Daily Archives: January 21, 2021

I made the Sprint-T heavier

It wasn’t by much, but the 31″ radiator is slightly heavier than the radiator that ships with the Speedway complete kit when empty. But when filled with coolant there is a large difference between the two, roughly 25-50 pounds (10-20 Kg). This means I have to raise the weight on the starting line to about 1950 pounds from 1900 with me and a half-filled race tank of gas. 

I have been keeping a running estimate of the weight on the starting line as the design progressed over the years from basically the Speedway kit with “square” tires (all 4 tires the same size), to the current race car that is barely mostly street-legal. Now the on-the-street weight has gone up a bunch as things like fenders and bumpers and aerodynamics have been added to the street part of the build. I’m currently looking at about 200 pounds of junk removed from the car at the track to get ready for racing, plus a much larger gas tank and of course, more gas at 6.5 pounds per gallon. The race tank holds as much as 3 gallons of E85, but the street tank has room for 22 gallons of pump gas. That’s an extra 350 pounds full of gas for the street version of the car or about 2300 leaving for a trip, compared to 1950 on the line.

The kit is listed as 1700 less driver with a half-tank or 8 gallons of gas with a small-block Chevy and a TH 350 transmission. While the LS is significantly lighter, the 4l60e transmission is about as much heavier, and there is a lot more metal in the exoskeleton roll cage/frame and full bellypan of the Sprint-T than the simple ladder-and-crossmembers of the kit, and there is exponentially more resistance to twist in the Sprint-T frame than there is in the kit, and not just because there is more metal but because of where that extra metal is. For an explanation look up Herb Adams’ excellent book on the subject. It graphically demonstrates the difference between a ladder frame and a full roll cage tied into a space frame. Anywho, that’s where a lot of the increase in weight comes from. Between the pontoon fenders for the street version and bumpers and the kit’s headlight brackets also being the front shock brackets the Sprint-T has a bunch more junk in street trim, and a bunch more frame and brackets either way. Not making excuses, just stating facts.

Look at regular buckets trying to autocross at Goodguys’ and you can see what I mean. They jack up the inside rear wheel during hard turns, and try to swap ends if they haven’t gotten completely straight before applying the power exiting a turn. https://www.youtube.com/watch?v=GozWIbIetMo&ab_channel=TylerGibson