Build a stable spring
What does it take to build a better valve spring for USAC National Midget use? Frank Honsowetz of Ed Pink Racing Engines (EPRE) in Van Nuys, California cites a long-term relationship with Steve Pound at PSI Springs as his great starting point.
“We use PSI springs in everything we do, not just in the Toyota midget engine,” he told me. “We have such a long relationship with them and we are able to work together to advance development of our springs.
“I think Steve looks forward to Ed’s input and talking with Ed about different solutions. We’re very cooperative with them because of our long, exclusive relationship. They see all of our parts and see what the springs are doing so they do have a lot of interest in development because they get exposure to our information,” Honsowetz said. The engine builder is on either their sixth or seventh spring iteration since beginning the Toyota project back in 2006.
What they look for in the valve spring specifications for the Toyota USAC National Midget engine is stability and reduction of inherent vibration. “You want everything to be stable. When you take the spring out, you can measure the tension and you want it to look like it’s had a pretty easy life. That is hard to do, very hard to do,” he admitted. “At 9200 rpm, which is where we run these engines, the valve spring opens and closes 76 times a second. That is a very hard life!”
The valve spring in question use a radius rounded at the tips, where the tail wire is squared off a little bit. The spring is a custom unit made specifically for the Toyota EPRE engine; it lasts about 150 miles – or about six shows – and is always replaced on rebuilds, Honsowetz said. “The detail on the ends of the wire is a very important feature of this spring.”
Working with the Toyota 166-cubic-inch USAC mill, “That midget engine needs every drop of power it can get so they do run right on the edge. When you figure in practice, qualifying, heats and feature races, each race is about 25 miles. Each spring gets a general inspection and it might go out for another six,” albeit in another engine.
The double wire spring used in the Toyota USAC National midget engine weighs about 142 grams; a standard 1573D triple spring with a flat damper – one of the more popular off-the-shelf units from this spring supplier – weighs 165.5 grams. In this instance, weight is a factor, one reason why Honsowetz persists with the custom spring from their regular supplier, even though they have tried the 1573D on occasion. The stability and vibration reduction they get with the custom product is superior; the USAC Toyota engine warrants the use of this product.
Written by Anne Proffit.