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, 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.