Projects Flathead valve lapping

I started lapping my valves and as usual, I have a question. How much of an area should have the grind mark on it for the valve seat? The exhaust seats are hardened, but the intakes are not. The machine shop ground the valves when they machined the block. I have new SS valves, stock intake 30 degree and exhaust 45 degree, I gave the shop the valves so they knew what I had. I lapped one side of the engine, intake and exhaust and they all seem to have the same small ring on the valve seat. How much is typical for having grinding marks on it? Also, one of the valves seems to have a little gouge in it that may or may not leak, how do I check this?

This is what the seat looks like after lapping


That is about .111" ring on the seat, about half the area after lapping


Ring on the valve from lapping


Unlapped vs. lapped valve

 

0.111 Contact area sounds fine to me
cant see it in the pickture but do you
got "lapping" marks 360 degres around the seat
Then its fine
Though for high perf use i hade made the
seat bigger as in farther out on the valve
not wider Contact area

 

It looks like to me the valve angle is not the same angle as the valve seat. The photo of the valve shows a very thin line this line should be much wider after lapping. Seeing just a fine line would indicate there's a big difference between the two surfaces.

 

A lot of that could be a 44* valve on a 45* seat.

 

Mine was quite a bit wider than that and I thought it should have been more.

 

U check with a vacuum setup.... drop valve in with no spring and put the vacuum guage/pump over port... I ran a Serdi for many years and the Vac checker was part of the machine used to final check the VJ. cant find a pic right now.
Yea seat looks a little low to me

 

A wide seat is not a good seat. You will burn the valves quicker with a wide seat. It will not seal as well, and does not transfer the heat as well.

 

My Ford shop manual says 45 deg seats both intake and exhaust, minimum 1/16" wide.

 

If you don't have a way to vacuum check the valve seal I've used gas. If it holds gas then it should be fine...can check rings like that too on an assembled engine. It'll leak through the rings but rate can pinpoint a problem.

 

kinda looks like the exhaust is 30 and intake 45 on the seats?

 

It is unnecessary to lap valves when the valves and seats are properly ground with precision machinery. When a interference angle is used 44 valves and 45 seats the interference angle will provide a line contact the valve will seal very well. The interference angle also provides a way for the valve/seat to force carbon out.
Another thing to consider is that the valves and seats expand a different amount so the lapped areas of the valve and seat will not match when the engine is running.
Marv. W.

 

Yes but typically when you lap a valve that has an 1deg interfearance fit it will quickly lap down and show a pattern for the full seat width. that thin band of a lap just does not look right to me.

 

I was always taught to go for the thinest ring that went all the way around. A multi angle grind which is even better will provide a very small contact ring.

 

A flathead has 45 degrees on intake and exhaust !
So you must have matching valves.
No 30 degrees

 

Thats true. I use the lapping only to check thats
the seat is true to the valve if you get lapping
marks around the whole seat its fine
Problem with a flathead is the headbolts
distort the seat so to get it 100% you need
to have a stressplate bolted down when you
grind the seat if whe want to bee anal about it.
wide seats is bad for sealing bad for flow
1.5 -2 mm is enough

 

I am not sure, aren't the intake valves 30 degrees? This is what I have...

Let me know if I have the wrong intake valves.

 

I have intake 1.2-1.5 mm ,exhaust 1.5-1.7 mm
Exhaust for better cooling through the block slightly larger

 

I always lapped with bluing liquid at this point. Makes for a better visual.

 

My first thought also..Lapping should end up as pic in post #5..Maybe the valves are packaged wrong, the op pics to me with the "ring" so far down the valve indicate 44/45° valve and 30° seat...

 

Look at the very first picture in the thread.....

 

I have used 45 ° for valve area, valve head 90 ° in the upper area, 75 ° in the valve base to cut free.
the 90 ° and 75 ° were milling cutter on a guide, 45 ° is fine grindstone on leadership.lapping was then almost unnecessary.

I hope my bad english is understandable

 

a) valve perfect

b) valve to high

c) valve to deep

 

valve seat correction

 

The question is, am I good to continue? I want to make sure these valves and seats are good before I continue with the build.

Thanks for all of the input. Based on the recommendations I have dyed the valves and seats using a sharpie marker. I have only done the driver side cylinders so far, they are number 5, 6, 7, and 8 from front to back, respectively. I have labeled the block for 5I and 5 E, for intake vs. exhaust. It seems that the intake seats sit near the edge of the valve and the exhaust sits toward the inside more.

Most are around .100", and one of the narrow ones is .060". Based on your comments I think I am ok to continue. I did notice a little tiny gouge on the 6 intake near the 6exhaust, I am not sure if that is something I can just lap a little more to clean up.

Cylinder 5


Cylinder 6


Cylinder 7


Cylinder 8

 

I don't like where the exhaust valve is seating....

 

Valve area grinding is your first job. Lapping is step two. Look at my Pics.


Posted using the Full Custom H.A.M.B. App!

 

I agree with Aonemarine. Seat should be much more centered

 

exhaust seat contact area needs to be moved outward, so the contact area looks like the intake valve. either that or you have the wrong valves. (too big?). 1.5 to 2mm width needed to help conduct heat from the valve to the block.

 

Yep, that is the standard procedure when grinding valves and has been for the 50 + years I have been working on cars.

The guys are right in that it does appear that the seats haven't been done to properly get the contact area on the seat so that it hits the face of the valve in the right spot. It looks like they installed the seats, gave them a clean up touch to get good contact with the valves but didn't take the time and effort to properly dress them so that they contacted the valves in the desired spot. The thinking was probably that they were leaving the seats so that they could be ground again with plenty of meat left for the second and maybe third redo.

 

You say stock 30 deg int no way that is stock they are 45 deg. Did the mach shop know you switched to 30 deg intakes. If they were unaware your seats will be 45 deg and did they have the valves to look at?

T