Zenith Carb vs 3/4 Updraft

[FarmallCubby1949]

Hello again everyone. I was curious what people on here think about replacing the standard 3/4 Updraft for a Zenith. My cub is a 1949, so it came with the 3/4 Updraft which is worn out for all practical purposes. I bought a new Zenith model 68 that is susposed to work on the cub. I understand in later years IH went to this carb for later model cubs. I also purchased a brand new manifold that has the same size flange as the Zenith. The reason I'm asking this is my old carb was leaking gas out of the bottom, around the float bowl when I would crank the engine. So I removed the old carb and manifold and installed the new carb and manifold. I go to crank the engine and the new carb sends a stream of gas out the bottom. There appears to be some kind of port there with a stone like material plug in that port. Is it possible that there is a devise in the float bowl that keeps the float from moving around during shipment thus protecting the float from damage? Also the choke on the 3/4 Updraft can be set manually. The choke on the Zenith is spring loaded. The reason I went with the Zenith was for more HP. My dad and I discussed this and came to the conclusion that it would run fine with a new 3/4 Updraft. The old Updraft bolts up to the new manifold that I bought for the Zenith. I appreciate the feed back on this.

[Don McCombs]

The reason you are getting fuel flowing out of the carburetors is due to the fact that the fuel/air delivery system is a updraft system. Vacuum in the manifold draws the fuel/air mixture up into the manifold. If the engine does not start (for reasons other than carburetion), the fuel flows back down and out the carburetor drain. It has nothing to do with the brand or function of the carburetor. There are several possible causes for your issue. Stuck valves, low compression, leaking manifold/carb gaskets, etc. I'd suggest a compression check and a thorough tuneup, including valve adjustment. Cleaning the old IH carb can't hurt either. Check for a warped top and leaking gaskets. All these things can be repaired/replaced.

Additionally, converting to a Zenith carburetor, alone, won't give you any horsepower increase.

[gusbratz]

lol, sounds like the old saying "90% of carburetor problems are electrical in nature"

[Boss Hog]

There were lot of good running 327 and 350 engines that lost power after putting a 650 double pumper Holley on them too, you need to change the pistons and governor to get a noticeable power difference in a cub. The zenith carb alone may even hurt performance.

[Gary Orr]

I had both carbs on one of my cubs and didn't see much difference.

[FarmallCubby1949]

Thanks too everyone who responded to my post. After further consideration I'm going to stay with the 3/4 Updraft. Seeing the responses here, and talking it over with my dad made me realize that it would be more trouble than it's worth to convert it over to the Zenith I'm taking the Zenith back. I do want to keep the originality of my Daisy. Is it worth rebuilding the original carb, or by a brand new version of it. I do know where there are new versions of the 3/4 Updraft, if anyone is interested in new versions of the 3/4. The new one is the same as the old. The only difference is that there is know IH symbol on the new one.

[Barnyard]

Is it worth rebuilding the original carb, or by a brand new version of it.

There are several guys on the forum who will rebuild your Carb for you. It really isn't all that hard sometimes you don't need an entire kit to refurbish it. It may be rebuildable (and cheaper) with only a few parts.

[FarmallCubby1949]

Thank you Barnyard. The weather forcast for this weekend is going to warm up. I'm going to do a valve adjustment. I'm figuring it should help. For me being a newbe here this is a wonderful site with very friendly people who really like to help. I would really like to get to meet you guys personally. I'm willing to help people out too in any way I can.

[Barnyard]

I would really like to get to meet you guys personally.

Check out these web sites, especially the CubFest calendar as it is updated through out the year. CubFests are the best way to meet other members from the forum. I hope we can see you at an event or two.

http://www.cubtug.com/index.html

http://www.barnyardbash.com

viewtopic.php?f=8&t=81945

[staninlowerAL]

"For me being a newbe here this is a wonderful site with very friendly people who really like to help. I would really like to get to meet you guys personally. I'm willing to help people out too in any way I can."

Consider going to a "Cubfest" if you can. You will learn a lot, meet some really nice (and knowledgable) people and in general, have a great time. (Oh yeah, the food is great too!!) EDIT: Barnyard is quicker that I am!

[Clip]

Grab a rebuild kit from Steiner and dig in. Carbs aren't hard at all to rebuild, just go slow. Pick up a gallon of carb cleaner or Chemdip and let the metal pieces sit overnight, then dry with compressed air and reassemble. Or you can go the soda blasting route like I'm doing currently. This is my first carb that I've blasted and I am really liking the results. No more waiting for a few days and brushing and brushing to get all the gunk out.

[Barnyard]

If you rebuild it yourself be sure you pull the two halves straight apart. If you don't you risk breaking the idle tube which passes through both pieces. You might also want to disassemble it prior to buying the kit. Many times you only need a few parts and a kit can be overkill as you won't use everything. Several of the members who rebuild these carbs on a regular basis have quit buying kits altogether.

[FarmallCubby1949]

Thanks again to everyone who responded to my post. I appreciate the info on this. I'm adjusting the valves tomarrow, and at that point, I'm going to see if she fires up. I put new points, wires, plugs rotor, cap, manifold. I made sure the gap on the new plugs is .025. Should the gap on the points in the J4 Magneto be .013 gap? From what I can read in the IH manual and owners manual both say .013 gap setting for J4 Magneto. Other people who have worked on these are telling me .020 gap. What do you guys have to say about that? Also thanks for informing me about the Cub Fests and the Barnyard Bash. Depending on time off I get from work, I will see what I can do. I would love to go to any of the events. I'm looking at the Barnyard Bash as one I could make it too. I will keep track of the events on here and see what ones I can make it to.

[Bigdog]

Magneto - .013" gap Distributor ignition - .020" gap.

[FarmallCubby1949]

Thanks Bigdog. That's what I figured. Both manuals I have say .013 for J4 Magneto.