where did the 70s take the horses

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Princess Valiant

Princess Valiant

A.K.A. Rainy Day Auto
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i recently had someone ask me if i still have the 318 that came out of my 68 coronet.

i told him "sure its still around, do you need a new engine for your dart sport?"......he has a 74 dart sport with a 318.

He said "well i would like to replace my 318 with the coronet one for more horsepower"

So the assumption is that the 68 318 is more powerful than the 74 318 and this assumption comes because literature out there suggests that the 68 318 has 230 horsepower and the 74 has 150 horsepower.

so its assumed that 80 horsepower is lost during the rise of smog controls between 68 and 74.

But here is where i stop you........if you take a look at a book titled "standard catalog of Chrysler" by John Martin lee......you will notice that the horsepower ratings are "Gross horsepower" before 72 and after 72 they are "net horsepower" ......what does that mean?

Gross horsepower: horsepower measured with engine on a Dyno at the flywheel.

Net horsepower: horsepower measured with engine in car with full exhaust and at the rear wheel.

So if its assumed that around 75 horsepower is lost through driveline with full exhaust in a real world application.......that suggests that not much was lost at all and its simply a numbers game.

So then comes the factor of a reduced advertised compression ratio, which on the 318 is a matter of 9.2 to 8.6 ......so that is a reduction of .6 which by definition should only be responsible for 5 to 10 horsepower in the application.

So my conclusion is that the 74 318 is superior to the 68 318 because according to number manipulation not much was actually lost to the compression reduction and that loss is most likely recoverd through the heads.......It would seem the later heads are designed to work in tandem with the lower compression and heads can overcome factors like that as seen with the 455 pontiac heads of the mid to late 70s.......its amazing.

So my recommendation would be to stay with the 74 318 and add a modest 4 barrel because the 8.6 compression can handle more than the leaned out 2 bbl. of 1974 and add headers!!! possibly add a cam, but only if you know what your doing to not overcam it.

The result will be an unleaded friendly (hardened valve seats on the later heads) that will meet or exceed the performance of the 68 318.

Do you guys see my logic on why the 74 318 could be the better engine of the two or am i overthinking it??
 
The engines from 71 and earlier are better. Higher compression, less emissions controls.

The emissions controls limited the power. EGR is like eating your own **** - literally, you can't process it twice...


As far as the horsepower ratings, you can't compare them. They were done with different standards. I forgot when, but they also started correcting for altitude and humidity and have a "standard" to adjust for any differences in temperature, humidity, and atmospheric conditions (mile-high in the Rocky Mountains compared to at sea level).
I don't think that the loss through the trans and axle are as high as 75 hp, but do reduce. Also, if you test your engine during the summer and then test it again in the winter, you can correct for the differences in atmospheric conditions.



They also test engine dynos and chassis dynos. The chassis dyno measures what is actually at the rear tires (and eat up your tires while testing).


*****************************************************************

Here's some info on dyno testing:



Dyno Correction Factor and Relative Horsepower


So what's all this correction factor stuff anyway??

The horsepower and torque available from a normally aspirated internal combustion engine are dependent upon the density of the air... higher density means more oxygen molecules and more power... lower density means less oxygen and less power.

The relative horsepower, and the dyno correction factor, allow mathematical calculation of the affects of air density on the wide-open-throttle horsepower and torque. The dyno correction factor is simply the mathematical reciprocal of the relative horsepower value.

Originally, all of the major US auto manufacturers were in or around Detroit Michigan, and the dyno reading taken in Detroit were considered to be the standard. However, as the auto industry spread both across the country and around the globe, the auto manufacturers needed a way to correlate the horsepower/torque data taken at those "non-standard" locations with the data taken at the "standard" location. Therefore, the SAE created J1349 in order to convert (or "correct") the dyno data taken, for example, in California or in Tokyo to be comparable to data taken at standard conditions in Detroit.

What's it good for?

One common use of the dyno correction factor is to standardize the horsepower and torque readings, so that the effects of the ambient temperature and pressure are removed from the readings. By using the dyno correction factor, power and torque readings can be directly compared to the readings taken on some other day, or even taken at some other altitude.

That is, the corrected readings are the same as the result that you would get by taking the car (or engine) to a certain temperature controlled, humidity controlled, pressure controlled dyno shop where they measure "standard" power, based on the carefully controlled temperature, humidity and pressure.

