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Old October 29th, 2011, 08:31 AM   #1
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1972 olds rocket 350

i have a 72 rocket 350 all stock with a 2 barrel carb and dual exhaust(factory exhaust manifolds, not headers) and i know it was rated at 160 hp but i also know that car manufacturers underrated alot of their cars so insurance would be cheaper. i was wondering if anyone could tell me how much horsepower my engine really has or if it is really 160. thanks, Dom
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Old October 29th, 2011, 09:21 AM   #2
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It is really 160 SAE net HP. With normal wear and tear, could be less.

There have been a number of threads on this question over time, the most recent from just this week.

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Old October 29th, 2011, 10:26 AM   #3
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You could look up the rating for the same engine in 1971 and it will be pretty close to the gross rating since 1972 was the year they went to net ratings. I believe the gross ratings were with open exhaust and air cleaner and taken off the back of the flywheel while the net ratings were with all accessories with the air cleaner and closed exhaust and taken off the back of the transmission. I know I am pretty close on that but if I am off I know somebody will correct me.
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Old October 29th, 2011, 10:36 AM   #4
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I don't know about the flywheel or the transmission, but the difference is that Gross is essentially a bare motor with no accessories (including water pump), running through an exhaust that is essentially headers, and Net is with all belts, pulleys and accessories attached, through stock manifolds.

Since 1971-72, manufacturers have been required to state HP as Net, rather than Gross,
so the answer to your implied question of "How does the 160HP rating of my engine compare to newer cars?" is that the 160HP should be on the same rating scale as modern engines, while HP numbers for earlier cars are exaggerated compared to modern numbers.

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Old October 29th, 2011, 10:45 AM   #5
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A '72 350 2v with dual exhaust was actually rated at 175hp and 295 torque. (Single exhaust 350 2v was rated at 160hp.)
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Old October 31st, 2011, 03:18 PM   #6
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ok i guess its 160 it has aftermarket duals, unless that pushes it to 175hp. that sucks haha i feel like a car so heavy and with not so much horsepower shouldnt be able to smoke the tire(open diff in my car) like it does. thanks for the replies guys
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Old October 31st, 2011, 04:41 PM   #7
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My stock '72 350 (4bbl though) did the same... smoke the original style 14" tires off that is. And that was with single exhaust. Lots o torque for stock. Nice torquey n quiet grocery getter.... I actually miss that setup.
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Old October 31st, 2011, 04:54 PM   #8
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Originally Posted by oldzy View Post
My stock '72 350 (4bbl though) did the same... smoke the original style 14" tires off that is. And that was with single exhaust. Lots o torque for stock. Nice torquey n quiet grocery getter.... I actually miss that setup.
I wish my 72 CS would smoke em off the line ... it has power , just not off the line.... the original motor was gone before I bought it , and from what im told on here , I have a 76-79 Olds motor in there now.... The motor sounds pretty mean , but not sure how or who rebuilt it , and why its slow off the line... probably a timing issue/carb adj.
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Old October 31st, 2011, 05:42 PM   #9
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Yeah, horsepower is really just a number used to sell cars to people, torque is what you should be looking for. Especially since Olds made some of (if not THE) torquiest motors ever built by GM. Torque is what will make your tires roast, bend your frame, and throw you into the back seat at open throttle. Basically its a measure of fun hahaha. Honestly you would be able to make great horsepower from that 350 with a few simple bolt on swaps. The olds 350 had the best bore/stroke ratio for performance of any of GM's 350s so it should respond extremely well to simple bolt ons.

Also remember that while net is closer to the real number than gross, GM definatly underrated a lot of their motors, so when all is said and done id say the difference betwen the loss of power from gross to net and the underrating lies GM weaved, the actual output is probly honestly closer to the gross rating than the net rating


For example (not real numbers just example numbers):

Gross:
GM's rating - 250hp/300tq
Actual output - 300hp/350tq

Net:
GM's rating - 200hp/250tq
Actual output - 250hp/300tq

See how the actual output of the Net rating matches GM's bogus rating of the Gross. This is how i determine "real" horsepower estimates. Of course time and wear and tear and slight minor differences will affect everything but for a general idea of the output this formula has been pretty good to me
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Last edited by Vega; October 31st, 2011 at 05:50 PM.
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Old October 31st, 2011, 07:00 PM   #10
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I think a few of us would be interested in seeing the sources for some of those numbers you've postulated, Vega.

