All Small Six Winter Project: Better breathing with a large log

[awasson]

I have often thought two 32/36 mounted like you describe would work really well. It could very well overcome much of the limitation of the log design. And you would get to enjoy the experience of flooring it and feeling the secondary's kick in! A flat top log head will fit a 2100 with machining and adapter mounted and the 32/36 is likely smaller base dimensions. The air cleaner would require some planning.

I was just looking at the log on my C9 head. The area where I would like to mount the carburetors is 2-1/8” (outside dimensions) at it’s most narrow point. I could get aluminum stock that I could machine for the 2V bores and mounting studs. Then I’d bolt and epoxy them to the log.

 

[DON]

My modified intake ( 2 barrel) has steel for the base and is brazed.
Myself, I think I would rather bolt it up instead of epoxy. I just don’t know if I would trust epoxy long term. I was checking into repairing a motorcycle gas tank with epoxy and there are people that have had problems and I don’t recall the directions saying it was impervious to gas. Just resistant. Two different things in my mind

 

[wme013]

Why stop at just 2 carbs?
Offenhauser 5970 or Offenhauser 5205
Although the SU's are way cool too.

 

[awasson]

My modified intake ( 2 barrel) has steel for the base and is brazed.
Myself, I think I would rather bolt it up instead of epoxy. I just don’t know if I would trust epoxy long term. I was checking into repairing a motorcycle gas tank with epoxy and there are people that have had problems and I don’t recall the directions saying it was impervious to gas. Just resistant. Two different things in my mind

I was just looking at the photos of yours. The braised steel plate looks like a good way to go. I would hope the brass would resist cracking from heat expansion too. That while whole head looks really decent.

 

[awasson]

Why stop at just 2 carbs?
Offenhauser 5970 or Offenhauser 5205
Although the SU's are way cool too.

What carbs are on that Offy intake? Are those Carter YF’s, some kind of Holley or something similar? That might be a better route after all. I’m not committed yet. I just want to make sure that whatever direction I choose will flow the best given the nature of the log intake.

 

[wme013]

Not familiar with either Holley # 1921-S or #2227-1A the Offy is listed to use in this app.
I think the 1921 is the 2 ends and the 222-1A is the center carb…
:
Not seen on Holley site or on fleebay either.
1904 too expensive…
can U use 3 of the same carbs?
How bout 3 sm YFs?

https://www.youtube.com/@VivaLaCruise
He has a multi post installation instruction

 

[DON]

I was just looking at the photos of yours. The braised steel plate looks like a good way to go. I would hope the brass would resist cracking from heat expansion too. That while head looks really decent.

I am not worried about cracking from heat. Fresh air/fuel flowing thru, water flowing thru block that’s what? 189-190 degrees. I can’t see the intake log getting over 200. Not sure of the metallic properties, but I would think brass would be more flexible than case iron. But more problems probably arise from different metals being attached to each other

 

[awasson]

I am not worried about cracking from heat. Fresh air/fuel flowing thru, water flowing thru block that’s what? 189-190 degrees. I can’t see the intake log getting over 200. Not sure of the metallic properties, but I would think brass would be more flexible than case iron. But more problems probably arise from different metals being attached to each other

Yep, that’s what I meant but didn’t explain it very well. Brass is flexible and should be safe from cracking. Epoxy would certainly crack before a braised piece.

 

[Frank]

With headers the intake will be quite cool relatively. 36* temp drop below ambient is the air/fuel entering the intake at the carb base.

 

[awasson]

Well… I am really leaning towards the Offy tri-power. I think it might solve a lot of issues I’m trying to work around on the log.

I want to prevent 1 and 6 from fuel starvation and I want to flow more air and fuel. I really like the Weber so I’d like to keep it in the mix. Maybe build a custom tri-power with the Weber 38/38 and then single 38mm carbs at each end? Building synchronous linkage shouldn’t be a big deal. It’s really a matter of building the mounting plates and brazing them in place and boring the log.

Any thoughts on that or suggestions? I don’t want to make a Rube Goldberg contraption if there’s a proven way that’s better.

EDIT: Maybe instead of the Weber 38/38 and two singles, I switch to Carter YF 150CFM singles? That would give me 450CFM and more manageable install and configuration. The floats would be forward so less issues with fuel moving around the bowls. Holley? Bigger Carters?

 

[Otto]

Just a thought, but what about the progressive 32/36 Weber at the ends? Seems it could be very smooth easing into the outer carbs with endless tuneability. And if the end carbs were too much, the secondaries could be disabled. Plus it would be quite a sight to see three in a row.

Spitballin' here.

 

[DON]

Food for thought:
The ford tripower idles on all three Holley 2300’s , and the outer two were progressive. They started opening around 1/3 throttle. Mechanical linkage. The outter two were also 50-75cfm smaller

 

[vssman]

The OFFY Tri-power runs 1 barrels. I happen to run Weber ICH/ICT combo and have plenty of fuel for my built 200. This place does everything Offenhauser: https://www.exeterautosupply.com/

You might as well get an AEM Wide band O2 sensor to make your life easier with tuning.

 

[DON]

What Offy intake for multiple carbs are you thinking about for a small 6?

 

[DON]

For what you are thinking of doing in kinda in uncharted waters for a small six. The best thing would be get something to monitor each cylinder individually. An o2 meter in the exhaust is not going to tell you what the outer cylinders are doing compared to the middle cylinders. The exhaust is going to mix cylinders

 

[awasson]

What Offy intake for multiple carbs are you thinking about for a small 6?

I was thinking of the Offenhauser 5970. I think it's the one that works with a large log. They have another that has more aluminum over the log but it's definitely for the small log.

If I were to go off into more interesting waters like @vssman has, I'll have to fab up my own brackets and my own linkage. I'll have to weigh the gains vs. effort before doing that.

I'm really encouraged by the change in behaviour adding the fuel pressure and adjusting for 3 lbs of fuel made. I assumed it was a little low, I just didn't realize it was super low. I went for a pretty spirited drive and it really performed well. The heat shield helped a lot too. The new head will bump the compression ratio from 8.58:1 to hopefully 9.49:1 so that along with more air and fuel should really help out.

* I might even be able to pull 9.89:1 but I don't know or think I can shave it that much and I don't want to risk having too much compression with that big iron head.