Measuring the block’s critical dimensions will determine if it remains within the tolerances recommended by the manufacturer. If the cylinder bores remain concentric and show no excessive taper, you may be able to get away with just honing them. But keep in mind that during the honing process, material is being removed from the cylinder walls, which may take the bore beyond tolerance. In other words, if in doubt, opt to bore the cylinders. Any high-mileage engine will greatly benefit from boring, as the process will restore the cylinders to a concentric shape and improve their alignment relative to one another.
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Once you’ve decided to bore the block, you must decide by how much. As a general rule, you want to bore the cylinders as little oversize as possible. For most engines, it is easy to obtain pistons and piston rings between .020 and .060 inch oversize. But in the case of Lima and some other series Ford engines, your options may be more limited. Machine shops will often recommend boring your cylinders to the next oversize that is closest to, say, a Chevrolet bore size, thus increasing the availability and reducing the price of piston rings. Pistons are another matter altogether, as there are a number of factors aside from oversize to be considered. I’ll discuss that in more detail a little further along in this chapter.
Cylinder Block Step by Step
Step-1: Set Up Cylinder Block in Boring Machine Work
After being measured, cleaned, and Magnafluxed, the block is set up in the boring machine. We decided to bore our block .030 inch oversize due to wear from high mileage and rust in the cylinders due to the engine having not been run for a number of years.
Step-2: Bore the Cylinders
The boring bar works to remove taper and makes each cylinder concentric again in preparation for finish honing. The actual boring process removes approximately two to three thousandths less material from the cylinder than the total planned oversize, allowing the honing process to finish the cylinder to the proper size for the piston.
Step-3: Hone the Cylinders
After boring, the block is set up in the cylinder hone for finishing. The machine uses stones with two different grits, while cutting oil is introduced to achieve the proper finish in each cylinder bore.
Step-4: Use High Plateau Hone (if applicable)
We’re using a High Plateau hone to aid in sealing with Moly piston rings. Gil Jordan recommends 15 to 20 strokes in each bore with the hone affixed to a 1/2-inch drill motor.
Step-5: Use Cross-Hatch Pattern
The desired finish for the cylinder walls is this fine cross hatch of approximately 30 degrees. This allows the piston rings to seat and seal quickly and thoroughly.
Step-6: Clean Up Lifter Bores
Use a ball hone to clean up the lifter bores. While lifter bores seldom display problems, they can be damaged due to lifter failure during high-performance operations or pitted due to rust. In these cases, lifter bores can be sleeved and honed back to factory specification to save an otherwise good cylinder block. Larger diameter ball hones are sometimes used to clean up cylinder bores that are not undergoing a complete machining process.
Step-7: Replace Cam Bearings
The cam bearings must be replaced any time a block has been chemically degreased. We have chosen these Dura-Bond high-performance bearings for the job.
Step-8: Install Cam Bearings
A specialized tool and some experience are required to install the cam bearings in the block. While Lima series Ford engines use just one size of cam bearing in each journal, others have specific bearings for certain journals (getting smaller moving back from the front journal where the loads are greatest). Using a single size for all cam bearings is considered one of the few weaknesses in the Lima series engines, as they sometimes have a propensity to spin cam bearings due to insufficient lubrication or clearance. As a result it is important to ascertain that the oil feed holes between the cam bearings and the cylinder block are properly aligned and that the camshaft spins freely when installed. Manufacturers have a recommended setback (from the face of the block) measurement for the number-1 (front) cam bearing. The most important thing is proper alignment between the bearing and the oil passages that feed them from galleries in the block.
Professional Mechanic Tip
Step-9: Modify Oiling System – optional (Performance Tip)
Step-10: Chamfer Oil Passage (optional)
Step-11: Match Oil Passage to Bearing
Step-12: Passages Chamfered
Crankshaft, Pistons and Connecting Rods Step by Step
Step-1: Connecting Rods
Step-2: Fit Rod Bolts
Written by Charles R. Morris and Republished with Permission of CarTech Inc