Daily Archives: December 17, 2018

It might happen

I have been watching Facebook and catching really cheap SBC engines and corresponding transmissions. Cheap as in $350 for a running engine and $500 for a rebuilt transmission. Or a mostly-built complete powertrain for <$1000. I might even be able to compete equally at Goodguys with it against the pro builds, if I get the suspension sorted properly. Even with an iron block and iron heads, and what they call an “RV” cam which is what most rebuilds get because they’re cheaper than a stock replacement cam when the cam is worn out, the power to weight ratio will still be sufficient to fry the tires if I put too much pressure on the right pedal. At this point I know I will need to dial the suspension a bit on the “tight” side (understeering), because I can get sideways (“loose”) with pressure on the “loud” pedal. This is called “power oversteer”.

Also the extra weight will help with the ratio between the spring/unsprung weight I brought up in an earlier post talking about the weight of the front axle assembly compared to the total weight of the mid-engine version of the car. Basically I need to get the weight distribution as close as possible to 50/50 because of how heavy both axles and associated elements are. There is only so much I can do for the rear axle, basically go as light as I can with brakes and brackets, but there are limits because I need to get a rear axle from a full-size car or pickup truck, and the parts have to fit and work with that. Even a relatively puny V8 build will destroy all the lightweight rear axles I can get in local junkyards, just look at what happens to Gen3 Camaros with the factory 7″ ring gear axle that started its production life under the 2.3L 4 cylinder Vega from the ’70s. Even with the OE 305 engine good grip and a heavy foot would cause broken differentials, ring gears, and pinions, what have you it probably broke on the V8 Gen3 Camaro. And for those thinking that won’t be a problem with the Sprint-T as light as it is, the load is independent of the weight of the car to a large extent, being mostly determined by power applied and grip. And grip is more dependent on tire choice than applied weight, and is highly dependent on where on the grip curve the particular tire is for the applied load. Which brings us back to tires being the most important choice in the design process…

So, there might be a budget to build the Sprint-T with an SBC and automatic transmission after all.