Best Gears for a 408 Stroker?

-
72DartGuy said:
Hi! I have an edelbrock on there, but I’m not getting enough fuel to it! It’s draining the secondaries when you stomp it on the freeway. Fills back up on the street. Weird. I did order 3:23 gears
Click to expand...
It's not that weird. It's not enough carburetor. You may not have an adequate fuel supply, but even when you get that fixed, it's still not enough carburetor. I think a 750 would be right in there for the street.
 
I have a 408, both 3:23 and 3:73 gears. The 3:23’s are more street friendly but it loses a lot of the snap. I don’t drive hiway much so use the 3:73’s. There’s calculators online where you can punch in gear ratios, tire size etc to see if 3:55’s rpm would work for you. That’s probably what I would get if I did it again
 
RustyRatRod said:
It's not that weird. It's not enough carburetor. You may not have an adequate fuel supply, but even when you get that fixed, it's still not enough carburetor. I think a 750 would be right in there for the street.
Click to expand...
I didn’t think about that. I thought a 650 would be economical. Man, this is my first Mopar build. I’ve learned more in the last 18 months than I ever learned working on Chevys for the last 45 years
 
Less gear, less snap. No way around it. 408's like to windup, so you will lose some grunt, but you and the engine will be happier. I had a 408 with 3:73's and a 4-speed and I liked it but, the highway was a problem. 3:23's will help but... .. "IMHO" without knowing your setup, a well tuned 750 should do you for your street car .. subject to disapproval of course :) :)
 
44070dart said:
Less gear, less snap. No way around it. 408's like to windup, so you will lose some grunt, but you and the engine will be happier. I had a 408 with 3:73's and a 4-speed and I liked it but, the highway was a problem. 3:23's will help but... .. "IMHO" without knowing your setup, a well tuned 750 should do you for your street car .. subject to disapproval of course :) :)
Click to expand...
Thanks! I’m dialing it in. I’ve spent extra money more than once here. It’s killing me, but in the end I should have a sweetheart of a ride!
 
Yeah, a 408 in a Dart is sweet. Sold mine to a member here, regretted it since it rolled down the street with him... Good luck.

thumbnail_DSCN3244.jpg
 
72DartGuy said:
Hi! I have an edelbrock on there, but I’m not getting enough fuel to it! It’s draining the secondaries when you stomp it on the freeway. Fills back up on the street. Weird. I did order 3:23 gears
Click to expand...
a 750 holley with vac 2ndaries would probably suit you just fine and retain some nice street manners...
 
Mopar put 3.23s in a lot of high performance cars. That's cause it is an excellent compromise gear. (That's also why 2.94s and 2.76s are hard to find. NOT intended for performance). A 4000 converter with 3.23s will leave harder than a 3.73 with a 2500. A GOOD 3500 will drive like a stocker.
Mind if I ask a question? If economy and freeway flying is important, why build a 408? Sounds like a 318 would suit.
 
If we were closer I would trade you a ready to bolt in center section 3.23 489 sure grip for the 3.73, I also have a 2.74 but it is in a 742 case.
I like low gears, only one main highway thru WV, so I drive mostly back roads.
 
33IMP said:
Mopar put 3.23s in a lot of high performance cars. That's cause it is an excellent compromise gear. (That's also why 2.94s and 2.76s are hard to find. NOT intended for performance). A 4000 converter with 3.23s will leave harder than a 3.73 with a 2500. A GOOD 3500 will drive like a stocker.
Mind if I ask a question? If economy and freeway flying is important, why build a 408? Sounds like a 318 would suit.
Click to expand...
Kind of a long story. I started with a 340 block that I planned on using. Turns out it was garbage. Bought a 360 short block intending to make it stock. My motor guy said it was a nice looking anchor. Basically a junkyard block with blue paint on it. They took it back, so then lockdown and I could only find the 408 short block. This build has been a nightmare. Thank god I love the car!
 
Hey. 66 Dart, 408, 680 holley, 3:23 gears, Gear vendor, in San diego Area. Had 3:55 gears. Was snappier. But not what I was looking for. With GV final gear is 2:91. It gets 22 MPG at freeway speeds. What I was looking for... And no slouch...
 
Mopar Tim said:
Hey. 66 Dart, 408, 680 holley, 3:23 gears, Gear vendor, in San diego Area. Had 3:55 gears. Was snappier. But not what I was looking for. With GV final gear is 2:91. It gets 22 MPG at freeway speeds. What I was looking for... And no slouch...
Click to expand...
Full roller engine, Rhodes roller lifters, Magnum based. Really works well for a street engine/HP engine. Research them. Full lift at 3K .
 