If you take your car to the dyno on a cold day at low altitude, it will make a lot of power. And if you take exactly the same car back to the same dyno on a hot day, it will make less power. But if you take the exact same car to the "standard" dyno (where the temperature, humidity and pressure are all carefully controlled) on those different days, it will always make exactly the same power.

Sometimes you may want to know how much power you are really making on that specific day due to the temperature, humidity and pressure on that day; in that case, you should look at the uncorrected power readings.

But when you want to see how much more power you have solely due to the new headers, or the new cam, then you will find that the corrected power is more useful, since it removes the effects of the temperature, humidity and atmospheric pressure and just shows you how much more (or less) power you have than in your previous tests.

There is no "right" answer... it's simply a matter of how you want to use the information.

If you want to know whether you are going to burn up the tranny with too much power on a cool, humid day, then go to the dyno and look at uncorrected power to see how exactly much power you have under these conditions.

But if you want to compare the effects due to modifications, or you want to compare several different cars at different times, then the corrected readings of the "standard" dyno will be more useful.


For actual equations see the article here:

http://wahiduddin.net/calc/cf.htm


Here is a link to SAE J1349:

[ame]http://www.mie.uth.gr/ekp_yliko/SAE_%CE%94%CE%A5%CE%9D%CE%91%CE%9C%CE%9F%CE%9C%CE%95%CE%A4%CE%A1%CE%97%CE%A3%CE%97_%CE%9C%CE%95%CE%9A.pdf[/ame]
 
EDIT KK beat me to it

Actually, Rani, "it's both."

Smog controls for certain took their toll. Reduced performance advance curves, leaned out carburetors, and in general, lower compression and diddled cam timing

And you are right "they" changed from gross HP to "net" HP

"Net" is SUPPOSED to be a more relevent representation, taking into account "the actual stuff" that an engine has to have to operate, including alternator, PS pump, water pump etc

BUT THE thing is, "numbers" get "diddled."

My favorite example (and there are many) is ratings on air compressors

"Once upon a time," compressors were rated by the air in cfm that they would output at 90PSI operating pressure

Then in the ?60's? Wards or Sears or someone "discovered" 'HEY' if we rate OURS at 40 psi instead of 90, THE NUMBERS GO UP.

THEN somebody discovered that if you rate them by scfm (suction, or intake, or atmosperic pressure) the numbers REALLY go up

So the very same compressor, at these three different ratings, "seems" bigger at 40 psi, and bigger yet at SCFM than it does at 90 PSI

The point is that "numbers" are only as good, meaningful, and accurate as the guy's ethics who wrote them

Battery ratings, many other things, are a Great Big Lie.
 
Rani, tell him you have the motor of his dreams! Very rare, and very valuable 68 318, with a forged crank to boot (same as 340)! All for the low, low price of $3000! :D
 
You are absolutely on the right track.

80 something percent of people don't get what you just explained.

Put a 71 motor next to a 72 motor, and there's about 5-10 HP difference if you measure them both on the same scale.

Enter the joker...the 318/5.2 introduced in 92 was rated 230 NET HP.
That's a far cry up from the 230 GROSS HP of 71 and earlier.
 
krazykuda said:
The engines from 71 and earlier are better. Higher compression, less emissions controls.

The emissions controls limited the power. EGR is like eating your own **** - literally, you can't process it twice...


As far as the horsepower ratings, you can't compare them. They were done with different standards. I forgot when, but they also started correcting for altitude and humidity and have a "standard" to adjust for any differences in temperature, humidity, and atmospheric conditions (mile-high in the Rocky Mountains compared to at sea level).
I don't think that the loss through the trans and axle are as high as 75 hp, but do reduce. Also, if you test your engine during the summer and then test it again in the winter, you can correct for the differences in atmospheric conditions.



They also test engine dynos and chassis dynos. The chassis dyno measures what is actually at the rear tires (and eat up your tires while testing).


*****************************************************************

Here's some info on dyno testing:



Dyno Correction Factor and Relative Horsepower


So what's all this correction factor stuff anyway??

The horsepower and torque available from a normally aspirated internal combustion engine are dependent upon the density of the air... higher density means more oxygen molecules and more power... lower density means less oxygen and less power.