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Old October 31st, 2011, 08:17 PM   #11
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Originally Posted by Vega View Post
Yeah, horsepower is really just a number used to sell cars to people, torque is what you should be looking for. Especially since Olds made some of (if not THE) torquiest motors ever built by GM. Torque is what will make your tires roast, bend your frame, and throw you into the back seat at open throttle. Basically its a measure of fun hahaha. Honestly you would be able to make great horsepower from that 350 with a few simple bolt on swaps. The olds 350 had the best bore/stroke ratio for performance of any of GM's 350s so it should respond extremely well to simple bolt ons.

Also remember that while net is closer to the real number than gross, GM definatly underrated a lot of their motors, so when all is said and done id say the difference betwen the loss of power from gross to net and the underrating lies GM weaved, the actual output is probly honestly closer to the gross rating than the net rating


For example (not real numbers just example numbers):

Gross:
GM's rating - 250hp/300tq
Actual output - 300hp/350tq

Net:
GM's rating - 200hp/250tq
Actual output - 250hp/300tq

See how the actual output of the Net rating matches GM's bogus rating of the Gross. This is how i determine "real" horsepower estimates. Of course time and wear and tear and slight minor differences will affect everything but for a general idea of the output this formula has been pretty good to me
There is so much bad info here that I will actually have to wait until the morning to address it.....
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Old October 31st, 2011, 10:04 PM   #12
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lol thank you, i was wondering how long it would take for someone to argue this...
Just as a reminder, this isnt a formula i developed for figuring out exactly what output any car on earth is making exactly to the rear wheels at any given time...this is a general idea...but i love how everyone is so eager to be the best teacher

Everyone has different oppinions and ideas. General info is different than specific, and one person doing something one way doesnt make it worse it just makes it different. Nitrojunkie, just build your 350 the way you want it, if you need factual info like rod length or valve sizes go ahead and ask but try to stray away from asking what "preffered builds" there are out there (thats assuming you want to build this motor) Because all you will get is a 3 page argument on what the "best" way is to build an Olds. One person does things one way and another does things another and if its any different than anyone else's way then the other person instantly calls foul on it. Its irritating. Especially when you just try to be helpful in factual and/or oppinionated ways and people are chomping at the bit to jump in and try to prove you wrong and cry foul over your ideas or theories >=/ This is why i like to build what i want to build and ask the least amount of questions needed
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Old November 1st, 2011, 04:55 AM   #13
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First off, I have always been a proponent of "HP is overrated", torque moves the car. HP is simply a function of torque and rpm.
This statement you made is simply false,
"Honestly you would be able to make great horsepower from that 350 with a few simple bolt on swaps."
Low compression limits cam, which limits rpm, which limits HP. Basic stuff like intake, mild cam, and exhaust upgrades will improve performance some, but "great horsepower"? Nope, not with 8.0 to 1 Cr.

You stated,
"The olds 350 had the best bore/stroke ratio for performance of any of GM's 350s so it should respond extremely well to simple bolt ons."
I agree with the first part, excellent bore/stroke and rod/stroke ratios. However, in stock form the heads are a severely limiting factor. They do not flow well enough. Also, the non divided center exhaust ports negate the scavenging benefits of headers to a degree. The heads can certainly be improved, for $1000 you can really have a nice pair of street heads, but not in stock form.

I have never given much credence to factory published numbers, but I do not see how you can just add 20%-25% off the top of your head.

You stated,
"Especially since Olds made some of (if not THE) torquiest motors ever built by GM."
I disagree with this, too. Torque comes from cubic inches, stroke, and port velocity. The Buick 350 makes more torque, as do many SBC 350s. What Olds engines do VERY well is make torque at a low rpm and across a broad range. IMO, they are less "peaky" than SBCs. 455 Olds engines are torque monsters, but so are the Buicks, Pontiacs, and BB Cadillacs.

