Page 20 - 2017-Fall Vintage RVing

Technical Corner MAINTENANCE, PARTS, TIPS, INNOVATIONS AND MOREHEI Remote CoilJR Wright | 1978 Buskirk 30' Stretch | Midland, MichiganShould you install a remote ignition coil on your GMC Motorhome HEI system?What I found was that because the distributor is located at the rear of the engine behind and somewhat underneath the air cleaner, restricting air flow and reducing cooling of the internal parts, that these internal parts, especially the coil, can get hot enough to burn your fingers – ask me how I know!The coils that I have replaced actually had cracks in the plastic covering over the windings. I needed to reduce the heat soak of the components inside the distributor with the coil being the largest mass. I did my research, found, and purchased MSD HEI parts to remote mount the coil to the rear firewall.Since doing the modification in the spring of 2013, I have not had any ignition problems and the Blaster coil mounted on the rear wall does not get hot tothe touch. In the past, I would have about one failure a year. Was I having more failures than other GMC owners, maybe, but since doing the conversion in 2013 and 25,000 miles it is still running well.Other things that you should do are adding a ground wire between the distributor and the ground, use nickel or copper never seize on the distributor shaft and add an O-ring under the distributor.Good Luck on which ever path you decide to go and this is my personal experience and results.Remote Mounting the Coil to Rear FirewallInstallation Instructionsdocuments.msdperformance.com/8401msd.pdfParts List | photos, illustration, and part numbers courtesy of msdperformance.comModified HEI Coil Dust Cover V8 #8401 MSDBlaster Coil #8200Coil Mount #8213Distributor Cap & Rotor #8416Coil Wire for Blaster Coil #84049Attention:Electric Wiper UsersKen Henderson | Americus, Georgia | 1976 BirchavenAt the Spring 2017 Vintage Motorhome Celebration in Shawnee, Oklahoma, I modified several GMCs with a variation on the electric wiper slow-down modification published in the Winter issue of GMC VintageRVing magazine at: gmcmi.com/vintagerving/2017- WinterVintageRving/#p=16.After that publication appeared, it occurred to me that it would be quicker and easier to insert the bridge rectifier in the ground lead rather than the power lead. Every time I installed the modification, I did it that way. It being such a simple change that we never tested it.I have since learned from one owner, and experienced myself, a situation I did not anticipate: SOME Lumina wiper motors are grounded not only by the pigtail’s ground wire, but by the motor housing. In that case, the modification causes no problem, but it also does nothing to slow the motor.So, if I, or you, installed the bridge rectifier in the ground lead and the wipers still run fast, that’s probably the problem. You will have to move the rectifier in accordance with the published diagram.NOTE: The switch is NOT required; it can be installed for additional speed control.Sorry about that – all my shop motors have isolated grounds.ELECTRIC WIPER SPEED CONTROL+-+ +MLOHIMED20 GMC VINTAGE RVING MAGAZINE | GMCMI.COMAC AC