Had some engine issues so I have dropped it off at the local prformance shop so it can be fixed and ready to cruise this summer. The car is a 68 dart with a 340. Has J heads with 2.02 1.60 valves, roller rockers, edelbrock air gap intake, holley 650 DP, lunati 268 voodoo cam, roughly 9.5:1 compression ( I will have an exact number when engine is finished), non OD 4 speed. Tires are 245 60 15. Just a weekend cruiser. I want to make it a little more cruise friendly and am having a tough time deciding if I should go with 3.55 or 3.23 gears. Would the 3.23's hurt the performance over the 3.55's with that cam choice. Should I rethink the cam. Thoughts and opinions needed. Thanks.
Should I swap the 3.91's for 3.55 or 3.23
- Thread starter duster360
- Start date
-
67Dart273
Well-Known Member
Of all the info you gave us, and that was great, you don't really say the "intended purpose." Are you more interested in loss at launch and low speed, or the effect at cruise, AND how fast you intending to "cruise?"
Here's a mph gear calculator from Wallace racing
http://www.wallaceracing.com/gear-speed.php
Here's a mph gear calculator from Wallace racing
http://www.wallaceracing.com/gear-speed.php
doogievlg
Well-Known Member
3:55 is a great cruising set for me.
Demon 408
Well-Known Member
All right, an opinion question. You will get all sorts of varying responses to this question. Here's mine; a 340 (or any Mopar small block), a 4-speed and 3:55s go together like peas and carrots. I'm running 3:55s with a 4-speed in my Demon with a 408 and I think it is a great combo, and I have driven on long road trips with no worries. Of course it's up to you and what you feel is tolerable. Here are some RPM figures based on your tire size (245/60-15) and the three gear sets:
3.91 @ 65 mph = 3215 rpm
3.55 @ 65 mph = 2919 rpm
3.23 @ 65 mph = 2656 rpm
3.91 @ 65 mph = 3215 rpm
3.55 @ 65 mph = 2919 rpm
3.23 @ 65 mph = 2656 rpm
ir3333
Well-Known Member
i've had them all and it's no contest...3.23 for me
scatpackbee
Well-Known Member
I went with a 2.76 in my 8.75 with a 340 4 speed.
Awesome cruising gear. 2600 RPM at 70 MPH with a 235/60/14 tire.
Just took the car on a 2 hour trip each way to the cottage with my wife, 2 daughters and the dog and it was very, very enjoyable.
Awesome cruising gear. 2600 RPM at 70 MPH with a 235/60/14 tire.
Just took the car on a 2 hour trip each way to the cottage with my wife, 2 daughters and the dog and it was very, very enjoyable.
If you do heavy freeway driving, 3.23's.
More of a mix, street and highway, 3.55
Only street, no highway, 3.91
That's how I'd look at it.
More of a mix, street and highway, 3.55
Only street, no highway, 3.91
That's how I'd look at it.
newby
Well-Known Member
My combo is very similar to yours and I switched from 323's to 355's and like the combo. It works well for both city and freeway.
Tire Size ...... 245 - 60 x 15" ........ 26.6" Tall
Old School .... F70 x 14 ............... 26.2" Tall
Everything points to +3.55's with the VooDoo 268 Camshaft,
if it's the #60403 Bumpstick.
And the Holley 650 Double-Pumper.
Too bad you couldn't get a taller tire.
AJ/FormS
68 Formua-S fastback clone 367/A833/GVod/3.55s
- Joined
- Jan 19, 2014
- Messages
- 25,026
- Reaction score
- 12,373
Post#9
and, I vote 3.23s. Heres why;
1) You have an M/T. If you need more torque on take off, its easy to find.
2) the 268 cam will be at its highest vacuum around 1800 or thereabouts, so for best fuel economy, you will want to cruise a little above that, and lean her out on the low-speedcircuit, and tune the timing to the nuts,The 323s run(see post#4), 44mph at 1800. So you are good to go.
