# 1973 Distributor



## glide (May 31, 2015)

Should a 73 400 have an HEI distributor? When did they switch?

Thanks!
John


----------



## ALKYGTO (Mar 29, 2010)

I believe 1973 was a one year only "unified" ignition that is hard to get parts for.


----------



## glide (May 31, 2015)

ALKYGTO said:


> I believe 1973 was a one year only "unified" ignition that is hard to get parts for.


First, thanks for the quick reply. 

I know it's a one year only body style but can you describe 'unified" ignition. 

Little backstory. Ordered plug wires from Rockauto and received HEI wires but my ride has a coil. Since it's nom thought maybe older 400 or did they change mid year like they did the motor color??


----------



## oldskool (Apr 26, 2015)

Here's a quote from a Googled site, about the HEI dist. 

"... introduced by General Motors around May 1974 on most GM engines. It was used on all engines in 1975 through the mid-1980s. There were many design variations over the years and provisions for computer controls were added for some applications starting in the late 70's. A predecessor system was optional on Pontiacs as "code 704 UPC K65 unitized ignition system" for the 1972-73 model year..."

So, if this is correct, many late '74 models may have had the HEI. It says the unitized was "optional".

My wife owned a '73 TA 455 4-speed. It had the old points style dist. 

Here's some details and pics of the "unitized ignition".

http://www.hotrod.com/how-to/engine/0304pon-pontiac-ignition-option/


----------



## Pinion head (Jan 3, 2015)

Most '73 V8 Pontiacs came with points type distributors. A few, usually SJ GrandPrixs and a few other higher line Pontiacs were optioned with the K65 option Unitized distributor. 

The change in the engine codes in the Spring of '73 was due to a Federally required change in emission controls, even the intake manifold had a different casting number for late '73 models. When the first production '73 455 SD's were finally built, in late May of '73, it's interesting that they only came with points type distributor, not a Unitized, like so many '72 455 HO cars. For '74 SD's, they also were only avail with points distributor, not an HEI which were beginning to introduced, late in 74 model.


----------



## glide (May 31, 2015)

Great read! I have the late 73 production with the L78/400ci 4-barrel so it was available but no K65 Unitized distributor option listed on build sheet. That answered my question and I learned something. Wonder why Rockauto sent HEI wires. They're calling it a catalog error. Ha! Nothing wrong with the others except they're not oem.

Thanks!


----------



## silversport (Mar 23, 2007)

interesting read as well...back when, my parents had both a '73 Buick Limited and '74 Buick LeSabre both with 455 ci engines...the '74 had the then new HEI while the '73 still had points...

Bill


----------



## geeteeohguy (Feb 2, 2008)

IME, 1973 would be a points ignition. 1974 was technically the first year for HEI, but the HEI used that year was a unique, one-year system with a weird cap and molded wires. In 1975, the HEI with the big distributor cap with the coil mounted on top of it came out, and that's the one that everybody is familiar with. Chrysler was ahead of the game, with electronic ignition beginning in '71.


----------



## ALKYGTO (Mar 29, 2010)

*Taken From HOT ROD MAGAZINE-*


The early '70s were an unsettled time for automobile manufacturers. New concepts were (and still are) continually developed in an attempt to keep one manufacturer ahead of the other. Since tailpipe emissions and fuel economy were at the top of manufacturer's agenda at that time, anything that might improve either area was given serious consideration and ultimately pushed into production in one form or another. Additionally, emphasis on less ignition maintenance and great spark output was quickly becoming a hot selling point. Seeing the advantages of offering such an option, Pontiac developed the Unitized distributor as an alternative to the traditional breaker point distributors. Designated with UPC K65, the $77 option was quite popular and much ahead of its time. However, by mid-1974 it was replaced by the High Energy Ignition and quickly forgotten by many after its short life span. As the forerunner to many future ignition systems, the Unitized distributor still remains a mystery to many Pontiac hobbyists.

Pontiac's Unitized Ignition system was the first self-contained breakerless distributor widely offered by Pontiac. With an overall appearance somewhat similar to a typical points-type distributor, the coil is located atop the cap as opposed to the externally mounted coil commonly associated with points-type systems. Functional operation was greatly changed as internal breaker points were replaced with a magnetic pick-up assembly consisting of a permanent magnet, pick-up coil, and shaft-mounted reluctor wheel. When the teeth of the reluctor wheel align with those of the pick-up coil, crossing voltage then signals coil firing properly timing each ignition cycle. Otherwise based on the amount of distributor cam degrees the points remain closed for coil saturation, dwell is regulated by an electronic control module mounted on the side of the distributor housing. Current is then transferred from the rotor though the cap to the plug wires. Anyone familiar with the operational characteristics of an HEI distributor will find the Unitized functions in a nearly identical fashion.


