Valve Seat Width 1ZZ-FE

[unckybob]

I am lapping a valve on my 1998 Corolla with a 1ZZ-FE engine. Does anyone know what the valve seat width should be? I also need to know the valve seat contact width as well.

[fishexpo101]

Just guard against removing too much material, as there isn't too much margin there compared to other engines. That said, the specs listed in the FSM are:

Minimum width on intake valve seat: 3.3 mm
Minimum width on exhaust valve seat: 3.2 mm
Valve contact seat width: 1.0 to 1.4 mm

[unckybob]

Unfortunately, I lapped the valve out to around 2.0mm before I even posted to this thread. I talked to an old timer who said on an exhaust valve you can grind out from .085 to .115 inches, which translates from 2.16mm to 2.92mm. Does this jive with your experience?

What happens if the contact area is too large?

[fishexpo101]

Kind of a mixed bag, if the seats are too narrow/wide. As for the numbers the older mechanic gave you, that works on SBC all day long, as they tend to spec 1/16" on the intakes (~1.6mm) and 3/32" on the exhaust (~2.4mm).

Generally speaking, you can safely run a wider seat contact on the exhaust valves than the intake ones.

Drawback of running too narrow of a seat:
Increased wear on valve and reduced heat transfer ability

Drawback of running too wide of a seat:
Increased likelyhood of leaking and excessive fouling from buildup of deposits

I'd definitely double check if there are truly 2.0 mm wide or a little tighter than that. I'd also double check the margin thickness (the thickness between the face of the valve to where the seat is formed). Should be no less than 0.7 mm. Also where the valve seat sits - is it closer to the margin (sits high) or away from the margin (sits low) - Toyota specs call for it to be centered, compared to others that light it closer to the margin.

Specs on this engine are unique in that the valve seats are chemically applied instead of the typical practice of pressing on the seats. This makes for much thinner seats that generally possible, coupled with the water jacket is very close to the valve seats - makes it much easier to pull heat away. Which makes for the use of thinner valve stems, lighter valve springs, thinner cam lobes, etc.

I think you may still be OK - depending on where the valve touches and how much the seats are lapped down.