3) The 323s wil let you cruise 8% faster with the same engine noise,vibration, and harshness, than what you could with the 355s.
4) Depending on your exhaust, conversating with 355s, at 70mph, is not really fun. Cruising with 323s will be 10% or better, less frustrating.
5)That VOODOO cam is not very fuel-friendly. The 323s will get the best economy of the listed rears.
and, I vote 3.23s. Heres why;
1) You have an M/T. If you need more torque on take off, its easy to find.
2) the 268 cam will be at its highest vacuum around 1800 or thereabouts, so for best fuel economy, you will want to cruise a little above that, and lean her out on the low-speedcircuit, and tune the timing to the nuts,The 323s run(see post#4), 44mph at 1800. So you are good to go.
3) The 323s wil let you cruise 8% faster with the same engine noise,vibration, and harshness, than what you could with the 355s.
4) Depending on your exhaust, conversating with 355s, at 70mph, is not really fun. Cruising with 323s will be 10% or better, less frustrating.
5)That VOODOO cam is not very fuel-friendly. The 323s will get the best economy of the listed rears.
dano
Evil Handy Man
Your engine, trans and gears are exactly the same as what I had (changing the heads now). That setup gets you out of the hole real fast. Its a fun setup. But yeah, I've considered changing out the 3.91's but I think I'd rather get an overdrive 5 speed and have the best of both worlds.
Engine Combination
* Edelbrock Air-Gap
* Holley 650 Double-Pumper
* Lunati 'Voodoo' 268 {#60403}
Doesn't everything point to a little more RPM's.
Going down to 3.23's may suffocate that 340 during 'around town hopping'.
* Edelbrock Air-Gap
* Holley 650 Double-Pumper
* Lunati 'Voodoo' 268 {#60403}
Doesn't everything point to a little more RPM's.
Going down to 3.23's may suffocate that 340 during 'around town hopping'.
roadrunnerh
Well-Known Member
x2
GEO
Sarcasm Inc.
I'd pick the 3.55's myself kinda the best of both worlds.
Not to big and not to small , but just about right.
But then again my cruiser runs 4.30's with N50 15 M/T tires , fine around town and cruising and short hops on the highway are still ok, but just barely
Not to big and not to small , but just about right.
But then again my cruiser runs 4.30's with N50 15 M/T tires , fine around town and cruising and short hops on the highway are still ok, but just barely
harrisonm
Well-Known Member
The 3.55s are a great choice. That is what I have in my 69 Cuda with a warmed over 340 4 speed. It does work well. However, I had a 340 4 Speed Cuda when I was in college (bought it new in 1969) with 3.23 gears, and it was AWESOME!!It pulled like a freight train, and I rarely got beaten in a drag race. When I power shifted into second gear, I would sometimes gain a whole car length and the in dash ash tray would pop open. I have considered changing my gears to 3.23s many times. You have to ask yourself what your primary goal is? There is no question that the 3.23s will be better for cruising and give you better fuel mileage, and smokey burnouts will still happen at will. But if trips to the track are in your future, then the 3.55s are the way to go.
skep419
5.9 Magnum 4 speed afficionado
I have a 3rd member set up with 3.91's and 3.23's. Everytime I swap the 3.23's they last about a week and the 3.91's go back in. I have a XE284 cam and they do not mix. Way more fun to cruise but out of the hole it feels like I threw out the anchor. I've been throwing around the idea of swapping the 3.23's for 3.55's. I think it would be the best for all around driving.
Johnny Fix-It,
Go with 27" tall tires, and go for the newer ratio > 3.73's.
Johnny likes the 3.73's with the Lunati 'VooDoo' 268* Camshaft.
Go with 27" tall tires, and go for the newer ratio > 3.73's.
Johnny likes the 3.73's with the Lunati 'VooDoo' 268* Camshaft.
-
