How to plan for an efficient driveline.

[customcam]

Steve can u translate that page for us

[Steve Chryssos]

The bottom line is that your complete engine/drivetrain combination boils down to "Wheel Torque" And wheel torque can be determined mathematically thru the following:
-Engine Power Band
-Coupling Device (converter or clutch) Multiplication Factor where applicable.
-Transmission Gear Ratios
-Rear End Gear Ratio
-and Tire Diameter.

For example, double overdrive is of little use if it takes your engine out of its power band. Gearing your engine to take advantage of double overdrive might render 1st gear useless. A drag car is usually more concerned with taking advantage of 1st gear, while a touring car is more concerned with making the most of overdrive.

We cannot and should not take this conversation further without first getting answers to the basic questions:

Manual or Auto? What will you use for rear tires? Will you also run slicks in addition to street tires? What is target vehicle weight? What are your intended uses for the car? Assign percentages for the car's life at the track vs street? What are cam specs? Carb or EFI? What is the altitude where you live (very important on carbureted monster big blocks.)

[drphibes]

Thanks for the replies. Steve you are going to make sure I get an answer! Thanks

Proposed specs:

Transmission: Auto
Target Vehicle Weight: 3400# max
Vehicle Usage: 90% Street 10% Track - Both drag and road.
Induction: Carb
Altitude: Sea Level
Rear End Gears: 3.72
Tires: Rear 345/30R18 Michelin Pilot Sports PS2 Street, Comparable size slick for track.
Engine Power Band: 4000 -5500 Max TQ at 4800

Probably TH400 trans, but don't know what gearing would be right now. That's what I am trying to decide. Which transmission, what gearing options I would have for it.

Thanks again.

Robert

[Steve Chryssos]

You mean 345 30's, right. 345/70's are 37" tall. That's donk territory. I'm guessing you have a Dominator. 3 circuit probably. Any idea on cam specs? I'm sure the specs look crazy (min 740 lift and 270 deg duration). But on a 598, the numbers are actually nominal. Does the dyno sheet show power levels below 4000 rpm?

Options are TH400 and 4L80E. By the way, I think Shafiroff had DSE build him a 69 Camaro. So I highly recommend that you pick his brain on the subject. If you get that chance, ask about available torque between 2500 and 4000 rpm. I think you will be spending a lot of time in that rpm range, so finding out power levels between 2500 and 4000 (even if they are guesstimates) is key.

[californiacuda]

On the street, won't tire friction be weak link in 1, 2, and maybe 3rd gear. The torque of a big block can only be used at the strip, or on the street over 100mph.

[deuce_454]

with all that tourque id build a driveline that gave me no headaches instead of worrying about the last 2%... my best bet would be a 4l80e with shrifter.. and a 9 inch (possibly with 12 bolt ring and pinion if you are really anal about efficiency)

also id get the regulkar 745 hp or 705 hp EC (extended cruicing) option from shafiroff instead of the SS that you are talking about... i mean fi you intend to run it 90% on the street then why get a Saturday-night Special motor.. besides you can always add a shot of nitrous in second and two in third if you feel things are a bit slow with a 750 Hp big block...

oh yeah, and you are NEVER going to get a decent launch on 30 profile tires... so be sure to get brakes that accomodate a 15 inch rim in the back...

and 3.73 might not be the best choice with an OD tranny..