Jim Smart
April 1, 2008

Have you ever had an engine built, only to find yourself unhappy with the result? Our budget FE 390 project was one of those disappointing engine-building experiences. Although it was built by a reputable machine shop, it had a hideous amount of vibration and wasn't performing well--proof that even the best machine shop is only as proficient as its weakest link. All it takes is one person having a bad day to send an engine build into a tailspin.

Because our confidence in the builder was shaken, we decided to visit one we trust--JGM Performance Engineering in Valencia, California. It may surprise you to know JGM Performance Engineering doesn't see very many Ford FE big-blocks. The engine JGM works on most these days is the small-block Ford in low and tall-deck versions in all kinds of displacements.

We're passionate about FE big-blocks and here's why. There remains no replacement for displacement and shear size--that raw, nasty, rotund mass thing that dates back to Roman chariots of yore. Size really does matter and always has. You can have a stump-pulling 427-inch Windsor small-block that makes heaping, helping amounts of torque and horsepower, but does it fill the engine room?

It's always interesting to tear into a fresh rebuild to see what went wrong. We're convinced something was amiss during dynamic balancing, hence the vibration. However, our 390 goes further than that. It's a study in what happens when we have an unhappy combination of parts combined with marginal building technique. Perceived vibration may not have been dynamic balance at all, but rather cylinder-power balance, inconsistent compression, and cylinder pressure between bores. It may also have been improper cam selection and degreeing.

Our 390 FE project demonstrates just how little some builders know. It's easy to hang up a shingle and call yourself an engine builder. We jokingly call them engine "assemblers" because they tend to overlook what's most important in a rebuild. It takes a real engine architect to plan and build an engine properly. For one thing, you can't approach an FE big-block in the same way you would the average small-block. The FE big-block is an old-school, skirted, Y-block design, with all kinds of potential for making big power. However, a street-driven FE should be built for reliability as well as power. To get power for the long haul, you need reliability, and we'll show you how to get it.

Next month, we'll wrap up our Budget FE project with top-end assembly and dyno testing.

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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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    Why Use a Torque Plate?
    Even though an engine block looks like a big, invincible chunk of machined iron, it's sensitive to virtually everything, including heat and stress. Install and torque a pair of cylinder heads and your block "moves" to that shape and union. Think about it--when you torque cylinder heads, you're "moving" bolt holes, decks, and cylinder bores. These elements change shape and dimension. We fire the engine and they change yet again with heat.

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    When your machine shop finish-hones cylinder bores, they must be the same shape they would be with the cylinder heads torqued in place. That's why reputable machine shops use torque plates that are torqued to specs for honing operations. This allows the cylinders and block to conform to the installed shape. Savvy machinists also understand there needs to be a cooldown period between honing phases because honing generates heat, which alters cylinder dimensions. Jim Grubbs hones a little, then checks dimensions top, center, and bottom before and after cool down.

    Oiling-System Improvements
    Even if you're building a stone-stocker, you should always be thinking about oiling-system improvements. All oil passages should be chamfered to reduce fluid turbulence and improve flow. Pressure is important, however volume is more important to not only lubrication, but also to heat transfer. Did you know oil does more than just lubricate? It also carries heat away from hot engine parts. Improving return oil flow to the pan is just as important. Chamfer oil-return holes and use red GE Glyptal paint in all oil flow areas--valley, heads, timing set region in front, even the inside of your oil pan. Before application of GE Glyptal, surfaces must be hospital clean or it will peel off. You can find GE Glyptal at Eastwood.

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    A Word About Bearings
    There are a lot of misconceptions about bearings. That little tang on main and rod bearings isn't there to keep the bearing in place; it's a reference tool to ensure proper bearing positioning. Never use engine oil or assembly lube between bearing and rod, or bearing and block. Contact between bearing and rod, and bearing and block must be bone-dry for security purposes. Crush and crosshatch keep a bearing secure; so do dry contact surfaces. Be sure to use generous amounts of engine assembly lube (do not use a moly-based lube) on journals and bearings. Make sure the bearing is properly centered and secured. Check the oil hole alignment of the bearing where applicable.

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    Why Degree?
    Blueprinting is the process of leaving no stone unturned in an engine build. Blueprinting means sweating details others tend to miss. It's one thing to call your build "balanced and blueprinted" and quite another to actually do it. When we degree a camshaft, we're examining the most important details of an engine build--rotating assembly and valve timing events.

    Because there's no such thing as perfection in mass production, you must always believe in failure potential. Assume the worst and hope for the best. New parts right out of the box aren't perfect. Like the best of machine shops, there are going to be factory workers who are having bad days--inattentive to things they should be attentive to, apathetic, careless, sloppy, eager for lunchtime or beer-thirty. Are you willing to gamble hard-earned dollars and your engine to this kind of carelessness? We didn't think so.

    When we degree an engine, we're checking two things if it's being performed properly. First, we're checking for true TDC (top dead center) on all eight cylinders. Reputable builders will check for true TDC on the No. 1 cylinder and see if it jibes with TDC on the harmonic balancer. Most of the time, it won't. When it doesn't, good builders will mark true TDC on the balancer--and degree the balancer for pinpoint timing. True TDC is dead-middle of the top-dead-center crank journal rollover when the piston dwells at the top of the bore.

    Wise builders will find true TDC on all eight cylinders more for curiosity's sake than anything. The truth is, true TDC will vary with even the best 4340 steel crankshafts. In a perfect world, we would have identical TDC on all eight cylinders, but this isn't a perfect world. Factory machining tolerances vary enough that you're not going to have eight cylinders that smack TDC with identical consistency; however, it's always good to know exactly what you have before buttoning up.

    Once you've established true TDC on the No. 1 cylinder, you're free to degree the camshaft. Degreeing a camshaft allows you to compare the cam card and camshaft. You're establishing valve-timing events and lift as they relate to crankshaft travel. If you're unhappy with valve-timing events, this is the time to make changes either with the existing cam or opting for another one.