*Introduced late in the '71 model year*, the K65 Unitized distributor first received mentioned in Pontiac Technical Service Bulletin 71-I-60, dated April 21, 1971. The bulletin introduced the new distributor speaking technically of its components and their function along with its limited availability as an option on L75/455ci 4-barrel equipped Grand Ville, Grand Prix, and Grand Safari models. The new distributor, which carried PN 1112072, had an advance curve identical to the points-type it replaced when optioned. The new distributor received a specific engine code and YA replaced YC (points) anytime Unitized was optioned for the remainder of the '71 model year. Being a late-year addition, no sales information or any other service information than the said bulletin was printed for 1971.

The next model year saw much the same for the Unitized without mention in the '72 Pontiac Dealer Sales Album. Though briefly mentioned without fan-fare in the '72 Pontiac Accessories catalog, the option boasted improved spark plug life and poor weather starting along with increased spark voltage making it an easy sell to many customers. It was available for '72s on a limited basis, relegated as an option on cars equipped with the L75/455ci 4-barrel and the Firebird Trans Am. However, anytime the LS5 455 H.O. was optioned on any LeMans model or the Firebird Formula, *the K65 Unitized distributor and WU3 ram-air were required options*. For 1973 and 1974, availability increased with popularity and reliability. Now available on any L78/400ci 4-barrel and L75/455ci 4-barrel car, Unitized was also included in the SJ package available on the Grand Prix.

Not only was the distributor mentioned more frequently in sales information showing pictures and providing more elaborate details on its advantages, it was also referenced to in many magazine road tests further increasing public awareness. The option did not last much longer and as the *HEI was phased into full production in May 1974*, the Unitized was phased out, never to be heard from again



As dealer sales forces were selling the new distributors, dealer service departments dealt with repairing them. Over its production run, various service bulletins were issued keeping service technicians abreast of the current goings-on. As a field test with any early distributor failure, service departments were instructed to remove the distributor as a complete unit and return to Pontiac for diagnostic inspection. As time progressed and repair procedures were established, the return policy was cancelled and service departments were allowed to handle distributor repair and component replacement.

Though not necessarily prone to failure, many times complete distributor failure was due to premature coil or module failure. A major flaw in the Unitized construction was coil location. Having the cap mounted, epoxy-coated coil centrally located produced insufficient heat dissipation allowing excessive heat to build within the coil. As heat increased and resistance built, coil output was reduced placing increased demands upon the module to produce the required spark voltage. Over time, these demands were more than the module could tolerate causing them to literally burn out leaving motorists stranded without any warning signs. Additionally, with enough heat over enough time, insulation on the windings within the coil would melt allowing them to contact causing an electrical short inside the coil or more commonly, weak coil output.

Not having just one major design flaw, another problematic area unique to Unitized distributor servicing was the spark plug wire set. All 8 plug wires originated from a single centrally located loom, which plugged into the top of the cap beneath the coil. Replacing 1 or several spark plug wires due to damage or improper operation required replacement of the entire wire harness containing all 8 wires. Since it was not a part widely used by all General Motors divisions, Unitized plug wire sets were costly to replace and sometimes difficult to locate. Wire sets were only produced by AC Delco and once supplies were exhausted, they were gone. No aftermarket manufacturers offered a stock replacement loom leaving owners without many options. Not helping with the heat situation, the wire loom literally surrounds the cap-mounted coil serving as additional insulation to retain coil heat, again leading to potential failure.

Not all being negative, the Unitized distributor was the future design of ignition systems. Being available at the time Pontiac production reached its highest volume, the Unitized distributor was more common than many realize. Once these distributors were no longer serviced under factory warranty, replacement parts became increasingly scarce before being discontinued all together. Any parts that were available demanded a premium forcing many owners convert to a points-type or HEI distributor where parts were much less expensive.

Without much usefulness to owners in their nonfunctional state, many were literally tossed into dumpsters without a second thought. Over 30 years later, they are most commonly seen on eBay and even then very rarely. We can only speculate how many Unitized distributors are left in their original applications. Of those that are, we can further speculate how many are fully functional. When viewing eBay the next time or crossing upon one at a swap meet, take a moment to think back on how unique these distributors are. Even though they are antiquated by today's standards, at one point they were the cutting edge of ignition systems.


Pictures of Unitized Ignition at the link below


Pontiac Ignition Option - Tech Articles - High Performance Pontiac Magazine


----------



## glide (May 31, 2015)

geeteeohguy said:


> IME, 1973 would be a points ignition.


You think it's dual points? Everything else on this car is HO.

Just curious to know if it was offered, as I'll find out sooner or later.

Thanks!


----------

