IHC Vehicle Distributor Identification

[Michael Mayben]

This thread will be a repository of information regarding any and all forms of ignition distributors used in ihc vehicle applications over the years. We'll discuss both breaker point-triggered inductive units, along with the electronic trigger units which were phased in during the early/mid 1970's.

 

[Michael Mayben]

edit 7/25/08:

I now realize I made some mistakes when I originally posted this response, I have now corrected the text as appropriate.

One of the big "urban myths" which go around regarding ihc-produced vehicles is that "all sv distributors interchange". While it's true that the distributor lower body/drive design does allow any IH-app distributor to be installed in any sv engine, the rest of that statement is bogus.

I'm currently compiling a definitive analysis of all distributors which were used in sv engines (any vehicle platform application), both breaker point-trigger and "electronic" trigger designs. It's not enough today to "ass-ume" that any sv engine has any particular distributor/ignition systems. The po virus can strike at any time, and the popularity and availability of boneyard crap makes distributor swap a common occurrence. But for working out problems regarding the sv ignition system, we gotta know "which" system and "which" distributor is being discussed.

There were/are at least n=thirteen distinct distributor systems used in any sv application dating back to sop of the 266, and ending with the 304/345/392 series sometime around 1985 (medium duty truck applications).

1) delco cast iron distributor (four distinct variations).

A) breaker point trigger
b) breaker point trigger w/governor
c) electronic trigger (magnetic pulse)
d) electronic trigger (magnetic pulse w/governor)
note: the "magnetic pulse" units are not the same items as the more prevalent delco remy "hei" electronic distributor intro'd around 1973 but never used oem for ihc.

2) Holley/IH cast aluminum distributor (five distinct variations)

a) breaker point trigger ("straight point" version)
b) breaker point trigger ("curved point" version)
c) electronic trigger ("gold" box)
d) electronic trigger ("black" box)
e) electronic trigger ("silver" box)

3) Holley/IH cast iron distributor (four distinct variations)

a) breaker point trigger ("straight point" version w/governor)
b) breaker point trigger ("straight point" version w/governor and tach drive)
c) breaker point trigger ("curved point" version w/governor)
d) breaker point trigger ("curved point" version w/governor and tach drive)

4) prestolite cast aluminum distributor (two distinct variations)

a) breaker point trigger
b) electronic trigger (integrated control module)

it is true that several of these units were not used oem in light duty vehicle apps, but as many medium duty vehicles are engine donors for any particular platform, there is no telling what distributor might turn up on any engine! And...there are a few of these items which might be a popular basis for performance upgrade if they can be positively identified!

Over the next several weeks, we'll try and identify each version pictorially and by part number. And to further muddy the waters, most of the distributors in service today are oem part number...those are units which were supplied only to the engine assembly line! If a distributor was replaced with a complete "service part" item obtained only from an authorized ihc dealer, then a different part number was used to denote "service part". In reality, both of the distributors would have been "spec'd" the same, but carry different part numbers either because of the service parts "emissions" rules (internal corporate policy) or because of packaging differences (assembly line stuff is bulk-packed, service parts are individually boxed, etc.).

Individual part number distributors are then referenced in the appropriate "truck service manual", which is the only place that full distributor specs May be found for comparative purposes. My initial analysis of distributors by part number, show more than thirty-six distinct part numbers/specs!!! And I know that is not all of 'em!

We're kicking this off with an analysis of only sv motor distributors since that's the most prevalent area of interest around here. We'll treat the various I-4 and six cylinder units used in light duty vehicles separately, though the I-4 stuff is virtually identical to the sv with the exception of the 4 cylinder triggering methodology and spec's.

 

[Michael Mayben]

Continuing on with distributor identification, here we have examples of two different "governor" distributors used primarily on both medium duty applications and stationary engine apps.

On the left is a cast iron Holley "1510 series" distributor which incorporates the governor system along with a mechanical tachometer drive. This unit was converted some time back to a pertronix trigger, though it is not the same p-tron as used in the more common Holley cast aluminum distributors which are common on IH light line vehicle apps.

