13 Step Cylinder Head Remanufacturing Process:
It is important to take a meticulous approach to remanufacturing cylinder heads. The process for rebuilt heads has been pioneered and refined over many years. During that time experts in the field have gotten cylinder head remanufacturing down to a science. The industry has developed a 13 step process for remanufactured heads which ensures the highest quality rebuilt cylinder heads are ready for the customer’s needs.
Step 1: Tear Down Process for Remanufactured Heads
The first step for remanufactured cylinder heads is the initial tear down process. Technicians remove all of the valves, guides, seats, springs and injector cups. The rebuilders then visually inspect each part as well run quality control and structural tests to see if any of these parts can be re-used. For example with the valves, the rebuilders should inspect the entire valve to see if there are any erosion pits. The majority of rebuilt cylinder heads have the erosion pits that need to be repaired. Later you must regrind to the proper angle and then regrind the stems.
Step 2: Initial Cleaning and Magnafluxing
The second step in the remanufacturing is the initial cleaning and magnafluxing. Cleaning the rebuilt cylinder heads is a very important step during the remanufactured head process. Oftentimes used heads arrive at the facility with dirty, grime, oil and lubricants embedded on the cast iron. In order to properly indentify cracks and evaluate structural integrity the remanufactured cylinder head must be completely clean. At this stage it is important to also measure the surface thickness based upon OEM specifications. For example the OEM specs for the Caterpillar D334 remanufactured heads are as follows: New Height is 3.400″ and the Minimum Height is 3.3940″. This gives the rebuilder a bearing of where thet need to grind later on in the remanufactured head process. If the height of the rebuilts heads is below the minimum height when the rebuild team receives it they should simply replace the entire head as it is deemed to be unfit for remanufacturing. The rebuilder must also check the warpage, compression and water port seal area.
Step 3: Deep Cleaning All Rebuilt Heads
The third step in the head remanufacturing process is the deep clean. Once the rebuild team removes the initial dirt and grime from the rebuilt cylinder heads the expert rebuilder must do one of three deep cleaning processes. The rebuild team can place the rebuilt head in a hot tank, a steam clean tank or a wash tank. The hot steam tank heats up the remanufactured heads to over 200 degrees Fahrenheit and literally burns off any component that is not part of the rebuilt head. Once the deep cleaning is complete the rebuilder taps all of the bolt holes and repair as needed. Expert rebuilders strongly believe in going the extra mile while cleaning the remanufactured cylinder heads, as even a minuscule amount of dirt can hamper the grinding or crack repairing process.
Step 4: Pressure Testing the Remanufactured Heads
The fourth step for remanufactured cylinder heads is pressure testing the unit for further structural integrity. Most rebuilders place the rebuilt cylinder heads in a Newclear Pressure Regulator Machine for 20 minutes. The Newclear Pressure Regulator Machine will subject the remanufactured head to 60psi at 200 degrees Fahrenheit. What this does is it pulls water through any cracks that may be present. The quality control manager should check the guide thread, in and around the seats and in-between the valves. After the rebuilt cylinder head is removed from the Newclear Pressure Regulator Machine it is important to inspect the remanufactured head for additional warpage and shrinkage which would be later removed during grinding.
Step 5: Researching Remanufactured Head Parts
The fifth step to manufacturing rebuilt cylinder heads is to determine what parts need to be replaced. The rebuilder then verifies the quantity and part number. You can either use your own internal OEM certified remanufactured parts or replace with brand new parts from reptuable suppliers if requested by the customer. Typically, you should replace worn seats, guides and valves for all of remanufactured heads.
Step 6: Inventory Management Process for Rebuilt Heads
The sixth step in the head rebuild process is to fill out a materials requisition form to for the parts department. Most inventory management systems direct the head rebuild management team to make the best decisions regarding what parts to use for the remanufactured cylinder heads process.
