Posted by Vaughn [172.68.141.247] on Friday, April 21, 2017 at 09:41:16 :
In Reply to: Hardened Intake Valves & Seats posted by Matt Wilson [108.162.221.37] on Thursday, April 20, 2017 at 23:40:05 :
Intake valves run fairly cool from fuel/air passing over the head so there really isn't the need to install special heat-resistant valve-insert rings. The valve's head is also cooled by the seat in the engine block. The valve-insert rings themselves interfere with the flow of heat between the insert and the cylinder block so the valve-insert ring runs hotter than just a seat in the block. Installing valve-insert rings on the intake side actually makes cooling the valve worse, resulting in a hotter running intake valve that wears more rapidly, something you don't want.
On the exhaust side of the heavy-duty engine of a power-wagon, valves can actually become red hot during operation depending on engine load or engine RPM, so for this reason, special heat-resistant valve-seat inserts are required and also a water distribution tube for cooling the seat area.
You now have the down side of seats on the intake side, and good machinists are very careful not to damage a customer's item.
If take head with overhead valves and have it reconditioned and when finished you see deep grooves on the mating surface or a burnt valve that was resurfaced and still has a burnt groove in it reinstalled in the head, you might not get a warm fuzzy feeling and would want to avoid using them in the future.
Everyone has an opinion, however, I don't recall ever seeing a post or multiple posts we the guys were complaining of burnt intake valves using unleaded or ethanol mixed fuels.
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