Rear Gear Ratios for a Big Block Stroker?

[Road_Runner]

Next question, so again the plan is either a 450 or 489 stroker 383 in the Roadrunner, built 727 and a beefed up 8 3/4 rear, all original numbers matching so to speak.  With either 9" or 10" wide street radials on back, with as much torque as either motor should put out will I still need a 3.91 or 4.10 to launch the big Bird?  I ran a 4.10 in the 70's and could get it to hook pretty hard on large bias ply tires, but I'm wondering if the stock 3.23, 3.55 or at most 3.73 would pull as hard or harder than the smaller 383 did with steeper gears.  I'm sure the tires are the limiting factor off the line, but I still want it to pull up through the gears as insanely as it did back in the day.  I've read other posts here about strokers being built to be "all in" by 5000-5500 rpm, but I've got a set of the CNC Stealth heads to go on and was planning to put a roller hydraulic such as Lunati sells that would hopefully not peak until at least 6000 rpm or more?  I'd love to be able to keep a reasonably highway capable gear in it because otherwise I'm probably going to have to go with a GearVendors or other overdrive.  Anyone here gone through similar decision, what did you choose and how did it work out?

Thanks, Jim

[marc70challenger]

 

Interested in responses and experience.

[1 Wild R/T]

Lot of guys report that 3.23's run within a 10th of 4:10's at the track because traction is the limiting factor...

[Road_Runner]

Lot of guys report that 3.23's run within a 10th of 4:10's at the track because traction is the limiting factor...

With that being the case I'm surprised anybody would run anything steeper on the street, but I guess old habits are hard to break which is kind of the reason for my question.  Back when I was a kid, I actually got better traction on the street with my L60x14's than I did the times I went to the track.  Any idea on what the guys running the 3.23's chose for torque converter stall speed?  I'm guessing no more than 2400-2800?  Thanks for the input, it helps.

Later, Jim

[1 Wild R/T]

2400-2600, use the torque, thats what strokers are really good at... Why build a long stroke then spin it like a small block....

[rUNCHARGER]

Not a wedge but my best street car so far was a 472 hemi in my 66 Coronet with 3.23 gears and a stock Hemi convertor. It obviously didn't 60 foot well but you could drive it out and get into it. It ran very strong and you could run on the highway all day as well. I really liked that setup. It needed better tires not more gear.

Sheldon

[Road_Runner]

Not a wedge but my best street car so far was a 472 hemi in my 66 Coronet with 3.23 gears and a stock Hemi convertor. It obviously didn't 60 foot well but you could drive it out and get into it. It ran very strong and you could run on the highway all day as well. I really liked that setup. It needed better tires not more gear.

Sheldon

My motor will hopefully put out close to what your hemi does especially if I go to the 489 stoker, and I'm considering Mickey Thompson bias ply street/strip  tires for exactly what you say, traction is king.  For launches I used to power brake my Roadrunner to about 2600 rpm with the stock 10 1/2" converter, let off the brake and as soon as it started rolling quickly roll into full throttle.  I never got beat off the line on the street, not once.  But times have changed, modern cars with traction control and similar HP would leave me at the line. I've been playing around with one of the online RPM calculators and it looks like 3.55 gears with my taller 28" tires that I'm currently running are almost exactly the same RPMs at 70 than the F70x14s it came stock with would be with 3.23 gears.  Since I'll probably stick with tall back tires since I like the look, I may go to 3.55 gears and call it a day. 

Thanks, Jim

[brads70]

If most of your driving is street driving than I'd pick a gear that matches your camshaft.  I have a 451" and an OD transmission. I went with 3:55 gear ratio and wish I had went with 3:70 or higher as the engine/cam is not
" happiest" at 60 mph. It likes 75-80 MPH better.  Meaning pick a rear gear that fits your combination/powerband at 60 mph.  Quality tires and the diameter are also a big factor. If off the line performance is your main priority than you still need to factor in your first gear ratio etc... to match your powerband. I have a 3.06 first gear in my combo as compared to 2.45 in a stock 727 so something like 4.10 wouldn't allow me to utilize first gear for very long. 3.73 I figure would have been about right as Dana doesn't have a 3.91 

[Road_Runner]

