1 December 2015

Classic Looks That Conceal A Hefty Punch

When time and miles finally make it necessary to dig into the engine of a vintage car or truck, decisions need to be made. Some owners choose to make updates at that point, taking advantage of the power and reliability of a factory-built crate engine.

Owners who prioritize authentic looks over all else may go for restoration over renovation. But there’s no reason they can’t add muscle while still preserving an original appearance under the hood. Even purists must acknowledge that cylinders often need to be bored in the course of a rebuild, and internal parts like bearings and piston rings will usually be modern replacements rather than original items. Adding some horsepower in the course of an engine rebuild by upgrading the internal workings is not a long stretch from using modern paints and reproduction parts when restoring the body.

One certain way to add horsepower without changing the engine’s appearance is with the old hot-rodder’s trick of going big. Denny Hummel, an engine builder in Clinton, Mich., said the displacement of any engine could be increased. For example, a mild-mannered 283-cid V-8 in a ’57 Chevy can be turned into a potent 327-cid power source by boring the cylinders 1/8-inch and fitting the longer-stroke crankshaft of a later 327. That yields more displacement and a higher compression ratio, both of which increase power.

“I sonic check the block both before and during the procedure to make sure there is enough cylinder wall material to handle that big a bore,” said Hummel.

A solid-lifter camshaft like that used in the 1964 375-horse 327 completes the combination. Installing larger valves in the ’57 heads will push it further. Externally, the engine remains a stock-appearing ’57 283, with all of the original numbers and casting marks intact.

The same strategy can be employed with almost any engine, but machine work, pistons and crankshafts can be expensive. That’s why the installation of a performance camshaft, coupled with a careful rebuild, is often enough to wake up an engine. Stick with cams recommended for street use to assure adequate low-speed torque.

A good valve job will help your engine take advantage of the better breathing that a performance cam enables. A three-angle valve job with a 45-degree seat, a 70-degree cut below and a 30-degree cut above improves flow. A narrow valve seat optimizes sealing. Experts recommend a .060-inch seat width for street-driven automobiles.

An engine built to ideal specifications will produce more power than one that is haphazardly bolted together. For example, camshaft timing, which can be checked with a dial indicator and degree wheel, is critical. Aftermarket cam manufacturers provide timing data and a diagram that illustrates what it all means. Data for original equipment cams can be found in service manuals.

Engine clearances are important. Piston-ring end gaps that are at minimum spec reduce blow-by and conserve cylinder pressure. On-spec bearing clearances optimize lubrication and reduce power-robbing friction. Generally, work to achieve clearances that are at the low end of the range. Use a torque wrench when assembling the engine, and tighten bolts to recommended values. You can find specs for most engines on the Internet.

Classics are deserving of exemplary care. Whether it’s in the car Dad drove or a valuable collectible, an engine that’s both pretty and potent is a great way to go.

2 Reader Comments

  • 1
    David Rogers Lodi Ca December 3, 2015 at 23:08
    I can't see taking a classic block and simply boring it to the max for the sake of a few ponies. Seems like a good way to destroy any hope of rebuilding it in the future.
  • 2
    Doug Michigan December 4, 2015 at 00:04
    These old engines were pretty crudely built. Lots of casting flash in the ports, intakes that only sort of line up with the cylinder heads, and camshafts that are more mild than your Grandma. You can gain a lot of power by cleaning up the ports, gasket matching the manifolds and installing a moderate hydraulic lifter cam. Most older engines can use higher compression pistons to take advantage of modern fuels, and removing any rough spots from the combustion chambers helps prevent spark knock. This will make the engine a lot easier to live with than that troublesome solid lifter cam, and probably give more power.

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