Rear Gear Ratios for a Big Block Stroker?

[Road_Runner]

Have you played with starting line ratio calculations? 

https://www.cartechbooks.com/techtips/drag-racing-traction-making-a-pass  It's a bit down the article so keep scrolling. It uses formula:  Starting-Line Ratio =  First-Gear Ratio x Rear-Axle Gear Ratio

Then use the chart which references stroke against car weight dictating the "target" or optimal SLR.

You'll see if your over or under and where you can adjust.

So with a 2.45 first gear & 4.10 rear, if I go with the 450 c.i. stroker with 3.9" stroke its right on the money for optimal SLR with treaded tires 11" or less which is the size tires I'm looking at, Cool!!  So although its definitely going to be more of a street car than drag car, its nice to know if I go with the 4.10 and an overdrive I'm right on the money.

Thanks, Jim

[marc70challenger]

So with a 2.45 first gear & 4.10 rear, if I go with the 450 c.i. stroker with 3.9" stroke its right on the money for optimal SLR with treaded tires 11" or less which is the size tires I'm looking at, Cool!!  So although its definitely going to be more of a street car than drag car, its nice to know if I go with the 4.10 and an overdrive I'm right on the money.

Thanks, Jim

Cool!  I know some guys like mid or low 3's. It depends on how, and how hard, you want to launch. What I was taught with using SLR ratio is that is full hook up with just that little bit of slip that's optimal and a decent launch RPM.  3k ish I would say foot braking your set up  (stall lock).  I'm No expert but what guys with 25 years experience are helping me with.

With our project car the previous owner had it dialed in to within .2 optimal SLR.  lol.  He ran consistant 11.5. That's with 4.56 rear and 5k stall.   

So we're in the same situation as you. To make it "streetable" the first reaction/option is to trim down rear ratio.   But of course with the same trans, weight and a rear end gear reduction it's going to drop SLR a lot. At least dropping rear to 3.73 we'd be a full point under.  So we'd be bogging a bit on launch - theoretically.

We could "cheat" the displacement with a hit of NOS or other PA to lower the optimal SLR.  I'd prefer not yet.  If we decide on keeping TF trans then probably Gear Vendors OD.   And dealing with high stall. I haven't been able to test it yet to see how loose it is. May need a new one. It was strictly a 1/4 mile dog.

It's the age old conundrum.   

First thing we need to do is finish our first phase and see how she holds together.   

[Road_Runner]

Cool!  I know some guys like mid or low 3's. It depends on how, and how hard, you want to launch. What I was taught with using SLR ratio is that is full hook up with just that little bit of slip that's optimal and a decent launch RPM.  3k ish I would say foot braking your set up  (stall lock).  I'm No expert but what guys with 25 years experience are helping me with.

With our project car the previous owner had it dialed in to within .2 optimal SLR.  lol.  He ran consistant 11.5. That's with 4.56 rear and 5k stall.   

So we're in the same situation as you. To make it "streetable" the first reaction/option is to trim down rear ratio.   But of course with the same trans, weight and a rear end gear reduction it's going to drop SLR a lot. At least dropping rear to 3.73 we'd be a full point under.  So we'd be bogging a bit on launch - theoretically.

We could "cheat" the displacement with a hit of NOS or other PA to lower the optimal SLR.  I'd prefer not yet.  If we decide on keeping TF trans then probably Gear Vendors OD.   And dealing with high stall. I haven't been able to test it yet to see how loose it is. May need a new one. It was strictly a 1/4 mile dog.

It's the age old conundrum.   

First thing we need to do is finish our first phase and see how she holds together.   

It will be a while before I stroke my motor, just trying to get the car on the road while doing projects like the rear I can do now and be done with it, so I'd really appreciate hearing how your progress down the path you're heading down.  Thanks again, Jim

[marc70challenger]

It will be a while before I stroke my motor, just trying to get the car on the road while doing projects like the rear I can do now and be done with it, so I'd really appreciate hearing how your progress down the path you're heading down.  Thanks again, Jim

Cool. Same here.  The shop owner knows some Mopar hardcore guys he'll reach out to as we get to that this winter. For sure keep the commo going.    roger that!

[Chryco Psycho]

Dfrazz has 3.23 behind his 505 " it is a little soft off the line but not much it just pulls all the way up

[dfrazz]

Dfrazz has 3.23 behind his 505 " it is a little soft off the line but not much it just pulls all the way up

Depends on your definition of "soft"

https://youtu.be/HIYHRgbeYOI

https://youtu.be/UrF7DdJVZFw

[Road_Runner]

Depends on your definition of "soft"

https://youtu.be/HIYHRgbeYOI

https://youtu.be/UrF7DdJVZFw

Gorgeous Charger, definitely pulls hard.

[Chryco Psycho]

It is a balancing act It could pull harder with a lower gear while maintaining traction but it will easily over power the gear & or the traction so needed more gear really only adds more traction problems !!

[todd383]

I have a 489/383 in my car, it has over 600ft.lb Tq,  and I have 355s,  with f60 15 polyglass, it sucks on the hiway, lol, but 1st gear is useless, and I can break the tires loose at 50 mph in 2nd gear, it's an automatic too, but this winter I'm gonna install 323s,  I know a few people with strokers with my setup running 11s with 323s and stockist converters.

[HP_Cuda]

I'd love to run lower gears than 3.23 but it would drive me absolutely nuts on the freeway.

The next jump will be to 3.73 or 3.91 when I get a 5 speed!