If most of your driving is street driving than I'd pick a gear that matches your camshaft.  I have a 451" and an OD transmission. I went with 3:55 gear ratio and wish I had went with 3:70 or higher as the engine/cam is not "happiest" at 60 mph. It likes 75-80 MPH better.  Meaning pick a rear gear that fits your combination/powerband at 60 mph.  Quality tires and the diameter are also a big factor. If off the line performance is your main priority than you still need to factor in your first gear ratio etc... to match your powerband. I have a 3.06 first gear in my combo as compared to 2.45 in a stock 727 so something like 4.10 wouldn't allow me to utilize first gear for very long. 3.73 I figure would have been about right as Dana doesn't have a 3.91

My driving will almost always be around town, but to get places around Atlanta an occasional highway blast is usually required, and folks  around here drive 65-70 in the slow lane.   I ran the car with a 4.10 back in the 70's right about the time they went to the 55 MPH national speed limit.  Even then folks drove 65+ and I can remember not loving life revving in the slow lane.  I'd 'like' to pick a gear that  accelerates well but doesn't make the motor scream cruising at 60-70, and all that without adding a Gear Vendors unit like I had been planning.  If that's the only way I can make the motor happy with a hot cam then I'll go with an O/D, but if the 3.73 accelerates well and only adds 155 RPM (3217 at 70 MPH) according to the calculator that could be the sweet spot?

Thanks, Jim

[rUNCHARGER]

I dunno: For me 3.55's suck at 70MPH even with a 28 inch tire. We all tolerate different things though. With a stroker and the right setup you shouldn't need to add a Gear Vendors into it.
A guy near me has a 500 inch Coronet with 3.23. He drives the car 500 miles, installs slicks, races and then drives it back home. That car runs low, low 11's and is truly streetable. That's the type of setup I like.

Sheldon

[brads70]

My driving will almost always be around town, but to get places around Atlanta an occasional highway blast is usually required, and folks  around here drive 65-70 is the slow lane.   I ran the car with a 4.10 back in the 70's right about the time they went to the 55 MPH national speed limit.  Even then folks drove 65+ and I can remember not loving life revving in the slow lane.  I'd 'like' to pick a gear that  accelerates well but doesn't make the motor scream cruising at 60-70, and all that without adding a Gear Vendors unit like I had been planning.  If that's the only way I can make the motor happy with a hot cam then I'll go with an O/D, but if the 3.73 accelerates well and only adds 155 RPM (3217 at 70 MPH) according to the calculator that could be the sweet spot?

Thanks, Jim

I don't think 3:73 would be good for you then.  I'd guess without knowing what cam you will be using that 3:23 or 3:55 might make you happier?  I'd shoot for 2300-2500 at 65MPH factoring in your tire diameter etc...  My problem is I'm only @ 2000rpms at 65 MPH . If your wanting OD sometime in the future then I'd suggest getting a gear to suit that as its not cheap to switch. OD really does make them more enjoyable to drive. 

[Road_Runner]

I dunno: For me 3.55's suck at 70MPH even with a 28 inch tire. We all tolerate different things though. With a stroker and the right setup you shouldn't need to add a Gear Vendors into it.
A guy near me has a 500 inch Coronet with 3.23. He drives the car 500 miles, installs slicks, races and then drives it back home. That car runs low, low 11's and is truly streetable. That's the type of setup I like.

Sheldon

I'd love to duplicate your friend's setup.  Low 11's and 3.23s seems like the best of both worlds.  Thanks, Jim

[Road_Runner]

I don't think 3:73 would be good for you then.  I'd guess without knowing what cam you will be using that 3:23 or 3:55 might make you happier?  I'd shoot for 2300-2500 at 65MPH factoring in your tire diameter etc...  My problem is I'm only @ 2000rpms at 65 MPH . If your wanting OD sometime in the future then I'd suggest getting a gear to suit that as its not cheap to switch. OD really does make them more enjoyable to drive. 

So the calculator has me at 2587 RPM @ 65 MPH with a 3.23.  If I don't decide on a 3.23 or 3.55, I'll probably do as suggest and either go with a 3.91 or 4.10 to work with a future O/D to be added later.

Thanks, Jim

[marc70challenger]

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.

[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.

Very cool, thanks for the link!