Universal Fit, .502" O.D. Guides

Hardened Cast Iron Valve Guides, 11/32" X 2.500" Long

Hardened Cast Iron guides have a spiraled ID which goes through the guide around 75% of the length.

Hardened guides require a few extra procedures after installation but once properly installed and mated with hard stem valves, (chrome and nitrided [melonite]), their wear resistance is outstanding!

Hardened guides should be given a carbon cut on all exhausts. This is done on the chamber side of the guide on the exhaust only. Intakes just get an ID chamfer on both ends and the exhaust gets a chamfer on the top side also. Carbon cuts are commonly done using a guide liner cutter/reamer or a reamer for oversize valves. .015"-.030" over is fine.  Just cut into the guide around .150"-.225" deep.

Hardened guides should be cleaned with a spinning nylon brush and cleaning solvent before assembly. Proper cleaning is imperative because any debris left hiding in the spiral groove can lead to galling and other forms of guide failure.

When hardened guides became more common, we had to learn the hard way about these extra details.

This type of guide is used in heads which have "integral" guides. This means the guides are part of the casting and are not removable.

Heads are set up in a "Seat and Guide Machine" and each guide is core drilled, then reamed to .500".

Guides are then pressed or "driven" into place. Any extra length is then machined off.

In our shop, after the guides are installed, we take a .500" valve seal cutter to clean up any old remaining guide material from the seal mounting area of the guide so .500" Positive seals could be installed.

If needed, guide inside diameters are then fitted by honing w/ Sunnen tooling.

     Specifications:

• .502" Outside Diameter
• 2.500" Overall Length
• .343" Inside Diameter
• Spiral ID: YES
• Plain ID: NO
• Material- Cast Iron, Hardened
• Manufacturer- Precision Engine Parts
  
• Quantity included in purchase- sixteen guides

TECH NOTE: Aluminum heads always have some form of guide inserts. This type of guide is not intended for such heads. Applications w/ aluminum heads normally require replacement guides with the same shape as what was removed.

    Alex's Parts- The smart choice in valve train parts~