how does a 71-72 360 have more hp than 73-78 and on

[roadgrime]

I was looking through the tech specs for the 71-72 360 and it list 50 more hp than 73 and on. additionally it has more than the 401? what changed?
http://www.ifsja.org/tech/figures/engines.shtml

71-72 245 hp 365 torque with a 2 barrel
73-78 195 hp 295 torque with a 4 barrel
74-78 401 215 ho 320 torque with a 4 barrel.

[Cecil14]

The way they rated engines is what changed. They went from rating the engine with NO accesories, free flowing air cleaner and exhaust and in a perfect environment. Mandating after '73 forced everyone to rate they're motors with all accesories/air cleaners/exhausts on so the numbers dropped considerably.

Anthony

[otis81WT]

81-86 129HP 245T 2bbl
87-89 175HP 285T 2bbl

Can anyone tell me why or how they gained that much HP from 81-86 to the 1987's?

[joe]

72 is when most of the industry changed from gross to net hp ratings but AMC didn't till 73. Depending on motor/manufacturer but todays(net hp) ratings are roughly 30% less than <72's

[Marvin Gates]

Also, when they started going nuts on the smog crap and HP died.

[fulsizjeep]

I don't trust any of the ratings in the mid 70s thru 80's. So many fed & insurance rules leaning on manufacturers to comply...

[roadgrime]

so is it know that any years are better air flowing through the heads or exhaust producing better hp?

[Elliott]

It was ~1970 when AMC went to the dog leg exhaust port heads and those heads are the best flowing production heads of any American V8, they outflow many aftermarket performance heads.

[Georgia Mike]

A lot of the differences in HP are related to compression ratios,valve sizing,head flow,cam grind,carb size,etc. Way back when,bigger was better,so,you pumped up the compression,which was fine and dandy with the high octane leaded gas of those days,put on a big carb,free flowing exhaust,and let 'er rip. This was,at least,the case with the muscle car era. Anyway,it is true about the way that HP is measured has changed. Back then,they didn't factor in losses of HP robbing accessories like a water pump,for example. Now they are measured as they are in-car. The smog equipment of the '70's and early to mid '80's nearly did in any HP potential that could be made in the old school manner. Thanks to the advent of computerized fuel injection,and other computer controlled items on modern cars,the HP race is on again,all in a more environmentally cleaner package,unless you count tire smoke! I guess this could explain the higher HP ratings between the 80's and 90's. It's all coming full circle again,and I'm waiting to see what comes up next to stop it. I see the gas prices rising all the time,and fuel economy going back down into the single digits on some factory hot-rods. I guess time will tell if this latest gas crunch is what will be the death of it this time. But you have to admit,trucks like that 500 HP Dodge Ram S/RT-10 looks tempting! If they only got more than 9 MPG around town!

[Cliff]

One point not mentioned - the 71 360 and 401 had 52cc combustion chambers, resulting in over 10:1 compression ratio. In late 71 they were enlarged to 58cc to lower the CR.

[ironroad29]

maybe you guys didn't get this

"81-86 129HP 245T 2bbl
87-89 175HP 285T 2bbl

Can anyone tell me why or how they gained that much HP from 81-86 to the 1987's?"

[Cecil14]

It's just how they rated them. I don't believe there really is any "noticable" difference in power. They wanted people to buy them ('87 is also when chryo took over) so they played with the numbers a bit.

Anthony

[ironroad29]

ahh yea this is very true i didn't think of the cyrsler corp fudging numbers

[The Anti-Chrysler]

Originally posted by ironroad29:
maybe you guys didn't get this

"81-86 129HP 245T 2bbl
87-89 175HP 285T 2bbl

Can anyone tell me why or how they gained that much HP from 81-86 to the 1987's?"To directly answer your question, there's no difference between an '81 360 and an '89 360. Minor emissions changes, etc., but they're all the same and are probably plus or minus 10 hp over that span of years. I've seen those rediculous listings before, but I have no idea why they did that.