Last edited by captjim; November 1st, 2011 at 05:03 AM.
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Old November 1st, 2011, 04:56 AM   #14
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Quote:
Originally Posted by Vega View Post
Everyone has different oppinions and ideas.
General info is different than specific...
... all you will get is a 3 page argument on what the "best" way is to build an Olds.
... when you just try to be helpful in factual and/or oppinionated ways and people are chomping at the bit to jump in and try to prove you wrong and cry foul over your ideas or theories...
Okay, let's get our nomenclature clear first, and then we can produce our three page arguments.

Power, as expressed in HP, is an objective measurement, like temperature in degrees or length in feet (or meters, for our fo-ryne readers).
It is not a matter of argument or opinion, and has nothing to do with any given thing being "best" or "worst."
Like measuring a line with a ruler, there is a right answer and a wrong one. That first day in shop class, when the teacher had everybody measure something, I was amazed that some people could come up with wrong answers, but some did, and that taught me a lot right there.

One horsepower is defined as 746 watts, 33,000 foot-pounds a minute, or 550 foot-pounds a second.
That's it. It is what it is.

There are different ways to measure horsepower, such as inertial versus real-time "braking" (inductive resistance), and there are different places to measure it, such as at the flywheel, or the driveshaft, or the rear wheels, but, as with any scientific measurement, measurements of horsepower must be repeatable to be accurate which is to say that you should be able to make the measurements at different times, with different measuring devices, under similar conditions, and get the same answer.

So, having gotten that out of the way, we can easily dispose of:
Quote:
Originally Posted by Vega View Post
Yeah, horsepower is really just a number used to sell cars to people...
The next obviously misleading bit is this:
Quote:
Originally Posted by Vega View Post
GM definatly underrated a lot of their motors
GM is believed to have underrated some of their top performance motors (such as the W-30 and LS-6), but they did not underrate their other motors.
Quote:
Originally Posted by Vega View Post
...so when all is said and done id say the difference betwen the loss of power from gross to net and the underrating lies GM weaved, the actual output is probly honestly closer to the gross rating than the net rating
Okay, like I said earlier, where did you get this information?
Just one objective source would be fine.
Quote:
Originally Posted by Vega View Post
For example (not real numbers just example numbers):...
So... If they're not real numbers, why should we read any further?
I mean, if you just made all of those very specific numbers up in your head, what value is that to anyone, except to confuse them?
Why would you present completely made-up numbers in the first place?
And how is making up nonsense numbers in any way "helpful" to other readers?
I'm just completely mystified.

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Old November 1st, 2011, 05:06 AM   #15
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ok i guess its 160 it has aftermarket duals, unless that pushes it to 175hp. that sucks haha i feel like a car so heavy and with not so much horsepower shouldnt be able to smoke the tire(open diff in my car) like it does. thanks for the replies guys
Don't confuse peak HP for off-idle torque and throttle response, that is what makes a street car fun to drive.
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Old November 1st, 2011, 03:48 PM   #16
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hey guys, thanks for the answers and heres what i really want to do to my engine: i want a 455 top end an edelbrock alum. intake and a nice carb. i was told a pair of 455 heads will bolt right on the 350's because they are essentially the same block just the 455 is a little taller i was told so i almost bought a set and i'd love to have them ported and polished. if i were to do this would i need a new cam, and what kind of hp and torque would i be making? oh and something my uncle told me and it makes great sense. torque gets you off the line horsepower keeps you going.
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Old November 1st, 2011, 04:12 PM   #17
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Just put the big valves in the heads you have along with a little bowl work. For a mild to moderate 350 I'm not sure I'd go with the bbo heads, they have much larger chamber so you'd have to mill them a bunch and use a different piston.

You can still make 350+ with the 7a's that are on there. Plus their smaller ports mean better throttle response.