The relative horsepower, and the dyno correction factor, allow mathematical calculation of the affects of air density on the wide-open-throttle horsepower and torque. The dyno correction factor is simply the mathematical reciprocal of the relative horsepower value.

Originally, all of the major US auto manufacturers were in or around Detroit Michigan, and the dyno reading taken in Detroit were considered to be the standard. However, as the auto industry spread both across the country and around the globe, the auto manufacturers needed a way to correlate the horsepower/torque data taken at those "non-standard" locations with the data taken at the "standard" location. Therefore, the SAE created J1349 in order to convert (or "correct") the dyno data taken, for example, in California or in Tokyo to be comparable to data taken at standard conditions in Detroit.

What's it good for?

One common use of the dyno correction factor is to standardize the horsepower and torque readings, so that the effects of the ambient temperature and pressure are removed from the readings. By using the dyno correction factor, power and torque readings can be directly compared to the readings taken on some other day, or even taken at some other altitude.

That is, the corrected readings are the same as the result that you would get by taking the car (or engine) to a certain temperature controlled, humidity controlled, pressure controlled dyno shop where they measure "standard" power, based on the carefully controlled temperature, humidity and pressure.

If you take your car to the dyno on a cold day at low altitude, it will make a lot of power. And if you take exactly the same car back to the same dyno on a hot day, it will make less power. But if you take the exact same car to the "standard" dyno (where the temperature, humidity and pressure are all carefully controlled) on those different days, it will always make exactly the same power.

Sometimes you may want to know how much power you are really making on that specific day due to the temperature, humidity and pressure on that day; in that case, you should look at the uncorrected power readings.

But when you want to see how much more power you have solely due to the new headers, or the new cam, then you will find that the corrected power is more useful, since it removes the effects of the temperature, humidity and atmospheric pressure and just shows you how much more (or less) power you have than in your previous tests.

There is no "right" answer... it's simply a matter of how you want to use the information.

If you want to know whether you are going to burn up the tranny with too much power on a cool, humid day, then go to the dyno and look at uncorrected power to see how exactly much power you have under these conditions.

But if you want to compare the effects due to modifications, or you want to compare several different cars at different times, then the corrected readings of the "standard" dyno will be more useful.


For actual equations see the article here:

http://wahiduddin.net/calc/cf.htm


Here is a link to SAE J1349:

http://www.mie.uth.gr/ekp_yliko/SAE_ΔΥΝΑΜΟΜΕΤΡΗΣΗ_ΜΕΚ.pdf
Click to expand...

Yup....
 
Note: not only does EGR not cost power (it is 100% inoperative at WOT), it is a BENEFIT. It is worth a noticeable mileage boost, because it lets you run LOTS of timing (50+ degrees) at cruise.
 
Net horsepower is not at the wheels, its still measured at the flywheel it is just with accessories like alternator, mufflers, air cleaner, fan. No where near 75hp worth of drop. If it included the transmission and axle then maybe but it doesn't. It was all car makers could do to keep up with rising emission standards into the 80's and they had to make terrible choices just to get a few numbers on an exhaust sniffer. Good news is it can be fixed and there won't be much of a difference between a 68 and a 74 318, pure stock measure both at the wheels, installed in the car and the 68 will make much more power. The best stock 318 as pointed out was the 92 up, they finally got emissions figured out, came up with better exhaust manifolds and heads and put a bigger cam back in it. Drop a 92 or 3 magnum 318 in there and you will really feel a difference.

PS: one obvious way to tell NET ratings were not done at the wheels is they would need different ratings depending on manual or automatic. It was actually misreported in many magazines in the early 70s NET was measured at the wheels but they had to correct it later.
 
Didn't they also lower the hp numbers from 72 on all cars, because of the manufaturers where concerned the insurance where taking the hp in consideration for the policies ?
 
318 is fine if you want to make a dependable cruiser car, nice and reliable.

it wont really make tons of power for racing etc unless you bolt on a turbo or shift at 8000 or something. then watch out. gonna cost some money and your reliability will suffer.

but for a general use car they are fine; that being said you could use a 318 from any year.
+/- 20hp wont make or break the car.
 
There's very little difference between any 318 except 4 bbl to make any huge power difference. If it's a good running engine in your 74 just do cam high rise and headers.
 
