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Now Available from Howell EFI – Wiring Harnesses for 4.3L, 5.0L, 5.7L, 7.4L GM Vortec Engines

#HV57T - VORTEC HARNESS: 1996-01 5.7L SFI w/ 4L60E/4L80E Transmission

Wiring harnesses for 1996 and later Vortec engine conversions are in stock and ready to ship

Marine City, MI, (March 14, 2023) – Howell EFI, specialists in EFI systems for 35 years, announces that the company now has a wide number of Vortec pre-LS engine (1996- 2007) wiring harnesses in stock and ready to ship. This includes 4.3L 5.7L, 7.4L and even 8.1L big blocks. Desired for their low maintenance, improved air-to-fuel flow, durability and fuel efficiency, Vortec SFI conversions are now in high demand. 

The Howell EFI 4.3L wiring harness for GM Vortec SBC engines can be sold either for manual or electronic transmissions. Designed for the installation of 1996 – 2007 4.3L Vortec truck engines into other vehicles, this wiring harness (part #HV43) allows for Sequential Fuel Injection (SFI) and operates with all stock sensors. It is sold with the option to use with or without extra oxygen sensors and emission controls. The 4.3L Vortec wiring harness for engines using a 4L60E transmission (part #HV43T) can be sold with emission connections if needed. This harness also allows installation into 1996 and later 4.3L, 305, 350 and 454 Vortec truck engines into other vehicles. Reprogramming of the existing ECM or ECM module supplied by Howell is required. ECM’s are reprogrammed to the vehicle’s engine and transmission specifications; i.e. gear ratios, tire size, cam changes, vehicle anti-theft (VAT’s) removal, etc. 

GM Vortec Products

The 5.0 and 5.7L Vortec harness (part #HV57T) also designed for 1996 – 2001 Vortec Small Block Chevy conversions allows for SFI for the 4L60E or 4L80E transmission and can be sold with or without emission connections.

The 7.4L Big Block Vortec harness for 1996 to 2001 SFI conversion can be used for either manual/non-electronic transmissions (part #HV74) and is also available for the 4L80E transmission for 1996 – 2001 Chevy Vortecs (part #HV74T). 

Matt Howell, Howell EFI President, says, “Supply chain issues are making it difficult for people to find harnesses for Vortec conversions. Fortunately, we are completely stocked up and have Vortec harnesses available to ship immediately. If you have questions about how to get started on conversion, we are here to help. Our staff is knowledgeable and EFI is all we do.”

For additional information visit, or call 810-765-5100. For the latest in Howell EFI promotions and company and product news, follow Howell EFI on Facebook, Instagram, or YouTube.

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Howell EFI Now Offers LT1/LT4 and EcoTec3 Harnesses for Classic Corvettes, Muscle Cars and Trucks

Marine City, MI… October 7, 2021  Howell EFI, a leader in EFI conversion kits (GM/TPI/TBI) and wiring harnesses for direct injection swaps, now offers plug and play LT1/LT4 and EcoTec3 wiring harnesses for classic muscle cars, Corvettes and trucks. Howell now offers multiple options to transplant power for both automatic and manual transmissions and even supercharged classics.

The LT1/LT4, and EcoTec3 wiring harnesses are customized to the customer’s specifications and include fuse block, check engine light, GM diagnostic connector, and electric fan control in a complete street rod type, stand-alone design to control engine functions. There is only one ground for the entire system and only three points of power to hook up the harness – battery, ignition, and fuel pump. They are available with or without wiring for electronic transmission and all emission connectors are included to ensure this harness is street legal in all 50 states as a replacement harness. All Howell EFI harnesses are OE quality, American-made, and backed with a lifetime guarantee and Howell’s experienced technical support staff. GM ECM programming or custom GM ECM tuning are available specific to your engine and transmission combination.

“We see a lot of online conversion kits that claim to be a one size fit all solution for folks converting their cars to electronic fuel injection,” said Matt Howell, president of Howell EFI.  “But the fact is that these are very complex systems that need special attention to the layout of the wiring harness and the right matching components. We spend a considerable amount of time during the order process to make certain every kit is what you need for true plug and play.”

Howell EFI harnesses are designed to transplant powerful engines into an unlimited number of applications from Street Rod, Pro-Touring, Off-Road, Sand Rails, Street Machines, and more.

For more information about Howell EFI LT1 wiring harnesses, view this video. For more information about Howell EFI, visit, or call (810) 765-5100. To review or download the LT-1 Fuel Injection Harness installation manual, visit here.

