Holley 1904 carb question


IHC in the early to mid-fifties.

Yard Art
Yard Art

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Post Thu Feb 04, 2021 1:24 pm

Holley 1904 carb question

I recently picked up a Holley 1904 that was on ebay. The stamped number on the carb is 124 474 R92. According to my MT-103 manual, 124 474 R91 was used on the BD240 engine without auto trans (I assuming the R92 is a replacement for the R91). I also noted from the "Thecarburatorshop.com" truck list that this carb was also used on the SD240. MY idea is to rebuild and keep this carb as a spare for my S120 with a BD240 engine. I also have a S100 with a BD220 engine.

Could the 124 474 R92 carb also be used as a spare for the BD220 engine? Would all I have to do is change out the main jet? The MT-103 shows a different main jets, a 73 375 R1 for the BD240 and a 73 376 R1 for the BD220. Where would a person get a 73 376 R1 main jet? is there a table to cross the IH number over to a Holley number?

Are there any other changes required to use the 124 474 R92 carb on a BD220?

Thanks for any advice!

Golden Jubilee
Golden Jubilee

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Location: Lyman, IA

Post Thu Feb 04, 2021 1:41 pm

Re: Holley 1904 carb question

I doubt you'd need to make any changes. Both engines require the same mixture and the difference inmax air flow isn't that great. Other things that sometimes effect how a carb is set up, like cam overlap and such are the same on both engines.
Jetting on the Holley 1 bbl is easy to get too and change, but I wouldn't change anything unless you have some noticeable problems.
Numbers after the "R" in IHC part numbers are minor changes and can be interchanged when the same basic part number is the same.

Golden Jubilee
Golden Jubilee

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Post Thu Feb 04, 2021 1:44 pm

Re: Holley 1904 carb question

Just for info only, I once took a carb off a 318 CID and stuck it on 400 CID and made no changes, it worked very well. The 20 CID differance wouldn't concern me at all.
I would have no problem placing that carb on a 282, the biggest IHC six that used that basic model.

Yard Art
Yard Art

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Joined: Thu Jul 18, 2013 10:45 am

Post Thu Feb 04, 2021 1:50 pm

Re: Holley 1904 carb question

Thanks CB89, good info! You may recall, the S100 with the BD220, is the truck in which you provide me with the Holley governor unit!

Since I first posted this question, I been thinking, are the intake bolt spacing for the carb base the same on a BD220 and a BD240? Both trucks are in storage, but the first chance I get, I'll go measure them both.

Golden Jubilee
Golden Jubilee

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Location: Lyman, IA

Post Thu Feb 04, 2021 2:16 pm

Re: Holley 1904 carb question

I have no idea on bolt spacing, they were made with different spacing and I think with different throttle bore and venturi diameter. What engine uses what, I have no idea.
BTW I have a 525 CID engine with a woppingly big 1 bbl!
A carb's job is to maintaine a correct mixture for all the air that passes thru it, it doesn't care what is "sucking" the air in (Yes, it is atmosphic pressure that pushes, not suck, but for simplicity...)

Golden Jubilee
Golden Jubilee

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Post Thu Feb 04, 2021 5:17 pm

Re: Holley 1904 carb question

Don,
Do you have the aftermarket Daytona? Don't member.
User avatar

Golden Jubilee
Golden Jubilee

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Post Thu Feb 04, 2021 6:27 pm

Re: Holley 1904 carb question

From the MT-97, it appears that early production SD240's used 73 375 R1 jets, which are #66. Late production used 73 376 R1 jets, which are #64. Early production SD220's used the 73 376 R1 (#64) jet, while late production used 54 745 R1, which is #63. At least that gives you some Holley jet numbers to correspond with IH numbers. A Holley #64 main jet from a 4 barrel is the same as IH 73 376 R1.

Yard Art
Yard Art

Posts: 91

Joined: Thu Jul 18, 2013 10:45 am

Post Thu Feb 04, 2021 7:05 pm

Re: Holley 1904 carb question

Kevin, I put that Daytona carburetor on my R-110 that I eventually sold to the fellow up in Hinckley, MN. Bought the Daytona cause I never could get the original Carter carb to run right. The new owner kept messing with the Daytona carb and asked me for the old Carter carb, which I think he installed before he sold it to the next guy.

Paul, thanks for the Holley jet numbers! Where on earth were you able to fin that info??

Golden Jubilee
Golden Jubilee

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Joined: Thu Nov 29, 2012 9:28 pm

Location: Lyman, IA

Post Thu Feb 04, 2021 7:15 pm

Re: Holley 1904 carb question

As a matter of running, I doubt anyone would notice the difference in how the engine runs with any of those jets. Where it would show is with a exhaust analyzer, may show in fuel economy and how much carbon ends up on the plugs.
Holley jets are the same for the 2300 and 4 bbls and the 190x 1 bbl. so a 63 jet for one will fit the others.
Years ago I played around with jetting on a 1920 1bbl, and found you had to make large changes to the jetting before you noticed a change in the drivability This is partly due to economizer or "power valve". When the engine runs lean, the power produced is lower and the throttle is opened more which drops the vacuum, which in turn opens the economizer, which adds more fuel and richens it back up.
For best economy, you would like to set it up on a dyno, where you can make a single change and see what it does under load.
Wet fuel height in the bowl will also effect mixture in a similar way that a change in jetting will.
My guess is that a 1901 with the leanest jet (#63) placed on the biggest engine (282) would still run very well.
More often than not, poor performance is ign or even valve timing issues but are blamed on carbs. I've seen worn timing chains (not an issue with IHC) make it almost impossible to get good running, but when it is replaced, the engine runs great with no carb changes.
I am very leary of jetting changes until all other factors are eliminated as a source of the problem.
Jetting is most noticeable at WOT/ high speed, that is when there is the greatest pressure differential across the jet. That is why, the best way to select a jet, is on a dyno, where it can be run at full load with an analyzer in the exhaust stream at the same time.

Yard Art
Yard Art

Posts: 91

Joined: Thu Jul 18, 2013 10:45 am

Post Thu Feb 04, 2021 7:38 pm

Re: Holley 1904 carb question

Great info guys! If this new carb ever ends up on the BD220, I'm going to leave it as is instead of messing with changing the jetting. DonO
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