Help on gear selection - 3.55, 3.73 or 3.91 for 727

[Playtimefun]

Good day all

I have a 1973 Cuda which I am rebuilding the motor for the 3rd time (unfortunately the 2nd go around lasted only 1250 miles and the last hour resulted in spun bearings). So, its a 340 thats been bored 0.060 over. Edelbrock RPM cylinder heads, Comp Cams Xtreme Energy 224/230 Hydraulic Roller Cam, KB hypereutectic pistons. 2400 B&M convertor. Compression should be right at 10:1 and lastly... I just picked up an Edelbrock Pro Flo 4 EFI for it. Because the last go around... the car started beautifully when cold or boiling hot. But say stop and have supper somewhere for 1.5-2.0 hrs and it was almost impossible to start. It was so bad, that there was no way the wife could drive it and I had issues barely being able to start it. Hence the Pro Flo system. Also planning on once the engine is done, putting in a 2300 watt stereo system because the 16 year olds on my street are wayyyyy too quiet and well behaved!!!

Here's the question folks... the 727 (3 speed automatic) has been rebuilt and is damn near bullet proof now. But I have 323 gears in a 489 case. The rear tires are 275/50R15 (25.8" tall). The car (before the motor let go) would FLY!!! I had no problem burying the speedometer past 150 mph, but I would not take it past about 154-157 according to my GPS speedometer app on the phone (which matched the rebuilt speedometer). BUT... you could not smoke the ties to save your life and that was embarrassing as heck to me. I mean if got them going because of dust on the road, or around a corner... GREAT. I could keep them going. I don't do much highway cruising, mostly its around the city, but I do like to open it up. I do a lot of street light to street light FAST and I have a couple of street lights where its basically 1/8th mile and have fun. So the question is... since i have the car ripped apart... its time to maybe get rid of the 323s and get something higher. But the car seemed to already rev pretty high just driving at 65 to 70 mph on the freeway sort of thing, but i dont recall what exactly the tach was showing. Perhaps the TTI exhaust just made it feel louder and working harder than it should have been??? I would like to make 2 trips with the car. One to a tennis tournament thats 2.5 hours away because the city has an awesome car scene as well. And perhaps to take it to another car show 3 hours away because there are tons of Dodge and Plymouth cars at that show.

I should add that when checking the gear oil, it seemed like i might have some shinny parts in it. So I am thinking that maybe... its getting close to going?

Recommendations on... stay with the 3.23s because even though it can't spin a tire but it sure gets up and boogies fast on the highway. (It is ideal for seeing torsion bars in action.) Go to 3.55s or 3.73s and hopefully have a bit of both worlds? Or 3.91 since most of it is city driving?

I will add that I don't care about gas mileage. When I take the car for an ice cream cone at Dairy Queen... that cone now winds up costing me about $65 or more. $5 for the cone, $30 in gas and $30 in tires. But the smile eating that cone and sitting in the car is as good as it gets!!! Thanks guys and gals!!!!

 

[Chryco Psycho]

I would stay with the 3.23 & increase the stall in the torque converter better for fun & driving IMO
Extended runs at 150 mph may be starving the engine for oil , , I would look into improving the oiling system for High rpm , a wider oil pan can increase capacity & a High volume pump will help also there are internal tricks suck as connecting a line across both lifter galleries under the intake to help as well as fulll groove main brgs .

 

[Gumby]

I would stay with the 3.23 & increase the stall in the torque converter better for fun & driving IMO
Extended runs at 150 mph may be starving the engine for oil , , I would look into improving the oiling system for High rpm , a wider oil pan can increase capacity & a High volume pump will help also there are internal tricks suck as connecting a line across both lifter galleries under the intake to help as well as fulll groove

Is a 392 oil pan wide enough?

 

[MoparCarGuy]

I have never seen a Cuda 340 that could not spin the tires with a 3.23 gear.
Are you absolutely sure that you have 3.23's installed?
Is it possible you have a 2.91 or a 2.76 in there?

Going to a 3.55 and a higher stall torque converter would help. Any higher, say 3.91's, and you will be driven crazy with the RPMs on the highway for any extended trip. Adding a GearVendors overdrive or a TF518 transmission can give you the best of both worlds.

 

[Dodgeboy]

If you just wanna spin the tires then go 3.91's, but if it used to spin and now it doesn't then I would check things over. A higher stall converter might fix your problem (that made a huge difference for me), did your kickdown lingage go out of adjustment? Timing out-to-lunch ?

 

[Chryco Psycho]

Just using a higher stall to allow the engine further up into the powerband will get the tires spinning .
Tuning the engine to get the peak out of it is a must as well , the 340 is not a high tq engine
Overdrive is another good option .
I am not familiar with the #392 oil oan but Milodan makes a wider road racing pan which is far more preferable on the street over a deep pan .

