Gear ratio recomendation

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elitesrock2

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I've got a 69 dart custom right now i'm gonna have going this spring. It will be a 340 4 speed car with 26 inch tall tires. 340 is .040 over with solid roller .654/.655 lift 302/309 269/276 at .050 on a 106 LSA x heads, peak power is at 6700 rpm currently. 11.5 to 1 compression. super victor intake 850 demon carb. Will be running a 742 case 8 3/4. looking for the best gear ratio for alot of street driving rarely going to the track. I work in a different state which is a 35 mile drive and would like a good cruise rpm for 60 mph. What would you guys recommend? From what i've researched a set of 3.91s puts me at 3000 rpm at 60 with this car. This engine isn't exactly street friendly but anythings streetable if you're gutsy enough
 
I would consider 3.91s as an absolute minimum. More like 4.30s.
 
Yeah it is. I run around with a guy that's got a 65 coronet 426 wedge tubbed with a dana 60 rear 4.56s spooled and runs it all over town. car tuns 11.24
 
If you have big enough tires, a spool on the street isn't that bad at all.
 
I had 4.56s for a very short time in my 340 Barracuda. It came that way. The guy I bought it from 25 years ago was going to race it. After I finished restoring it for the first time about 22 years ago, I drove it for a while with the 4.56 gears. I could not stand to drive it on the highway even from one side of town to the other. The revs were WAY too high. To each their own, but I'd think a 35 mile drive at close to 4,000 RPM would be very uncomfortable. I run 3.55s now.
 
This is one of those situations where we wants it all (ex. kick *** street/strip performance, highway drivability, etc.) and the rest of us chime in with suggestions but we tend to lean one way or the other (usually not towards the saner side). ;). As I (and others) have always said, cars (and all of there subassemblies should be purpose built. If this is the main/only means of transportation and there is 35/70 miles daily highway commute (and given the engine specs and that it is a 4-spd), I personally wouldn't go steeper than 3.91s. Of course, the upside to our 8 3/4s, is that it's a cakewalk to switch out third members so if there's some business that needs to be handled on the street/strip, kerplunk those 4.56s in and go get some. Just my .02.
 
With what your trying to do 3.91s as they are a good street gear with performanve in mind. I ran this with my built 346/727 mostly street. 20 to 30 miles daily for a long time and around 18 mpg. New engine is getting 4.30s though lol. (Tunnel rammed 416, with 4 spd is the "plan")
 
When I was reading through your thread I was thinking 3.91's if you want a steeper gear than that and the car is a keeper and the budget allows then why not go with a gear vendor's. It's strong enough and you have an O/D. Then the car won't beat you up when you drive it around town.
 
269/276 at .050 is a VERY radical cam for a 340 that will rarely see the track. I would backup on the cam. A bunch. like 20 degrees or more.
 
If you got the 4.56.... Thats what I would go with... And go as tall and wide of a tire as you can get away with..My second choice would be the 4.30... Just my 2 cents...
 
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