Reference Details
- Common issue
- A later service block or assembled 421 can duplicate performance without proving factory installation.
- Confidence
- documented
- Correct value
- Period-compatible four-bolt 421 block, forged 542990 crankshaft, 529238 rods, forged pistons, and supporting dates
- Where to check
- Block, crankshaft, rods, pistons, casting and stamping locations, dates, and documentation