IH 405004R91 carb vs zenit carb h on later cubs

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inairam
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IH 405004R91 carb vs zenit carb h on later cubs

Postby inairam » Wed Oct 12, 2016 9:44 am

There are a number of discussions about IH vs zenith carbs. I am interested if anyone has thoughts on the last IH carb the IH 405004R91 used on later cubs and I think early 154s vs zenith in terms of reliability and power on a late 70s cub. Thank you.
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Re: IH 405004R91 carb vs zenit carb h on later cubs

Postby Eugene » Wed Oct 12, 2016 10:07 am

Owing Cubs with both the IH and Zenith carburetors, there is no difference is power or reliability.
I have an excuse. CRS.

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Re: IH 405004R91 carb vs zenit carb h on later cubs

Postby Matt Kirsch » Wed Oct 12, 2016 1:29 pm

X2. Both carbs work equally well and there isn't enough difference in power output from one to the next to measure.

Most tuning you can do on a large car engine only nets you small gains there. Tuning that would net you 5HP on a big V8 engine won't get you 5HP more out of a Cub. It might net you .1HP on a Cub engine. A lot of work and expense to get you about as much extra power as putting a harness on your cat and hitching it to the tractor...

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Re: IH 405004R91 carb vs zenit carb h on later cubs

Postby LRiddle » Wed Oct 12, 2016 2:45 pm

Not to hijack the post, but it the zenith a direct bolt on replacement of the IH? Same throttle and carb linkages?
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inairam
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Re: IH 405004R91 carb vs zenit carb h on later cubs

Postby inairam » Wed Oct 12, 2016 3:42 pm

LRiddle wrote:Not to hijack the post, but it the zenith a direct bolt on replacement of the IH? Same throttle and carb linkages?


The zenith does bolt on the older manifolds, but you may need an extra gasket for to the throttle plate to clear. The zenith has a different air inlet tube and the linkage is somewhat different but not difficult.
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Re: IH 405004R91 carb vs zenit carb h on later cubs

Postby LRiddle » Wed Oct 12, 2016 3:45 pm

inairam wrote:
LRiddle wrote:Not to hijack the post, but it the zenith a direct bolt on replacement of the IH? Same throttle and carb linkages?


The zenith does bolt on the older manifolds, but you may need an extra gasket for to the throttle plate to clear. The zenith has a different air inlet tube and the linkage is somewhat different but not difficult.


I've actually replaced the old manifold with a new one since the old one was pitted and the exhaust was stripped. So it should bolt up. What about the linkages and the air inlet tube? Do those stich over too?
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Re: IH 405004R91 carb vs zenit carb h on later cubs

Postby Cubfriend » Sun Dec 31, 2017 10:02 am

I know the air inlet is larger on the Zenith. The factory made a long hose to go between the air cleaner and the carburetor to accommodate the larger size inlet.
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Re: IH 405004R91 carb vs zenit carb h on later cubs

Postby Dale Finch » Sun Dec 31, 2017 6:27 pm

These are the 2 different inlet set ups for the 2 carbs (from TM Tractors):
http://www.tmtractor.com/new/ae/265fp.htm

http://www.tmtractor.com/new/ae/4537fp.htm

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Re: IH 405004R91 carb vs zenit carb h on later cubs

Postby Glen » Sun Dec 31, 2017 8:27 pm

Hi,
The gas line is different also, the fuel inlet is in a different place on the Zenith.

Below are pics of a new Zenith at TM Tractor, notice the gas inlet points up.

http://www.tmtractor.com/new/fl/2376fp.htm
Last edited by Glen on Mon Jan 01, 2018 8:54 pm, edited 1 time in total.

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Re: IH 405004R91 carb vs zenit carb h on later cubs

Postby Dale Finch » Mon Jan 01, 2018 12:31 am

I have cubs with both the IH and the Zenith. The choke rod works on the Zenith just fine...my 2 '55 cubs with Zenith carbs use a rod, not a cable. (Not sure when they switched to a cable) You use the same choke lever that is on the IH. And the gov to carb rods work as well. You just need to go through the length adjustment.

