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  #181  
Old 11-19-2014, 12:43 AM
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Kitdy Kitdy is offline
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Nice completion to the catalogue Fleet. Good to see you back around here.
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  #182  
Old 11-19-2014, 02:25 AM
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Fleet 500 Fleet 500 is offline
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Originally Posted by Kitdy View Post
Nice completion to the catalogue Fleet. Good to see you back around here.
Thanks, Kitdy.

It's amazing how those rare things show up on eBay.
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  #183  
Old 11-19-2014, 01:04 PM
dog ear dog ear is offline
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Originally Posted by RealityCheck View Post
If you look at the way the engines were tested, they were actually generating a "net" bhp figure in some cases. So the 275 bhp gross advertised number was probably more like the actual net bhp for the 1968-71 engines.
Gross and Net horsepower figures are in fact derived at by widely diverse formulas and are not interchangeable. Only way to accurately produce true net figures is to actually install said engine on a dyno using ALL factory OEM equipment right down to the original factory exhaust manifolds, mufflers, and piping. This was / is not always possible, or even plausible given dyno facility layouts.

Gross figures were historically derived through omission of factory manifolds, mufflers, pipes, air cleaners, and most ancillaries including alternator / generator, smog equipment, fan, belts, etc. Gross figures also included headers, modified timing and carburetion.

Formula for net figures have also been changed through the years with end result being LESS advertised horsepower due to warmer ambient temperatures used to generate dyno figures. Net horsepower figures first came into vogue beginning in 1971. By 1972, they were universally used by all manufacturers. Since that time, NET numbers have been downgraded twice, through tighter regulations

In other words, the same engine in 1971-72 era will produce less horsepower today using modern standards because of the latent formula used to derive said figures.

Exact figures cannot be expressed but the general excepted norm is at least 5-8 % difference through the years.

Most (dyno) facilities using the old gross system exact their numbers via the once excepted 68 degree ambient temperature formula. If you were to use todays figure of 74 degrees, you will find that horsepower drops considerably, even if you were computing said engines with the GROSS system save the higher ambient temperature.

On another note, most engines on the dyno today are not in fact ''stock.'' Newer pistons replacing old worn out cores are typically used. Non factory aftermarket replacements are usually lighter and have optimised blueprinted blocks, heads, gaskets, rings, etc., that raise horsepower figures slightly from true stock. Most dyno engines have optimised compression ratios and calibrated timing spot on.

Dealership engines installed at factory were never fully optimised in the car you could buy. Anyone serious enough wanting to fully realize the potential of their engine would have it MODIFIED from the factory settings, with calibrated ignition and carburetor adjustments. This in itself could raise horsepower at least 5%. One only need to peruse several of the original online road tests of the day, (numerous Royal Bobcat Pontiacs) to see how these performance mods really woke up the engine.

In regards to the recently quoted 340 dyno tests, it is obvious that the engine was not remotely close to a true net setting. No fan, belts, alternator, factory air cleaner assembly, etc,.

I am a big fan of the Mopar 340 but I maintain that it's factory horsepower was very close to it's gross published figures of 275. Net would be less; somewhere between 240 - 250 for the 68-70 automatic cam versions. manual cam 340s were only available in 1968. There were probably 10 horsepower more than their auto cam counterparts.

Later 1971 340 was the epitome of small block tech using the larger 800 cfm Carter Thermoquad with appropriate intake manifold. Those engines might make 10 horsepower more than their older breather. Let's say as much as 260 (net) horsepower. A good stock well tuned 1971 340 might come close to 300 actual gross horsepower. Nuff said!
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  #184  
Old 11-19-2014, 01:14 PM
dog ear dog ear is offline
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Hey Fleet500, I am happy to see that you picked up the 1970 and 1/2 Supercars Annual magazine. I am interested in reading a few of those tests.

Street / Strip Tuning 70 Supercars
350 Ram Air Cutlass
454 Monte Carlo
455 Grand Prix
455 GTO
454 SS Chevelle

He! He! He!