33IMP said:
Mind if I ask a question? If economy and freeway flying is important, why build a 408? Sounds like a 318 would suit.
Click to expand...
i don't understand why people leave gearing and stall as an afterthought, a 408 with 3.73 will have similar torque to the ground as a 512 with 2.94 gear, on a street car most will self impose a gear and stall limitation, just build for it not against it. With all these displacement and power adder options easy to build lot of hp at street speed rpm. 1500-4500 rpm.
 
72DartGuy said:
Hi guys, I have a 408 Stroker in my 72 Swinger. I gave a 489 rear end with 3:73 gears. I’m pushing 3500 RPM at 65mph. Not good! What’s the best gears for both street and freeway? 3:23’s or less? Thanks for the help!

View attachment 1716075887
Click to expand...
72DartGuy said:
Help! I’ve got a 8 3/4 rear end with a 489 case and 3:73 gears. I’m pushing 3500 RPM at 65 MPH. That’s not workin for me. What should I put in there? I’d like it to be snappy on the street, and I’d like to be able to drive it on the freeway. I gave a 408 Stroker with a 650CFM carb. What’s the best gears for this? Thanks guys!

View attachment 1716075892
Click to expand...
You should be doing around 75 mph at that rpm. 35-3800 rpm 75-80mph.
We would need to know how small the cam is to determine how numerically low your setup can get away with. Off the bat I would toss out not going less than 3.55... but that doesn't account for your combo.
 
sireland67 said:
If we were closer I would trade you a ready to bolt in center section 3.23 489 sure grip for the 3.73, I also have a 2.74 but it is in a 742 case.
I like low gears, only one main highway thru WV, so I drive mostly back roads.
Click to expand...
That would have worked! Of course we couldn’t be farther apart, lol
 
273 said:
i don't understand why people leave gearing and stall as an afterthought, a 408 with 3.73 will have similar torque to the ground as a 512 with 2.94 gear, on a street car most will self impose a gear and stall limitation, just build for it not against it. With all these displacement and power adder options easy to build lot of hp at street speed rpm. 1500-4500 rpm.
Click to expand...
I agree with the above. and I think that every street build should begin with the gearing question already decided. Doing it the other way, may force your engine into an unpleasant box.
If I had a 408,
it would have a A518 behind it, with ratios of
2.45-1.45-1.00-.69od and I'd get me some gears to cruise in the range of 2000 to 2400 at whatever hiway speed I tend to drive, which, in Manitoba is mostly ~65 mph. That would be ~4.30s.
This would make my starter gear 4.30 x 2.45=10.54, which is ludicrously large, for an automatic but Ludicrous Gear will be fine with the stock stall and, this 4.30 combo makes a reasonably nice Second gear of
4.30 x1.45=6.24 which will get me 65@5600. After that, I don't care.

The A518 has regular splits of;
.592-.69-.69 / Since I am a streeter, that .59 is the one that I gotta live with. If my shift rpm was to be 6000, then .59x 6000=3550@41mph is the rpm at which Second gear will begin, so my 408 is gonna have to have some balls at 3550@41 mph; so this then dictates the cam, which dictates the DCR; while reving to 6000 still pulling, governs the head choice.
I mean if I had a 408
 
I would never go below a 3.23 on anything. Just lose way to much acceleration. 3.23s and a 255 60 15 would work fine. They are 27in. Tall
 
72DartGuy said:
Hi guys, I have a 408 Stroker in my 72 Swinger. I gave a 489 rear end with 3:73 gears. I’m pushing 3500 RPM at 65mph. Not good! What’s the best gears for both street and freeway? 3:23’s or less? Thanks for the help!

View attachment 1716075887
Click to expand...
I like a 3.55 gear with an OD transmission. The 3.23 gear would also work well with the OD and your 14" wheels. Get highway cruise RPM down to the 2,000 range to reduce noise and wear as well as most likely boosting economy.
 
Dale Davies said:
I like a 3.55 gear with an OD transmission. The 3.23 gear would also work well with the OD and your 14" wheels. Get highway cruise RPM down to the 2,000 range to reduce noise and wear as well as most likely boosting economy.
Click to expand...

EDIT: I will start a different thread. I shouldn't hijack this one. "Nevermind" :)
 
You must log in or register to reply here.
-

Back
Top