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  #16 (permalink)  
Old 08-04-2010, 06:22 PM
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Sounds like a free-for-all SNAFU. Maybe all you guys who aren't winning should pitch in toward the purchase of a cubic inch tester....
http://www.precisionmeasure.com/test1.htm

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  #17 (permalink)  
Old 08-04-2010, 07:00 PM
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A couple things to get more vacuum:
  • Biggest possible displacement.
  • Wide LSA, reduced overlap, earlier intake closing.
  • Small intake runner cross section, head and intake.
  • Smallest practical carb.
  • Best ring and valve seal.
  • Rhodes-type lifters using lighter viscosity motor oil (ONLY if rules require hydraulic cam), otherwise a solid roller, ground w/the ability to loosen the lash if necessary.
  • Advanced ignition timing at vacuum checking RPM.

Cam timing and phasing will be an area where you should get w/a good custom cam grinder who can give some insight into what will be the best compromise to get the necessary vacuum along w/the needed HP.

If you have an adjustable ignition box, the advance can be added at the vacuum checking RPM range, then tailored to the engine's performance above that RPM- unless the rules say this is illegal.

The rules are so wide open for cheating, until I don't doubt that no one wants to throw the first stone. Likely, they're ALL cheating to some extent.
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Old 08-05-2010, 04:57 PM
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Thanks for the info!

Given that I would like to maximize power and vacuum (kinda hard to do), what engine build do you suggest? Maybe I should stroke a 454 to 496. I would have to run modified though. Would that be a good engine?

The 427 was recommended, why should I build this over a 454?

I am at a loss now.. I really don't know what I should build.
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Old 08-05-2010, 06:12 PM
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Quote:
Originally Posted by plutonium233
The 427 was recommended, why should I build this over a 454?
You midunderstood my answer. Here's what I said:
"If this is a matter of lbs per cubic inch, I'd rather use a BBC 427. Waaayyy easier (and probably cheaper) to make the power you want in my opinion."

I come from a drag racing background. In Competition classes, we use the engine cubic inches divided into the car weight to determine class. I was just saying that if you guys were using the same system of classification, I would rather use a BBC that is close to the same cubic inches as the 434 SBC because of the larger bore and much larger valves in about the same cubic inch displacement motor.

Build the biggest BBC you can bolt together.
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Old 08-05-2010, 07:14 PM
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OH! ok sorry about that. I didn't go back and read it; I saw it yesterday and it stuck in my head. I understand what you are saying.

I have another question that is somewhat unrelated to the engine, but I don't want to make a new thread to ask it. My friend with the 466 runs a 4500rpm+ stall torque converter with 4.56 gears, 35" tires, and np-205 xfer case. He had been running it in 4-low and did well, but it always seemed like to me that he would accelerate to a certain speed and run out of gearing about 1/2-3/4 track.

After one of the races his fuel pump went out and he left the truck at the track, and we went back the next day to put a new fuel pump on it and bring it home. I convinced him to try 4-hi just to see how it would work. Up until that day he wouldn't do it because he tried it once last year and it didn't perform well at all for lack of torque so he was afraid to try it again. Well I talked him into trying it since he had made several improvements and installed the higher stall torque converter. Let's just say the truck ran better than it ever had. So he decided to start using 4-hi.

The next race rolled around and he was still a little skeptical but he tried it anyway. Everyone noticed the difference and wanted to know what he had done to the truck. When he told them he started running 4-hi, they were calling bs on him and saying that the only way it would work is if he had a minimum of 800 hp.

My take on it is this: the torque converter takes whatever the engine is giving it and tries its best to make the input of the transmission spin as fast as the engine (minus slip). I think that he is at a point where he is gaining performance since he is able to spin the wheels faster, but I also believe there is a lot of slip going on in the torque converter because of the large step up in gearing (basically double). This is causing lost power in the form of heat.

Tell me if you agree with me on this: He probably should make his gearing a little higher and go back to running 4-low. If he doesn't do this, will he hurt anything other than he's wasting power to heat in the torque converter?
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Old 08-06-2010, 08:13 PM
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Another quick question. Will it be easier to put updraft headers or normal headers in the s10? The only area I can think of would be the brake booster that would be in the way. We had to relocate my friend's brake booster by angling it toward the fender to make his headers fit.
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Old 08-06-2010, 10:27 PM
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On the gearing question it makes absolute sens me that the truck would run better in 4 hi than 4 low .. we try and gear so we run out of motor at the finish line..if you run out of motor too soon most likely all you are doing is spinning the tires on the line..if too tall a gear then you are leaving some motor on the table..Mud drags are really not all that different from asphalt just a bit slicker is all..

Sam
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