The Technology Behind Shocks - Shock Value

The early Model A Houdaille is pretty popular in the hot rod world. Here are a couple of units, one assembled and one opened up to show off its internals.

The Houdaille design consists of a chamber filled with fluid that provides the dampening action within the shock. The chamber is divided into two equal chambers by a stationary shaft. A rotating winged shaft activated by the shock's lever rotates back and forth, forcing fluid back and forth between the two chambers. The shock's resistance depends on how rapidly the fluid is moved between the chambers and the flow is regulated by the size of the opening between the two. That regulation is handled by an adjustable needle valve, just as used in the adjustable tube shocks you see today.

This is one of those winged shafts. It's very common for them to be frozen in place, so a bit of persuasion through heat and a mechanical puller are used to dislodge `em, so a standard rebuild can take place.

The lever-action shock's adjustability is controlled by valving in the center of the winged shaft. These photos show the two most common types of valve; the first is a needle-type and the second is called a rotary-type.

When it comes to making adjustments there is a bit of a difference between the two. For needle types a good rule of thumb for warm weather is made by screwing the needle valve closed until it seats.....

......and then backing it off a 1/4 turn for rear shocks and 3/8 of a turn for the fronts. Rotary type valves are set at the factory. Early types have two marks scribed on the end of the shaft; these valves should be adjusted so that the center of the pointer is mid-way between those marks......

......On later types the point should be in line with the single factory setting mark scribed on the end of the shaft between the two shoulder stops.

GM's version of lever-action shocks (for use up front anyway) were for the most part double arm designs. Again, these operate on the same principle (fluid passing through a passageway between two chambers) to provide damping. The obvious difference is the double arm setup--the arms in these types of shocks actually act as the upper control arm and are connected directly to the top of the spindles. Though not a design I've ever seen used on a hot rod, they are common on GM restorations and many lowriders.

Five Points is more than happy to accommodate rodders wishes by working closely with them when it comes to looks as well as operation. Five Points can arrange for powdercoating or chrome plating too if you so desire.

Mathew tells me that these GM dual arm units make up a large part of Five Point's business; there were a good half-dozen pair in-house waiting for rebuilds.

Rather than the expense and work of spray painting newly rebuilt units, Five Points dip-paints their finished products by literally submerging them in automotive lacquer.....

......Doing it in this way not only satisfies the EPA but ensures complete coverage and a factory-like finish.

Mathew and his pop have decades of experience in the care and rebuilding of lever-action shocks and are willing and very able to help any traditional hot rodder stay true to tradition by supplying shocks that not only work like new but look that way as well.