Headers radiate a huge amount of heat under the entire coach. Verses the stock manifolds. It's all in the surface area of each. Muffler size also plays into this heat transfer issue. Wrapping any exhaust components will greatly reduce their service life. In 2008 we were in Lake Havasu City Az. Early Aug. The outside temps were around 115 degrees. With the gen running the roof A/C. Our 78- 403 Royale's GVW is just under 12,000 lbs. Plus we where pulling a trailer with a car on it. Total GVW was at just over 17,000 lbs. We have no extra venting above the front wheels. Pure stock exhaust that includes gas tank heatshields between the tail pipe, and both gas tanks. I had made, and installed new heatshields that were longer, and taller then the stock ones. Then attached them to the floor above. Used the stock engine fuel pump with a boost pump at the rear for the carb.
I now have 2 pumps at the rear. That are mounted on the outside of the frame. Along with the 2 filters, relay, and steel line to just behind the left front tire. This feeds a Howell/GM EFI.
2 years ago I installer 2 Magna flow series 40 muffler copies. The Magna Flows are about $78 each. The copies are $33. on Amazon. There're about 8 inches shorter then stock.( Thus less heat transfer to the bottom of the GMC. ) With a big plus of being made of a heavy welded steel construction. It's all in the details. Bob Dunahugh 78 Royale Iowa
I now have 2 pumps at the rear. That are mounted on the outside of the frame. Along with the 2 filters, relay, and steel line to just behind the left front tire. This feeds a Howell/GM EFI.
2 years ago I installer 2 Magna flow series 40 muffler copies. The Magna Flows are about $78 each. The copies are $33. on Amazon. There're about 8 inches shorter then stock.( Thus less heat transfer to the bottom of the GMC. ) With a big plus of being made of a heavy welded steel construction. It's all in the details. Bob Dunahugh 78 Royale Iowa
