valve lapping how-to
supafly
I just spun it 30 seconds or so back and forth and all around until it
seems to fit nice and smooth.
Is that good enough?
anybody know the pros or cons of water or oil based lapping compound?
-supa
Kevin
"supafly" <j.su...@gmail.com> wrote in message
news:1148813233.4...@i39g2000cwa.googlegroups.com...
One method that is easy to use for checking the valve seating is to remove
it after lapping and wipe the cylinder head seat and the valve face very
clean, then use a No. 2 graphite pencil to mark radial lines on the valve
face about every 1/4 inch (like a wagon wheel). Then without using any
compound, lap the valve again. Just a few seconds of spinning should
suffice. Now take the valve out and look at the markings on the face. The
pencil marks will have smeared only where the valve is contacting the seat
on the head. You are looking for a nice even thin line that is well centered
on the valve face. You can even use a dial caliper or precision machinist's
rule to measure the thickness of the seating area and compare to the repair
manual specifications for that engine, to see if it is correct.
If the seat contact area is not centered or not the specified thickness,
there are methods to correct that. They involve grinding the seats with
various degree angled stones. You would do best to leave that up to an
experienced machinist.
I have never used water based valve grinding compound so I have no
comparison to offer you on that one.
--
Kevin Mouton
Automotive Technology Instructor
"If women don't find you handsome, they should at least find you handy"
Red Green
N8N
I've been told that most modern engines shouldn't need to have valves
lapped in, that the machining is precise enough that a little touch up
is all that should be required.
That said, you can check your work by putting some Dykem (machinist's
blue dye) on the seating surface of the valve, inserting the valve into
the head, giving the valve one sharp rap with a hammer, and looking to
see if you have a nice even transfer of the dye from the valve to the
seat.
I have no input on water vs. oil based compounds.
Before you go too nuts you ought to roll the valve across a piece of
flat glass to check for wobble. If you have a dial indicator set it up
so that you can rotate the valve in its guide and check for head
concentricity (i.e. wobble that isn't evident to the naked eye but
still might be a problem.)
good luck,
nate
Jasper Janssen
>How long should I spin a new valve when I'm lapping it in? In the past
>I just spun it 30 seconds or so back and forth and all around until it
>seems to fit nice and smooth.
>Is that good enough?
When you take the valve out of the seat, you should be able to see where
it was ground down during the lapping process, and on both valve and seat
these marks should go thoroughly all the way around the circle.
Jasper
jim
supafly wrote:
>
> How long should I spin a new valve when I'm lapping it in? In the past
> I just spun it 30 seconds or so back and forth and all around until it
> seems to fit nice and smooth.
> Is that good enough?
You should be able to tell the contact area by just looking at the
pattern of the grinding compound on the valve and seat. Also after
clean-up the area that is ground (where seat and valve mate) should have
a texture that looks different (sort of matte finish) then where it
wasn't ground.
-jim
>
> anybody know the pros or cons of water or oil based lapping compound?
>
> -supa
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Chas Hurst
Don't spin the valve. Turn it only 1/2 to 3/4 of a turn. Otherwise a high
spot can give you an erroneous trace.
I use a magic marker (less messy than machinist layout dye) to color the
valve and the seat before lapping. This gives a much clearer trace of the
valve to seat contact.
I also use oil based compound and like the others never used water based.
*
Valve lapping went out with the Ford Flathead engine......
Engine builders and engineers long ago realized that when the engine fires
up, the valves and the valve seats - being two different materials - expand
at different rates as they rise to normalized combustion chamber
temperatures where they most-often operate, so the valve does NOT seat
itself on the room-temperature, lapped-in portion anyway.
Combustion chamber temperatures are much higher than the ambient room
temperature at which lapping takes place.
The relationship between the valve and the seat at room temperature if far
different than it is at normalized combustion chamber temperatures where
everything is heated to normal operating temperatures.
Just do a good, multi-angle valve job.
