Exhaust valve face angle 45 vs 43 degrees

[dibbons]

This chart is from the 1973 Plymouth factory service manual. Do you really think machine shops are following this guide (or are even aware of it) which shows different valve face angles for intake and exhaust valves (45 degrees and 43 degrees respectively)?

 

[moper]

I'm sure they don't. That being said - that spec is for a single angle valve job for use with leaded fuel that helped protect and lubricate that exhaust seat. About 8 years after that was published as a spec performance valve jobs were on hardened seats, with multiple angles, for use without the lead. There is no performance or longevity reason to use it now, and a shop would have to buy and maintain another specialized cutter for it.

 

[yellow rose]

I am aware of it. And I ignore it.

I grind all of my 45* seat valves on a 44* angle.

It's done to minimize the change in length of the valve from grinding.

Now, if you are doing a 50* seat you need to machine the valve ....