What is or isn't IMCO?

[Frankenstang]

I'm starting this thread to see if others can confirm, deny, or expand upon what information I've found on this subject.
The subject just came up in another post which reminded me to do this, and rather than hi-jack the PO's thread I thought this subject might deserve a heading of its own.

Okay, so what I've been able to find so far is linked below...

1)
http://www.fordification.com/tsb/viewto ... ?f=5&t=613

EDIT: Article 966, TSB #55, Group 10 Fuel System Specifications has more detailed info on the Carter YF and Autolite 1101 regarding calibrations for IMCO and Thermactor (see "Read More" button)
http://www.fordification.com/tsb/viewto ... =659&p=721

2)
http://www.mustangbarn.com/vacuum.html
http://www.mustangbarn.com/images/vacs/68%20f32.jpg
http://www.mustangbarn.com/67vacuum.html

3)
http://www.mustangsunlimited.com/itemdy ... 1=39430+01

So what I conclude from the sources and examples above is that IMCO was a ford term for 'Improved Combustion' that began in 1968 ('67 in California). There were essentially two types of ford 6cyl setups from 1968 on until the evolution of Duraspark, feedback carbs, egr, fresh air emission systems, etc.

For all 200ci models '68 and after, one system was referred to as Thermactor and the other was IMCO (but is more commonly known as 'non-Thermactor' or generically 'the setup without the emissions stuff').

From what I've been able to find, these are the only solid conclusions I've come to, and are submitted for :thumbdown: approval and critique.
1) IMCO included the later and larger C8 exhaust manifold with a 2" outlet (but without egr, smog pump, or other special exhaust based emissions equipment).
2) IMCO carburetors were not 'engineered' any differently than Thermactor or other carburetors of the time, but did have some small 'tuning' differences
3) IMCO may have also included the first increase in combustion chamber size from 51-53cc to 62cc
4) The MAIN significantly different component part of IMCO was the 'dual vacuum advance' 1968 distributor that utilized a spark retard hose plumbed to the canister as well as a distributor vacuum control valve coming off the intake manifold that controlled the vacuum 'retard' signal.


In general what I can find leads me to beleive that IMCO encapsulates the running changes made to all 200ci engines beginning in 1968 and the term has little component specific attributes other than the unique ignition system that soon gave way to Duraspark.

EDIT: So what do you think is this a fair assessment?

Interested in all opinions adding to, subtracting from, or even shooting holes in...
Thanks!

 

[bubba22349]

I throw in the first proverbial .02. California emissions began on the 1966 engines the start of the cars built only for California market mostly this was just a different carb and distributor spec. Besides these requirements for the new cars in Southern California we also had emissions programs for used cars first was a crude PCV valve kit, next NOX kit the rules changed every few years.

Compression ratios were lowered beginning (i.e. different pistons or larger chamber depending which engine family) on 1967 engines I believe this was a 50 state change.

 

[xctasy]

I'm downloading files IMCO was still the offical title of later leaded fuel Ford empire engines in early 1980.

 

[hickorystang]

So, would I be right in saying that if you do not currently have an IMCO exhaust manifold then there should not be any issues with replacing yours with an IMCO EM?

 

[CZLN6]

Howdy Robert and All:

YEs, you've got a good survey and summary, However I cannot resist some refinements.

"1) IMCO included the later and larger C8 exhaust manifold with a 2" outlet (but without egr, smog pump, or other special exhaust based emissions equipment)."
*THe 2" outlet exhaust manifolds first appeared on '63 170 & 200 engines. These early versions utilized a better donut gasket sealing system, but were cast alot lighter then the '68 versions. The '68 castings are alot less prone to cracking, warping and having ears break off. This is true of all small six engines- both Calif Em and 48 state.

"2) IMCO carburetors were not 'engineered' any differently than Thermactor or other carburetors of the time, but did have some small 'tuning' differences."
*'68 and'69 Calif/Em engines all got a specific version of the Carter YF, while 48 state engines keep downsized Autolite 1100s. The YFs first appeared on Calif/Em engines in '67. By '68 both Calif/Em and 48 state YFs and 1100s lost the Spark Control Valves (SCV) and the Load-O-Matic distributor. The carb change came with a new distributor which featured centrifugal advance as well as vacuum advance/retard distributor hooked to a Ported vacuum source on the carb. The 48 state 1100s were down sized in CFM from 185 to 150 on 200 engines.

3) IMCO may have also included the first increase in combustion chamber size from 51-53cc to 62cc.
*Calif/Em 200 engines got at larger dished piston-6.5 cc to 13 cc dish volume, resulting in a reduction in advertized CR of about a point. Chamber volumes didn't consistently increase until the '69 "M" castings and later. A pre/post date for a change in chamber volume does not exist.

4) The MAIN significantly different component part of IMCO was the 'dual vacuum advance' 1968 distributor that utilized a spark retard hose plumbed to the canister as well as a distributor vacuum control valve coming off the intake manifold that controlled the vacuum 'retard' signal.
* Well done. The other that is worth mentioning is the unique head required for use with the Thermactors pump system. These heads have taps and tubes inserted into each intake port for injecting unburned exhaust.

Thanks for sharing your findings. It all helps.

Adios, David

 

[xctasy]

Its just the early leaded Pre USA 1975 emission system.

We used the US Pinto 2.0 emission system on our 2 liter Cortinas, and a watered down version of the 1969 49 states 200/250 engines emission set up on the 1976 to 1982 Ford Falcon 200 and 250 engines

In Australia, its regulations copied US 1975 unleaded for our 1986 ADR 37 cars,
and US 1973 leaded fuel regs for our 1976 ADR 27A cars.