Having said that, I prefer the oil-based lapping compound over water-based
when I am doing engine-turning on aluminum plates in my milling machine. It
makes less of an oil/water mess on my machine.
Kevin
"*" <nos...@this.addy.com> wrote in message
news:01c6827c$c337afc0$0f93c3d8@race...
>
> Valve lapping went out with the Ford Flathead engine......
Hmmm. First I hear of this. Where have I been? <grin> But seriously, I like
to stay up on current technology and industry practices. It is sometimes
difficult to keep up with changes because I seldom do any live repair work
anymore, and I have to follow text book procedures. If I understand you
correctly, you are saying that machine shops no longer lap valves in after
re-facing or replacing them. I will have to take your word for it until I
find out otherwise. Thanks for the information.
Any other machinists out there concur with this? BTW, I'm not talking about
race type repairs, but just good old commuter car repairs.
Kevin
Shep
the valve on the seat rotate the valve to wipe the compound on the seat ,
take the valve out clean it and drop it back in turn it and look at the
contact on the valve face, worked on my 9 second Hemi SS car.( All this done
as a final check step after the valve job)
"Kevin" <kmou...@cox.net> wrote in message
news:JPleg.50942$9c6.32087@dukeread11...
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the fly
>
>"*" <nos...@this.addy.com> wrote in message
>news:01c6827c$c337afc0$0f93c3d8@race...
>>
>> Valve lapping went out with the Ford Flathead engine......
>
>Hmmm. First I hear of this. Where have I been? <grin> But seriously, I like
>to stay up on current technology and industry practices. It is sometimes
>difficult to keep up with changes because I seldom do any live repair work
>anymore, and I have to follow text book procedures. If I understand you
>correctly, you are saying that machine shops no longer lap valves in after
>re-facing or replacing them. I will have to take your word for it until I
>find out otherwise. Thanks for the information.
>
>
>
>Any other machinists out there concur with this? BTW, I'm not talking about
>race type repairs, but just good old commuter car repairs.
>
I last worked as an automotive machinist in 1969. We were
taught then that a three-angle cut with stones was all that was
needed. Of course, you check the seating accuracy with the
lead-pencil method already mentioned, but lapping with compound has
been considered kind of a quaint anachronism for quite some time.
Lapping also defeats the purpose of cutting the seat angle one
or two degrees different from the valve face.
Kevin
"the fly" <tset...@swbell.net> wrote in message
news:09vj72d6r99lnca5i...@4ax.com...
I can see that. Makes sense to me, but our text books still teach lapping
after the grind. Learn something new all the time. I feel kind of silly for
making my students learn how to hand lap a valve. I still have to teach it
though because it is a required part of the curriculum, but I may not put
much emphasis on it if the standard industry practice is to avoid the
lapping.
Chas Hurst
> news:01c6827c$c337afc0$0f93c3d8@race...
>>
>> Valve lapping went out with the Ford Flathead engine......
>
> Hmmm. First I hear of this. Where have I been? <grin> But seriously, I
> like
> to stay up on current technology and industry practices. It is sometimes
> difficult to keep up with changes because I seldom do any live repair work
> anymore, and I have to follow text book procedures. If I understand you
> correctly, you are saying that machine shops no longer lap valves in after
> re-facing or replacing them. I will have to take your word for it until I
> find out otherwise. Thanks for the information.
>
>
>
> Any other machinists out there concur with this? BTW, I'm not talking
> about
> race type repairs, but just good old commuter car repairs.
>
>
> Kevin
>
Valve lapping was with us long after the demise of the Ford flathead, but
most machines shops no longer do it.
A shop that has done much work for me uses a vacuum device to ensure that
the machined fit is air tight.
Don
wrote:
>
>"Kevin" <kmou...@cox.net> wrote in message
>news:JPleg.50942$9c6.32087@dukeread11...
>>
>> "*" <nos...@this.addy.com> wrote in message
>> news:01c6827c$c337afc0$0f93c3d8@race...
