Can some explain valve throating for me?

[Texarkana]

Hey all, In my engines class we just started getting into upper end theory and service. My homework is key terms from the upper end chapter. One of these key terms is “throating” and all my book tells is how to throat a valve in a machine shop.

Can someone explain to me what a valve throat is, how it affects engine performance as well as the pros and cons of valve throating? Thanks!!

Topic

[Alex F.]

Im sorry i dont have and answer,but High school or college?

[Texarkana]

Community College. I’ve come to realize the program I am in is poorly funded and planned out which making learning more difficult than it needs to be. I end up spending a lot of time on google and wikipedia because my book is poorly researched and written. It seems like the author assumes you already know quite a bit about the subject when the reality is I’m still a novice.

[Dustin Hicks]

[quote=”Texarkana” post=66710]…Can someone explain to me what a valve throat is, how it affects engine performance as well as the pros and cons of valve throating? Thanks!![/quote]

“Throating” & “topping” are terms describing how to adjust the position where the valve contacts the seat. Prussian blue is used to find where the contact points are. If the blue is centered on the valve face and contact width is in specs, no extra work is needed (other than lapping). If the blue is too high on the valve face, the contact area is lowered by a “topping stone” My Dodge’s shop manual recommends a 15 degree stone, others say a 30 degree stone. If the blue is too low on the valve face, a “throating stone” of 60 degrees is used to raise the contact area. Remember – throating or topping NARROWS the contact area width, so the seat contact area may have to be widened slightly to return to spec. ALL THIS IS DONE ON THE SEAT, NOT THE VALVE.

This work is done to ensure a good seal between the seat and the valve. It also increases valve longevity. Although I wouldn’t do it, you might get away without it in a low buck, stock build with new seats and valves. It’s CRITICAL to do this in a high buck, high performance engine even with new seats and valves.

[Alex F.]

I’m sorry to hear that, im 14 and trying to prepare for an automotive future (Thats why i asked)—I’m sorry i cant help you—I cant stand the society were a “Theater” class is more funded than an auto class
To quote Hank Hill ” See how long your girlfriend stays around when your truck is on the side of the road and you start asking your carburetor HOW IT FEELS” :angry: :sick:

[Author]

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