Valve Grinding Question

I am attempting to service the valves on an aluminium head, my first such
attempt. On my first valve, exhaust, mating surfaces were fairly good and
required only a buff. The intake valve is caked up with all sorts of
hardened deposits, and the mating surfaces on the valve and seat are covered
with blemishes. I used a fine grinding paste on that valve. My questions -
is it OK if there are dark blemishes or spots left on the valve and seat? To
waht extent do I have to remove the hardened deposits around the flare of
the valve? Can anyone point me to a site which describes a valve servicing
procedure? Should I just give up and take the head to a machine shop?

Thank you very much.

Henry.

Answers in-line

> I am attempting to service the valves on an aluminium head, my first such
> attempt. On my first valve, exhaust, mating surfaces were fairly good and
> required only a buff. The intake valve is caked up with all sorts of
> hardened deposits, and the mating surfaces on the valve and seat are covered

When I do a valve job - 1st I steam clean the head and valves - next I use glass
bead or sand blaster to check head for cracks. Crack will show up as small
lines. Lines may start from spark plug hole to a valve seat. Or May possibly
from seat to seat. If you see any line or cracks - then the head needs to be
either welded or replaced.

> with blemishes. I used a fine grinding paste on that valve. My questions -
> is it OK if there are dark blemishes or spots left on the valve and seat? To

If everything checked out ok - next I would peen the head and valves - once head
is clean - - next I'd remove and replace the valve guides - next I would check
that the valve seats were in good condition -- next is to grind valves - next
because it is an aluminum head I would cut valve seats @ a min. of 3 cuts per
seat. You may need a peener to clean properly! If there are dark spots on a
valve or seat after they have been thoroughly cleaned -- then replace that valve
or seat in question

> waht extent do I have to remove the hardened deposits around the flare of
> the valve? Can anyone point me to a site which describes a valve servicing
> procedure? Should I just give up and take the head to a machine shop?

Best bet is to take it to a machine shop that has experience with aluminum heads

BBA

>Can anyone point me to a site which describes a valve servicing
>procedure?

This one describes the procedu
http://www.autosite.com/garage/encyclop/ency20c.asp

And these two describe related considerations:
http://www.autosite.com/garage/encyclop/ency01c.asp
http://www.autosite.com/garage/encyclop/ency01i.asp

Good luck!
-Ted

Thank you for the info, guys. I have enough reading for several hours. In my
case, though, my daughter's car (which I am working on) is a twenty year old
Ford Laser, and I just want it to last another year or two.

Thanks once again.

Henry.

"hemyd" > wrote in message
u...
> I am attempting to service the valves on an aluminium head, my first such
> attempt. On my first valve, exhaust, mating surfaces were fairly good and
> required only a buff. The intake valve is caked up with all sorts of
> hardened deposits, and the mating surfaces on the valve and seat are
covered
> with blemishes. I used a fine grinding paste on that valve. My questions -
> is it OK if there are dark blemishes or spots left on the valve and seat?
To
> waht extent do I have to remove the hardened deposits around the flare of
> the valve? Can anyone point me to a site which describes a valve servicing
> procedure? Should I just give up and take the head to a machine shop?
>
> Thank you very much.
>
> Henry.
>
>

On Tue, 11 Jan 2005 22:35:51 +1100, "hemyd"
> wrote:

>Thank you for the info, guys. I have enough reading for several hours. In my
>case, though, my daughter's car (which I am working on) is a twenty year old
>Ford Laser, and I just want it to last another year or two.
>
>Thanks once again.
>
>Henry.

Henry, the caked up gunk on the intake valves is the result of
excessive clearance around the intake valve guide seals. It's
possible this is due to wear of the valve stem itself, but is far more
likely to be either a worn valve guide or worn out valve guide seal.

What the worn guide seal does is allow oil or oil vapor to get down
past the seal and get cooked onto the backside of the intake valve
head.

Blasting it off with a blaster designed for the purpose is the best
way to remove it, but you can also brush it off using your wire wheel.

You should not leave it on.

If you do nothing more than lap in the valve but do not replace the
seal or the valve guide, you run the risk of producing a real smoker
of an engine. This is because lapping in the valves will increase the
suction of the combustion chamber a bit which will suck more oil past
the still worn valve guide seal than in the past.

Since you have the head off, you might want to bring it to a machine
shop and have them clean it off and check the valve guide to valve
stem clearance. Experienced machinists can tell you if the guides
need replacing simply by inspecting the guides (wear will be
apparent), or rocking the valves back and forth in the guide. They
won't need to measure it to tell you the guide is worn, if the wear is
significant it will be obvious in how far the valve moves when pushed
back and forth.

Even if after all this, you go ahead and get the valve guides replaced
and install new guide seals, the increased suction may now pull oil up
past the oil rings on the pistons.

If the guides are replaced, it is very likely that the valves will no
longer seal properly. New guides almost inveitably cock the valve
ever so slightly to one side or the other, which is why the seats need
truing after valve guide replacement. You can do this yourself using
lapping compound and the lapping stick but it's a long and tedious
job.

Corky Scott