Technical AFR gauge with ZOOMIES

Morning, I'm wondering if anyone has ever found a way to use a AFR gauge with Zoomie headers (NO I'm not drilling holes in ceramic headers), I just installed tripower BIG 97 strombergs on a mild 355" SBC, starts and runs strong, but running real rich at idle, pic is 10-15 minutes idleing, Thanks for any direction.

 

I have an older Innovate afr meter. It has a clamp on device that holds the lambda sensor at the end of the exhaust pipe and sticks inside the pipe about 5 or so inches to make sure it is getting exhaust gases and not air from the outside. I’ll see if I can find it later today and get a picture for you. Last time I saw it, it wad on an upper shelf that I might not be able to get to currently.

 

There are several different styles of clamp on attachments to hold an AFR sensor.

 

Innovate has a clamp-on device, and their wideband setups are top quality. I have been using Innovate MTX-L's for years. Clamp it onto #6 cylinder (leanest cylinder on SBC) for most accurate reading. You can also tune via vacuum gauge.

https://www.innovatemotorsports.com...blJ9-xdPQW00hMAIzO273MVPjYyjbeVl_V_RseGy9vTaS

 

I've seen many clamp ons, but I'd have to change 8 times for every cylinder? I guess that may be the only way-even tho every cylinder would prob be a little different because of manifold flow.

 

If you want to be able to read a bank at a time, and if you don't mind some fab work, it wouldn't be that complicated to make a slip on log style manifold with the sensor threaded in the end.

 

If it’s just for tuning any reason you couldn’t swap exhaust, tune it and put the zoomies back on? Sbc isn’t exactly the hens teeth of exhaust options?

 

That's not a bad idea....

 

Of course the change in exhaust restriction is going to change the air fuel ratio while you have the manifold installed vs the zoomies.

 

I agree the clamp-on sensor that sticks in the end a few inches would get you pretty close. You could swap cylinders once you get it more dialed in, just to confirm the values are approx equal; especially side to side.

Have you set the idle mixture screws using vacuum? Being so rich you can get it a lot closer to ideal with vacuum, just adjust the mixture screws for maximum vacuum. Are the three carbs all idle circuit? Progressive or straight linkage? Factory 3x2 setups typically had idle only on center carb with progressive linkage to open the end carbs at more heavy throttle.

 

Yes, all 3 have idle circuits, they are the Big97's with progressive linkage

 

I have one in a set of zoomies but put the port in when we built the headers. I “hid” it on the backside so you can’t see it about halfway up the tube. Seems to work ok, but this all happened before I had the headers coated.

 

As promised here’s a picture of the Innovate adapter.

The sensor goes into the boss at the end.

It then goes into the exhaust pipe and returns the gases into the exhaust stream. This one has been used on things like lawnmower engines, light duty diesels, wood stoves, and various sundry car engines. It’s a good way to get a lambda sensor on an engine for intermittent use.

 

I have a couple of those LM-1 setups and there's one thing I can promise you - that engine is seeing air reversion all the way into the combustion chamber, so using an AFR gauge is going to always be radically skewed and unreliable. Even if you added a 3/8 metal line into the end of the pitot tube (tailpipe clamp) and extended it all the way up to the exhaust gasket, the high temps and close proximity to the head will result in the sensor potentially overheating and failing prematurely.
Rich at idle is more often a timing/ignition issue. A tri-carb setup like that will run best set up for 20 degrees+ BTDC at idle. If it was my car and had a radical cam in it, I'd likely be running 24 BTDC. Find peak vacuum at idle and you'll find your ideal timing setting. Then tailor the distributor to give you the 34-37 total your engine wants, depending on compression.

 

Thank's I'm gonna start as you say...

 

Since it's rich at idle, have you checked the carbs while running to make sure that you don't have fuel entering for sources other than idle jet? I have played with a lot of 6X2 and 3X2 carb setups and found most with mechanical linkage (no vacuum actuated) work best with straight (not progressing) linkage.

 

this carb set-up works with progressive linkage (designed that way) 1 primary-2 secondaries, These are the BIG 97-250cfm ea.

 

Even #s of carbs are more Ideal then
Odd #s of carbs , On V8 , 8 carbs are more the way to go ,
1 per runner & cylinder ,
Next 1 carb per 2 cylinders.
I was fortunately able to talk with engineer that developed 3 carb set up
For Pontiac, They had to develop specific parts & spec to make 3 carbs work as intended , i Including many hours of development testing,
& $$$$, same with other manufacturers that use three Carb set up,
Yes over years many have used & we have seen 3 carbs ,
Mechanical much better then Progressive linkage On Non OEM set ups .
Many say fun good No issues,
But in Reality stick on Dyno , monitoring all eight cylinders , it will be seen the AFR are all over the place , between each cylinder & all threw , Rpms ,from Idle , Cruise to wide open !
""Wide open"" more stable & Balanced
But still not Equal unless you tune for wide open ,,

Ons SBC , #6 cylinder
is most time Leanest of the 8 ,

 

Thank You, makes sense..

 

Not trying to be Negative,
Just letting you know ,Its difficult even using a dyno to balance AFR across all
8 cylinders, from I , C , Wot
Its a lot easier to run 3 carbs on stockish
Engine,
O2 afr on Zoomies difficult without drilling for O2 or Egts

 

Yeah, if you want things to work well and be easy to tune you don't want any cylinder to draw air through multiple carbs at the same time, you won't know which one to adjust when some cylinders are tuned right and others are wrong.
Then again, most carb setups on hotrods seem to be more meant for looks than function, and that's fine as long as you are happy with what you've got.

 

Random... What type of fuel pump, An whats do You have it regulated to ?

 

2psi

 

Well, what you don't realize is!!!!!!!!!! I'm running this in a 2,000LB car and trust me a light car with flaws will scare the shit out of you....

 

Really, do you have anything else Negative to say today, I have what I want and BTW this T-Bucket does have GO.

 

low pressure 4-7 electric pump and Mallory reg, set at 2psi, checked with 3 gauges

 

The type of linkage does not effect idle.
What is the rpm at idle?
What is the vacuum at idle?
Is there power valves involved?

 

I would just as soon not have you trolling my post that I was looking for positive help.....

 

Idle is 700
vac is 13"
PV shouldn't be involved at idle?

 

So jet it down , lower the floats , turn the timing up and add another return spring on the throttle cable for good measure ! oh and turn the temp up also unless it is already at 200 or so.