Also the timing was set differently from 68-74. even in a 74 motor adjusting the timing to a more aggressive setting is a huge difference.
 
Right but pure stock there is a big difference. I also bet the cam is much less aggressive come mid 70s but that also is often changed at the same time as intake and headers are added.
The gross to net changed because the federal government required it, but it became a convenient excuse when selling cars when HP numbers did drop because of other mandates in emissions. The air pump was another big power robber those years that just pulling the belt off fixed.
 
all paper comparisons aside i can remember a '68 318 satellite and a '70 318 duster that when new were faster than seemed possible.
....i knew both cars and they were stock.
 
My research indicates that except for 67 (first year for LA 31 8, all the cams were the same until the 87-ish roller motors.

318 2 barrel 67 Hydraulic 390/390 244/244
318 2 barrel through 88 Hydraulic 373/400 240/248

Going from 390/400 lift to almost any of the 441-ish "mild" cams that don't even require new springs or valve guide work has GOT to be a substantial improvement.
 
YY1 said:
My research indicates that except for 67 (first year for LA 31 8, all the cams were the same until the 87-ish roller motors.

318 2 barrel 67 Hydraulic 390/390 244/244
318 2 barrel through 88 Hydraulic 373/400 240/248

Going from 390/400 lift to almost any of the 441-ish "mild" cams that don't even require new springs or valve guide work has GOT to be a substantial improvement.
Click to expand...


Not really. If you go back starting in 67-74 and track the 273/318 hydraulic cam it changes slightly.

I did a study many years ago (can't find it now without researching all service manuals again). The duration changed in the 240, 248 ranges. sometimes split duration, sometimes even. And I think lift was .399" or like .410" without going back and doing it all over again. You have to really pay attention to detail to catch the differences. It slipped by me for a while and I had to go back and recheck when I first did my study.
 
Granted, stock 318 cam info is not the easiest research project.

My point was that there was no major cam change that accounted for a major difference in horsepower.

I've owned at least a half a dozen 318 cars, and known intimately several times that.

The only ones that perform in a noticeably different manner are the 92 and up magnums, and the 66 and earlier poly, and in that case only slightly more torque, seat of the pants wise.
 
The power didn't go down near as much as the way it was measured changed.
 
I think Ms Raini, (the OP) did an very good job on her assessment and explanation.

Anyone who's owned and/or regularly driven examples from the various years- say a 66, a 67, a 73, an 86, and a 92, can attest to the same findings.

The bottom line is- it didn't go anywhere.

9.x compression to 8.x compression, then back to 9.x (LA roller), then back to 8.x (Magnum), and all very similar cams (until Magnum) also proves "it's all in the heads".
 
One big reason: gearing! A typical 60's 318 car would have 3.23 or 2.94 gears. A 318 5th Avenue could easily have 2.26 gears!
 
She had a misconception that net ratings are at the wheels, net ratings were at the flywheel just with the motor in a more normal state of installation. I agree the later motors can be fixed but pure stock in their stock tune with all emissions in place they were well short of a pure stock 68.
 
I'm sure someone can post the equation for HP gain (or loss) per point of compression, and that will also confirm that it's about a 5-10 HP loss if both engines are measured on the net scale and maybe 20 if measured on gross.

We've already established that there was no radical cam change, so the only other major areas are heads and compression.

I'm not aware of any huge head mods from 68 to the early 80's except for hardened seats.
I think we are also all aware of the mid 80's 302 heads.

That leaves the compression and that's simple math.

OK, maybe also exhaust. HP vs std manifolds have been discussed ad nauseum and the consensus is also 5-10 HP. Not sure of the flow differences in the castings in the specified years.

I will call attention to the factory 73 318 with dual exhaust (Roadrunner) which the factory thought was good for 20 HP (170 net vs 150).
 
To answer the original question: yes you are thinking properly.
Use the engine that can run on unleaded and maybe add some reasonable upgrades (mild cam & four barrel intake & carb).
The output rating as numbers used for advertising.
 
Pure stock you also have air pumps, distributors with less advance both mechanical and vacuum, carbs leaned way out, etc. Yes the mid 70s can be fixed but there is a reason they have less hp and its not just the way it was measured.
 
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