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What happened to North American 4.5 in 1979-1980?

3K views 27 replies 8 participants last post by  unavita 
#1 ·
The horsepower dropped from about 180 down to 160 in 1980.

Was this just a three-way catalytic converter?

A lambda system?

Or additional accessories like a smog pump that sucked power all the time?

I wasn't ever too curious before, but now I am.
 
#5 ·
No. I fellow posted the question in a thread I created about 5.0 SLC documentation and I asked him if we could take the topic elsewhere. He very politely deleted his post for me. So he's done me the favor. The least I can do is try to find the answer to his question.

I do have a curiosity to understand this kind of stuff.

Coincidentally, he's the guy that helped me to understand that smaller diameter wheels and higher profile tires are almost always lighter. It seems he is asking some darn good questions and reading a lot more than he is posting.

So what was it that made the 1980 so much less powerful?

- the guy suggested maybe the 2-way cat. (Converts NOx and HC / CO, not just HC/CO, like earlier ones). Is this true? We're 2-way cats used on the 1980 model??!

- compression. My gut says compression couldn't get too much lower than the 8:1 used in the earliest of 4.5 107s.

Pic below from automobile-catalog.com
 

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#6 ·
Well, one difference that would certainly affect performance would be the rear differential. Per Automobile-catalog.com, the 1980 got a 2.65 differential where all the others got a 3.07 differential. This certainly seems like a fuel saving effort.


Perhaps with the lower ratio differential, there was a need for more torque, and the engine was tuned for more torque and less HP. The 1980 does have a little more torque than the 1979. 230 vs 220 ft-lb (72-73 had 240). That all very likely could be a simple tuning of the timing as isthisdave mentions above.

Are there any real mechanical restrictions? Are the cams actually different? If so, they would show a different part number in the EPC. Well, I'm not sure I'm going to dig that far on this "favor". If others are interested, I assume they can dig. My curiosity has run up... For now.
 

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#7 ·
Well, fuel savings was king in 1980, in case you weren't around at the time. We were just recovering from the first oil shock in 1973 and then in 1980 you were lucky to find any gas at all. Luckily, that year I was safely tucked away in grad school and was lucky if I moved my 1971 Toyota Corolla once a month.
 
#8 ·
Cutting power alone isn't necessarily going to save fuel, but changing the differential, and tuning the engine for torque over power to compensate certainly makes sense to me.

Did I get it? Just the rear diff and an increase in torque and coincidental decrease in power?
 
#13 · (Edited)
I think it is pretty impressive how quickly this group gets to the bottom of a technical question. Thank you all!


PS
It can be a little comical how so many people say, "it just all that pollution control crap" or claim it's all about smog prevention, when in reality, a clean burning engine is just an efficient one, getting the most power out of every drop of fuel. (Too rich, CO and HC in exhaust. Too lean, and risk of burning valves, NOx in exhaust. It's not as if pollution makes a more powerful car. :) )
In this case, the reduction in power (and increase in torque) seems to be all about fuel economy, not pollution control. I wonder if a 1980 is more likely to chirp the tires than a 1979 with the added torque... probably not with that lower diff ratio.
 
#14 ·
Hello and thank you.

Both of you make two great arguments. I too read the data that the final drive ratio was changed for that year. however, 3.07 was offered as one of three for AMG.

Apparently the catalytic converter was changed to a three way converter. The car accelerated wonderfully though. There is a good deal of torque.


Thank you for starting this string. I could not for the life of me find a tab allowing me to create a new post. My apologies for dropping in on the 5.0 string. It was the only string that came up when I typed "450 SLC Horsepower".

Thanks again.


I have been making "period correct" modifications to the car and only adding what was available from Mercedes via the factory, the dealer or AMG. I posted about the 4 cam AMG motor fitting in the 107's. I've not seen one in a 107 but if there was enough desire to it could be done albeit with a great deal of modification that isn't worth doing to a car that is 33 years old.

My car was ordered by a United and WWII B17 bomber pilot. The care and notes were meticulous. I am not sure if the car can take a catalytic from an earlier model or if a '77 differential I found will work. The earlier sway bars were larger which did give the car flatter handling in turns but less turning ability for daily use which may have contributed to other failures such as power steering.
My car had a couple leaks- PS and AT. So I put in Lucus as a first measure. Now there are no more power steering noises/ leaks and transmission leaks are gone. The suspension does need bushings all around.

This is my second MB. My first was a '09 CLK 350 with the AMG performance package. The AMG option was funny to read because they wrote that though they changed the exhaust there were no additionally claimed horsepower gains. I prefer the earlier cars with their lack of overriding controls made for non-drivers who over drive their car.

I have read that parts are interchangeable i.e., that a 5.0 head will fit on a 4.5. That baffles me as to why someone would want to do that with out swapping the block. It's obvious to me that the 5.0 was "more" free revving. Placing the opened up heads from a 5.0 would net such little power without reworking the block to give it the ability to rev more freely and push more air. This also goes for the person that suggested putting on a Mega Squirt. However, it has been suggested that the mega squirt saves gas. Hardly enough to cover the cost of the item I am sure.

Then there's the aluminum engines. They have more failure issues most probably due to the fact that it was a new engine concept and several things may not have worked well together.

Perhaps the best suggestion I have heard is opening the throttle body up give the engine a wee bit more air. But even more air without more fuel... and more fuel without more capacity and excursion (a point I heard little about) is pay Peter to screw Pauls girl.

But then you can't really port a 450 head because where are you going to find bigger valves? You can however port the exhaust ports and, if you can find a performance manifold certainly increase all factors of the engines performance.

Well that's what I've got this morning from my office... gotta run.

Thanks again.
 
#15 ·
In this case, the reduction in power (and increase in torque) seems to be all about fuel economy, not pollution control.
Meanwhile, back at the ranch in Stuttgart, the engineers were busy with a complete refresh using a smaller, lighter all alloy engine. They even went so far as to make the timing chain thinner to reduce weight....

Makes the car easier to push while waiting one's turn in the gas lines. The cheap rusted out cars I had in those days were easy to roll.
 
#16 ·
LOL, that's funny... "Back at the Ranch" because they do love Cowboys. Every time I visit they always try to mimic a Western accent. LOL.

I agree with you on their weight saving idea but apparently there was great frustration with the engine. It was not as robust and had a great many more engine failures. But as history can tell us, the mechanical and electrical engineers finally got it right. Today's MB engines are utterly amazing. They are told what to do and then are designed to do it well.


Yes I thought my car rolled very easily as well. I would replace the exhaust system with something more efficient... if we are defining efficiency by flow and not longevity.

Off to test the AC/Heater vacuum for leaks. mild exhaust odor...
 
#26 ·
well got the Nardi and boss, burl wood shifter, chrome shift gate. Found a SLC in a salvage yard, pulled the rear window. The puller cracked it a little... which it then ran more... faced with leaving the badly damaged (from defrost) original.
Found louvers. Paid 270. for the pair. Get them. Glass not sealed, paint job looks like that of a teenager. I'll have my paint and body guy re do it. Then I have him do the ones that are in it and sell them.
So right now I have 2 of all of the about: steering wheel. Boss. shifter gate. Rear window. Louvers.
Found a set of 15x7 BBS for 570 total.
 
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