The governor unit is in actuality a small vacuum pump built into the distributor assembly, IH refers to that item as a "spinner valve"! This one carries an IH p/n of 427967 c91 and is an oem part for a 392 in a school bus chassis.

On the right in the pic is a virtually identical distributor but without a mechanical tach drive. The part number tag on this item is missing, but I believe the IH p/n to be 427965 c91. The p-tron installed in that one is a somewhat older design, most likely from the time when pertronix was known as "perlux".

Both of these distributors are of the "curved point" design originally, and use the same breaker point set, condenser, rotor, and cap as the Holley aluminum distributor in their original form.

In order for these governor distributors to work properly, they need to be connected to an appropriate governor carburetor which was supplied by Holley to ihc, either a 2300 2v mixer, or a 4150 4v carb.

However, either of these distributors will serve in a non-governed application just fine. The units are far more robust in design and manufacturing than the aluminum-body Holley, especially in the shaft support/bushing interface. Contrary to urban myth though, they are not "ball bearing" distributors.

Both of these items need an extensive service procedure before they could be put into service. Both mechanical advance units are very gummy, along with the vacuum advance/breaker plate interface. The vacuum advance cans on both units are identical to the similar parts used in light line applications, providing 5*>7* of movement when activated.

 

[Michael Mayben]

Here is a pair of virtually identical Holley/IH aluminum distributors, also referred to in IH-speak as the model "1510", both originally equipped with breaker points.

The one on the left is a typical "a-1 cardone" remanufactured unit. These are usually high quality remans and many times include a new vacuum advance can. However, they use a media blasting process to clean the cores which usually obliterates the identification/part numbers on the boss under the cap retainer spring. That's the case here, though sometimes with some careful work with a magnifying glass and dykem, the p/n can be brought out.

The unit on the right is one of my own reconditioned Holley units, did that one yesterday. It will be converted to either a crane xr3000 optical trigger system or a pertronix trigger, depending upon who's motor it ends up sparkin'. I don't run points in any distributor anymore except the one on the left. It's my "dead dawg recovery" distributor and gets stuck in any dead dawg IH crapball I May need to "make run" in an emergency in order to load onna trailer or move around a lot.

These distributors were oem with a "female" terminal-type cap. The cap and the shape of the vacuum advance can is completely different as compared to a prestolite unit, which makes for the primary identification notes. And a breaker point Holley will have only one wire from the coil negative terminal to the distributor/breaker point terminal.

A pertronix-converted breaker point Holley will have two wires exiting the body which lead to the coil.

 

[Michael Mayben]

Continuing on here with distributor I.d., here's a delco cast iron body distributor. These units were used in both I-4 and sv applications, only difference is the breaker point cam lobe configuration (either four lobe or eight lobe). In some cases, the vacuum advance can and overall advance curve varied so for positive id ya need the number off that aluminum band wrapped around the lower distributor body. That number can then be crossed over in the specifications charts in the appropriate service manual for details regarding the setup.

I personally think that these distributors were the best units used, extremely durable as compared to a Holley. The top bushing is lubricated periodically from the oil cup as shown.

The breaker point gap/dwell is adjusted with the appropriate hex key through the sliding window in the cap.

 

[Michael Mayben]

Another shot of the delco unit for an sv application, this one ahs the earlier style point and condenser set that were separate items and could be replaced individually.

The 2nd gen design of the delco unit used a "uniset" point/condenser combo which eliminated the separate electrical components, and combined 'em into a single part that was much easier/quicker to service. The uniset assembly can easily backfit into the earlier distributor with no difference in dwell adjustment procedure.

There is no difference between the unisets used on I-4 apps as compared to the sv, they are the same part. And...an sv distributor cap May be used on an I-4 distributor, but it's best to blank off the unused plug wire terminals using some sort of rubber plug.

Because the mechanical advance assembly is located under the rotor, it's very accessible for diddlin' with changes in the advance curve.

