When Chevrolet introduced their High Energy Ignition (HEI), in 1974, this electronic ignition was designed to be an improvement over traditional point-style ignition. The HEI had a long life, and was used on GM cars until the mid-‘80s.
There is no denying that HEI distributors are a popular swap into older, point-ignition equipped GM cars. The HEI delivers a more powerful ignition spark, and this allows the use of wider spark plug gaps to help ignite fuel quicker, and deliver a more complete combustion.
In the world of aftermarket distributors, Davis Unified Ignition (DUI) has been delivering top-of-the-line HEI units for decades. But over the years, installing a distributor into a small- or big-block Chevy is getting increasingly harder, and the reason for this has to do with engine rebuilding. Each time an engine is rebuilt, it typically receives some sort of milling of the surfaces. This means the cylinder heads and intake can actually sit lower on the engine. Have you ever tried to install a distributor, and have it bottom out on the oil pump? That’s why. The DUI Deluxe Street/Strip distributor can eliminate that issue with its adjustable collar.
The adjustable slip collar gives the user a total of 7/8-inch of adjustability. This is a great feature if the heads, intake, or even the block has been milled. If you have ever needed to add shims under your distributor, you’ll know what we mean.
Being able to adjust the distance between intake mounting location and where the distributor gear meshes with the camshaft gear can save a lot of headaches. Speaking of the distributor gear, no longer do you need to keep buying bronze gears if you are running a roller camshaft.
Those old, bronze gears were a must when running a billet roller camshaft, but the downfall was, they wear quickly, and distribute that bronze material throughout your engine as the gear wears. That issue is alleviated, as the DUI distributor uses a Carbon Ultra-Poly composite gear instead. This composite gear is compatible with any camshaft, unlike a cast or bronze gear. This distributor doesn’t care if you’re engine is equipped with a solid or hydraulic flat-tappet, or a billet roller camshaft, the gear is universal.
If there is one issue that plagues all Chevy engines, it’s the routing of the spark plug wires. There really is no easy way to cleanly run the wires from the distributor to the spark plugs. This distributor fixes that issue as well. The cross-fire cap cleanly routes each bank of plug wires from the appropriate side of the distributor for a nice clean look. But, this distributor is not just a designed to deliver good looks.
Under the cover and cap, are a pair of DUI staples – the Dyna Module, and a 50,000-volt DUI coil. In stock trim, the HEI was plagued with high-rpm spark delivery issues, and the distributor even gathered a reputation for dropping spark at around 5,000 to 6,000 rpm. The DUI coil is reported to deliver a solid spark, even at 7,000 rpm. Each DUI Deluxe Street and Strip distributor is calibrated on a distributor machine before you get it, which virtually guarantees a smooth advance curve that provides instant throttle response and one thing we are all looking for, more power.
So, by designing a distributor that eliminates the need to add shims after machining is done, uses a distributor gear that is compatible with any camshaft and doesn’t distribute metal filings through your engine, and uses a cap that routes your wires in a clean fashion, this could be the last distributor you ever need to purchase.