Valves & Valvetrain Parts

Valves allow gases to flow in and out of the cylinders, and seal the combustion chambers so compression can develop. They open and close in response to the lobes on the camshaft via the valvetrain. The air/fuel mixture flows in when the intake valve opens, and the spent exhaust gases flow out when the exhaust valve opens after the power stroke. Every engine has at least one intake and exhaust valve, while many have a pair of each.

Valvetrains differ according to camshaft location. On Over Head Valve engines the cam is in the cylinder block. On Over Head Cam engines one or two cams are on the cylinder head. On OHV engines lifters ride on the camshaft lobes, pushrods transfer motion up to the cylinder head, and rocker arms pivot on shafts or studs actuating the valves. OHC valvetrains may have pivoting rocker type followers and lash adjusters or buckets between the cam and valves.

Valvetrain problems are often caused by excessive clearance. As cam lobes, lifters/followers, pushrods, and rocker arms wear, clearance is increased. Once clearance starts to increase, the pounding experienced by each component becomes greater as the lash opens and is taken up during valve operation. This can result in bent pushrods and broken rocker arms. The most common valve failure is overheating, especially on exhaust valves, which causes the valve to “burn” and distort and/or crack.

Miles and engine heat can also take their toll on valve springs. The valve springs must have enough pressure to keep the valves closed and maintain valve lash. Seat pressure is usually 70-90 lbs. on a stock engine with open pressure at 200 lbs. or more. Weak valve springs can’t exert the proper amount of pressure, which can cause misfire and loss of power as engine speed increases, resulting in “valve float”, where the valves fail to close. In extreme cases valve float can allow the valves to contact the pistons on some engines, bending or breaking the valves and cracking or breaking the pistons.

Performance valvetrain components must be much stronger to function at high RPMs and overcome stiff valve spring pressure to open larger valves. Higher valve spring pressure is needed to prevent valve float at high RPM. Performance rocker arms and valve spring retainers are made of lighter materials to enable the engine to rev easier and achieve higher RPM, and components like roller lifters and roller rockers reduce power-robbing friction. Most performance pushrods are made of strong chrome moly steel, and larger diameter pushrods are available for some applications. No matter whether you’re looking for a stock replacement or a performance unit, we are your one-stop shop.