It's a fairly easy swap. As mentioned, though, you do need to buy or bend a new fuel line, unless you are using a "rubber" one, which should work fine.

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Re: IH 405004R91 carb vs zenit carb h on later cubs

Postby Glen » Mon Jan 01, 2018 1:18 am

Hi,
IH changed to the choke cable when they started using the Zenith carburetor, in mid 1975, at the first Long Stripe Cub.
The parts manual page says tractor serial number 248125.
Last edited by Glen on Mon Jan 01, 2018 8:56 pm, edited 1 time in total.

inairam
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Tractors Owned: 1948 with international 1000 loader
1949 with kub klipper belly mower.
1957 with c-2 mower & c-54 grader blade
1965 lo-boy with c-3 mower
1975 with homemade mower
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Re: IH 405004R91 carb vs zenit carb h on later cubs

Postby inairam » Mon Jan 01, 2018 9:30 am

I was a little surprised to see my year old post resurface today. Thank you for your responses.

My question was not how to switch to a zenith curb but the engine performance with the later 405004R91 IH carb vs the zenith.

The zenith cards were used on the later higher horsepower Cubs but for a short period so were the larger ih 405004R91 and the 63349C91. There is a great deal of discussion and opinions about the IH vs the zenith.

My original question was has anyone specifically compared the engine performance of the large bore IH carb vs the Zenith?
When you only have 9 horsepower you need to know the names of all of the ponies!

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Re: IH 405004R91 carb vs zenit carb h on later cubs

Postby Stanton » Mon Jan 01, 2018 11:00 am

Eugene wrote:Owing Cubs with both the IH and Zenith carburetors, there is no difference is power or reliability.


Matt Kirsch wrote:X2. Both carbs work equally well and there isn't enough difference in power output from one to the next to measure.
Most tuning you can do on a large car engine only nets you small gains there. Tuning that would net you 5HP on a big V8 engine won't get you 5HP more out of a Cub. It might net you .1HP on a Cub engine. A lot of work and expense to get you about as much extra power as putting a harness on your cat and hitching it to the tractor...


They didn't mention whether they had experience with the specific 405004R91 IH carb, but didn't Eugene and Matt basically answer your question?
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inairam
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Re: IH 405004R91 carb vs zenit carb h on later cubs

Postby inairam » Mon Jan 01, 2018 11:42 am

Stanton - that is my question - specific experience with the 405004R91 IH carb vs the zenith.

In most of the posts I have seen about the IH vs the zenith they do not mention the parts numbers of the IH carbs. The early IH carbs are not a fair comparison to the zenith.

I have a new to me 74 with a not rebuilt zenith and a 75 with a newer rebuilt 405004R91 IH carb so it is not apples to apples. I also have a new to me 1953 with a low hour 15-year-old engine rebuild with a zenith and IH carbs on a 48 & 49 and 65 Loboy again not apples to apples.

I prefer the look and size of the IH carbs and I am more familiar with them and have more run time hours with them. It may be my imagination but the IH carbs appear to be easier to start & not sure I see a performance difference but I have less experience hours with the zeniths.

Just checking to see if I am missing something.
When you only have 9 horsepower you need to know the names of all of the ponies!

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Re: IH 405004R91 carb vs zenit carb h on later cubs

Postby Eugene » Mon Jan 01, 2018 12:02 pm

Just my opinion. Which carburetor part number is better than another is immaterial. Does the tractor do what you want it to do is the question.

As I stated earlier in this topic, I own tractors with the IH and Zenith carbs. Both tractors start equally well. The 154 with Zenith carb is a bit slower starting. The 154 takes about 2 revolutions of the engine to start. The standard Cub cranks over much faster than the 154, so, it appears to start faster/earlier.
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