This unit is easily adapted to an electronic trigger by using either a variation of the pertronix unit, or even better, using a crane xri conversion unit. The advantage to the crane unit is that is is a "lobe sensor" technology and does not require a separate rotating magnet system attached to the breaker point cam or rotor as does the pertronix.

 

[Michael Mayben]

This shot is a prestolite breaker point distributor. Aluminum body but the breaker system and shape of the body is completely different as compared to a Holley distributor.

Notice the square shape to the lower main body, and the large "hex" nut on the vacuum advance can, those are dead giveaways to this being a prestolite unit.

A prestolite distributor (either breaker point or electronic) used a cap with male terminals. Some folks mistakenly attempt to install a Holley cap onna prestolite or vice versa. It will not work properly! The prestolite cap is too loose to locate and index correctly on the Holley distributor.

The Holley cap is a force fit on a prestolite and will also not be indexed properly, and could easily crack when force is applied to make it fit.

 

[Michael Mayben]

Here's the breaker plate assembly in the prestolite unit. The point and condenser assembly is a totally different design as compared to the Holley "curved point" unit. It is similar to the Holley "straight point" distributor on that it incorporates an insulated connecting point on the plate for the electrical connections.

Like the Holley, the mechanical advance mechanism is located underneath the breaker plate.

This unit May also be converted to an electronic trigger by using the appropriate pertronix module.

 

[Michael Mayben]

While not an oem distributor, this shot shows a very popular replacement distributor for all sv and I-4 applications. This the mallory 25 series "dual point" unit, first introduced for IH apps nearly 40 years ago and still in production today.

This unit is a mechanical advance version only, no vacuum advance provision. The mechanical advance is also completely adjustable by simply removing the cap and doing the deal!

Very high quality piece, it's also available with vacuum advance. Two other variations make this main body state-of-the-art today. One is the "unilite" version which uses an optical trigger system, the other is a magnetic trigger unit (mbi) that can also trigger an msd or mallory cd box, and if used with a msd efi computer, can be controlled from the box also.

Any early mallory dual point distributor can be converted to either a unilite system or a mag trigger system.

 

[Michael Mayben]

Here's as shot of the guts of the mallory 25, the internal component quality is very apparent!

Since the dual point assemblies take up all the interior space of this very compact unit, the condenser is mounted externally on the body.

The only drawback to this distributor series is the fact that they are sold without a drive gear! A used gear must be swapped on and the end play of the unit set once the gear is chosen and trial fit. The end play is compensated as on any other distributor, by selective fit shims.

 

[Michael Mayben]

Next up we have a Holley "gold box" electronic distributor system (IH model 1530 designation).

The gold box label can be a misnomer...depending upon which IH platform these units were installed in, the electronic module could also be either silver or black in color.

The distributor body, shaft, and mechanical advance is essentially the same items as used in the Holley breaker point distributors (cast aluminum body). However, a "reluctor" is present in the electronic distributor which takes the place of the breaker cam component in the points unit.

There were many different part number distributors used throughout all IH applications, the differences are in the mechanical advance curve, and in the vacuum advance canister calibration.

This design is referred to as a "hall effect" trigger and that trigger must be used in conjunction with the properly matched electronic module, the hall effect sensor in the Holley unit will not trigger an aftermarket ignition box such as a mallory 6 series, msd 6 series, etc.

Regarding the distributor in the pic, the vacuum can is dead...a common fault regarding Holley distributors as found on IH stuff in general. New cans are not available any longer, however, a few companies do "rebuild" non-func vacuum cans routinely.

The electronic module is currently available as a new replacement as well as the trigger/sensor.

This is an edit to correct the air gap spec previously posted:

if the trigger is ever removed from the body for either cleaning or replacement, then the "reluctor air gap" must be set using a non-magnetic thickness gauge, that spec is 0.008" +/- 0.002".

 

[jeff campbell]

next up we have a Holley "gold box" electronic distributor system (IH model 1530 designation).