>>>
>>> Valve lapping went out with the Ford Flathead engine......
>>
>> Hmmm. First I hear of this. Where have I been? <grin> But seriously, I
>> like
>> to stay up on current technology and industry practices. It is sometimes
>> difficult to keep up with changes because I seldom do any live repair work
>> anymore, and I have to follow text book procedures. If I understand you
>> correctly, you are saying that machine shops no longer lap valves in after
>> re-facing or replacing them. I will have to take your word for it until I
>> find out otherwise. Thanks for the information.
>>
>>
>>
>> Any other machinists out there concur with this? BTW, I'm not talking
>> about
>> race type repairs, but just good old commuter car repairs.
>>
>>
>> Kevin
>>
>The OP asked for help about lapping valves, not if it was still done.
Information that is no longer commonly recommended would qualify as
"help about lapping valves" in my book.
>Valve lapping was with us long after the demise of the Ford flathead, but
>most machines shops no longer do it.
For good reasons.
>A shop that has done much work for me uses a vacuum device to ensure that
>the machined fit is air tight.
A much better approach.
Chas Hurst
"Don" <d...@NO-SPAMdonsautomotive.com> wrote in message
news:l47k72haip1dmblki...@4ax.com...
Who said it was no longer recommended? That a machine no longer does it is a
sign that's not economical, that's all.
For the DIYer or a shop that relies on older machinery, it's still a viable
way of checking valve seating.
*
Kevin <kmou...@cox.net> wrote in article
<oRneg.50946$9c6.15531@dukeread11>...
>
>
> I can see that. Makes sense to me, but our text books still teach lapping
> after the grind.
I taught Vocational Automotive Technology at the secondary level for 10
years - leaving the political B.S. behind in 1984.
Even brand-new texts - due to bureaucratic decision-making at the
publishing houses - continue to carry forth many "old grandpa" tales
regarding automotive service and maintenance.....I'm sure you could point
out several of them from your current texts.
No offense intended, but many publishers rely primarily on teachers for
their technical updates - teachers who have been far-removed from the
day-to-day roiutines of the industry for many years.
Some teachers seem to believe that lapping valves is, somehow, a
near-religious experience - a right of passage to automotive service and
repair. That plus it can be made to keep the kids busy for hours - a
"makework" situation.
When I was teaching, I used to often say, "The problem with education is
that it is run by educators - not business people." Yeah, THAT made me
popular, all right!
I'm surprised they don't still suggest the carrying of a chamois to strain
fuel.
I was in charge of curriculum development for my own program, and could
substitute newer, more commonly accepted information for obsolete
information anywhere I chose. My main goal was to make sure my students
were prepared for entry-level employment in the industry - using currently
accepted industry practices.
The fact that I was also required to maintain a volunteer advisory or
"Crafts Committee" composed of people from the automotive business, went a
long way towards de-bunking textbook errors.
Valve-lapping is one example. At a monthly meeting after my C.C. had taken
home textbooks to review, my automotive machine-shop C.C. member stated
that it was no longer common industry practice to lap valves.....which I
already knew having come into teaching right out of the automotive service
and repair trade.
That went into the minutes of the meeting with supporting statements from
the others, and from that point forward, I no longer had valve-lapping as a
task page in my Trade Analysis.......although, I would still often mention
the concept just as "nice to know" information.
> Learn something new all the time. I feel kind of silly for
> making my students learn how to hand lap a valve. I still have to teach
it
> though because it is a required part of the curriculum, but I may not put
> much emphasis on it if the standard industry practice is to avoid the
> lapping.
>
If you REALLY want to understand exactly how un-common lapping valves is,
in my area, in MANY wholesale (professional) auto parts stores - such as
NAPA, Carquest, etc. - lapping compound is a special order, while in MANY
retail (DIY) auto parts stores - such as Pepboys, Auto Zone, etc. - it sits
there for the DIY who learned from his grandfather that you MUST lap
valves.
I know, because I still buy it occasionally to do engine turning on
aluminum.