You post some and I will post some more…

PS
Good to see on here again. Missed you.
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  #185  
Old 11-19-2014, 04:33 PM
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Fleet 500 Fleet 500 is offline
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Quote:
Originally Posted by dog ear View Post
Hey Fleet500, I am happy to see that you picked up the 1970 and 1/2 Supercars Annual magazine. I am interested in reading a few of those tests.

Street / Strip Tuning 70 Supercars
350 Ram Air Cutlass
454 Monte Carlo
455 Grand Prix
455 GTO
454 SS Chevelle

He! He! He!

You post some and I will post some more…

PS
Good to see on here again. Missed you.
Dog ear, I will certainly post the most interesting specs. The cars I mentioned and the ones you mentioned.

The magazine is shipping from my state, so that should help delivery time.

CARS magazine usually tested muscle cars with low axle ratios. Sometimes, another magazine, like Car Life or Motor Trend will test something like a 454 Monte Carlo with ridiculously high 2.73:1 gears! It really hurts acceleration time. But it did make 2nd gear good up to 105 mph! (with the 3-speed automatic).
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  #186  
Old 11-21-2014, 04:58 PM
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Fleet 500 Fleet 500 is offline
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I received the magazine today. Still going through it. 15 out of 26 cars listed ran the 1/4 mile in the 13s or faster.

The 454 Monte Carlo I mentioned before fortunately did not have super-high gearing, but the 3.36 ratio it did have is not exactly the best choice for running the fastest 1/4 mile times. It ran 14.96@94.20 mph. Weight was 3,800 lbs.

The good thing about the 3.36 ratio was that it helped the car give 8-14 mpg, quite a bit better than most of the other cars in the magazine!

Also tested was a Phase III 427450 hp Camaro. With 4.10 gears, it ran mid-12s and with 4.56s, the 1/4 mile came in at 11.98@117.80 mph. 0-60 mph was 4.5 seconds. Tires were J-series Inglewood.

Scans coming up soon.
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  #187  
Old 11-21-2014, 05:07 PM
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Fleet 500 Fleet 500 is offline
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Quote:
Originally Posted by dog ear View Post
Hey Fleet500, I am happy to see that you picked up the 1970 and 1/2 Supercars Annual magazine. I am interested in reading a few of those tests.

Street / Strip Tuning 70 Supercars
350 Ram Air Cutlass
454 Monte Carlo
455 Grand Prix
455 GTO
454 SS Chevelle

He! He! He!

You post some and I will post some more…

PS
Good to see on here again. Missed you.
Dog ear, so you don't have to wait any longer about the specs of the cars you listed:

------------------------------- Axle ratio/trans-1/4 mile---------- 0-60 mph

350 Ram-Air Cutlass------- 4.33/4-speed--- 13.94@100.05--- 6.6

455 Grand Prix-------------- 3.55/automatic- 14.90@95-------- 7.2

455 GTO--------------------- 3.90/4-speed--- 13.90@103------- 6.1

454 Chevelle---------------- 4.10/automatic- 13.50@103------- 6.7

One more, since others are probably curious about the Hemicuda:

Hemicuda-------------------- 3.91/4-speed---- 13.65@106------- 6.5
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  #188  
Old 05-22-2015, 05:15 PM
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Fleet 500 Fleet 500 is offline
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Here are some scans from the 1970 1/2 Supercars. The 454 Chevelle did very well especially considering that it was the LS5 version (360 hp) and not the more powerful LS6 version (450 hp).
Attached Images
File Type: jpg IMG_8192.JPG (593.5 KB, 5 views)
File Type: jpg IMG_8194.JPG (784.3 KB, 5 views)
File Type: jpg IMG_8195.JPG (757.6 KB, 4 views)
File Type: jpg IMG_8196.JPG (754.4 KB, 4 views)
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  #189  
Old 07-28-2015, 06:48 AM
dog ear dog ear is offline
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70 1/2 SCA Road Tests

TY Fleet500 for the various road tests you posted. Interesting!

Gearing, weight, driver skill, track conditions, general tuning and car preparation determine ultimate times in any individual car. Misused press pool cars were often poor performers. On the other hand, many were obviously drag strip prepped and not representative of what you could actually buy off of the show room floor. Much harder to do that today with modern cars and testing methods.
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