#DELCO VACUUM PUMP IN BIG CAM 350 FULL#
#DELCO VACUUM PUMP IN BIG CAM 350 PLUS#

But for later model engines with better chambers, that could be improved to 9.0:1 dynamic. This tends to be true for older, traditional engines with less effective combustion chambers. The generally accepted conservative estimate is 8.0 to perhaps 8.5:1 dynamic compression ratio for 91 octane pump gas. With these inputs, the UEM calculator offered 8.198 or 8.2:1 dynamic compression.

#DELCO VACUUM PUMP IN BIG CAM 350 PLUS#

Avoid wide piston-to-head clearances of over 0.050-inch.įor that same stroker LS engine, we plugged in 10:1 static compression, a 6.125-inch rod length, a stroke of 4.00 inches, and a 0.050-inch intake closing number of 47 degrees plus 15 degrees. A tight quench area improves mixture motion and will actually enhance combustion efficiency. So, for an engine with a 0.003-inch piston-to-deck, adding a 0.041-inch gasket would produce a piston-to-head clearance of 0.044-inch. That’s the static compression ratio.Ī tight quench is achieved by minimizing the piston-to-head clearance to less than 0.045-inch for 4.00-inch bore wedge head engines. If we then push the piston to the top of its stroke, in our particular case we’ve now squeezed that same volume almost exactly tenfold, creating a volume of only 5.1 ci or 83.6 cc for a compression ratio of 10.0:1. If we compute the volume of a stroker 6.0-liter LS engine with a 4.030-inch bore and a 4.00-inch stroke, this generates a volume of 51 cubic inches (ci) or 836 cubic centimeters (cc). This is literally the ratio of the volume of the cylinder with the piston at the bottom compared to the volume with the piston at the top of its stroke. When we talk about compression, this should be more accurately defined as static compression ratio. But from a mechanical standpoint, there are also several steps the engine builder can make to add compression while also minimizing the chance of detonation. The simplest and easiest remedy is to add octane to the fuel, and we’ll make some suggestions toward the end of the story that are both affordable and work extremely well. This is what causes that all-too-common rattle or knocking sound.ĭetonation is bad and should not be allowed to continue because it can break parts, damage combustion chambers, and wreck head gaskets. This creates a pressure spike that tends to vibrate the piston in the bore.

At some point, if the octane rating of the fuel is insufficient, the end gases will light off on their own in a spontaneous mini-explosion in a part of the chamber where the end gases have collected. As combustion occurs, the cylinder pressure continues to rise - along with the temperature. In an engine, the spark plug begins the fire in one corner of the top of the piston that is our grassy prairie. Think of the combustion process not as an explosion, but rather, more like a brush fire burning across a large field of dry grass. This is defined as uncontrolled combustion that occurs after the spark plug has fired. The biggest limiting factor when attempting to increase compression ratio is the threat of detonation. The jagged edges are uncontrolled and extreme pressure spikes that tend to rattle the piston in the cylinder and cause engine damage. Graphically, this is what detonation looks like on a pressure trace. This means that merely changing from a 9:1 to a 10:1 static compression ratio on a 400 hp small block would be worth as much as 16 horsepower.

#DELCO VACUUM PUMP IN BIG CAM 350 FULL#

The generally accepted estimate is an improvement of three to four percent per full point of compression. While 9:1 is a safe number, maximizing compression is a great way to increase power while also improving fuel mileage, throttle response, and drivability. This is in order for the engine to safely work with pump gas, which for much of the country, is limited to 91-octane. The standard recommendation for street engines running on pump gas has always been to shoot for a 9.0:1 to perhaps 9.5:1 compression ratio. In this story, we’ll touch on several points relating to compression and how you can make this squeeze work to your advantage.Ĭompression is one of the few areas in an engine where the “more is better” theory really holds true. One way to make more power with a normally aspirated engine is to start with a strong compression ratio. If you call yourself a gearhead, then you most likely appreciate horsepower.

Delco vacuum pump in big cam 350