 

[Playtimefun]

Yep... I have checked the gears and they are definitely 3.23s.

The tires are 275/50R15 so I have always assumed that it was a combination of tire width and perhaps soft shocks (as I think they are factory) That results in the car just squatting down and basically putting the power down to the ground.

Unless... when everyone is talking about smoking the tires... I have assumed that you are not doing brake stands? I have a hydra tech brake system on the car and it works tremendously well. Best dollars I have invested in the car. But without some dust or water on the ground, or going around the corner because of the sure-grip, the tires just grab.

Showing off in terms of stop light acceleration is impressive, but the only sqwak of the tires happens from 1st to 2nd as you get a chirp of the tires but otherwise its going.

 

[Playtimefun]

I had a transmission shop check the kickdown linkage and they thought that it was adjusted perfectly. I have a Lokkar (if I remember the name) cable kickdown linkage. So easy to install and adjust.

 

[Dodgeboy]

Just gonna put this out there: you could install line-lock on the front brakes using a toggle switch. Activate the line lock and just step on the brake peddal, just enough to get the car to start slowing down, then hammer on the gas. Once your satisfied with your burnout just turn the linelock off. Spinning an't winning but long burnouts are cool

 

[blubyou340]

Good day all

I have a 1973 Cuda which I am rebuilding the motor for the 3rd time (unfortunately the 2nd go around lasted only 1250 miles and the last hour resulted in spun bearings). So, its a 340 thats been bored 0.060 over. Edelbrock RPM cylinder heads, Comp Cams Xtreme Energy 224/230 Hydraulic Roller Cam, KB hypereutectic pistons. 2400 B&M convertor. Compression should be right at 10:1 and lastly... I just picked up an Edelbrock Pro Flo 4 EFI for it. Because the last go around... the car started beautifully when cold or boiling hot. But say stop and have supper somewhere for 1.5-2.0 hrs and it was almost impossible to start. It was so bad, that there was no way the wife could drive it and I had issues barely being able to start it. Hence the Pro Flo system. Also planning on once the engine is done, putting in a 2300 watt stereo system because the 16 year olds on my street are wayyyyy too quiet and well behaved!!!

Here's the question folks... the 727 (3 speed automatic) has been rebuilt and is damn near bullet proof now. But I have 323 gears in a 489 case. The rear tires are 275/50R15 (25.8" tall). The car (before the motor let go) would FLY!!! I had no problem burying the speedometer past 150 mph, but I would not take it past about 154-157 according to my GPS speedometer app on the phone (which matched the rebuilt speedometer). BUT... you could not smoke the ties to save your life and that was embarrassing as heck to me. I mean if got them going because of dust on the road, or around a corner... GREAT. I could keep them going. I don't do much highway cruising, mostly its around the city, but I do like to open it up. I do a lot of street light to street light FAST and I have a couple of street lights where its basically 1/8th mile and have fun. So the question is... since i have the car ripped apart... its time to maybe get rid of the 323s and get something higher. But the car seemed to already rev pretty high just driving at 65 to 70 mph on the freeway sort of thing, but i dont recall what exactly the tach was showing. Perhaps the TTI exhaust just made it feel louder and working harder than it should have been??? I would like to make 2 trips with the car. One to a tennis tournament thats 2.5 hours away because the city has an awesome car scene as well. And perhaps to take it to another car show 3 hours away because there are tons of Dodge and Plymouth cars at that show.

I should add that when checking the gear oil, it seemed like i might have some shinny parts in it. So I am thinking that maybe... its getting close to going?

Recommendations on... stay with the 3.23s because even though it can't spin a tire but it sure gets up and boogies fast on the highway. (It is ideal for seeing torsion bars in action.) Go to 3.55s or 3.73s and hopefully have a bit of both worlds? Or 3.91 since most of it is city driving?

I will add that I don't care about gas mileage. When I take the car for an ice cream cone at Dairy Queen... that cone now winds up costing me about $65 or more. $5 for the cone, $30 in gas and $30 in tires. But the smile eating that cone and sitting in the car is as good as it gets!!! Thanks guys and gals!!!!

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That's a wide open question. It all boils down to what you want to do that day! I have a high rear gear in my chall. I like it myself. I can cruise @ 90. Very smooth and low rpm and gas peddle its a 71 340. I think if i were in your shoes i would convert to a 4 or 5 or even 6 speed then you could have fun pull the fronts and cruise my 2 bits its what you want man have fun i really like your car even know im not big on yellow .but there ya go its what you want theres so many diff things you can do in this day and age cool car thats what makes us mopar gearheads tic baby have fun your gonna do the right thing or is the really a right? Do you dude. Have funnnn!