The gold box label can be a misnomer...depending upon which IH platform these units were installed in, the electronic module could also be either silver or black in color.

The distributor body, shaft, and mechanical advance is essentially the same items as used in the Holley breaker point distributors (cast aluminum body). However, a "reluctor" is present in the electronic distributor which takes the place of the breaker cam component in the points unit.

There were many different part number distributors used throughout all IH applications, the differences are in the mechanical advance curve, and in the vacuum advance canister calibration.

This design is referred to as a "hall effect" trigger and that trigger must be used in conjunction with the properly matched electronic module, the hall effect sensor in the Holley unit will not trigger an aftermarket ignition box such as a mallory 6 series, msd 6 series, etc.

Regarding the distributor in the pic, the vacuum can is dead...a common fault regarding Holley distributors as found on IH stuff in general. New cans are not available any longer, however, a few companies do "rebuild" non-func vacuum cans routinely.

The electronic module is currently available as a new replacement as well as the trigger/sensor.

If the trigger is ever removed from the body for either cleaning or replacement, then the "reluctor air gap" must be set using a non-magnetic thickness gauge, that spec is 0.014" +/- 0.002".

Brass only! --Jeff

 

[MarkO]

So the $64k question, in your opinion, which distributor works the best?

Does a Scout's driving characteristics differ enough to warrant different distributors from those found in 3/4-ton and larger trucks?

Do you advocate the electronic over the breaker point types?

Is something like the mallory dual points set up worth the $$ in comparison over stock?

 

[Michael Mayben]

The distributor that works best is the one that is the freshest with the least amount of end play vs. Spec.

The only thing I use a points distributor for with points...is a fresh unit I use to swap in when doing vehicle recoveries. That gets wired to a coil I carry and a "hot wire" switch setup...soon to be a completely self-contained ignition system that is not dependent upon the vehicle wiring or battery.

Any breaker point distributor I use or build for folks receives either a p-tron, or a crane xri (soon to be a pertronix iii) if a delco. I'm also playing with some mag trigger ideas that May be a drop-in onna Holley distributor. If crane keeps the bizz alive or sells off the assets to someone else, then the optical trigger (universal install) ranks in there also...that is not the same as the xri which is similar to a p-tron but is a "lobe sensor" system that requires no adapted reluctor or flying magnet.

The mallory dual point unit I have will receive a mallory mag trigger conversion once I have some more budget, all my "free" parts have been tapped out for the time being. No distributor will beat a mallory for adjustability,and if equipped with a mag trigger (not dual points) I'd consider it the "ultimate" right now if used in conjunction with a cd box and proper coil.

If I were going to use a Holley gold box distributor, I'd pop a dedicated p-tron conversion into it and do away with the gold box itself.

I certainly like the prestolite electronic unit for it's quality and internal electronics design.

But overall...the cast iron delco units provide the most bang for the buck as the advance curves are easily tunable for any engine app, ya can stick in a p-tron or xri trigger, ya can find vacuum cans at 7-11 for those along with several variations of aftermarket "adjustable" vacuum cans, and they are bulletproof in the longterm durability department.

The next distributor going into my dd 392 system is a cast iron Holley with a tach drive, that will raise the cap about 3" up out of the hole and make it much nicer to access. Already has a p-tron in it.

For setting/checking reluctor or flying magnet air gap, any type of non-magnetic thickness gauge can be used...some are a non-mag stainless alloy, some are titanium, some are acrylic (plastic), some are brass, etc.

 

[GS340]

Do you offer a rebuilt Holley without a core or another distributor that will work with a loadstar 345 engine? One with pertronix maybe?

I'm thinking about the hei setup you have but I don't think it will clear the coolant neck.

 

[Michael Mayben]

In addition to a new dui distributor (which I personally think is major overkill for your application), we can fix you up with a fresh distributor of nearly any version.

A pertronix converted Holley points unit, or a rebuild and pertronix upgrade on your current distributor, or a "built" delco, or ????

