How to Rebuild Pontiac V-8s - Updated Edition. Rocky Rotella

equipment

      •Valve refacing equipment

      •Valve guide and seat equipment

      The high numbers of low-cost aftermarket crankshafts currently on the market has limited the number of cranks that a machine shop must prepare on a regular basis, and the high cost of such equipment can prevent newer shops from purchasing a crankshaft grinder. Unless your plans include an aftermarket Pontiac crankshaft, however, the machine shop you choose should have that ability to perform that task or confidence in the company it outsources it to.

       Any quality machine shop should have modern valve guide and seat equipment to precisely prepare its customer’s cylinder heads. This equipment from Serdi can cut multiple angles into a valve seat in a single pass, using the valve guide to properly locate the cutter in relation to the seat.

      I also feel that the best shops are those that offer engine break-in with a test stand or engine dyno. This allows you to verify that your engine starts immediately, idles and revs smoothly, is free of oil and coolant leaks, and ultimately confirms that your engine has been broken-in properly before ever leaving the machine shop. If you chose to spend the extra money, a dyno tune can be a great tool to measure your Pontiac’s output and ensure that it’s performing reliably and optimally under full-throttle conditions.

      Before contracting a shop for your rebuild, clearly discuss your expectations and specifically disclose the wear parts (valve springs, bearings, gaskets, etc.) you’ll be expected to buy from them. Most businesses have some type of policy in place that allows it to add a certain percentage onto the cost of the project if a customer supplies parts, and at that point, any warranty against failure is void. Some shops may even go so far as to simply refuse to assemble anything they didn’t supply. Some shops just aren’t willing to take this risk of failure.

       If new valves are part of your rebuild, then there’s a chance that your machine shop does not need to use this piece of equipment. If you’re planning to reuse your existing valves, however, a valve grinder like this is required to restore the surface of the seat angle or add other cuts that could possibly improve airflow.

       A surface mill is required when removing material from the mating surfaces of a block or cylinder head. Other uses include resurfacing a manual-transmission flywheel, or intake or exhaust manifold flanges. It’s a valuable piece of equipment that any machine shop should have.

      Once you have selected the machine shop you feel most comfortable working with and your rebuild project begins, it’s advisable to check in often to follow your engine’s progress. Asking questions and being visible is an easy way to learn and to be sure your project is on track. But you must also understand that, in business, there’s a fine line between being inquisitive and being a pest!

       When Rebuilds Go Bad

      A good machinist takes pride in the work and sincerely feels that what leaves the shop is as functionally sound as if it were as good as or better than new. Just because a machinist has good intentions doesn’t mean that accidents can’t happen, however. A good machinist can have a bad day, but the best machinists routinely check their work throughout the course of any task to prevent any associated failure.

      For any number of reasons, it’s sometimes easier to allow a shop to assemble your engine for you, and careless assembly can have a catastrophic outcome. If you choose to handle your own assembly, as a smart owner you can check your engine’s tolerances just before assembly to be sure your machinist wasn’t having a bad day when machining your components. That might help you gain trust in the machinist and the shop if future engine rebuilds or various projects are on the horizon.

       It’s obvious that a significant amount of material has embedded into this bearing. As bad as this might look, it actually performed its intended task. There was almost no major wear on the corresponding crankshaft journal.

       By design, bearings are sacrificial components. Minute particles passing through the lubrication system embed into them, saving the crankshaft journals. Once a bearing is no longer able to perform that task, distinct wear patterns can begin appearing on the corresponding crankshaft journal surface. This crankshaft was reused after removing 0.020 inch of its surface.

       This connecting rod bearing has experienced complete failure. Metallic particles in the lubrication system and extreme heat wore through all of the Babbitt layer and most of the copper layer, exposing the metal backing.

      A local assembler rebuilt this Pontiac 455 for its owner. It was a very basic rebuild like many of the Pontiacs the assembler rebuilt before. But it wasn’t broken-in on a test stand before it was returned to the owner. The owner simply installed it into his Pontiac, and it immediately started showing signs of significant internal issues. After a handful of miles, it was evident the freshly rebuilt engine required an immediate teardown. These photos reveal what was found.

      Working with an independent machinist to gain an understanding of what occurred, the best guess seemed to be that the rear camshaft plug was driven in a bit too far, and when the camshaft thrust plate was installed, all camshaft clearance was lost. It appears unlikely that the engine assembler had checked for any clearance during the rebuild.

      With the camshaft’s first revolution after immediate start-up, it’s evident that it churned into the steel plug, which sent metallic filings into the oiling system, where material was distributed throughout the entire engine. The metallic particles quickly damaged the piston skirts and bearings, several of which failed completely.

       This steel plug was driven too far into the rear opening of the camshaft bore, and when the camshaft and thrust plate were installed, the engine assembler neglected to check for proper clearance. The wear that followed sent metallic particles throughout the engine, causing a significant amount of damage and effectively destroying a freshly rebuilt engine.

       After removing the bottom plate from the oil pump body, there’s no question that metallic particles were being carried throughout the engine by its oiling system.

       Unfortunately, another set of new pistons is required during the rebuild. The deep grooves and embedded material can prevent the piston from properly maintaining cylinder seal.

      Unfortunately, examples like this are common. Though it may have looked like this 455 would never run again, it was completely disassembled and the reusable components were thoroughly cleaned. Several new components were purchased and the entire engine was properly rebuilt by another machinist shortly after these photos were taken. It has since given its owner a number of issue-free miles, but it was a rebuild that cost this owner twice as much as it should have. ■

       Found while rebuilding a different engine, the dark areas on the deck surface of this block are soot trails. This indicates that the cylinder head bolts used on this engine were not torqued properly or fatigued from overuse,