Installing bronze valve guides requires precision and the right tools. This guide provides a detailed procedure for removing old guides and installing new ones without damaging the cylinder head. While specialized head machine is ideal, this process can be achieved carefully with the proper preparation and technique.
Here’s a step-by-step procedure for installing standard bronze .502″/.343″ guides with a .530″ top for the seals:
Tools Needed:
- 3/8-16″ tap
- 15/32″ core drill
- 15/32″ conventional drill bit
- 1/2″ (piloted) reamer
- Guide driver
- Hammer (or an air tool)
- (8) 3/8″-16 bolts, 1/2″ long
Removal Procedure:
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Tap the Guide: Tap the top (seal-side) of the guide with a 3/8″-16 tap deep enough to accommodate the 1/2″ long bolt.
Alt: Close-up view of tapping a bronze valve guide with a 3/8-16 tap in preparation for removal.
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Prepare for Drilling: Leave the bolts in position.
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Core-Drill the Guide: Core-drill most of the guide from the bottom until the drill-tip (pilot end) hits the bolt.
Alt: A 15/32″ core drill removing the majority of a bronze valve guide from the cylinder head.
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Conventional Drilling: Using the conventional 15/32″ drill bit, drill down again until the drill hits the bolt.
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Remove Remaining Shell: At this point, most of the guide should be removed. Using the guide-driver (through the guide “shell”) against the bolt, drive the remaining “shell” out, either by hand-held hammer or with an air hammer. The remaining piece should come out with minimal effort.
Alt: Using a guide driver and hammer to gently remove the remaining shell of a bronze valve guide after drilling.
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Clean-Up the Hole: Using the 1/2″ guide-reamer by hand, turn it through the guide holes to “clean-up” the existing holes. This step ensures a smooth surface for the new guide.
Installation Procedure:
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Cool the Guides: Place the new guides in a small cooler with dry ice for about an hour. This will cause the guide to contract, making installation easier. Alternatively, if dry ice is unavailable, a conventional freezer can be used.
Alt: Bronze valve guides submerged in dry ice inside a cooler to reduce their size for easier installation.
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Heat the Head: Heat the head in a barbeque for about 1/2 hour (near 300°F). The exact temperature isn’t critical, but heating the head will expand the guide holes.
Alt: Cylinder head being heated in a barbeque to expand the valve guide holes before installing cooled bronze guides.
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Install the Guides: Wearing gloves, lay the head on the bench. Take the (ice-cold) guides one at a time, dip the tip in some oil, and push into the head. They should go in at least halfway by hand. Finish the installation with a driver. Use a hand-held hammer and the correct installation driver. This will be a different driver than the one used for removal.
Important Considerations:
- Seat/Guide Alignment: This procedure will maintain the seat/guide alignment accurately, assuming all was concentric initially. Quick-check the concentricity by lapping the valves.
- Preparation: Prepping, heating the head, and freezing the guides are critical for a successful installation. While the drilling can be time-consuming, the overall process is straightforward with the right tools.
- Guide Material: Use high-quality bronze valve guides, such as those from Ferrea or Brodix.
- Gentle Installation: Never hammer on any guides during removal with aluminum heads/bronze guides without prepping the original (worn-out) guides first. Never “just hammer the new ones in.”
By following these steps, you can install bronze valve guides effectively and maintain the integrity of your cylinder head. Remember that precision and patience are key to a successful outcome.
