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Old 04-02-2008, 08:07 AM   #1
Michael Mayben
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Default Holley 19XX Series Carb Stuff

Let's use this thread to discuss anything related to the Holley 19xx series carbs (1904, 1908, 1920, etc.) that were oem on IH products back in the day.
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Old 04-02-2008, 11:13 AM   #2
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Default Re: Holley 19XX Series Carb Stuff

For identification purposes, here's a shot of a "typical" 1904 used on IH-produced 6 cylinder and the 152 4 cylinder engines. There were many variations of this carb used throughout the automotive industry for many years.
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Old 04-02-2008, 11:36 AM   #3
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Default Re: Holley 19XX Series Carb Stuff

For identification purposes, here's a shot of a "typical" 1940 used on some IH-produced 196 4 cylinder engines along with the amc 258 used in both Scout 800 and Scout II platforms. There were many variations of this carb used throughout the automotive industry for many years.
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Old 04-04-2008, 01:26 PM   #4
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Default Re: Holley 19XX Series Carb Stuff

A Holley oem 1904 series mixer will have identification data located on the main body in one of two locations. It will have both an IH part number stamped into the body (not cast, a cast number is a p/n for that part only), and the Holley "list" number (primary identification feature). Most common location is on the flat boss at the fuel inlet fitting. This one shows the fuel inlet boss location.
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Old 04-04-2008, 01:28 PM   #5
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Default Re: Holley 19XX Series Carb Stuff

Here's the other location where the I.d. Numbers might be located on a oem 1904. This on the top of fuel bowl area on the main body, again, a stamped number, not cast.
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Old 04-04-2008, 01:31 PM   #6
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Default Re: Holley 19XX Series Carb Stuff

And here is where the I.d. Numbers will be found onna 1940. Underneath the throttle lever when it's held in the wot position.

This particular application is a 1975>1978 I-4 196.
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Old 08-30-2008, 05:05 PM   #7
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Default Re: Holley 19XX Series Carb Stuff

It seems like the vacuum port on the back of a 1904 is of the ported variety, is that correct? What's the thinking there as far as getting the vacuum advance correct? It was my understanding that using ported was more of an emissions thing, but that would be after the 80's were done I'd think.

Do some people use straight manifold vacuum for the advance and just plug the carb port?
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Old 08-30-2008, 06:41 PM   #8
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Default Re: Holley 19XX Series Carb Stuff

It is ported vacuum, with the circuit just above the throttle plate. In my '60 Ford variation of the 1904, it uses a diaphragm similar to a power valve to kick in the vacuum, they call it the spark valve.
I believe it was to improve idle performance allowing some advance but not as much without it. It became part of an emissions package later on as many things were tried; it couldn't be on the f100 as it still has the road draft tube!
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Old 08-30-2008, 08:45 PM   #9
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Default Re: Holley 19XX Series Carb Stuff

IH never used the "spark valve" on any version of the 1904.

All s80/152 used the 1904 with ported or "timed" vacuum source for the distributor. As well as the IH 6 banger stuff (not the rambler 6 bangers). With the vacuum pump for the wipers disconnected and capped (always do that for tuning purposes), at 550rpm idle, the ported vacuum point will provide1"hg>4"hg. That will not actuate the vacuum advance unit in either the delco or the Holley distributor. Those take between 5"hg and 7"hg of vacuum to initialize. So "disconnecting" the vacuum line for setting the base timing is a bogus statement in any IH service reference, total waste of time. But disconnecting the auxilary vacuum source is necessary...and the manuals never address that point!

In fact, the same holds true for all other IH motors, no matter what distributor is used.

Ported vacuum to the distributor is not an "emissions" thing. That's some kinda bullshit crap that started years ago on the bb and in many other sources. It did become standard though with the advent of second tier emissions stuff in the mid/late 60's with the incorporation of temperature control for ignition advance/retard, along with egr actuation. Many early>mid-60's IH stuff used manifold vacuum on the distributor oem. There are three members on this forum right now that are working with those systems.

The only thing that matters regarding this subject is how each rig is plumbed for either an "original, by the specs" restoration...or if tuning whatever system for max performance. If in doubt, leave it alone unless you know enough about this stuff to play with it and have the parts to do so! If the motor and all peripheral systems are stock, then leave it as it came from the factory!

