AFR tuning w/lakester headers

I’ve searched for diy/homemade lakester headers and I’m finding nothing. Lots of "lakes (side) pipes or not" and solutions for custom eng swaps but not lakester header design/function/tuning. I’m welding up a set of “lakester” style headers for the 351m in ratty ’40 sedan. Making my own cause I’m that way and can’t find anything that works for exhausting it in the original frame/ch***is. Question is, regarding the tapered manifold pipe of the traditional style, is that the best choice or would a straight dia be better for tuning purposes. I understand that originals were often made from torque tubes and that is why the taper. Since I’m making my own, and function takes priority over form, I figure I should do it the way makes for most even afr’s at each cylinder. I’m using tubing from Summit and have already sliced, sectioned and welded up tapered pipes but I’ve only tacked the individual port pipes (1.75" w/3.5 clr's) to the manifolds(tapered 1.75/2.5"). Still way easy to back up and use straight pipe for the manifolds. Top performance is not the issue so much as even tuning of the afr’s cyl to cyl. These will run down to full length and functional lakes style side pipes. I use dual band Innovate DLG-1 Dual Lambda Air/Fuel Ratio Gauges on anything I build these days, but will also be reading plugs for the cyl to cyl readings. Will I notice a difference one way vs the other, or will it be close enough I won’t see the difference plug to plug? I’d just hate to use traditional looking tapers and find that one end of each bank is lean and the other is rich. 351 is totally stock, may add alum 4bbl intake, maybe. Thanks again. Slick …

 

you might find that most of the "tuning" of lakes pipes, is to make them look good

 

My suggestion would be get it drivable before getting too wrapped up with fine tuning.

 

If you are going to use modern tools for tuning (A/F reading), why not use modern tools to design the equipment you are concerned about (Computational Fluid Dynamics or CFD)?
Here's one example.
https://motordyneengineering.com/****ysis-of-exhaust-headers/

It's more math than I'm willing to try, but this is where trying to use old school stuff (Lakes header) to achieve modern tuned length EFI-like A/F Balance is going to be either a ton of cut and try or model for best result then make them.

I agree with @pprather , toss it together and see if it needs further refinement.
It's very rare to measure A/F per cylinder. Most stuff I've seen use thermocouples (temp sensors) for cylinder balance checking. I haven't researched why, I'd guess it's faster, cheaper and more accurate or some combo of those qualities.
https://www.explainthatstuff.com/ho...text=Thermocouples are widely used in science

 

If your exhaust system is closed by running it into full length side style pipes, it should function just like any other normal exhaust system. The air and fuel flowing into the engine will be affected by the shape and position of the intake runners. That is why an LS Chevy produces better results than a smallblock. The smallblock has different length and different shaped intake runners. The LS has "replicated" ports which are basically identical.....so that equalizes what each cylinder gets.
Your Ford probably is very similar to the smallblock Chevy in that its ports are not the same. If you place a throttle body or a carburetor atop an intake manifold, there will be differences in what each cylinder receives. The O2 sensor will only tell you the result of 4 cylinders mixed into one sides exhaust. It will not tell you which cylinder is rich or lean and the result may show an average thats says its all correct. The only way to tell each cylinder is to have a sensor for each cylinder. So no matter how you do it with 2 O2 sensors, there will be averaging involved..........but its still helps identify any major differences. Probably smoothing out any obvious mismatches between intake and head and behind the intake /exhaust valves (pocket port) to try to insure all cylinders get reasonably similar air flow, and using multi-point injection (one for each cylinder) will create a best condition as far as insuring each cylinder gets the same fuel flow and a reasonably similiar airflow (hopefully). Eliminating the twisting path for the fuel flow solves the equal fuel per cylinder part of the issue. (MHO)

 

@victorslik
Do not know your fabrication skills,
Or Tig , Mig , Stick, Braze .
You say not realy interested in Performance ,,,
When comes to AFR , there are Just few things to think about , Even when not looking for Max performance,
With out getting to deep On none race engine , Just typical average 400 hp.
First , Know what's the Lean's cylinder.
Gen 1 sbc / bbc is #6 So I make that
Cylinder the happiest,,
Then Intake type , design runner length plays apart of AFR per cylinder ,
From idle , cruise , WOT .
Position of the carburetor in 360 degree's
Yes , We had a Gene Futton engine made Over 30hp (36) with carb mounted backwards & like a 70 deg angle of Rotation ,,
Then on Exhaust side , Length, shapes .
ControlIng /monitoring AFR
With Spark plugs , different Heat ranges
Protected non-protected , electro designs.
Also when serious on AFR , EGT or O2
In each Exaust port
In Reality you want all cylinders to be equal in power ,
But in Your Application stick focus on
The Leanest cylinder & mix match spark plugs , & Times staggering Jets and all four corners .

 

thanks to all. I understand that 2 o2 sensors, 1 each side, is averaging each bank. That's why I would be reading plugs for each cylinder and adjusting heat ranges based on those readings. My question was really asking if I should be going with straight -vs- tapered "log". It is much easier to make a change now as opposed to after all else is done and I'm wanting to tool around some in this ratty old machine. I use the afr gages on carbed vehicles that don't get driven on a regular basis just to give me a peak at the fuel system's condition. Under $400 cheap for knowing if fuel is going bad, choke needs adjusting etc. The question had been nagging at me for a couple days once I started fab-bing these up. As is often the case, after I said it out loud(submitted the question) and had a chance to sleep on it, the answer occurred to me. DUH... Since I will be running into single "pipes" down the length of each side, the pressure(and therefore flow) ultimately will be fairly close(enough) for each cylinder, allowing "heat range" plug tuning to get it all close enough for old school carburetion/intake& exhaust ports. If the "lakesters" were running open I could see it having more of an effect, but if it was really a big lean/rich issue, I'm sure all those old time lakes racers would have done something different all those years ago. Thanks again.

 

I'm glad you've settled on a build plan. Get it drivable and enjoy it.
Then, if you're still inclined, work on the detailed tuning.

Here's another interesting tuning tool.
https://thecarbcheater.com/

 

A dynamic vacuum leak.

 

Yes it is. And it appears to dynamically tune the static carburator.