Editing GMC V6 engine (section)

==Diesel V8==
The D637 and DH637 also share the same 17.5:1 compression ratio with their diesel V6 counterparts, introduced in 1966 on the 70-series trucks as an alternative to the established [[Two-stroke engine|two-stroke]] [[Detroit Diesel]] [[Detroit Diesel Series 53|''6V-53N'']].<ref name=67-trucks>{{cite web |url=https://www.xr793.com/wp-content/uploads/2021/08/1967-Chevrolet-Series-70-and-80.pdf |title=1967 Chevrolet Trucks: Conventional Cab Models |date=August 1966 |publisher=Chevrolet Motor Division of General Motors Corporation |access-date=10 June 2024}}</ref>

===D637===
Like the gasoline 637, the D637 shares the same {{cvt|5.125|×|3.86|in}} bore and stroke as the D478 with a total displacement of {{cvt|637|cuin|L|1}}. It was introduced in 1966,<ref name=DW-Allen/> featuring a gross and net peak power output of {{cvt|195|and|185|hp}} at 2600&nbsp;RPM, respectively, and peak torque of {{cvt|450|and|440|lbft}} at 1800&nbsp;RPM, respectively.<ref name=67-trucks/>

===DH637===
The DH637 is an uprated version of the D637, with slightly higher redline. Its gross and net peak power outputs are {{cvt|220|and|205|hp}} at 2800&nbsp;RPM, respectively, and peak torque outputs are {{cvt|458|and|444|lbft}} at 2000&nbsp;RPM, respectively.<ref name=67-trucks/>