EngineLabs

Not the game of peakaboo you want to be playing...

Low-tension piston rings have become common in performance and racing engines. However, piston ring tension is more complex than the terminology might suggest. Choosing the correct oil ring tension isn’t as simple as picking a number from a catalog.

Understanding what the number represents and how it was measured is essential when selecting the right ring package. The key is understanding the difference between tension force and bore friction. Although related, force and friction represent different aspects of ring behavior.

In our latest article, we cover the differences between tension and friction, and explain the testing methodology for each, with the help of Total Seal.

Camshaft timing is a popular subject among engine builders and enthusiasts alike. It is an area of great debate due to the effect of changing the valve events in relation to crankshaft rotation has on performance. There are three ways to control timing: chains, belts, and gears.

Timing chains are the most popular method of controlling camshaft timing, especially in American V8 engines. There are two types of chains: link belts and roller chains. Link belts are made of metal links pinned together to form a chain. The chain links slide over sprockets with teeth mounted to both the crankshaft and camshaft. Roller chains are made of pins and axles forming a captive bearing between the links, allowing the chain to spin freely.

The second type of design is a gear drive. This design uses gears to drive the camshaft in lieu of a chain. As with chains, gears have a couple of different styles, namely the dog bone and idler styles. The dog bone style has a center set of gears that ride between the top and lower gears, while the idler style is one gear that is mounted in position.

Belt drives are mostly used in high-end racing applications like NASCAR and Pro Stock. Two styles are used. One is a tension fit, and the other uses an idler pulley. Tension fit systems have been tuned for belt resonance.

Four Flats Equals Two Jets
There are six flats on a Holley carburetor float adjustment hex-head screw. If you raise or lower the float level adjustor by four flats (two-thirds of a turn), this is the equivalent of two jet sizes. For example, raising the float level four flats would be the same as changing from 78 to 80 jets. Lowering the float level will lean the air-fuel ratio.

This is based on the height of the fuel level in the float bowl. Increasing the float-height richens the mixture because it increases the pressure on the main jets located at the bottom of the column of fuel in the bowl. This is not a carved-in-stone rule, but changing the float level will certainly affect the overall air-fuel ratio and can be used for minor changes in overall jetting. It’s best not to alter the float level beyond this point in either direction — but if you need to make a change in a hurry, it will work.

When it comes to the list of the top 10 most iconic engines, Jeep’s 4.0-liter straight-six definitely has earned a spot on there somewhere.

So, when we heard Keith Newcomer was working on a new high-horsepower naturally aspirated build, we definitely had to check it out. This engine is being built for a dirt drag racer running a Jeep Cherokee. Keith knew right off the bat this engine was going to need to produce lots of torque on the low end to pull out of mud holes and also plenty of horsepower for top speed. That’s a tough task with a straight-six that has to be naturally aspirated according to the rules.