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 Post subject: Gear Ratio Selection
PostPosted: Tue May 26, 2015 8:14 pm 
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2 BBL ''SuperSix''

Joined: Mon May 25, 2015 9:23 pm
Posts: 16
Car Model:
I am building a V/SA Dodge Diplomat. So, basically a stock 225 with a good blueprint job and a cam with all the duration I want. Looking for a suggestion for a rear gear and torque converter specifics. Thanks


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 Post subject:
PostPosted: Wed May 27, 2015 3:55 am 
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Supercharged
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Joined: Sat Feb 16, 2008 1:25 pm
Posts: 5613
Location: Downeast Maine
Car Model:
Basically the bigger the cam (increase in overlap) the shorter the rear gear and higher the stall of converter.

This marriage of optimal engine torque rpm due to cam choice, converter stall, and rear gear (including tire size) has to be calculated to end up with a combination the works well for vehicle's intended use. Miss the mark with any one of the above parameters and the car won't function as well as anticipated. In other words it becomes an expensive dog.

One has to first decide what the car is going to be, a full out race, street & track, daily driver, and design drive train from there.

One needs to know cam specs, engine dimensions, compression ratios (Static & dynamic) calculated torque curve, before rear gear, tire diameter, and converter stall is selected.

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82' LeBaron Convertible; the new Chrysler Corp
07' 300 C AWD; Now by Fiat, the old new Chrysler LLC

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 Post subject:
PostPosted: Wed May 27, 2015 5:26 am 
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Turbo Slant 6

Joined: Sun Jun 01, 2014 10:27 am
Posts: 548
Location: Waynesboro VA
Car Model:
V/SA looks like and SCCA class to me but SA means 'Stock, AWD' so that can't be it! What is V/SA?

As above, give more info on what you want to do with the car. Cam and gears will change radically with the application. Is this a 3 speed Mopar trans (904/727)?


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 Post subject:
PostPosted: Wed May 27, 2015 6:35 am 
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2 BBL ''SuperSix''

Joined: Mon May 25, 2015 9:23 pm
Posts: 16
Car Model:
Drag race only.


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 Post subject:
PostPosted: Wed May 27, 2015 2:36 pm 
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Supercharged
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Joined: Sat Feb 16, 2008 1:25 pm
Posts: 5613
Location: Downeast Maine
Car Model:
[quote]Drag race only.[/quote]

So how much money is available to be sucked up in this project, or rather, how crazy do you want to get with this build? Slants are not cheap dates when one wants to make one go real fast.

For an example:

My car is fully dressed 1967 GT Ragtop, 225cid that was built as a drag queen early 90’s:

Head ported, oversized valves, shaved 9.5:1 compression

Clifford 4v short intake, Holley 390 cfm, and shorty headers.

Cam of unknown manufacture, which will allow engine to turn 6000 rpm & 0.030â€￾ over pistons.

904 with performance valve body, 2600 rpm stall converter, deep pan, oil cooler.

8 ¾â€￾ Suregrip, 3.55:1 rear gear, 24.5â€￾ tall tires.

Sub-frame connectors, front K-H disk brake, tubular upper control arms, reinforced lower control arms, 1 1/4â€￾ anti-sway bar, stage II firm feel power steering box.

Last time I ran her a few years ago on 1/8th mile track: 10.3 seconds, at 68.3 mph. This car was built for quarter mile track.

_________________
67' Dart GT Convertible; the old Chrysler Corp.
82' LeBaron Convertible; the new Chrysler Corp
07' 300 C AWD; Now by Fiat, the old new Chrysler LLC

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 Post subject: Class Racing
PostPosted: Wed May 27, 2015 5:46 pm 
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Board Sponsor
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Joined: Tue Oct 29, 2002 8:27 pm
Posts: 9714
Location: Salem, OR
Car Model:
Quote:
So how much money is available to be sucked up in this project, or rather, how crazy do you want to get with this build? Slants are not cheap dates when one wants to make one go real fast.
Regardless he is shooting for a certain class so he has an 'index" per the NHRA handbook that takes factory weight vs. HP into account... V= 15.25 on the 1/4 mile race and SA = Stock Automatic...so he may also be limited on what mods and equipment can be used under the hood pending the NHRA rule book.


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 Post subject:
PostPosted: Wed May 27, 2015 7:43 pm 
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Board Sponsor & SL6 Racer
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Joined: Fri Nov 08, 2002 4:48 pm
Posts: 5835
Location: Burton BC canada
Car Model:
Mike Jeffries

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Yeah....Im the one who destroyed this rare, vintage automobile.....

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