1979 GMC High Sierra 4×4
This is one of the new project vehicles here at RPM Army. I got a good deal on this truck earlier in the summer of 2017, and at the time we needed a decent truck to run parts for the other projects in the shop. The previous owner had it built up some with a GM Goodwrench 4-bolt main 350 and added Vortec Heads, an Edelbrock 4bbl intake, and Edelbrock 600cfm 4bbl carb. At some point in the last several years the truck also had the TH350 trans overhauled. Other than a few shiny bits, new tires, and Ion rims, the truck is otherwise stock looking.
It ran pretty good for awhile, but developed some problems. We haven’t pulled the motor yet, but by my estimation, one of the rod bearings became starved for oil and spun. While it’s unfortunate that the truck is down until it’s serviced, It provided me the opportunity to re-arrange the engine stock in the shop. Currently we have a GM LM7 from a low mile Chevy Silverado on the engine stand, and we haven’t really done anything with it for awhile.
The Swap
What you see here is the new motor destined for the K10. It is a GM Gen III LM7 that was sourced from one of the local Chevy dealerships several years ago. It belonged to a 2000 Chevy Silverado, and was a lower mile truck when it was wrecked. Overall the engine was in pretty good shape, and could have been dropped in as-is. While it would have been perfectly fine, I decided that It could use some help. I installed a Comp Cams XFI RPM XR 265HR Cam with 212/218 duration, 114LSA 5.22/5.29 lift. Texas Speed has a very similar cam with .600 lift on the intake and exhaust, but I figured the power difference wouldn’t be worth the extra stain on the valvetrain. After the cam was installed, a set of Chevy Performance Beehive Springs were installed that are good to .550 lift.
Once the cam and springs were installed, I buttoned up the engine, painted it to match the truck, and added an Edelbrock Performer RPM Intake.
It is a pretty mild build, but I didn’t really want to sacrifice low end power because we plan on using the truck to haul pretty decent loads.
Stay posted for a write-up detailing the swap and parts used.
