Zenith Carb ? ?

Postby **Lurker Carl** » Thu Dec 02, 2004 1:15 pm

George,

That small Olds engine, did it happen to be the alumium 215 V8? If so, do you still have the original 4GC Rochester that came off?

Carl

Postby **Jim Becker** » Thu Dec 02, 2004 2:58 pm

Lurker Carl wrote:The Cub engine has the capacity to pull 15 cu in of air per revolution, only one cylinder draws air per revolution.

It pulls 15 ci per half revolution or 30 cu per revolution. I think you need to plug a factor of 2 into the rest of your Cub calculations. Otherwise, I think your observations are spot on.

Postby **George Willer** » Thu Dec 02, 2004 3:14 pm

Lurker Carl wrote:George,

That small Olds engine, did it happen to be the alumium 215 V8? If so, do you still have the original 4GC Rochester that came off?

Carl

Carl,

All of the project was given to our local EAA chapter (#50) long ago. Yes it was the 215. The conversion was only 58# heavier than the equivalent aircraft Continental (O-200).

It wasn't really my idea... it was first done by Steve Whitman, a legend among air racers and homebuilders. He flew his V-Whit for many years before he and his wife were killed flying it due to a structural failure accident in the last couple years.

Postby **Harold R** » Thu Dec 02, 2004 3:33 pm

Carl,
Not to blow this thing up into a math lovers delight, but what's the 66% efficiency? The cfm that exits the carb versus the amount that makes it to the combustion chamber for the power stroke?

Postby **Lurker Carl** » Thu Dec 02, 2004 4:45 pm

Jim - You're absolutely right - I started with stroke, replaced it with revolution when I factored in GW's B&S experiment. It was all down hill from there. I fixed the error. Thanks!

George - Sorry to hear the old Rochester is gone, I could use the floats.

HR - The efficiency factor accounts for all the resistance air encounters between the air cleaner and exhaust tip by measuring actual volume of air the engine draws versus the calculated volume. Think of the engine as an air pump. Pumping the pistons in an engine without the head represents 100% efficiency. Efficiency drops when you start adding restrictions like the cylinder heads, valves, manifolds, air cleaners, exhaust pipes and carburetors. Friction and turbulance slows the air flow so only part of the engine's full capacity realized. I used 66% efficiency because that's a typical efficiency rating for one lung engines. With the Cub's longer and more intricate intake and exhaust systems, it's probably lower.

Efficiency decreases as engine speed increases, but that's another topic!

Postby **Harold R** » Thu Dec 02, 2004 5:12 pm

Friction and turbulance slows the air flow so only part of the engine's full capacity realized

This was the crux of my question. I was wondering if this was a varible due to being an updraft or evaporation because of a shared manifold.
Anyhow the 66% sounds pretty restrictive.

spaceghost · Postby **spaceghost** » Thu Dec 02, 2004 5:26 pm

I donâ€™t know about all this technical vapor stuff, but I put a zenith card on my 58 lo-Boy and the cub starts and runs much better and I am very happy with the card.
I did not have any problem with bolting it on.
The choke has a spring on it so now I have to hold the choke rod when I start the cub.

beaconlight · Postby **beaconlight** » Thu Dec 02, 2004 5:30 pm

I guess all that scientific data and formulas agree with the shade tree mechanic "it wouldn't be enough to pull the out house over"???
Bill

Postby **Harold R** » Thu Dec 02, 2004 6:35 pm

guess all that scientific data and formulas agree with the shade tree mechanic "it wouldn't be enough to pull the out house over"???

Well, no. But there are some really sharp people on this forum. They help us all understand.
Tomorrow, Carl delves into something that will pull your outhouse over!

Just kidding.....trying to get in the Christmas spirit!!

Postby **Bigdog** » Thu Dec 02, 2004 6:37 pm

Maybe billyandmillie can fit that into a cub!

Donny M · Postby **Donny M** » Thu Dec 02, 2004 6:48 pm

HR,

What does a blower have to do with getting in the Christmas spirit :?:

...Oh

I get it now :!:

Postby **Lurker Carl** » Thu Dec 02, 2004 6:50 pm

Oh yeah, baby! That Cub would spin around like possum on a spit as soon as you started her up.

Donny M · Postby **Donny M** » Thu Dec 02, 2004 7:06 pm

If you need valve springs for your engine try these:
http://www.cleartracksports.com

This is my friends site. He builds engines for sprint cars. 800+ hp in a 1300 pound car :!:

Oh what fun :!:

0 to 60 in 2.8 seconds, now if I could just mow that fast :lol:

Postby **Arizona Mike** » Fri Dec 03, 2004 8:03 pm

The carb. looked ok so I finally got it installed this morning.

Its started up without any problems, but its not running as smooth as the IH carb. Seems to be running too rich, but not sure yet :roll:

Mike

Postby **John *.?-!.* cub owner** » Fri Dec 03, 2004 8:30 pm

The one on my 48 tends to be a little rich until you put it under load, then it's ok.

Farmall Cub

Zenith Carb ? ?

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