Jmo.
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Old November 1st, 2011, 04:20 PM   #18
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Just a footnote to MDchanic's post. The actual horsepower on a modern v8 has NEVER been measured. NEVER. Torque is measured, then a formula is used to compute/estimate horsepower. Problem is, on an engine dyno, rate of acceleration is contriolled by the dyno. That changes the results. On a chassis dyno, traction is an issue.
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Old November 1st, 2011, 06:10 PM   #19
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Sigh......here we go again. A dyno is no more than another tool. I have never had any dealings with a chassis dyno. The engine dyno does make certain calculations using torque and RPM. A properly tuned dyno adjusts results to sea level. That way you can tell what good/bad things your tuning does from pull to pull. I do know what my motor produced and with the help of a weather calculator plus honest weight of the car can predict what it will run. This figured out to within .02 of actual ET the first day out. Lets face it, engines are rated by HP not TQ.
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Old November 1st, 2011, 07:56 PM   #20
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Not to be a buster, but HP is definitely measurable.

Just because you can't put a "HP meter" on an engine and measure it directly doesn't make it any less measurable. Many common power measurements, like watts in electric circuits, aren't measured directly either - this does not in any way reduce the accuracy of the measurements.

It's true that an easy way to measure HP is to measure torque. That's because HP is defined as torque over time. Therefore, if you can measure both time and torque, you can measure HP (the same way that you can measure electric power, or watts, if you can measure both volts and amps).

All you do is measure increasing torque over a period of time, and you have HP - 1 HP = 550 ft lbs a second.

My point? Don't demean the measurement of HP through torque - it is a perfectly valid measurement, in accordance with the laws of classical physics.

In other words:
Torque is a measurement of instantaneous force, with no time duration.
Work is a measurement of force applied to move an object (a car) over a distance.
Power is a measurement of work over a period of time, which is to say that the same amount of work can be done slowly or quickly - my 6.2L diesel can accelerate my 4,000 pound pickup to 60 mph without a problem, it just takes a minute or so, while a 2,000HP jet engine could do the same amount of work in far less time.

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Old November 2nd, 2011, 01:15 PM   #21
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Thanks cutlassefi, that sounds like a good way to go to me, and alot cheaper. what would be a good camshaft suggestion for low and mid-range power with a mild idle?
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Old November 2nd, 2011, 01:20 PM   #22
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oh and i read in a book the formula for finding horsepower is force pounds times feet divided by 33,000 times 2 pi. i am no math genius and i have absolutely no idea how to actually use it but it was in a technical book so it seemed right to me
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Old November 2nd, 2011, 03:54 PM   #23
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The problem is that the dybno controlls the rate of acceleration, and thus HP. Explain to me why on a chassis dyno the HP changes if you make a run in 2nd gear vs final drive? Same engine, same power output.

My point is that for most of us with street cars, 50 more ft/lbs at 3800 rpm is much more important than 50 more HP at 6200 rpm.
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Old November 2nd, 2011, 04:33 PM   #24
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Thanks cutlassefi, that sounds like a good way to go to me, and alot cheaper. what would be a good camshaft suggestion for low and mid-range power with a mild idle?
It depends on your compression, gear and whether or not you're going to use stock manifolds etc.
But a middle of the road cam would be something around a 214/220 at .050 with .472/.504 lift on a 110, maybe even a 108.
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Old November 2nd, 2011, 09:43 PM   #25
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The problem is that the dybno controlls the rate of acceleration, and thus HP. Explain to me why on a chassis dyno the HP changes if you make a run in 2nd gear vs final drive? Same engine, same power output.

My point is that for most of us with street cars, 50 more ft/lbs at 3800 rpm is much more important than 50 more HP at 6200 rpm.
Jim, I'm afraid I don't understand. The only thing I can think of is that the dyno is actually testing the converter. That or the chasis dyno is not very accurate. Do you come up with the same numbers twice in a row/same gear/RPM? Face it the industry bases their engines on HP. You always heard a 300 horse 327, never a XXX torque 327.
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Old November 3rd, 2011, 06:02 AM   #26
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Yeh but Nick they do that because that's what has always help sell cars. You know yourself that 99% of the general public doesn't know what torque is.
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