Differences between 71 and 72 engines?
#1691771
10/28/14 08:58 PM
10/28/14 08:58 PM
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Joined: Jan 2003
Posts: 28,067
Irving, TX
feets
OP
Senior Management
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OP
Senior Management
Joined: Jan 2003
Posts: 28,067
Irving, TX
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I know that the change from net to SAE rating systems knocked the numbers way down.
The compression was dropped significantly but I don't know how much of an impact that had on the engine output.
Did the cams change?
I've got an old Motor repair manual that shows a slight change in timing.
Anything else change?
Looking at the old road tests it seems the 1971 and 1972 Imperials ran about the same times (slow as molasses) with the 90 hp rating change and a swap from a 2.94 gear to the 3.23s.
We are brothers and sisters doing time on the planet for better or worse. I'll take the better, if you don't mind.
- Stu Harmon
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Re: Differences between 71 and 72 engines?
[Re: feets]
#1691774
10/28/14 11:50 PM
10/28/14 11:50 PM
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Joined: Jan 2003
Posts: 10,538
Freeport IL USA
poorboy
I Live Here
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I Live Here
Joined: Jan 2003
Posts: 10,538
Freeport IL USA
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Feets,
The changes between 71 and 72 were 2 fold.
1) lower the numbers to make insurance companies happy
2) more restricting emission standards. Though the auto companies knew tightening standards were at the door, they largely ignored it was coming. I suspect they thought the general population and their lawyers would be able to make the new standards go away. When that didn't happen, they hung a lot of stuff on the motors to meet the new tougher standards. They d-tuned the motors (lowered compression, retarded ignition and cam timing, leaned out the carbs, just to name a few) and the add on stuff( egr valve, air pumps) choked the motors even more. Some of the stuff they did could be easily reversed (ignition timing, removing the air pump, enriching the carb), while other stuff was more difficult to reverse (cam timing, compression) They got a break in 73 when the government allowed the use of cat converters, but hung more junk (or rehung the junk they were able to remove because of the cats) on after 73 until they finally started designing the motors to meet the standards. Gene
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Re: Differences between 71 and 72 engines?
[Re: poorboy]
#1691776
10/29/14 03:25 AM
10/29/14 03:25 AM
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Joined: Feb 2010
Posts: 18,493
Granite Bay CA
Kern Dog
Striving for excellence
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Striving for excellence
Joined: Feb 2010
Posts: 18,493
Granite Bay CA
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Quote:
They got a break in 73 when the government allowed the use of cat converters, but hung more junk (or rehung the junk they were able to remove because of the cats) on after 73 until they finally started designing the motors to meet the standards. Gene
Your points are valid but it was 1976 when the catalytic converters were first installed. There never was a 1973, 1974 or 1975 Mopar with a catalytic converter. I've owned Chevies and the same holds true there.
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Re: Differences between 71 and 72 engines?
[Re: Kern Dog]
#1691777
10/29/14 11:15 AM
10/29/14 11:15 AM
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Joined: Nov 2003
Posts: 12,494
Western Colorado High Desert
moparmarks
I Live Here
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I Live Here
Joined: Nov 2003
Posts: 12,494
Western Colorado High Desert
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Quote:
Quote:
They got a break in 73 when the government allowed the use of cat converters, but hung more junk (or rehung the junk they were able to remove because of the cats) on after 73 until they finally started designing the motors to meet the standards. Gene
Your points are valid but it was 1976 when the catalytic converters were first installed. There never was a 1973, 1974 or 1975 Mopar with a catalytic converter. I've owned Chevies and the same holds true there.
True. Also I've owned a butt load of 72's and none had an EGR valve or air pump.
72 Satellite Sebring Plus 440, 72 Dart 5.9 4-spd, 68 Valiant, 73 W200, 78 D100 sb, 78 D200, 98 DAKOTA, . Moparmarks Parts & Restorations Desert Mopar Metal Grand Jct. CO 970-261-7039 http://moparmark.com/motormangj@gmail.com
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Re: Differences between 71 and 72 engines?
[Re: feets]
#1691780
10/29/14 01:29 PM
10/29/14 01:29 PM
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Joined: Jun 2006
Posts: 5,161
CT
GTX MATT
master
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master
Joined: Jun 2006
Posts: 5,161
CT
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Quote:
Any idea what the cam specs for the 440-4v are for 71 and 72?
From what I've been told the cam specs didn't change from the mid 60s through the end of production, non HP engines still used the same cam 260/268 Duration, 0.425"/0.435" lift. HP cams were still 268/284 Duration, 0.450"/0.458" lift.
There is a lot of fuzzy and cloudy info on these engines, but this is what I've been told (here and other places) and it seems logical. The published specs even differ from source to source on the early engines regarding the lift on the HP cams (some say .458, some say .465 lift). I'm not sure if they ever moved the cam timing around, not that they degreed them anyway.
I believe the only significant difference on the later engines should be compression ratio. Head/intake part numbers changed, and they used TQs, but as we know all the heads and intakes flow basically the same in stock form. Also, I've never seen a later set of HP exhaust manifolds, anyone know what those look like? Were they even any different? Did the later HP engines use a windage tray?
Last edited by GTX MATT; 10/29/14 01:45 PM.
Now I need to pin those needles, got to feel that heat
Hear my motor screamin while I'm tearin up the street
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Re: Differences between 71 and 72 engines?
[Re: 72roadrunnergtx]
#1691783
10/29/14 02:36 PM
10/29/14 02:36 PM
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Joined: Nov 2003
Posts: 12,494
Western Colorado High Desert
moparmarks
I Live Here
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I Live Here
Joined: Nov 2003
Posts: 12,494
Western Colorado High Desert
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Quote:
"True. Also I've owned a butt load of 72's and none had an EGR valve or air pump"
Some California big blocks were equipped with air pumps in ’72.
Yes but was not standard on all US cars. I've seen air pumps on GM cars as early as 69.
72 Satellite Sebring Plus 440, 72 Dart 5.9 4-spd, 68 Valiant, 73 W200, 78 D100 sb, 78 D200, 98 DAKOTA, . Moparmarks Parts & Restorations Desert Mopar Metal Grand Jct. CO 970-261-7039 http://moparmark.com/motormangj@gmail.com
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