The changes were first evolutionary, but around the dawn of the 21st century, new ground-up engine designs like the GM Gen III LS small-block, Ford Modular engines, and Chrysler 5.7/6.1 Gen III Hemi appeared. The goal of 21st-century cylinder head engineering is controlling and managing the combustion process by combining radical combustion chambers with new port layouts to improve mixture motion. By equalizing variations in cycle-to-cycle and cylinder-to-cylinder flow, less compromise in timing and fuel delivery are needed to cover the worst cylinder or valve-lift point.
SWIRL IN IC ENGINES
“Swirl”—the rotational motion of the incoming air charge about the cylinder’s axis as it enters the combustion chamber on a two-valve head—is determined by the intake valve’s position relative to the bore axis, the chamber shape around the intake, and any helix in the induction tract. Swirl is maximized by paying careful attention to a wedge head’s valve positioning. Think of swirl in an IC engine like the vortex generated by a flushing toilet. Swirl should always be in one direction; swirl that changes direction at different amounts of valve-lift leads to unstable combustion, requires more ignition lead, and reduces knock-limited power potential. Optimized swirl-port heads sometimes flow less air on a flow bench but still yield measurable power gains on a running engine.
TUMBLE IN IC ENGINES
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Dress it Up
HOW TO MAKE AN LS ENGINE LOOK AND PERFORM BETTER
Solid & Striped
The Lokar/Street Rodder ’34 Ford 3-Window Coupe 25th in a Long Line of Road Tour Hot Rods
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So, you bought a “new to you” project car and want to start the build right. That means tearing out the interior and making sure the floor pans are sealed and rust free. If you find Swiss cheese, check out “How to Fabricate and Install Replacement Floor Pans” on hotrod.com on how to replace your floor pans. If you find minor surface rust and the occasional pinhole, keep reading and we’ll show you everything you need to know about classic car rust prevention.
This 1967 Mustang Is the Perfect Blueprint for an Engine Swap
California Coastal Road Trip
Like many people around the country, we have had little occasion to travel this year. With car shows and events like the Power Tour and Drag Week postponed and rescheduled due to the coronavirus, we’ve mostly been stuck at home. I recently had occasion to travel to Santa Rosa, California, for a photo shoot with Scott Birdsall, owner/builder of Old Smokey, the Cummins-powered Ford F1 that beat the diesel-engine record at the Pikes Peak International Hillclimb. Motor Trend’s William Walker was the shooter, with me serving as assistant and camera car driver. It seemed like as good excuse as any to make a trip out of it.
25 Years of the Crusher Camaro
I’m gonna tell the story of the Crusher Camaro because it’s celebrating 25 years as a project and because it’s presented me with a fresh dilemma. The story begins in 1994 when California law allowed gasoline companies to crush older cars in exchange for smog credits that allowed continued polluting from wells and refineries.
What Is Cylinder Head Swirl and Tumble, and Why Is It Important?
We think of electronic engine management systems and multiport electronic fuel injection (EFI) as primarily responsible for the improved air/fuel distribution and performance as Detroit clawed its way back in the mid 1980s, but—good as they were for that day—initially the new electronics were just Band-Aids grafted onto carryover engine designs. The big change started in the 1990s, when the OEs started tinkering with cylinder head design to induce swirl and tumble in internal combustion engines.
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An upstart electric vehicle maker said that it now has more than 100,000 orders for its new pickup truck.
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