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Old 11-16-2003, 02:46 PM
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dave571 dave571 is offline
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Default Magazine performance vs real world

This seems to be talked about frequently.

I have an example of one that I often rember.

When I was attending technical school, to be an auto tech, a classmate and fellow gearhead, brought me an article on something called "hurricaning".

This was the late 80's and swirl technology was being applied to fi cars.

A magazine had decided to try and see what would happen if they tried to improve the swirl of an old sb chevy head.

They 1/4 mile tested a car with this sb chevy. The heads had some mild port work and polished combustion chambers. I don't remember the et. Then they tore it down, and did this "hurricaning". What they did was lay out a grid on the combustion chamber, and put marks in the chamber, where the lines crossed. Like a checkerboard, with punchmarks at the corners of the squares.

Then they 1/4 miled it again and saw a decent improvement in 60 ft times, and et.

We thought this was great, so we showed the article to an instructor. He was an old time dirt racer, and drag racer. Knew lots of guys, like art and les walls(former land speed record holders)

He browsed through it, and handed it back to us.

"that's great" he said. "But what do you think happens to those punch marks after a few runs down the track?"
We were dumbfounded.
"Do you think they fill up with carbon?" he asked
"I guess they would" my classmate replied.
"Well....That probably doesn't hurt it much, because the carbon builds up into an uneven surface, so it probably does the same thing as the punch marks did" he replied
We thought we were redeemed at this time.
"But that raises a question" our instructor said. "If the rough surface of the carbon, does the same thing as all those little punch marks, then why did you bother to polish the roughness off of the casting, then simulate it, by putting a bunch of punchmarks in the same surface?"

We left his office, with red faces, and deposited the article in the appropriate round file.

Magazines are magazines. The real world is something different.

Any input on this subject is appreciated, and encouraged.
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Old 11-16-2003, 10:20 PM
jelsr jelsr is offline
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A striking resemblance to the old SAE HP rating and the present NET rating descreptancy. The purpose was to sell cars with the big HP numbers. The magazines use big claim headlines to sell magazines. Smoke and mirrors!
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Old 11-16-2003, 11:31 PM
Mopar_Maniac Mopar_Maniac is offline
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dave571...

It sounds to me like you had a GREAT instructor.

He made YOU think, and didn't just say that the article was full of BS. Sounds to me like the kind of guy that I would like.

Good luck,
Mopar_Maniac
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Old 11-17-2003, 03:50 AM
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cuda66273 cuda66273 is offline
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I think what you we're reading was the embryo of Combustion chamber "Dimpling"......which has now grown into full grown 204MPH Prostock runs.
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Old 11-17-2003, 05:40 AM
DartGT66 DartGT66 is offline
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I first saw that kind of chambers & piston tops in some late 80's Pro Stock engine. Don't think they are used anymore though. As far as what sence does it make to first polish the chamber, and then punching it rough; none. Except, if you alter the combustion chamber shape; that's pretty hard to do without removing hte rough surface.
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