Jim Smart
April 1, 2008

What Is Blueprinting?
Every engine build should be a blueprint, which means you've got to have a plan. We don't know who first used the term "blueprinting" in the world of engine building, however it's appropriate because you want to plan your engine build, not approach it with reckless abandon. Blueprinting means you're going to check anything and everything that can be checked; then you're going to act on these findings.The first phase of blueprinting is inspection. Even brand-new parts must be inspected and measured thoroughly. Need some good examples of why you should inspect new parts?

  • Core plugs found inside a new engine block's water jackets
  • Oil-pressure relief valve stuck in a new pump, causing oil filter to explode all over a dyno cell
  • Water-pump seal leak in a new water pump
  • All 16 valveguides out of parallel in a pair of new
  • aftermarket performance heads, discovered by JGM Performance Engineering during a small-block buildup
  • Valve stem to guide clearances too tight in another pair of aftermarket performance cylinder heads, which means valves would have seized when we fired the engine
  • Severe core shift in a new block to where boring and honing would have taken us into the water jackets (we returned the block)
  • Water-jacket passageway not drilled through on a '70 vintage 351W cylinder head, which would have caused the head to run hot.
  • Misdrilled oil-galley passages in main bearing saddles, causing oil starvation at main bearings (this was a Ford block)

The next phase of blueprinting is improvement. Improvement begins with machine work on the block and cylinder heads. Even if you have new cylinder heads, they should be disassembled, inspected, and machined as necessary. This is why we had Edelbrock send us bare castings for our 390. We didn't need Edelbrock's valvesprings and retainers. We had Crane's. We did have Edelbrock send us 16 valves. JGM machined the heads to its specs.

Cylinder-head improvement includes:

  • Before you machine, check head castings (even new ones) for cracks
  • Machine (or replace) valveguides to proper stem/guide clearance
  • Three-angle valve job (perfect for street because this improves flow, yet allows for adequate valve cooling)
  • Machine decks to true (always--even new ones)
  • Remove risers (high spots) in chambers that can become hot spots
  • Install hardened exhaust valve seats (when not equipped in old iron heads)
  • Screw-in rocker-arm studs and guideplates (stud-type rocker arms only)
  • Chamfer oil drainback holes to improve return flow
  • Port-match (match intake and exhaust gaskets) to improve flow
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