I have many distributors with various vacuum advance units, each distributor part number has a different advance curve/specs! That subject is currently being covered here as I play through this stuff. Some of my experiments result in improvements in performance, most do not! Doing this kind of stuff is very time consuming as I try to quantify changes using the equipment I have which is an engine/ignition analyzer, dialback timing light, shop-quality vacuum gauge, and several shop tachs. And a gps that is very exacting in display of road speed.
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Old 08-30-2008, 11:46 PM   #10
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Default Re: Holley 19XX Series Carb Stuff

Quote:
IH never used the "spark valve" on any version of the 1904.
I never said IH did Mike. It was pointed out only as a variation and vintage of the same carb.
I was trained to plug whatever the vacuum source for timing, covers all bases. Some of us pass that on 'cause that's what the school taught, or in a course book by crouse, or a shop manual says. I got one that in the IH section, an early Scout is to be static timed. You'd go bonkers if that was ever posted here; and I know not to put it on the dub dub dub.

Quote:
let's use this thread
Maybe you ougtta change let's to I'll.
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Old 08-31-2008, 04:35 AM   #11
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Default Re: Holley 19XX Series Carb Stuff

Interesting about the vacuum from the wiper pump. I measured the vacuum at the back of the carb and it was low, but not insignificant, like maybe 10 at idle (can't remember exactly). Sounds like you are saying that the pump vacuum can somehow backfeed to this port?

Can you explain why plugging/disconnecting from the vac advance would be any better or worse from the perspective of setting the timing? Either way, the vac advance would be taken out of the equation.

Just for the purpose of general understanding, when does the ported source provide vacuum? I think I've read two different variations: one is that it's kind of the same as manifold vacuum except blocked off at idle. The other is that it only provides vacuum during changes in throttle (or something like that).

Thanks.
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Old 08-31-2008, 08:27 AM   #12
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Default Re: Holley 19XX Series Carb Stuff

Quote:
Originally Posted by greg r View Post
I never said IH did Mike. It was pointed out only as a variation and vintage of the same carb.
I was trained to plug whatever the vacuum source for timing, covers all bases. Some of us pass that on 'cause that's what the school taught, or in a course book by crouse, or a shop manual says. I got one that in the IH section, an early Scout is to be static timed. You'd go bonkers if that was ever posted here; and I know not to put it on the dub dub dub.


Maybe you ougtta change let's to I'll.
My statement was for a point of reference only so that folks won't go looking for the "spark valve" on an IH list 1904. And it's called out in typical carb kit instruction sheets. There is a boss and sometimes even a "blanked" threaded port for that item in some IH list carbs. That's why I get two/three emails a week about this same subject!

On the same subject, I get pics from folks very often showing me their 1904 with the spark valve and the glass bowl that is on their Scout 80! Only problem...that's a Ford app carb that's been swapped on and is not calibrated/jetted for a 152!

Same as a s80 1904 is not correct for a dam 6 hole Ford f100, 1953 vintage.

That's why we deal in facts on this forum, unlike the bb.
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Old 08-31-2008, 09:02 AM   #13
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Default Re: Holley 19XX Series Carb Stuff

Mastiff...a functioning vacuum wiper booster segment onna 152 adds around 3>4"hg at idle to actual manifold vacuum. My current toy has all new componentry with a fresh carb, it reads 22"hg which is impossible to obtain onna 152 motor even when new due to it's oem camshaft specs! Put a vacuum gauge on the intake manifold tap and disconnect the pump, then make a reading with the pump active. You will see the difference.

If you believe the manifold vacuum data with the pump active, you will think yore motor is tuned pretty well. But that is a false reading!

Ya wanna know "when" and "how" the ported vacuum begins to kick in as engine rpm/throttle plate angle increases on any engine/carb which includes that feature? Put your vacuum gauge on the port and check it! Every engine setup is gonna be somewhat different, that is why I always give a "range" of vacuum readings for "typical" stuff like this. Every setup is gonna be different, just as every vacuum gauge is gonna display only within +/- 2"hg unless it's a recently calibrated gauge. It's all relative, we're simply looking for needle wiggle to indicate an issue in diagnostics and a range of vacuum readings that indicates "best" operating conditions.

And actual manifold vacuum reading on any engine under any load condition/throttle plate angle varies tremendously with the operational altitude. That is why I always reference my altitude where I take my readings for comparative purposes. That is a reference point only , not "spec".

In the service industry, the "reference" point for vacuum readings is assumed to be at 70*f and sea level. Some service references will make that blanket statement up front, but today since all motors are efi, nobody hardly uses "vacuum" as a diagnostic or tuning aid.

Setting base ignition timing in the static mode is actually the best method. We've been doing that in motorcycle and marine applications for 70+ years. Ya wanna see how much worn out distributor componentry affects timing through the rpm/load range? Then static time a motor, using a timing "tester" buzzbox, and a dial indicator for locating tdc. Then run the motor and shoot with a timing light. There will be gross change in the actual firing point as indicated by the light. The difference is in the accumulated slop in the wore out distributor.

