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
Peart checks deck height with...
Peart checks deck height with a dial indicator because we want to know what this engine is right off the truck. This is not only a teardown--it's a fact-finding mission. We want to know why this engine build failed.
A lot of trash in the Cobra...
A lot of trash in the Cobra T-pan indicates oil contamination with finite metal particles. Some of this is moly-based assembly lube, but there's more. We're convinced piston-to-cylinder wall clearances are excessive. Our 4.050-inch bores have already been punched 0.030-inch oversize. We'll have to take it 0.010 inch more because we're on the high side of 0.030 inch.
Although these C3AE-A rods...
Although these C3AE-A rods have been reconditioned, workmanship is disappointing. Rod bolts were not replaced when they should always be replaced. Large ends are egg-shaped. Side clearances are within factory specifications.
We don't have a cam card from...
We don't have a cam card from the previous build, but we do know this is a high-performance, flat-tappet, hydraulic camshaft. Peart determined lift to be 0.325 inch intake and 0.325 inch exhaust (at valve, 0.572 inch). Duration is 236/236, with 108-degree lobe centers. This is an aggressive flat-tappet hydraulic street cam with a lumpy idle. We'll tone it down with a hydraulic roller cam.
We were surprised by the condition...
We were surprised by the condition of this aftermarket balancer, which had been forced onto the crank. Luckily, there was no damage to the crank. We had to throw this balancer away.
Because we're going to 0.040...
Because we're going to 0.040 inch oversize, JGM wants to be sure our block sports proper cylinder-wall thickness. Although we've seen our share of FE big-blocks (except 427) go to 0.060 inch oversize, iron can sometimes get thin in places. Peart sonic-checks all eight cylinders--top, middle, and bottom primarily on the thrust side. The thinnest we found was 0.162 inch, or shy of 1/4 inch thick.
Peart measures all crankshaft...
Peart measures all crankshaft journals and makes a determination about machine work. Crank journals will need to be polished and oil passages chamfered. We were surprised to see oil holes that weren't chamfered.
JGM Performance Engineering...
JGM Performance Engineering put our block through an extensive cleaning process that makes old iron look like new. Peart checks the line bore and finds main bearing saddles out of alignment. We check line bore to see if our crank sits in the saddles nice and straight. If it doesn't, we eat up main bearings, for starters. When the crank and block are out of alignment, everything is, from crank to piston crown.
When resizing the line bore,...
When resizing the line bore, we begin with main bearing caps, shaving a couple thousandths off where caps meet the block to perfect mating surfaces. This, of course, makes the main journal passage smaller. We are also machining the sides to get them true.
If you've ever wondered why...
If you've ever wondered why machine work is expensive, consider setup time. To line-hone this block, Peart has to set up the machine, which takes a lot of time if it's being done properly. He installed our ARP main studs, which will have to be modified to clear the Cobra T-pan. Here, he dresses each stud with molybdenum lube and torques the main caps.
We line-hone main saddles...
We line-hone main saddles for much the same reason we hone cylinder and lifter bores: to get them straight and true. What's more, we're crosshatching bearing contact surfaces, which makes the bearing more secure. Factory-production machining tolerances aren't as precise as a machine shop's because there's no time for it. When we blueprint an engine, we're checking and machining everything, which frees up power and improves reliability.
As Peart line-hones, he checks...
As Peart line-hones, he checks dimensions; then he installs the main bearings and measures inside dimensions as a result of bearing crush. We want proper crush (and not too much of it) to where we achieve perfect journal clearances with the crank installed.