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Howell Engine Developments, Inc. Reports the Passing of Founder and Automotive Industry Legend Billy Haegen Howell

Bill Howell Grand Marc Car
Billy Howell Obituary

Marine City, MI… August 26, 2021 – Automotive pioneer and industry legend, Billy “Bill” Haegen Howell, passed away on July 22, 2021, after a battle with ALS, aka Lou Gehrig’s disease. Recognized as a leader in the development of Chevrolet performance engines and electronic fuel injection, Howell’s career with Chevrolet spanned from 1961-1987. While at Chevrolet, he became one of the core team members in the development of the new big block Chevy motor that replaced the 409 while working as a test engineer in high-performance engine development for the Chevrolet Product Performance Group. During his career there he also served as the company’s representative for many racing sanctions throughout the country including the ASA series where they promoted first Pontiac, and then Chevy body styles. 

Upon retirement from Chevrolet in 1987 and always a trendsetter, Howell focused his attention on developing electronic fuel injection. At the time, only Corvette had port fuel injection and people were beginning to put Corvette engines into other classics. In 1988, Billy and his son Matt Howell formed Howell Engine Developments, Inc. and began to build EFI wiring harnesses for Corvette/Camaro TPI engines and TBI V6/V8 fuel injected truck engines. Hot Rod Magazine was quick to take notice and helped spread the word among race and performance enthusiasts in an article in May 1988. The business that started in the basement of their home was off and running with the phone ringing off the hook.

Soon thereafter, Chevrolet proposed to ASA that they switch to the new Corvette LS-1 engine in basically stock configuration – sealed engines with only a dry-sump scavenge pump, cam change, and valve springs. ASA had been looking for an option to leave the V-6 engines, as they were getting more expensive. Matt shares that Howell was able to get the contract to build the wiring harnesses and service the systems at the racetrack. GM ran a test program throughout the 1999 season to develop the package and bulletproof it. They switched the series to the LS-1’s in 2000, and they proved to be easy to tech and bulletproof. We maintained the harnesses and provided tech support for the series until ASA sold it. 

The IndyLights program started in 1993 and the Indy Racing League program started in 1995. “Of the 33 starters in the Indianapolis 500 in 1998,1999 and 2000, 30 used engine wiring harnesses manufactured by Howell Engine Developments,” says Matt Howell. 

Howell Engine Development, aka Howell EFI today is a leading supplier of wiring harnesses for direct injection swaps for classic muscle cars, Corvettes, Jeep, and trucks for both automatic and manual transmissions with unlimited applications for Street Rod, Pro-Touring, Off-Road, Sand Rails, Street Machines and more. Howell EFI is now in the company’s 34th year of operations from their headquarters in Marine City, MI with Matt Howell serving as president/co-founder.

Billy spent most of his life in Detroit, MI, and then for many years in Lake St. Clair near Algonac, MI. He retired in October of 2003, to Punta Gorda, FL. During his retirement, Howell continued to travel and to demonstrate his innovation genius. Here is one story from his long illustrious life that gives insight into the man who loved speed and performance and was responsible for the development of many iconic engines and engine components. 

Bill Howell Mike Marilyn Miller
Bill Howell (far left,) ASA Driver Mike Miller and Marilyn Howell

In 1989, TV personality Don Johnson had an ocean-racing catamaran with 4 large MK IV supercharged engines that were having durability problems related to fuel starvation. They developed 1100 BHP each, with 2×4-barrel carburetors on each engine, and any loss of fuel pressure would cause detonation and a head gasket failure. They were built and maintained in Harold Grady’s shop in Ft. Lauderdale. Convention in those boats was to use two electric fuel pumps per engine. Holley carbs can stand only about 7 or 8 PSI fuel pressure at idle, or they will flood the engine with fuel. At speed, this fuel pressure goes down slightly with more fuel demand. This would give an occasional lean-out if there was any problem in the system or a pump malfunction. As a fix, he recommended they change to belt-driven fuel pumps which would provide more fuel delivery as speed increased. This cured the problem.  During this program, Bill went to races at Marathon Key and Key West, Florida, and got to ride in the boat at a test on Lake X in Kissimmee, Florida at over 100 MPH.

Billy Howell is survived by his son and the co-owner of Howell Engine Developments Inc. Matthew Howell (Gina), and his daughters Deborah Bradford (Jerry) and Molly Reeves (Tracy), a sister, Barbara “Bobbie” (Pete) Petersen, and his loved grandchildren, great-grandchildren, and great-great-grandchildren. He was preceded in death by his mother, father, and beloved wife, Barbara Ann Caudle Howell. The family is thankful for all the kind words of support and shared experiences during their time of grief and has asked that memorial donations be made to either St. Jude Children’s Research Hospital, Doctors Without Borders, or to the Wounded Warrior website. To read Billy Haegen Howell’s full obituary, visit here

For more information about Howell EFI, visit, or call (810) 765-5100.