The US 1970 regs was copied for the 1973 ADR 27 emission regs.

Each Aussie engine spawned standard non emmissions New Zealand engines which were dirty high octane 97 research rating .85 mg/liter leaded engines. The IMCO engines got the lead plugs removed, no EGR, no air pump, and half of the emissions gear was removed. It still ran the same engines and emission control systems up till the 1985 lean burn engines; After that, it was USA 1975, 91 oct unleaded plodders.

 

[Frankenstang]

Many thanks for the replies and information gentlemen

"2) IMCO carburetors were not 'engineered' any differently than Thermactor or other carburetors of the time, but did have some small 'tuning' differences."
*'68 and'69 Calif/Em engines all got a specific version of the Carter YF, while 48 state engines keep downsized Autolite 1100s. The YFs first appeared on Calif/Em engines in '67. By '68 both Calif/Em and 48 state YFs and 1100s lost the Spark Control Valves (SCV) and the Load-O-Matic distributor. The carb change came with a new distributor which featured centrifugal advance as well as vacuum advance/retard distributor hooked to a Ported vacuum source on the carb. The 48 state 1100s were down sized in CFM from 185 to 150 on 200 engines.

Thanks David for the refinements, this makes the picture clearer. I've edited the original post to include Article 966/TSB #55 that includes information on Carter YF and Autolite 1101 model numbers and calibrations (see Group 10 Fuel Specifications, "Read More" button). One other interesting bit from the fordification site was that the IMCO carters (maybe autolites as well?) were equipped with nylon or some sort of "cap" plug over the mixture screw to 'discourage'/prevent adjustment...not like the 'casted' over mixture screws of later emission era carbs, but guess the intent was the same.

Its just the early leaded Pre USA 1975 emission system.

We used the US Pinto 2.0 emission system on our 2 liter Cortinas, and a watered down version of the 1969 49 states 200/250 engines emission set up on the 1976 to 1982 Ford Falcon 200 and 250 engines

Thanks Dean! The nutshell conclusion at the top of your thread seems to capture it...the first broad based 'emission' efforts on straight sixes.

It’s interesting that your ‘76+ IMCO incorporated EGR (if I’m following your information correctly…many thanks for sharing the aussie docs) while the kiwi’s ran with a more true ‘US 49’ IMCO for so long.

Noting from one of your manual pics that the aussie IMCO also incorporated the “inlet air temperature regulating system” at the air breather. I’m not sure what year this became standard component of US 49 emissions (particularly on the 170, 200 and 250).

As bubba suggests, and I’m pretty sure is personally aware of, it seems Cali has always been the beta tester of emissions standards prior to application aka mandates to the other 49...lucky guys

Again, thanks! Lots of great info

 

[xctasy]

It may be semantics, but Ford pretty much exported its unleaded emissions tech systems to Australia, as its fairly obvious that with a market 1/10 th of the size, it was by 1983, about 10 years behind the US in emission control legislation, crash regs, car design, transmission and especially, electronics and fuel economy improvements. I mean, in 1983, they were using 1973 era emissions features on its last 351 Clevelands, and six cylinder Cortina 200 and 250 engines. It only got half breed Bosch made small body electronic ignition on 1976 V8's, then alloy head 1980 1/2 3.3/4.1's got a watered down Bosch Duraspark ignition system, not dual advance, and not similar to the US 1973 up Duraspark. Our Aussie igntion systems were outsourced Motorcraft components supplied by Robert Bosch under an Australian Duraspark part number. So there were US and Aussie Durasparks, with the Aussie Duraspark a Bosch item also doing duty on Australian GM Holden and Chrysler Hemi Sixes and Fireball/ELB 5.2 V8's. So the Aussie IMCO sytem didn't have dual advance on the Cleveland V8 or X-flow sixes, but the Pinto 2.0 engined Cortina missed out on the European Duraspark, and used the old 1970-1974 Ford Pinto/Bobcat/Capri 2000 points distributor. 10 year old technology by 1983, and perhaps why a 2450 pound four cylinder Cortina 2.0 with 88 or 98 hp net used more fuel than a 2910 pound 121 hp 2-bbl alloy head Falcon 3.3.

The manual I copied was the July 1979 revised 3.3/4.1 engines used in the XD and TE Cortina. These lightly emissionised engines soldiered on till early 1983 in the Aussie Cortina, with no changes bar the Aussie Duraspark ignition and the Honda alloy head. I think there was a New South Wales tighter emissions spec for 1982, which resulted in minor legislation based EGR changes, but the iron and alloy Cross flows were IMCO, as Honda only did the casting of the alloy head, not the emission control. The Cortina stayed with the 1-bbl Bendix Stromberg right till the end in 1983.

Getting back to US IMCO, every 1969 on 250 six lookes to have the inlet Air Temperature control system, comprising of a heat stove from the exhast, and a thermatic valve which regulates the inlet air temperature.

First is an early 250 six with an air cleaner which is nothing but straight 1982 F150. I've seen a similar offset air cleaner to this one used on early California V8's. Second is an ebay 70 1/2 Falcon with stock air cleaner missing a few bits, but the heat stove is there, and the control valve would have been there. This is stock x-shell 200/250 six stuff, (Maverick/Granada/Versaillies/,1966-1969 Fairlane- body Falcon/Ranchero 250, uni body 1970 Torino body Falcon/1969 Ranchero), and the oddball separate frame 1972 and 1973 Torino 250,

 

[hickorystang]

Thanks guys for all the information. Very informative!!!