Call Jeff and discuss your big picture, then he'll get with me if need be and we'll set up a distributor for your application. This is not a "one size fits all" kinda deal, the advance curve needs to be proper for your engine setup now, that is why we need to know which distributor you currently have and it's part number from the body. Then we can determine what the setup on it is and advise accordingly.

But we must know exactly (preferably with pics) what distributor/carb setup you currently use...if you currently have a governor setup, then those are completely different animals from the light duty/non-governor stuff...even though the engine mechanicals are basically common. For the governor motors you must think of this stuff as a systems approach.

 

[GS340]

Here are a few pictures of my distributor. Let me know what you can offer. I would like to buy something outright vs shipping this one for rebuild or core.

I'll give Jeff a call tomorrow...

Thanks
Robert

 

[GS340]

I don't think the vac advance is working since I can suck air all day long through it. This is my first car/truck with points and the truck is older then I am!

 

[Michael Mayben]

The distributor you have is a plain old Holley "1510 series" points-trigger unit. However, the IH p/n I don't find in my techinfo...so I can't I.d. The advance curve right now. That can be done onna engine when running if you have a accurate "shop-type" tachometer and a dialback timing light.

But if the vacuum advance is nonfunc that is a dealbreaker. New advance cans are not available, we do have a few used ones and they May also be remanufactured by one of our suppliers but are pricey. You should not be able to "suck air" through it unless the diaphragm is perforated (which means it's ng). Look on the bottom of the actuator arm and you will see a number, normally either a "5" or a "7". That is the amount of advance the actuator can provide when fully operated. That number is read in "degrees". When vacuum is applied to the nipple, the arm should not move until a nominal 5"hg of vacuum is applied...then it should just start to move and be fully pulled at 10>12"hg and stay in that position as long as vacuum is maintained. When vacuum is cut, then the internal spring returns the diaphragm/arm to it's "atmospheric" position. That test must be repeatable over and over to determine if the vacuum can is usable.

So either the rig never had a governor system, or someone has swapped in a different distributor...what about the carburetor...did you identify it as to whether it's a governor unit also?

Your existing distributor can be easily remanned and have a pertronix or a pertronix II conversion trigger installed. Call Jeff at ihon for options in dealing with this.

 

[GS340]

the distributor you have is a plain old Holley "1510 series" points-trigger unit. However, the IH p/n I don't find in my techinfo...so I can't I.d. The advance curve right now. That can be done onna engine when running if you have a accurate "shop-type" tachometer and a dialback timing light.

But if the vacuum advance is nonfunc that is a dealbreaker. New advance cans are not available, we do have a few used ones and they May also be remanufactured by one of our suppliers but are pricey. You should not be able to "suck air" through it unless the diaphragm is perforated (which means it's ng). Look on the bottom of the actuator arm and you will see a number, normally either a "5" or a "7". That is the amount of advance the actuator can provide when fully operated. That number is read in "degrees". When vacuum is applied to the nipple, the arm should not move until a nominal 5"hg of vacuum is applied...then it should just start to move and be fully pulled at 10>12"hg and stay in that position as long as vacuum is maintained. When vacuum is cut, then the internal spring returns the diaphragm/arm to it's "atmospheric" position. That test must be repeatable over and over to determine if the vacuum can is usable.

So either the rig never had a governor system, or someone has swapped in a different distributor...what about the carburetor...did you identify it as to whether it's a governor unit also?

Your existing distributor can be easily remanned and have a pertronix or a pertronix II conversion trigger installed. Call Jeff at ihon for options in dealing with this.

The arm has a 5 on it.

I'm not sure if the truck had/has a governor system install or what a governor looks like either carb or dis.

I installed a rebuilt carb from Holley. Same model that came off the truck... Here is a picture of the numbers off the carb. I thought replacing the distributor would be as easy as the carb but that doesn't appear to be the case.

I'll so more research and see what I can come up with. Thanks for your time and help.

Robert