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Lapping valve issues
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MrChilliVanilli
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PostPosted: Tue Feb 16, 2021 6:50 am    Post subject: Lapping valve issues Reply with quote

Hi guys,
I need some advice with lapping new valves into the seats.
Itís an Empi Head with intake 40 exhaust 37,5 valves and Iím trying to fit the new valves into the seats. Somehow Iím 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

Image may have been reduced in size. Click image to view fullscreen.


Image may have been reduced in size. Click image to view fullscreen.


Image may have been reduced in size. Click image to view fullscreen.


Old valve already looks like it wasnít seated properly
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Dan Ruddock
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PostPosted: Tue Feb 16, 2021 6:58 am    Post subject: Re: Lapping valve issues Reply with quote

Looks in the pics like your new valves are bigger.
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MrChilliVanilli
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PostPosted: Tue Feb 16, 2021 7:11 am    Post subject: Re: Lapping valve issues Reply with quote

I have the same issue with all valves. The intake valves are 40 and Show the same issue
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Dan Ruddock
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PostPosted: Tue Feb 16, 2021 7:43 am    Post subject: Re: Lapping valve issues Reply with quote

Are the original valves smaller than the new ones? Could just need the seats to be re-cut.
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MrChilliVanilli
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PostPosted: Tue Feb 16, 2021 7:58 am    Post subject: Re: Lapping valve issues Reply with quote

Old valves are the same size, but they also don't look like they were sitting properly in the seats. Thatís why Iím wondering if the seats are properly cut.
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MrChilliVanilli
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PostPosted: Tue Feb 16, 2021 7:58 am    Post subject: Re: Lapping valve issues Reply with quote

Old valves are the same size, but they also don't look like they were sitting properly in the seats. Thatís why Iím wondering if the seats are properly cut.
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Ohio Tom
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PostPosted: Tue Feb 16, 2021 9:25 am    Post subject: Re: Lapping valve issues Reply with quote

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.
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FreeBug
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PostPosted: Tue Feb 16, 2021 9:58 am    Post subject: Re: Lapping valve issues Reply with quote

Ohio Tom wrote:
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.


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vwracerdave
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PostPosted: Tue Feb 16, 2021 11:29 am    Post subject: Re: Lapping valve issues Reply with quote

With the precision valve and seat cutters used today there is no longer any need to hand lap the valves.
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PostPosted: Tue Feb 16, 2021 12:28 pm    Post subject: Re: Lapping valve issues Reply with quote

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.
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Brian_e
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PostPosted: Tue Feb 16, 2021 1:32 pm    Post subject: Re: Lapping valve issues Reply with quote

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.

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spencerfvee
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PostPosted: Tue Feb 16, 2021 3:07 pm    Post subject: Re: Lapping valve issues Reply with quote

MrChilliVanilli wrote:
Hi guys,
I need some advice with lapping new valves into the seats.
Itís an Empi Head with intake 40 exhaust 37,5 valves and Iím trying to fit the new valves into the seats. Somehow Iím 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

Image may have been reduced in size. Click image to view fullscreen.


Image may have been reduced in size. Click image to view fullscreen.


Image may have been reduced in size. Click image to view fullscreen.


Old valve already looks like it wasnít seated properly
Image may have been reduced in size. Click image to view fullscreen.
..............................................................................................hi by looking at your old ex valve it was not seating right on the valve seat .way to to low on the valve .empi is great for selling heads that they say are 37.5 valves they put a 37.5 valve on a stock seat . i see this all the time . but a set of 35mm ex valves and that will be the fix i all so lap all my valves . you would not be live how many new heads leak spencerfvee
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MrChilliVanilli
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PostPosted: Tue Feb 16, 2021 11:36 pm    Post subject: Re: Lapping valve issues Reply with quote

Sorry guys, my mistake... the exhaust valve is actually 35.5 not 37.5. I donít know why I had this number in my mind Rolling Eyes

Thank you for all the help. Iíll try to cut the seat deeper. This was also my first thought, that the seat is not cut deep enough, but I wasnít 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.
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PostPosted: Tue Feb 16, 2021 11:44 pm    Post subject: Re: Lapping valve issues Reply with quote

Lapping will NOT fix it. You need a valve grinder and seat grinder.
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spencerfvee
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PostPosted: Wed Feb 17, 2021 4:44 am    Post subject: Re: Lapping valve issues Reply with quote

MrChilliVanilli wrote:
Sorry guys, my mistake... the exhaust valve is actually 35.5 not 37.5. I donít know why I had this number in my mind Rolling Eyes

Thank you for all the help. Iíll try to cut the seat deeper. This was also my first thought, that the seat is not cut deep enough, but I wasnít 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.
....................................................................lol show me a man that never made a mistake . and that man has never done any thing . i have made a lot of mistakes in my life lol. . all so you need to get the valve seats cut so the valve seat matches the center of the valve for a good seal .check the valve guides. they might be bad . most of the time the valve guides are bad . take care spencerfvee
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Brian_e
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PostPosted: Wed Feb 17, 2021 9:43 am    Post subject: Re: Lapping valve issues Reply with quote

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
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PostPosted: Wed Feb 17, 2021 9:46 am    Post subject: Re: Lapping valve issues Reply with quote

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.

Image may have been reduced in size. Click image to view fullscreen.


Image may have been reduced in size. Click image to view fullscreen.


Is it possible someone could post some pics of proper seated valves and seats?
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PostPosted: Wed Feb 17, 2021 10:51 am    Post subject: Re: Lapping valve issues Reply with quote

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

Image may have been reduced in size. Click image to view fullscreen.

Image may have been reduced in size. Click image to view fullscreen.


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.

Image may have been reduced in size. Click image to view fullscreen.



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PostPosted: Wed Feb 17, 2021 11:36 am    Post subject: Re: Lapping valve issues Reply with quote

1 rong size valves,2 needs proper valve job.and cleaning.
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MrChilliVanilli
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PostPosted: Wed Feb 17, 2021 12:41 pm    Post subject: Re: Lapping valve issues Reply with quote

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

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