool now.