scuff on valve seat

Slysc

Registered User
I am reassembling my cylinder heads after putting in some new springs and doing a little more port work and during the port work, I ran the shaft of the die grinder along my intake valve seat. It put a little scuff in it, not a scratch or a gouge, just a slight scuff. So last night I was lapping in all my valves and the scuff isn't lapping out. So I wondering:

1. should I just keep lapping the valve and it will come out eventually?
2. do I need to get that valve seat re-ground?
3. since it's really slight and only .005" wide and runs perpendicular to flow, the valve will seal fine and I shouldn't worry about it and just put them back together?
 
I would think you could lap .005 with course grit compound.
I would use an old valve to lap it the mark out.then finish lapping
with new valve.Fine grit compound.

How many angles have you cut on the seat?

You can test seal if valve is installed ,by pouring gas in
port.

Randy
 
Randy,

Thanks for the reply. I don't have an old valve that is the same size.
Is there a point at which the sealing surface is getting too wide from lapping?
I didn't cut the valves myself. It was an expensive super duper race car valve grind so I hope it has lots of angles.:D

So if the gas doesn't leak through I should just forget about it and put them back together?

Dan
 
Slysc said:
Randy,

Thanks for the reply. .:D

So if the gas doesn't leak through I should just forget about it and put them back together?

Dan

Yes, assemble the valve. pour a small amount of gas in port.
Let head set a couple minutes.Then raise head so you can see
valve face.If combustion chamber is dry,It is sealed.

To bad you don't live closer.I can cut seven angles on seat,
plus 2 back cuts on valve,9 angles total. I would loan you
some cutters.But shipping would be high, to get it to you
and back fast.. And I have a few plus thou in them. I
would be afraid you would forget my return address.
:)

Randy
 
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Just lap them and be done. The valve more than likely has two cuts in it so there's a max of two angles on the seat that the valve actually seats on. Lap them and you'll figure it out.
 
I assembled them and poured some gasoline in the chamber and let it sit. There was a very small amount of gas that leaked through after a minute or so.:mad:
 
Your valve will seat some more after running the motor.

If it took a minute and was a just a damp spot, not a running
leak.It may seat in after running the motor.

Sounds like this is one of those judgment calls when you have
normal good luck. I would go with what you have.But I am not
lucky so I would fix.

And when I lap valves, To speed the process up. I some times
use a electric drill connected to the valve stem. And raise
and low valve face on seat while spinning the valve with drill.
With what ever grit compound you are using on the valve.

If your unhappy with seat margin width after lapping .
You need to make a cut above or below or both, of the
46 degree valve seat face margin on valve seat to make it
a narrower margin for valve face..

Another tip that I do when porting after valve job, and even
before valve job is finished. I somtimes slip a small rubber fuel
line hose over the die grinder dies stem and over the locking nut
on die grinder that lock the carbide bit or sanding drum in place..
For the price of a peice of scrap fuel line hose, you would not
be having this problem. At the least it will reduce the damage
such as this from occurring .

Randy
 
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I took the heads into the machine shop today and the guy said he would re-do the intakes for $3 each and have them ready tomorrow. I guess I'll wait for them just to have the piece of mind. I'm not to lucky either. If something can go wrong, it usually does. So I'll feel better losing another week but having them right.
 
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