As a note to start. We have a 78- 403, 3:70 FD Royale. With a Howell EFI. The Royale's weigh more than any other GMC. At about 12,000 lbs. And always have something in tow. When pulling Linda's lift van. Total GVW is at 17,000 lbs. When pulling my 24 ft enclosed trailer. With a Chevelle convert inside. 24.000 lbs GVW.
This has been discussed over many years. But I believe a review for new owners is in order. Starting with the radiator. The stock radiator when new. Was over sized. And can handle a lot of bugs in it. I've never seen one that didn't need a good cleaning. The best way to do a proper inspection. At night. Put a very big/bright flood light in front of the grill. About 6 ft away. Then go inside with a mirror. In this way. You can examine all areas. Look for areas that let very little light in. Use a hose. With the water stream from the back. toward the grille. That has a very aggressive stream of water. I've had it take over an hour of spraying to get the job done. A power washer will also work well. But be careful to not bend the fines. This cleaning. Well lower over all, under body heat. By increasing pure air volume.
As a note. If you have a 455. Find a junked GMC that came with the 403. Late 77, and all 78's. These all had 403's. The radiators in those. Had greatly improved air ducting in front, and the backside of the rad.
Your always welcomed to privet e-mail. Or phone call Iowa. 319-521-4891 Cell
Bob Dunahugh
78 Royale since 2003
4 real Copo Yenkos
This has been discussed over many years. But I believe a review for new owners is in order. Starting with the radiator. The stock radiator when new. Was over sized. And can handle a lot of bugs in it. I've never seen one that didn't need a good cleaning. The best way to do a proper inspection. At night. Put a very big/bright flood light in front of the grill. About 6 ft away. Then go inside with a mirror. In this way. You can examine all areas. Look for areas that let very little light in. Use a hose. With the water stream from the back. toward the grille. That has a very aggressive stream of water. I've had it take over an hour of spraying to get the job done. A power washer will also work well. But be careful to not bend the fines. This cleaning. Well lower over all, under body heat. By increasing pure air volume.
As a note. If you have a 455. Find a junked GMC that came with the 403. Late 77, and all 78's. These all had 403's. The radiators in those. Had greatly improved air ducting in front, and the backside of the rad.
Your always welcomed to privet e-mail. Or phone call Iowa. 319-521-4891 Cell
Bob Dunahugh
78 Royale since 2003
4 real Copo Yenkos
