putting a toploader behind a sbc blower motor and really cant get a good opinion on which ratios to choose I have the wide ratios in it and its mostly a weekend warrior it has a soild roller cam in it and the power band is from 3000-7000 I have 4.10s in it now not really worried about highway driving Iam just trying to work with what I have and I gotta rebuild it so now is the time to consider a ratio change and also has anyone used the bigger 1 3/8 input with the lakewood bellhousing conversion to sbc lakewood couldnt give me an answer on if the bellhousing can work with 1 1/16 or 1 3/8 input shafts.....thanks
Figure MPH = 10 +221(HP/WT)^0.33 = 133 for 475 HP and 2800#. The formula for 1st gear is LGR = TW x MPH/HP, LGR = low gear ratio TW = tread width e.g. LGR = 8" x 133/475 = 2.24. for slicks, even less for treaded tires. So in this case close ratio. This assumes you have the ideal rear gear ratio. RGR = RPM x TD/(310 x MPH), TD = tire diameter, e.g. RGR = 6000 x 28/(310 x 133) = 4.07. So with 4.10 1st would be 2.24 x 4.07/4.10 = 2.22. If you plan a 10" slick you could use wide ratio.
well that sums it up car is 3400 lbs so I guess I will break out the calculator....Thanks for the help
My blower car seems to like the wide. I'm running a Muncie out of a 70 Pontiac with a Iron mid plate, with a 2.52 first, 3.90's in the rear and a 28 tall tire...
I run a Close Ratio in my 32. Rear tires are 31" tall. Even with the 4.11's it takes a little clutch slip to get going, when it had 3.00 rear gear and a 27" tire it was almost undriveable. For Street/Strip, unless it was a torquey Big Block, I would run the wide ratio given a choice.
I've always heard the same, that wides are better on the street and drag racing. I have a wide ratio SB Toploader that I bought for a street car a few years ago. Sold the car, kept the Toploader. I'm gonna use it behind the blower flathead, I figure the torque band will be pretty flat across through most RPMs, so I don't have to hold it at a real tight RPM, so get the big first gear and don't worry about it. My Galaxie is the complete opposite, close ratio. It might not be better for drag racin', but if I put that big first gear here it would be getting pretty damn squirelly on the street, especially at the slightest hint of moisture. I really like winding out that first gear. The ratios are close enough that you can keep it dead in it's powerband the whole time after you get the RPMs up. Downshift to second into a hard turn, then jerk it into 3, and that'll make you smile.
Simply put Close ratios are for normally aspirated Small blocks which turn 7000 to 8000 and have power all in the top end. This allows you to stay in the power band when you shift. A blower motor would not need this
Provided you run enough gear to get out of the hole and up on the cam if you're drag racing. As covered here before, this whole close ratio thing was started by Chevrolet ROAD racing their Corvettes and wanting a low gear high enough to be usable in the low speed corners. With four usable gears instead of two or three, they could keep the motors "on the cam" coming off the corners, and have less RPM drop between gears also allowing them to stay in the torque band of the more powerful but RPM dependent cams they were using. My 68 Z car, designed by Chevrolet for the same thing, used a 3.73 rear gear and a M21 2.20 low Muncie. With the stock 302 cam it was an absolute pig to drive around town and a joy out in the country where the roads weren't straight. Drag racers quickly figured out if they ran a low enough gear (gear ratios in the sixes weren't unheard of with a hot small block Chev), keeping the motor on the cam was easier for them too, and would actually launch better too, provided they could get the available at the time tires to hook, and didn't blow up the motor from too high a trap RPM.
That's where my close ratio really shines, some spirited twisty drivin'. Not only do the work for high revvers, I only shift my Galaxie at 6500 RPM, but a setup like mine has enough torque to power through first gear, I really do like not having to jump to 2nd as soon, it's nice build up some speed in a long first, then pop to 2nd and really stay right in its sweet spot. It's been a while since I had her out, but you can get goin' pretty fast in first. When it's rainy here, everyone drives like it's the end of the world, The speed limit to my house from my office is mainly 45, people slow down enough I've driven all the way home in 1st. Once it's hit its powerband, the close ratio gears let me stay right in it. Really makes it alot of fun to drive. But I definitely agree with the wide ratio for draggin', it just makes logical sense. I figure it's going to make a real nice companion for my flatty.
Lots of videos on youtube of cars launching at the strip Lots of cars pulling the wheels up on the first gear then falling on their face trying to make the jump to lightspeed and pull second. I don't know what they're running but it doesn't look like fun. Looks more like when you say hi to someone and then they turn their head and trip.
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