"Cheating only means that you take winning seriously." - Red Green
*
Chas Hurst <hur...@comcast.not> wrote in article
<NoWdnbY0f79...@comcast.com>...
>
> The OP asked for help about lapping valves, not if it was still done.
Sometimes, the best "help" is to recommend not doing something......or to
point out that it is no longer "standard practice."
> Valve lapping was with us long after the demise of the Ford flathead, but
> most machines shops no longer do it.
So once a machine shop has set up a standard 29° valve face and a 30° seat
for a knife-edge fit, why would *anybody* encourage someone else to go
ahead and destroy that fit by lapping their valves?
And, per an earlier request, we're not even talking about a racing
three-angle setup......
> A shop that has done much work for me uses a vacuum device to ensure that
> the machined fit is air tight.
As do many shops......
I used to sell the Mity-Vac hand vacuum pumps, and I still have a few
samples laying around in my shop cabinets.
A friend of mine who rebuilds 20-or-more Ford Flathead engines every year,
spotted my leftover samples, and after I explained what the various pumps
were set up to do, he just could not let it rest until I sold him the one
with the cups for checking valve seal.
Here's a guy in his 70s who is not afraid to keep up with the times. He,
too, no longer laps valves in.
*
Chas Hurst <hur...@comcast.not> wrote in article
<XbednRVG4K2...@comcast.com>...
>
>
> Who said it was no longer recommended? That a machine no longer does it
is a
> sign that's not economical, that's all.
> For the DIYer or a shop that relies on older machinery, it's still a
viable
> way of checking valve seating.
>
Using "Dykem", Prussian Blue, Magic Marker, even soft pencil marks will all
check valve seating while not destroying the one-degree "interference" that
was set up when the seats were ground at 30° and the valves at 29°....nor
will any of these methods create a much rougher surface compared to what
the machines left on the sealing faces of the valve and seat.
And, such methods are really only good for checking seat seal location -
not its ability to seal well. As a matter of fact, roughing up the mating
surfaces almost guarantees more leakage than the near-mirror-smooth sealing
surfaces left by the machines.
Spinning the valve will, actually, hide any imperfections. A high spot on
the seat, for example, will leave a line scribed all the way around the
valve, while a high spot on the valve will do the same to the seat.
It is entirely possible to have a valve seating on two high spots that
shows a complete ring around the valve and seat due to spinning the valve
on the seat.
Current technology of creating a vacuum to check the seal seems to be best.
Nate Nagel
>
> If you REALLY want to understand exactly how un-common lapping valves is,
> in my area, in MANY wholesale (professional) auto parts stores - such as
> NAPA, Carquest, etc. - lapping compound is a special order, while in MANY
> retail (DIY) auto parts stores - such as Pepboys, Auto Zone, etc. - it sits
> there for the DIY who learned from his grandfather that you MUST lap
> valves.
>
>
> I know, because I still buy it occasionally to do engine turning on
> aluminum.
I keep a tin of it around for a little extra "bite" on problematic screw
heads... :)
nate
--
replace "fly" with "com" to reply.
http://home.comcast.net/~njnagel
Bob
"Nate Nagel" <njn...@flycast.net> wrote in message
news:e5g7m...@news4.newsguy.com...
>* wrote:
>
>>
>> If you REALLY want to understand exactly how un-common lapping valves is,
>> in my area, in MANY wholesale (professional) auto parts stores - such as
>> NAPA, Carquest, etc. - lapping compound is a special order, while in MANY
>> retail (DIY) auto parts stores - such as Pepboys, Auto Zone, etc. - it
>> sits
>> there for the DIY who learned from his grandfather that you MUST lap
>> valves.
>>
>>
>> I know, because I still buy it occasionally to do engine turning on
>> aluminum.
>
> I keep a tin of it around for a little extra "bite" on problematic screw
> heads... :)
>
> nate
And it does work damn good for that! But that's the only use I've found for
it in at least 20 years.
Bob