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Sat May 16, 2015 3:17 pm

Putting a pair of 40IDFs on my bus' 2180 cc engine .
CB Los Panchitos
Engle w110 w/Scat 1.25 rockers
1 1/2" exhaust
019 w pertronix
8.8:1 cr
etc

Carbs now have:
28 mm venturis
200 Air correction
F11 Emulsion tube
115 Main jet
50 Idle

According to ACN they should be pretty close - Any thoughts or suggestion ?

Sat May 16, 2015 3:24 pm

Id start 52/130/200.

Sat May 16, 2015 3:57 pm

Sat May 16, 2015 4:12 pm

Because I have tuned many many many 40 idfs, and even a 1776 needs more than a 115. Shove a wideband on there and you will see. 40's and a 2180 will be deep into the 16-17 AFR range at 3500 with 115's. Do this ...keep your 115's and just buy 130's. Try both...you'll see which ones you'll need. Might even be 135's. My guess your idles will be 52-55 too.

Sat May 16, 2015 4:22 pm

I'd suggest 32mm venturies 50/135/190

Sat May 16, 2015 4:33 pm

Hmmm... Maybe 44IDFs might be a better fit for this motor .

Sat May 16, 2015 4:46 pm

I'd go 32mm venturis, and no bigger than 130 main.

Sat May 16, 2015 5:01 pm

32mm vents for sure.
130 main 200 air
or, if lean hole surfaces
135 main 220 air

Sun May 17, 2015 2:49 pm

Murzi - What do you think of using 32mm venturis ? It's not a race car it's a big heavy bus , I thought 28s might give it more bottom end torque for these steep hills in socal .

Sun May 17, 2015 3:49 pm

If you do not believe in using larger venturis..... Why do you have CNC ported heads and high ratio rockers? Makes no sense at all.

Sun May 17, 2015 4:12 pm

It's not that I don't believe in them I just don't want to spend the money right now ,just lost my job and the transaxle is setting me back over a grand . I guess I need to step up and drop another $100 to get her back on the road.
Damn. What do you think of running 44mm IDFs w/36mm vents , to big?

Sun May 17, 2015 4:28 pm

[email protected] wrote: I'd go 32mm venturis, and no bigger than 130 main.

I agree with the larger vent deal. Maybe not the end jetting...but I am at the opposite end of the spectrum of elevation from John and Modok...sea level... I will always have to jet richer and they leaner.

Two things going on here. You sized the cam too small for a large engine. Your engine will want to run/cruise at 3500, but be done by 5000, producing a narrow power band. I would have done a FK42 or w120 with 1.25's. Or even a FK8/1.25.

I would have also teamed that larger cam with 44's. You already have the carbs, do the 32 vents, but verify the jetting with a wideband.

Sun May 17, 2015 4:29 pm

It will run with 28s, just not optimal. I feel 44s are too big for this engine, but you can also put 32mm venturis in them instead of the stock 36mm.

Sun May 17, 2015 6:55 pm

I consider the venturi to a be a jet. they cost around 12$ each. Or you make them yourself. Or use a lathe to enlarge them. 22degree leading angle and 6-7 diverging angle.
I would setup the carbs to match the engine before bolting them on, seems easier to me.

You can certainly make it run fine spending under 10$ if that's what you need to do. Put the carbs on, and if it is too lean drill the mains up one size. So at worst you need to buy one or two small metric drill bits. i don't really know if it will want 120 or 125 main, as never tried that small a vent with that large an engine. I did run 30mm on a 2165 once and ended up with 130 mains, but the carbs were clearly too small for the app, and putting on larger carbs with 34mm vents was better at all rpms.

44 IDFs would work ok, with 32 or 34 venturis