Help with Rear end gear ratio

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gipperco

gipperco

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I am building a bracket car for my wife. 1974 Dart Swinger. Strip only. I have a set of Good Year 30x10.5x15 that I will be putting on it. It will have an 8-3/4 housing, 727 Trans and a Mild 318 to start to get her some seat time. The goal is to get her seat time this year and then build a 360 for some HP to get her into the low/mid 11's. I am planning on doing a Spool but have no idea what gear ratio to use. I have been told 411's and I have been told 430's anybody have some advice that I can sort this out. If you need more info that I have not provided please just ask.

Thank you
 
Do you have any idea how many rpm's you will plan to push the 318 ?? My son uses 3.91's in his Dart with a 400 and he has 26" tall tires. He was shifting at 6400 and trapping at 6500. But last time out he was pushing it to 6800 and ran his best so he needs more gear but its a street car. My 63 has 4.30's and I run a 29" tire. I shift about 6100 with my 440 and trap about 6300. Depending on the heads and cam you use will have alot to do with the rpm the 318 will pull. I would say with a 30" tire I would run 4.30's or even 4.56's. Ron
 
With a small block and a 30" tire you are going to want lots of gear. I would run either 456 or 488s.
 
not sure what it will be at. It basically is stock 1987 318 With the swirl ported heads, factory roller cam, and an Edlebrock Performer intake. It will have headers. Not putting a lot into this motor as I said it is just a seat time/experience motor at this point. I figure we hopefully will be mid/high 12's
 
gipperco said:
not sure what it will be at. It basically is stock 1987 318 With the swirl ported heads, factory roller cam, and an Edlebrock Performer intake. It will have headers. Not putting a lot into this motor as I said it is just a seat time/experience motor at this point. I figure we hopefully will be mid/high 12's
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Are you going to re gear it when you build the 360 ? What are you goals as far as ET with the 360 ?
 
Not to spoil your day, but that mild 318 will not push that car below 14's. I wish you the best in your build, but be careful to not overtire the car. Like stated above you will more than likely need to regear later for a more substanial build. I would rec'd going to a 26x9 tire and a 4.10 gear. That combo will easily move an A body to low 11's and not have traction problems if you do the rest of the suspension correctly. Just to give you an idea, at 3400lbs race weight you will need approx 480 hp to accomplish mid 11's
 
E T with the 360? We are hoping to be in the mid high/mid 11's when all said and done. As for regearing for the 360 build, would really like not to have to do that. Even if it means that it doesn't perform the best right now. We are only looking at running the 318 for 1 season like I said originally just to get her some seat time and to save up some cash for the 360 build up. If it only runs in the 14's like Aquick408 says so be it. I have been told differently so I don't know. Which is part of the problem. I have been crewing on Blown Injected Funny Car for the last 2 years and this is a whole different ball game.
 
3.91 to 4.30 will work great in both applications. With the 318 a really loose converter will help some so the little teen doesnt bog and will work great when you step up.Also both these will work with a stout 360 and you will be able to run a nasty cam between 3000 to 6500 rpm in its power band
 
okay guys, I have everything from 3.91's to 4.88's. I already have the 30" tires so I don't want to have to buy another set. I got these for 50.00 and they only have 10 runs on them. So I really need to come to some sort of resolution here. In a perfect world I would like to only have to buy one set of gears. I was planning on running a 5500 stall, and a trans brake. Haven't decided if I am going to use Super Stock Springs or CalTracks. I like the dollar figure on the Springs vs CalTracks.
 
Gipper I agree with Aquick408, I think you need to rethink tire size and your 318 build. A good running factory 340 with a 3.91 gear will usually only turn high 13`s. If you`re building a bracket car for your wife though, the key is to make a reliable car that`s consistent. That way she can get plenty of runs in and a feel for doing her burnout, staging, cutting a good light, shifting at the right point ,keeping the car in the groove, and doing all of those things within a 10th of a second on every run. She can learn that at 11 or 14 seconds at a time,either way it`s good practice. One thing you can do and won`t cost you anything (this is if the car is for racing only) is to remove as much weight from the car as safely possible. From there I would think a 3.91- 4.10 gear with a 26-28" tire would be more realistic with a mild 318. A converter with about 2800 stall would help as well. A decent set of headers, bigger cam, hot ignition, better intake ,and carburetor should wake up that 318 some and get it into the 13`s. Keep us informed. Good luck and have fun!
 
I dont know what combination you are going to build but will tell you my combo. It is a 360 W5 engine that runs 10.59 at 127mph at 3000lbs. I am running 31x13.5 tires with a 4.56 gear, shifting at 6200 and crossing the line at 6500. When I put my 28" tires on I would cross the line at 7000 with same shift points. If you already have the tires I would go 4.30 or 4.56 gears. I am planning on trying a 29.5" tire next time I buy some.
 
I'd go 4.56 or 4.88's with a 30" tire. You're never going to hit 11's with a mild
318 but it will get you off the line. Besides , it will be the gear you'll want to use for you're future engine unless you build a stroker.
I used to have a link to a site called automath.com . It has a bunch of templates for calculating shift rpms, tire sizing etc....
 
If you only want to buy one gear then use the 4.56's. It may be a bit much for a stock headed 318 but should work well with the 360.
 
i run a built 360 in my duster.full steel body and full interior.ran 11.60's with a 3.91 gear.turning around 6500rpm trap.i put a set of 4.30s in the car the the same 28x11.5 tires.the car is turning 7000 trap rpm.i gained 0 time in the 60',1/8,or the 1/4.i am putting the 3.91 back in the car
 
74360duster said:
i run a built 360 in my duster.full steel body and full interior.ran 11.60's with a 3.91 gear.turning around 6500rpm trap.i put a set of 4.30s in the car the the same 28x11.5 tires.the car is turning 7000 trap rpm.i gained 0 time in the 60',1/8,or the 1/4.i am putting the 3.91 back in the car
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But his tires are 2" taller. Hes going to need more gear to rum mid 11s with a 360 and a 30" tire.
 
What 74360duster is true. The 360 has a very flat torque curve so the RPM spread in which it works is pretty wide. The 318 however is much narrower and needs to be twisted higher.
 
Check out the Richmond Gear website. They have a gear/ET calculator that gives you great info.
 
4.56 would be what I would run if I were doing what you are, we run a 30 in. tire ,shifting 6000, traps 6300-6400 W 4.30 gear 10.52 1/4 @ 127 mph
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