You want a block with perfectly machined surfaces that mates well and seals tight without conflict. This calls for extreme measures in machining—and painstaking attention to detail. Before you spend a lot of money on a block, it must first be cleaned and inspected, then confirmed fit for service. You’re not going to find a machine shop that cleans and machines a block, then refunds your money because it is cracked, bored oversize beyond salvage, windowed by a stray connecting rod and repaired, or suffers from some other type of defect. You must first know if you have a usable block. Begin with a pressure test to confirm integrity. Then, give it a complete thermal cleaning including removing all freeze and oil galley plugs followed by a visual and magnetic particle inspection.
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Go into the water jackets with a highpower magnet to catch slag and other metal debris. You will be amazed at how much you find in there from the foundry, which can cause hot spots and overheating. There have been freeze plugs found inside water jackets, knocked inside by careless rebuilders and autoworkers. Do this even if it’s a new block, especially if it’s a new block. Measure cylinder bore size from top to bottom, and sonic check walls and decks. While you’re at it, do a pressure test. Line bore should also be checked. Check cam bore to line bore centerlines. Check the cam bore. Examine lifter bores.
Block cleaning should be an ongoing process throughout the machining phases. Have your machinist clean the block after each machining phase to ensure debris doesn’t accumulate in oil galleys, water jackets, and other cavities. Not everyone agrees with this because it’s labor intensive and adds to the cost; however, it is just good housekeeping. The logic here is even the smallest metal particle (grit) can and will damage moving parts. Even a hair-thin score in a journal costs you oil pressure. Oil galleys and other passages must have a thorough cleaning with long and aggressive rifle cleaning brushes again and again until you are confident all debris is gone. Another aspect of cleaning is slag and stress riser removal. Slag can impede oil and cooling system passages. Stress risers can lead to cracking.
Machine work includes cylinder boring and honing if bores are tapered beyond .0001 inch. Maximum wear limit is .010-inch over before you must go to the next oversize. Where possible, bore and hone to .020-inch oversize instead of .030 inch, which buys you more block time. If wear is minimal and boring unnecessary, at least do a fine finish hone and ridge removal. The purpose of boring isn’t just to take cylinders to the next oversize, but to also match each piston to a hone-matched bore. In other words, measure each piston and hone a cylinder to match, but only once dynamic balancing is complete and you have eight slugs and rods balanced to a specific location on the crankshaft. Piston rings should be end gapped and installed.
Make sure your machine shop uses a torque plate for honing, which simulates cylinder head installation and gets the bore as it will be once heads are installed. Hone without a torque plate and you have cylinders that are irregular when heads are installed and torqued. Always use a head gasket with the torque plate— it’s that important. Three different stones are typically used in the honing process becoming progressively finer.
Main saddles need to be line honed until they are true. Line honing puts a nice crosshatch pattern in the bearing saddles, which provides crush and security. Main saddles require boring when they are worn beyond limits, which involves milling main cap mating surfaces, then boring and honing the installed caps. One thing machine shops rarely do is cam bore line honing. However, for good cam bearing security, ask them to hone yours. It’s worth the expense to get a good crosshatch pattern. Ideally, your machine shop has the right equipment to rotate the block during the line honing process. Not many shops do this, but it’s a nice feature when you can find it because it gets the main bearing saddles perfect.
Decks should be measured across and corner to corner, then milled the minimal amount necessary. Warpage any greater than .003 inch across a distance of 6 inches or more calls for milling. How much you remove from the deck depends on what you want the deck height to be. (Deck height is the distance from the crankshaft centerline to the top of each deck.) Of course, you have to dial in crank, rod, and piston dimensions to determine compression and quench, which involves a lot of math. Once decks are milled, your machine shop should put a nice taper at the top of each bore for ease of piston/ ring installation.
Once all machine work is complete and you’ve performed a thorough cleaning, and all oil galley and freeze plugs are installed, perform a pressure test to confirm you still have a solid block. Once the pressure test is complete, properly mask off everything that should not be painted. Once your block is in paint, spray cylinder walls and interior surfaces with WD-40 for corrosion prevention. You don’t want rusty cylinder walls and bearing saddles. In a damp climate, it doesn’t take long for them to get that way.
Some block cracking can be repaired via welding or JB Weld, which is a twopart catalyzed product that works well with cracked cast iron. Properly mixed and allowed time to cure, it will last the life of any engine block. For JB Weld to work effectively you need a clean surface and a crack that has been carefully stop drilled at each end. Just a small 1/16-inch hole at each end slows and stops cracking. Then weld or JB Weld the crack. I suggest against the use of JB Weld at the cylinder walls and decks where stresses can be extreme. Your machine shop can advise you; some blocks are cracked beyond repair.
Fasteners and Threads
Your block preparation should include thread chasing, which not enough of us do. Every bolt hole should be lubricated with WD-40 and chased with a thread chaser until fasteners roll smoothly. Damaged threads should be tapped or repaired with a helicoil insert. Once the threads are clear, blast them with a soapy solution and compressed air, then WD-40 in the hole for corrosion prevention. Fastener threads should also be chased while you’re at it.
Use Grade 8 fasteners throughout for a high level of fastener integrity. As one example, some ARP kits don’t have all of the correct fasteners, which means you need to do it piecemeal and order specific fasteners for your Cleveland. There are also AMK Products for those who wish a factory look using OEM fasteners.
Go with main studs instead of bolts in the bottom end, even with a stocker. Main studs offer greater structural integrity preventing main cap movement. Head studs make cylinder head removal difficult if they’re in a car. However, if you’re going to push the limits of a Cleveland block—such as nitrous, supercharging, or high RPM/high compression for extended periods—studs are the better choice. Give all fasteners a trial run through bolt holes to check for resistance. Never torque fasteners without lubrication and always torque them in three phases, then recheck.
Written by George Reid and Republished with Permission of CarTech Inc
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