Step 7: Surfacing the Deck of the Remanufactured Heads
The seventh step regarding head remanufacturing is to surface the remanufactured head as needed. It is recommended to use the Berco Grinding and Milling Machine on all of remanufactured cylinder heads. The Berco Grinder uses a carbonate cutter which uses the flat cutting technique. The rebuilder then mills the top completely off the rebuilt cylinder heads which is referred to as “surfacing the deck”. Expert rebuild teams do both metal stitching and hot welding techniques to repair cracks in the rebuild heads. Metal Stitching involves boring a series of holes completely removing the crack, threading the holes with pins/plugs and then resurfacing the raised surface on the rebuilt cylinder heads.
Hot welding involves placing the entire remanufactured head in the hot oven, heating up the cast iron to 1100 degrees Fahrenheit and then doing an arc weld while the entire head is hot. After arc welding the rebuilder places all of the remanufactured cylinder heads in a sand pit for 24-48 hours so that metal contraction occurs at the same rate in an insulated environment. Remanufactured heads rebuilt using the hot oven technique must be cooled in the insulated environment so the various metals in the cast hold the weld.
Step 8: Installation of Injector Tubes Back Into the Remanufactured Cylinder Heads
The eight step in the head remanufacturing process is to install the injector tubes. The teams typically replace the injector tubes during the head remanufacturing process. Most rebuilders use either brass, copper or stainless steel injector tubes. Then the teams use a punching machine to seat injector tube correctly into the injector hole. The injector tubes purpose is to seal out coolant passages as well as seal the combustion chamber. Some rebuilt heads have O-Rings seated around the injector tube, others do not. The type of injector tube used depends on the head composite metal and what the OEM specifications call for. The rebuild team can use OEM or Aftermarket injector tubes depending on customer preference.
Step 9: Pressure Test the Rebuilt Heads a Second Time
The ninth step in the remanufacturing process is to pressure test the rebuilt cylinder heads for a second time using the Newclear Pressure Regulator Machine. It is important to pressure test all completed remanufactured cylinder heads a second time to make sure the hot weld or cold weld procedure has maintained its integrity. The quality control department should check for any leakage using both visual inspections through a glass magnifying screen as well as measurements of water underneath the head. The transparent pressure plate provides 360° rotation capability which allows for an adjustable center of gravity for the rebuilt cylinder heads. The system also contains an in-line heater system for both cold hydraulic and hot hydraulic testing on remanufactured heads.
Step 10: Prepare the Remanufactured Heads for Assembly
The tenth step for remanufactured heads is to prepare the head for assembly. Once the rebuilt cylinder heads have been surfaced and pressure tested it is then time to reassemble the head. The team wire wheels all ports and surfaces then grinds and lap valves & seats. After that is completed the team checks valve recession. Checking for valve recession is critical! The valves need to be flush as the piston strikes up +.001″ or -.001″. The quality control department inspects and if necessary immediately fixes valve recession issues on all of the rebuilt heads.
Step 11: Final Wash of All Finished Rebuilt Heads
The eleventh step during the remanufactured head process is to steam clean or use a wash tank. The steam clean process takes the remanufactured heads and pre-washes it in a steam bath. The steam bath removes additional grime and solvents that may have accumulated during the grinding process. After the remanufactured heads are cleaned the rebuild team stamps the serial number on the rebuilt heads as well as the estimate number and the employee’s initials.
Step 12: Paint and Package All Remanufactured Heads
The twelfth step for rebuilt heads is to assemble the entire package. The team reassemble the seat keepers, then paints or Cast Blasts and package. All of the remanufactured heads are then painted to OEM specifications using industrial paint. The paint the team uses helps prevent rust and durable enough withstand environmental changes.
Step 13: Rust Prevention Measures and Preparation of the Remanufactured Heads for Shipping
The thirteenth and final step for rebuilt cylinder heads is to spray with a rust preventative oil and package again. The rebuild team should supply custom boxes per each remanufactured head then wrap in plastic and place the entire remanufactured cylinder head in a wooden box for shipping.
Capital Reman Exchange has been in the business of remanufacturing engines and parts for years and has gained a reputation as remanufactured cylinder head experts. To learn more about remanufactured or rebuilt cylinder heads view it here:
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