Horsepower Discrepancy

-
attack tiger

attack tiger

Well-Known Member
Joined
Jun 29, 2010
Messages
50
Reaction score
1
Location
Denham Springs, LA
Why the HP discrepancy between the early-70's 318s and the mid-70's 318? I ask because I was recently informed that my 318 in my '74 Duster is out of a 70 model Duster, and that it's "supposedly" better. After some quick research I found that the HP ratings went from 230 to 150 between the '72 and '73 years (or was it '73 and '74?). What changed?

Thanks for the info!
 
the early numbers were at the flywheel. the later were at the wheels with all the accessories i believe
 
accessorys added to the equasion on rateings. Insurance companys payen off politicans, and the birth of save the planet policys. We did`nt really need all that extra horsepower did we ?:angry7:
 
Arab oil embargo for one. The other is called "emission standards".
 
Both are rated at the flywheel. Earlier engines were gross hp. Later engines were net hp. Gross is no accessories, no air cleaner, open exhaust. Net is how it would be if installed in the car; full exhaust , air cleaner, fan,etc.
 
forphorty said:
Both are rated at the flywheel. Earlier engines were gross hp. Later engines were net hp. Gross is no accessories, no air cleaner, open exhaust. Net is how it would be if installed in the car; full exhaust , air cleaner, fan,etc.
Click to expand...

Not sure about the no muffler part. but exactly.
 
Okay, I guess that makes sense...except I would never have thought that the accessories were soaking up more than a third of the engine's power.

So nothing actually changed...the CR, head flow, fuel delivery, etc. remained the same?

Bonus question: this little 318 is supposedly stock except for the Holley 670 and the 2.5 inch Flowmaster exhaust with performance headers. It feels like WELL over 150 horsepower. What kind of power do you guys think I'm running?

The guy I bought the car from threw in a 318 magnum engine that he had planned to drop in the car. Would that be a noticeable improvement over the old LA? (converting to carbureted, of course)

Thanks again, guys!
 
attack tiger said:
Okay, I guess that makes sense...except I would never have thought that the accessories were soaking up more than a third of the engine's power.

So nothing actually changed...the CR, head flow, fuel delivery, etc. remained the same?

Bonus question: this little 318 is supposedly stock except for the Holley 670 and the 2.5 inch Flowmaster exhaust with performance headers. It feels like WELL over 150 horsepower. What kind of power do you guys think I'm running?

The guy I bought the car from threw in a 318 magnum engine that he had planned to drop in the car. Would that be a noticeable improvement over the old LA? (converting to carbureted, of course)

Thanks again, guys!
Click to expand...


I'd go with the 318 magnum. The heads flow quite a bit better than LA heads and I hear you can really wake them up by converting them over to a carb...
 
It was mostly the net vs. gross rating but they did drop the compression some too. Some companies also retarded the cams some to help with emissions. Not sure if Mopar did that but it's possible.

No real guess on the hp of yours but the 318 mag will run quite a bit better. Better flowing heads, higher compression, and a roller cam. I had a stock 93 Dakota with a 318 mag that ran 14.50's. Nothing but bolt on's and a mopar perf. computer.
 
Here's the story I get from the Society of Automotive Engineers, the guys who set standards for such things.

SAE Net Horspower In 1972, American manufacturers phased in SAE net horsepower. This is the standard on which current American ratings are based. This rating is measured at the flywheel, on an engine dyno, but the engine is tested with all accessories installed, including a full exhaust system, all pumps, the alternator, the starter, and emissions controls. Both SAE net and SAE gross horsepower test procedures are documented in Society of Automotive Engineers standard J1349.
SAE Gross Horsepower This is the old process that American manufacturers used as a guide for rating their cars. It was in place until 1971. SAE gross also measures horsepower at the flywheel, but with no accessories to bog it down. This is the bare engine with nothing but the absolute essentials attached to it; little more than a carb, fuel pump, oil pump, and water pump. Because the test equipment on the engine is not the same as in SAE net, it is impossible to provide a mathematical calculation between SAE net and SAE gross. As a general rule, however, SAE net tends to be approximately 80% of the value of SAE gross. SAE J245 and J1995 define this measurement.
 
When did you guys go to EGR's, unleaded fuel and catalytic converters???
This may be the drop in performance issue too???
In Australia, we went to EGR in 1976, and unleaded with Cats in 1986.
Fuel injected cars weren't common place till 1988.....and at that time a lot didn't have EGR anymore, as the injection systems got them under minimum emission standards......wasn't till late 90's that EGR's came back in.
Locally built Chryslers died here in 1981......:cry:
 
Hummmmm, I'm not dead sure, but, I think (Key word and a dangerous one, think)

72 or 73 was the first egr valve useage
Cats dribbled in a year later, '74 but stayed off of trucks so they can keep the power up and deliver the goods across the states.
F.I. was seen early, in the 50's as a mechanical device. Later, electronic F.I., what we have today, kind of, came back around the early/mid 80's.

I can remember the Chevy Monte SS cars went FI in 84 I think. (Danm, theres that word again, think.)
Forgive me, I was more interested in chasing tail than cars. My car worked, and that let me chase tail.
 
The family Monte Carlo had a catlytic converter in '73, but since Dad was a Deputy the Cat was gutted and totally legal, he said8). First electronic Fuelie I ever saw was about '78, VW Scirocco and "Daaammmnn" did it scat.
 
You must log in or register to reply here.
-

Back
Top