TECHNICAL INFORMATION

At AV&V, we take an extra step to centerless grind the stem to a micro finish surface before the final nitriding or chrome process. This gives our valves that very slippery surface for an exceptional wear characteristic. For the tip, we have chosen to go with a friction weld bearing alloy material. This hard tip can be reground in the future and is more suitable with rocker applications.

As for the stem diameters, we have made the exhaust models slightly smaller than the intakes so the engine builder can use the same AV&V reamer on intake and exhaust guides. (Note: This only applies for manganese bronze guides. Cast iron guides used on exhaust may require more clearance.)

There are two series of valves available from AV&V, the Replacement series and the Black Tulip & Chrome Tulip valves series. Both feature the same material and surface characteristics but have different profiles.

The length and head diameter on the heavy-duty stainless replacement series are identical to the OEM dimensions, with the exception of the Shovelhead intake, which is 1.955’’ instead of 1.940’’, to achieve a better 3 angle seat job. The head’s shape has been optimized & swirl polished to improve flow characteristic.

"Always check and confirm running clearance when installing new valves. Stock cast iron exhaust valves guides may need to be honed to get correct valve to guide clearance."

On the Black Tulip & Chrome Tulip series, countless hours of flow testing has been done to improve the shape of the valve for better airflow. The smooth dish face of the intake valves promotes a better combustion in the chamber while the exhaust valves features a thick margin for better flow. All chamfers and radiuses on both intake and exhaust have been optimized for better airflow. Side by Side, our 1.570’’ exhaust Tulip valves for Evo or Twin Cam engines can flow the same or better than some 1.625’’ valves presently available. Also, by using a smaller exhaust valve, it allows you to use a larger intake or a longer duration cam. If you wish to use a larger exhaust valve, you can use the AV&V 1.610’’ valve for a higher flow.

Now look at AV&V valve guides features & advantages:

A.) CNC machined to exact specifications for each different application.

B.) Smooth finish to prevent damaging the I.D. of the head receiver holes.

C.) A self centering tapered section on each guide to allow a fast, effortless and precise installation.

D.) Valve guide I.D.’s are chamfered on both sides so you don’t need to chamfer it after reaming or honing. It’s already done! The chamfer prevents the oil from being scraped away at every stroke of the valve (A leading cause of premature wear on stem.)

E.) A ‘’Super Grip’’ finish provides a non-slip surface for all styles of valve seals. Note: We recommend using a small amount of Loctite as insurance when using OE style seals.

F.) Shorter valve seal area for high lift application on every guide. Except Evo/Twin Cam stock replacement models. We also incorporated a small flange on every Evo/Twin Cam guide to stop it at the right depth. This design improvement will save time and installed height is always correct.

G.) Viton O-ring. This is a free insurance to prevent against oil infiltration between guide and head. (This could happen when guide removal or installation has been done the wrong way the previous time).

H.) AV&V engraved part number: Useful to identify part number, model and oversize.

I.)  The I.D. of the guide is unfinished, so after it is installed, it is ready to be precision reamed with AV&V special reamers or honed using the Sunnen method.

AV&V manufactures valve guides from two different materials; manganese bronze or micrograin cast iron.

Myth: Bronze guides don’t last.

Fact: Early silicon based bronze alloys used in valve guide applications quickly earned the reputation of having poor wear performance. It wasn’t until high nickel based bronze alloys (AMPCO 45) were introduced that the valve guide market was able to offer a superior bronze valve guide, suitable for high heat applications (Nitro-methane etc…).

But still, people realised that that material was not lasting as long as cast iron. One of the main reasons is because this material needs to be fit at a looser clearance to prevent seizing problems.

After extensive research, the majority of automotive and motorcycle racing head manufacturers and rebuilders are now installing manganese bronze alloy guides. The two principal advantages of this alloy is superior heat transfer and also that the engine builder is able to fit the guides at a tighter clearance for a better oil film control and longer life. We should call this alloy ‘’zinc bronze alloy’’ instead of manganese bronze because it contains nearly 30% zinc, 2-3% manganese. Manganese is the hard part of the recipe and the zinc is the bearing ingredient, a material which is also a self lubricant.

Myth: Why use manganese bronze alloy when I know that a stock Evo or Twin Cam guide can last 60,000 miles or more?

Fact: It’s true that for stock replacement, cast iron guides work fine. However, the problem starts with the high performance applications. In high lift applications, the guides need to be shortened. With more heat and side load from the valve involved, the oil film between valve and guide deteriorates more quickly. In addition to increased viscosity breakdown, cast iron guides are also an abrasive material which induces the premature wear that we’re used to see with this application. In cases where valves have collided with each other or with the piston, cast iron guides have been found to fracture and deposit damaging fragments into the cylinder and combustion chamber. This is not the case with manganese bronze guides.