MERRY Christmas, readers, and happy New Year.
Hats off to all the people who participated in Hot Rod Drag Week in the US and our own Street Machine Drag Challenge here in Australia. What a fantastic effort. It’s great to see real street cars that get driven in the heat and through rain on real roads and then go racing; they are putting the ‘street’ back into street machine!
Last issue I stated that if I was a millionaire and could have any car I wanted, it would be Sonny Leonard’s street-driven, 840hp 615ci ’57 Chevy. And looking back at the cars I’ve owned, I loved my 396 big-block ’57 Chevy A/MP-class drag car and 265-cube Blue Flame six ’57 tow car. The popularity of tri-five Chevs is growing, so here are some thoughts on building one.
First of all, 11.0 seconds is the ANDRA cut-off before a steel rollcage, side intrusion and taxi bars have to be fitted. For a daily-driven street vehicle, it makes sense to limit a car to run 11.0s or slower, especially if you want to carry passengers in a two-door. If I was going to build a sub-11-second, street-registered ’55- ’57 Chevy I’d choose a four-door body, as the cab is structurally stronger and passengers can still get in and out of the back even with a ’cage fitted.
Tri-five Chevys might look big and heavy, but they are a lot lighter than they appear. My old rat-powered shoebox only weighed 3200lb, so a total weight of 3600lb for a comfy, airconditioned, power-steering cruiser is not unreasonable. And it only takes 480 Moroso horsepower to run 11.0@120mph at 3600lb.
To run flat 11s, an LS small-block is the obvious choice, but there’s also nothing wrong with an old-school, 23-degree smallblock under the bonnet. With the high-flowing alloy or cast-iron heads available these days, it’s very easy to make 480 Moroso horses with a 23-degree-headed small-block Chevy.
I particularly like the Aussie-made Racer Pro heads, and I’d probably build something like a 383 stroker from a 010 four-bolt block with 10.5:1-compression forged pistons and a 3.75-inch crank, or buy a short 383 crate motor.
Another option is the 400ci small-block truck motor. The humble 400 is often overlooked in the performance world because of its siamesed bores, cast-iron crank and twobolt mains, but they make wicked street/strip engines. They’re like a poor man’s big-block in a small-block package.
If I went the LS way, I’d go for a 427 LS crate motor with a small 218-degree intake/224- degree exhaust/110-degree LCA cam. It would be super-reliable, good on fuel and lighter than a big-block. I’d replace the factory EFI with a single four-barrel manifold and throttlebody.
Fitted with a Moroso-type air filter, it would look like a traditional carburetted engine, sound good out the exhaust with the small hydraulicroller, and go very close to an 11.0.
Big-blocks in tri-five Chevs fit like they belong there. There’s a smorgasbord of big-block crate motors available that will push a mid- 50s shoebox into the 10s or quicker easily.
Power is only limited by how fat the wallet is.
But one of the issues when fitting a big-block is the pipes. Despite ’55-’57 Chevs having a much larger engine bay compared to many
other cars, a really good 632-cube, 1200hp crate engine could lose 100-200 horses simply because the pipe diameter, length and collector are compromised to fit inside the stock inner guards and frame rails. Another consideration is the extra weight of a big-block. A lighter smallblock will sit further back and is better for weight distribution, and will be easier to hook up.
Speaking of hook-up, big, wide, fat rear tyres look cool on any car from hot rods to late-models, but without some rear-end mods, a 275 tyre is about all that fits under a stock tri-five’s rear guards, as the leaf springs are mounted on the outside of the frame rails.
That’s unless you ‘retro’-radius the guards, like the ’55 in Two-Lane Blacktop or Dennis Taylor’s wheelstanding ’55 (SM, Dec ’17, p71) for that nostalgia gasser look.
If 11.0 is the limit, a 275 drag radial on a prepped track will be more than enough rubber to hook up. There are really good adjustable shocks available these days for both the front and back, and I reckon I’d ring up the Gazzard Brothers and ask for a set of their shocks. I’d fit Moroso coil springs in the front and slapper bars in the rear. I know CalTracs work really well, but I think with adjustable shockies the slapper bars will launch consistently with the drag radials.
So what if you wanted to go quicker than 11.0, and were prepared to do whatever it took to meet all the ANDRA safety rules in a streetdriven shoebox? The stock tri-five’s rear leaf springs would have to be relocated or replaced with coil-overs, and there are an overwhelming number of options available in the chassis world, from leaf-spring pocket kits and minitubs to a full chassis swap. To me, Sonny’s ’57 is one of the best street/strip cars I’ve ever been in, and it’s fitted with an Alston four-link rear end. For Australian rego, I think a properly set up, mini-tubbed, four-link rear end would be easier to get engineered and approved than a full chassis swap.
Old cars get more valuable with time, and the ’55-’57 shoebox Chev is a very desirable collector’s car, so be careful how you modify them if you want to maintain their value. If you keep them relatively stock, they will still be valuable in 10 or 20 years’ time. s