Valve Guide
The valve guide allows movement and displacement of the valve as a result of acceleration of the camshaft and keeps the valve in the center of the valve seat. Valve guides are used to resist lateral forces operating on the valve stem. They conduct part of the combustion heat from the valve head to the cylinder head. These extreme loads define the correct choice of material with appropriate characteristics for the valve guide, which is of critical importance for product quality.

The key characteristics of the materials used for the valve guides are low friction and high thermal conductivity. We are able to manufacture a motor valve guide, usually made of cast iron, aluminum bronze valve guide, and brass material valve guide.

Qualified Material for Valve Guide
Sr No. Material c Si Mn Cr Cu Sn S P Fe Pb Al Zn Ni
1 Aluminum Bronze 0.6% - 0.9% 2.0% - 4.0% 57.60% 0.25% Max 0.3% - 0.6 % 1.5% - 2.0% Balance
2 Cast Iron 0.3% - 3.90% 0.2%-2.90% 0.60%-0.70% 0.30%-Max 0.50% - Max 0.10% - Max 0.15% - Max 0.40% - 0.70% Balance
3 Brass TR 56-58% TR 0.35% 2% - 3.4% TR TR

In most types of reciprocating engines, a valve guide is provided for each poppet valve in the cylinder head. Together with the valve spring, it serves to positively locate the valve so that it can make proper contact with the valve seat. A valve guide is a cylindrical piece of metal, integrally pressed or cast in the cylinder head, with the valve reciprocating inside. The guides also serve to direct heat from the combustion process out of the exhaust valve and into the cylinder head, where it can be absorbed by the cooling system. Bronze is commonly used, as is steel; A balance between valve stiffness and wear is essential to achieve a useful life.

The clearance between the inside diameter of the valve guide and the outside diameter of the seat valve stem is critical to proper engine performance. If there is very little clearance, the valve may stick as oil contaminants and thermal expansion become factors. If there is too much clearance, the valve may not seat properly and excessive oil consumption may occur.

Over time, the inner diameter of the valve guide and the outer diameter of the valve stem can wear out. In the 1980s, many U.S. production engine remanufacturers began reaming, rather than replacing, valve guides as part of their remanufacturing process. They found that by reaming all valve guides on one head to a standard size (typically 0.008-inch diameter) and installing remanufactured engine valves that have stems that are also oversized, a typical engine head can be remanufactured in much less time. Since the reaming process leaves the valve guide with a much better surface finish and shape than typical replacement guides, and since oversized valves often have chrome stems, remanufacturers also found that the train warranty of valves is practically eliminated.

Studies have been conducted showing that through proper reamer selection and reaming, valve guides can be reamed quickly and efficiently to a consistently repeatable size.
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