This methodology was the norm before development of a reliable "timing light" along with a way to interface the light. That was not possible onna model "a"" Ford that had "open" copper straps for spark plug cables! Same for the use of breaker points for the switching device. Once electronic triggers came into play (instead of points), then this method faded away, but all applications had calibrated reference marks for using the static method even on full electronic, capacitive discharge systems. You can also use a simple analog ohmmeter (not a dvom) for doing this if the condenser is disconnected from the breaker point terminal.

A delco distributor with 0.080" endplay in either a I-4 or sv application will have a variable timing range of as much as 6 degrees at any one steady rpm point. That is a mile! I set those up with only 0.010" endplay, just enough to allow for expansion/contraction due to engine temp. Then add in a worn out shaft and mechanical advance unit...the timing at any point is all over the place!

Why does installing a new dui or mallory distributor seem to make so much difference in performance/drivability in this old junk??? Because suddenly the timing is back to being accurate! Performance motors are built today using "blank" distributor drive gears, the timing is calibrated using dial indicators and an accurate degree grid on the balancer or flywheel. Then the drive gear is "located" and the anchor pin hole drilled for that engine/distributor combo.

Ported vacuum level increases from "base" as the throttle plate angle increases. Every carb design that incorporates this feature will vary somewhat, that is a design element for "control" of ported vacuum kick-in point. It's totally dependent upon where the signal point in the carb throat is located. Some are up high just under the choke plate/air horn assembly, some in the middle, some just above the throttle plate in only one throat on some 2v and 4v carbs.

Just an example...right now I have two Scout II/304 combos I'm assisting customer/owners in converting carbs from the oem Holley 2210 to a centerhung 2300. Those carbs have a ported vacuum tap on the passenger side of the metering block. One of the carb/engine combos at 700rpm idle provides only 1"hg with best engine tuning. The other one provides 3"hg. The difference?? Each engine is unique, they are not identical twins in every respect! And each vacuum gauge is different, they are not calibrated together! One of the rigs is located at about 600ft. According to my digital topographic map data based upon gps waypoints, the other is at a nominal 3200ft.!
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Last edited by Michael Mayben; 08-31-2008 at 09:11 AM..
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Old 08-31-2008, 11:21 AM   #14
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Default Re: Holley 19XX Series Carb Stuff

I never thought of auxillary vacuum components until that phone jaw'in some year or so ago. I do now, and have it set up in way that connecting the gauge is taking the wipers/pump completely out. I have much more consistency ever since.
You're motorcycle static method is slightly Different then what I use. I get the crank into position within 1/2 a turn of the timing Mark(for that particular engine's spec). Then I continue to rotate without stopping until it's dead on the Mark. If I go past the Mark for even a fraction, I back up 1/2 a turn and start over. That way at least takes the slop factor for the cam gear, or timing chain, and distributor drive out of the equation. I use a test light while rotat'in the distributor for correct position indication. As you say, it works pretty damn good. Your machine/diagnostic lane at the bee this year sure showed distributor slop in my 800. Only 3 or 4 degrees, but never seen with just a timing light.
The vintage contribution was a way of say'in the same thing, ported vacuum was not originally intended for emission.

Mastiff the only reason, including train'in, I disconnect vacuum lines for distributor timing, unless it's static timed, is as Mike has pointed out the different sources of vacuum and different advance can specs. It's a universal approach.

Last edited by Greg R; 09-01-2008 at 12:43 AM..
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Old 09-06-2008, 05:08 PM   #15
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Default Re: Holley 19XX Series Carb Stuff

Is there a way to tighten up the throttle lever at all? I have slop in it such that it wiggles outside of the plane of rotation, if you know what I mean. I wouldn't think this would matter, but the throttle cable is kind of far outboard such that it's twisting the whole throttle arm and causing a slight bind. Not sure if you can follow what I mean...

I'm fighting to get a smooth throttle response right now. I thought I had it, but the throttle return spring was not working quite well enough such that I wasn't going all the way down to the real idle speed all the time. It would kind of stop pulling with about 150 rpm to go. Once I started tweaking that, my sticky throttle came back.

Besides anything I can do with the throttle play, I was thinking of attaching a little arm to the throttle lever itself (going forward when it's at the idle position) and attaching the throttle cable to that. I think the extra leverage would help smooth things up. You'll notice that at idle, the attachment point is quite close to the axis of rotation, so there is very little leverage.
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