Vast distinctions exist among overhauling, rebuilding, restoring, and blueprinting engines. As a customer, you should know exactly what you are seeking from a machine shop. Communication, clarity, and a clear understanding of terminology are critical to achieving the desired result.
Basically, an overhaul could include deglazing cylinder walls,re-ringing existing pistons, a possible bearing change, and installing new gaskets, just to get the engine running. Rebuilding may include new parts but not necessarily complete machining of cylinder bores or crank grinding; it might require only a polish. Restoration usually includes all new parts and complete machining to factory specs as outlined in the factory manual. Blueprinting includes installing all new premium parts, complete machining to specified tolerances, balancing, and more to achieve optimum performance and durability.
Depending upon where you live, finding a machine shop to tackle your block may or may not be easy. The flathead is not a complicated engine, but it does have its idiosyncrasies, and a shop that typically rebuilds small-block Chevys might not be the place to go. We mean no disrespect, but the shop needs to know flatheads. If it doesn’t, don’t pressure the shop into learning or experimenting on yours. It might be a costly mistake for both parties.
Be sure to take plenty of photographs of your block and any little identifying marks it may have. You don’t want to hand over a fairly good block but receive a different and perhaps poorer-quality block after the work is done. You might even want to put your own mark on the block before handing it over or shipping it out of town.
I heard one story of a guy shipping a complete, brand-new rotating assembly to an engine builder. When the engine came back, however, it soon seized. Tearing it down revealed that the builder had switched out the good internals for a set of not-so-good originals. It pays to be aware of such possibilities.
It’s always smart to do plenty of research before you settle on a machine shop. You can learn a lot about a shop by checking the Internet, where people are quick to air their grievances. You can also ask fellow enthusiasts about their experiences. Caveat emptor (let the buyer beware) is the phrase to keep in mind
Blueprinting and Balancing
These words hold much mystique, and summon images of a black art. However, they mean nothing more than making sure that parts are balanced and that the engine is assembled to certain specifications and tolerances recommended by the manufacturer for optimum performance for the desired application, such as street use, racing, or touring.
If you are rebuilding a stock engine, it’s fairly easy to follow the Ford specifications found in the various service bulletins. Most people building hot rod engines use components from a variety of sources. Nevertheless, you should still follow specs for main bearing clearances, ring gap clearances, cam timing, head port and chamber volumes, torque for bolts, and so on.
Factory specs are parameters that suffice for mass-production engines (taking into account time, labor, materials, and so on). They meet the driving needs of the general public with a broad range of driving styles. A blueprinted engine meets and exceeds those factory parameters.
Theoretically, there is no tolerance for a blueprinted engine. It either is or it isn’t, and there’s no in-between. If you build two engines to factory specs, there will always be variances between rod and main bearing clearances, variances in piston clearances, deck height differences, valve-spring pressure differences, and intake and exhaust port and chamber volume differences. If you blueprint an engine for racing at Bonneville, for example, there should be no variances. It should be built to a specific race spec.
Properly blueprinting an engine takes many hours, a lot of patience, and a lot of skill. To achieve a properly running, reliable engine, you need to follow procedures and not just throw it all together.
Balancing is also worth worrying about, because a well-balanced engine is like a well-balanced checkbook: Keep it on the good side and life will be good. Theoretically, to do it correctly you should preass emble the engine before balancing the components, so that any subsequent machine process or task does not affect the balancing act. The order of the day is: pre-assemble, machine if necessary, and balance.
If you are running a mixture of aftermarket components (crank, rods, pistons, and so on, all from different suppliers), it is essential to balance the parts. Of course, you can avoid this work if you buy a rotating assembly from one manufacturer. Even if you do, it is still worth checking the parts for quality. I was a crank grinder in my youth, and there were days when I ground good cranks and days when I was in a hurry and just wanted to get it done. Those grinds were within tolerance but were not my best work.
Weight matching and dynamic balancing are the two steps to balancing an engine.
To weight match, you weigh the pistons and the rods individually on a balancing scale to determine the lightest of each. Then, remove a little metal from each, until all of the pistons weigh the same as the lightest piston and all of the rods weigh the same as the lightest rod. Parts are usually measured within .25 gram.
A balancing fulcrum is also used to determine how heavy a rod is at either end. If a rod is a little heavier on the big end (the main bearing end), a little weight is removed from that end to balance the rod. (The procedure employed at H&H is outlined in this chapter.)
Dynamic balancing is the process of balancing the rotating assembly, including crank, rods, and pistons. Although the crank itself is put in the balancer, bob weights are installed to replicate the rod and piston assemblies. Be sure to record all of the weights for the rods, pistons, and associated components; they will be needed later when you balance the crank.
Almost no factory production engine comes precision balanced. Even some so-called performance engines aren’t balanced to within 1 gram, as are the engines balanced by H&H on its Hines electronic balancer.
Does balancing make any difference? The answer is yes. According to Mike, “A well-balanced flathead makes for a smooth-running car. It produces efficient power by eliminating power-robbing vibration and imbalance.” A flathead is balanced internally, as opposed to a 454 Chevy, a 400 Chevy small-block, and 460 Ford trucks, which are balanced externally; each uses a harmonic balancer.
Balancing and Honing the Rods
Although the rods produced by companies such as Scat are extremely well balanced, Mike likes to double-check them because balancing flathead internals is important to a smooth-running engine. In addition, Mike suggests that if you’re reusing stock rods, you should definitely resize the big ends, because years of wear will have forced them out of round. Moreover, you should definitely balance them, because Ford’s tolerances were more liberal. Ford service bulletins give an acceptable weight of 451 to 455 grams; with a little care, all of the rods can weight exactly the same.
Assuming that your desire is a smooth-running, long-lasting engine, then taking your time and being careful will be rewarded. Precisely honing both rods is paramount.
You can balance connecting rods at home, and with a little care, you can match them exactly. You will enjoy a feeling of satisfaction for a job well done.