Engine Rebuilding : Engine final assembly>Assemble heads

Assemble heads

Part 1. Preparation and safety

Objective

• Assemble the heads.

Personal safety
Whenever you perform a task in the workshop you must use personal protective clothing and equipment that is appropriate for the task and which conforms to your local safety regulations and policies. Among other items, this may include:

• Work clothing - such as coveralls and steel-capped footwear
• Eye protection - such as safety glasses and face masks
• Ear protection - such as earmuffs and earplugs
• Hand protection - such as rubber gloves and barrier cream
• Respiratory equipment - such as face masks and valved respirators

If you are not certain what is appropriate or required, ask your supervisor.
Safety check

• Make sure that you understand and observe all legislative and personal safety procedures when carrying out the following tasks. If you are unsure of what these are, ask your supervisor.

Points to note

• Be sure to keep the valves and the springs and retainers in the right order, and double check to make sure that the valves are going into the correct head. 

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Part 2: Step-by-step instruction

1. Prepare for assembly
   Take all the keepers and put a small dab of grease inside each of them with a cotton swab. Then, do the same for any valve guide or umbrella seals, if you will be using them. Make sure to wipe a little bit where the seal will contact the valve stem.
   Go to your valve train organizer and pull the valves out one at a time and lubricate the valve stems with assembly lubricant. Remember, only do one at a time to keep them in order.
2. Install valves and springs
   Be sure to keep the valves and the springs and retainers in the right order, and double check to make sure that the valves are going into the correct head. The identifying mark should still be on at least one of the heads.
   For stock style metal oil shields you will need a set of sixteen O-rings to seal the valve stem. With standard style retainers like these, oil can drip through the springs onto the valve stem and slide right down the valve guide. To control this, a seal can be pressed onto the guide if your heads are machined to accept this kind of seal.
   Another way to keep too much oil from going down the guide is to slide an umbrella seal onto the valve stem.
   Some engines use mushroom type oil shields to keep most of the oil off the valve stem, but they need to have an O-ring to seal the drips that would come down past the retainer and keepers.
   Put the shim and spring on and then the oil shield. Don't put the O-ring on yet, the retainer has to go on first and the spring needs to be compressed as far as possible. Now, put one of the O-rings on to the valve tip. It will want to stay in the first groove where the keepers go, so carefully push it down into the second groove of the valve stem. A small flathead screw driver will usually do this, even if the spring won't compress very far.
   When the O-ring is fully seated in the second groove, install the keepers in the first groove and release the compressor. The retainer will pinch the O-ring against the keepers and the valve stem to keep oil from dripping directly down onto the valve guide.
   Other engines have a regular style retainer with no oil shields. In this case, install the umbrella seals first. If the head uses guide seals, there's usually a protector cap for the valve tip and the seal can slide by the grooves without getting scratched.
   On some engines there are umbrellas that simply slide on before the spring and retainer.
   Rotate the springs a little to make sure they are sitting properly in their seat positions in the head, then squeeze them with a valve spring compressor.
   If you need to adjust the compressor to put the keepers in, keep some pressure downwards on the fork so that it doesn't slip up and off the retainer. The dabs of grease should hold the keepers in place, to leave both hands free to work the compressor. Be aware that new springs or springs with shims will feel a lot tighter then the old ones.
3. Repeat the process
   If you have all the parts laid out in the right order, it should be easy to work down the line, one after the other, but don't rush this. Take your time and make doubly sure that the right valves are going into the right guides in the head. This is especially important if, for any reason, the valves did not need to be ground and they are going back into the head as they came out, but with new valve stem seals. In this case the valve faces have to match back up with their correct valve seat in the head.
   When all the valves and springs are in, check to make sure that all the springs are seated correctly in the head. Then, check the gaps between the keepers at the valve tip. They should not be butted together on one side with a large gap on the other. They should be as evenly spaced as possible like this, to distribute the holding tension more evenly on the valve tip.