Lapping valve issues

[MrChilliVanilli]

Hi guys,
I need some advice with lapping new valves into the seats.
It’s an Empi Head with intake 40 exhaust 37,5 valves and I’m trying to fit the new valves into the seats. Somehow I’m only grinding on the inner edge of the valve and the outer edge of the seat.
Do I need to cut the seat more deeper or does someone have an idea what the issue is?
Attached are some pics to make my issue more clear.

Greets

Old valve already looks like it wasn’t seated properly

[Dan Ruddock]

Looks in the pics like your new valves are bigger.

[MrChilliVanilli]

I have the same issue with all valves. The intake valves are 40 and Show the same issue

[Dan Ruddock]

Are the original valves smaller than the new ones? Could just need the seats to be re-cut.

[MrChilliVanilli]

Old valves are the same size, but they also don't look like they were sitting properly in the seats. That’s why I’m wondering if the seats are properly cut.

[MrChilliVanilli]

Old valves are the same size, but they also don't look like they were sitting properly in the seats. That’s why I’m wondering if the seats are properly cut.

[Ohio Tom]

My recommendation is to have a proper valve/seat grind done.

Obviously, there is an angle, or diameter issue going on. A proper grind will set the seat margins for both the valve and the seat. This is the "skill" that a proper head guy goes thru when grinding.

I frequently run into this same thing when installing new valves in old heads.
The solution is to start over and grind everything. Lap the seats, then grind the other angles to meet up to the seats.


Lapping is just to clean up the seats. It's not meant to create new seats.

[FreeBug]

[vwracerdave]

With the precision valve and seat cutters used today there is no longer any need to hand lap the valves.
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[Ohio Tom]

I use lapping to put witness marks on the seat and valves so I know where to stop grinding the other angles.
Dychem works too.

[Brian_e]

You say they are 40x37.5, but it looks like you should be using a 35mm exhaust valve instead.

You need to measure the ID of the seat ring, and then add about 88%, and that should get you close to the OD your valve needs to be.

Those are single angle seat cuts. If you take the heads to any engine machine shop, they can do a real multi-angle valve job for you. A correct valve job can pick up close to 20cfm over that you have going there.

Brian
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[spencerfvee]

[MrChilliVanilli]

Sorry guys, my mistake... the exhaust valve is actually 35.5 not 37.5. I don’t know why I had this number in my mind

Thank you for all the help. I’ll try to cut the seat deeper. This was also my first thought, that the seat is not cut deep enough, but I wasn’t sure how far I can go and if there might be some other issues.
Unfortunately we bought the engine like this and have no history about the parts and the rebuild.

[evanfrucht]

Lapping will NOT fix it. You need a valve grinder and seat grinder.
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[spencerfvee]

[Brian_e]

You need a larger diameter seat insert. Cutting the seat wider won't help. It will end up seating out on the aluminum past the steel insert.

Those might be copies of a 041 VW head. They had 39x32mm valves. Measure the ID of the seat and compare it to the OD of the valve. I am betting if you lap a standard 32mm exhaust valve it will be positioned on the valve face in the right spot.

That might be the correct fix for this.

Brian
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[MrChilliVanilli]

The valve guides are still ok, I checked them already.
I started to recut the seat with a 45 degrees cutter and it looks much better.
Now the question is, how far can I go?
Here are pictures of the current seat.

Is it possible someone could post some pics of proper seated valves and seats?

[Brian_e]

Here was a crappy pics of a multi angle seats I cut.

Here is a lapped intake valve with a back cut added. Push the intake out to the edge of the valve, and try to center the exhaust seat on the valve face. I like to narrow the seat width down to .040" on the intakes , and .060" on the exhausts. Adding the extra angles will make a HUGE difference in flow over the single angle.

Brian
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[mark tucker]

1 rong size valves,2 needs proper valve job.and cleaning.

[MrChilliVanilli]

EXhaust ID 31mm OD 37mm
Intake ID 35 OD 41mm

Is there a list of which valve should go with which seat?