mackei23b
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| posted on 20/2/15 at 08:13 PM |
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How to check valve lapping
Hello
I've lapped all my valves.....what is the best way to check that I've actually done a good job...?
I've filled the chambers with petrol and I get a small weep out of most of the valves.....but with water it look OK???
Any advice appreciated.
Thanks
Ian
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theconrodkid
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| posted on 20/2/15 at 08:26 PM |
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water is too "thick",petrol evaporates,we used to use parafin....if it leaks it will leak when it,s running.
who cares who wins
pass the pork pies
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DIY Si
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| posted on 20/2/15 at 08:40 PM |
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When you were lapping the valves, did you get a nice even grey ring on the valve? If you managed that on all of them, with the springs fitted it
should seal.
Let your plans be dark and as impenetratable as night, and when you move, fall like a thunderbolt.
Sun Tzu, The Art of War
My new blog: http://spritecave.blogspot.co.uk/
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PAUL FISHER
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| posted on 20/2/15 at 08:41 PM |
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Engineers blue.
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rusty nuts
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| posted on 20/2/15 at 09:14 PM |
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quote:
Originally posted by PAUL FISHER
Engineers blue.
The reliable way of checking valve seats. Even after nearly 50 in the motor trade I still use it
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perksy
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| posted on 20/2/15 at 09:32 PM |
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Engineers blue is good
With the last XE head I did, when I was happy that I had a nice lap area, I filled the chambers with WD40 and left it over the weekend.
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fesycresy
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| posted on 20/2/15 at 09:39 PM |
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Always use diesel myself.
Did a head last month and all the valves lapped in well, but one failed the diesel test.
Usually happens on a valve you usually haven't decoked enough.
-----------------------------------------------------------------------------------------------------
The sooner you fall behind, the more time you'll have to catch up.
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britishtrident
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| posted on 20/2/15 at 09:45 PM |
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With head standing on its' side fill the ports with paraffin and from the combustion chamber side direct a jet of compressed air round edges of
the valves if you get bubbles in the port the valve isn't sealing.
[I] What use our work, Bennet, if we cannot care for those we love? .
― From BBC TV/Amazon's Ripper Street.
[/I]
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britishtrident
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| posted on 20/2/15 at 09:48 PM |
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With head standing on its' side fill the ports with paraffin or gas oil/derv and from the combustion chamber side direct a jet of compressed air
round edges of the valves if you get even tiny bubbles in the port the valve isn't sealing properly.
[I] What use our work, Bennet, if we cannot care for those we love? .
― From BBC TV/Amazon's Ripper Street.
[/I]
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richard thomas
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| posted on 20/2/15 at 10:59 PM |
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Is anyone still doing this the good old fashioned way by hand - and rotating the valve 90 degrees every now and then, or using an air powered
lapper?
Engineers blue is the way to go, and no cheating by putting it on too thick neither ;-)
Edit - powdered coloured chalk in green oil will make a cheap substitute for blue...certainly easier to wash off your fingers....
[Edited on 20/2/15 by richard thomas]
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DIY Si
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| posted on 20/2/15 at 11:29 PM |
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I did mine by hand, but only because they just need a tidy up, rather than because they were knackered. I do still need to check them all though.
Let your plans be dark and as impenetratable as night, and when you move, fall like a thunderbolt.
Sun Tzu, The Art of War
My new blog: http://spritecave.blogspot.co.uk/
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adithorp
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| posted on 20/2/15 at 11:56 PM |
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Yep, I still do it by hand (not that it gets done much these days). Nice and therapeutic but you have to play a tune doing it. I was taught just to
put a series of pencil lines across the valve seat; Works as well as engineers blue and less messy and you can't cheat.
"A witty saying proves nothing" Voltaire
http://jpsc.org.uk/forum/
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mcerd1
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| posted on 21/2/15 at 10:54 AM |
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I still do them by hand too 
I was taught just to watch for the grey line/ ring, but I sometimes use engineers blue as a double check
-
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pewe
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| posted on 21/2/15 at 01:02 PM |
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This thread made me smile  .
I was waiting for questions as to "what's valve lapping" and/or "what's engineers blue" but seems as if
we're a load of old farts on here who grew up doing it the right way i.e not throwing it away and replacing it all at the first hint of
trouble.
Especially like the chalk and green oil solution - very locost!
My favoured technique is paraffin in the combustion chambers overnight but just ensure the head's on a suitably large catch tray - ask me how I
know!
BT's method though strikes me as providing a faster result.
Cheers, Pewe10 
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rusty nuts
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| posted on 21/2/15 at 02:04 PM |
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I've used an air powered valve lapped, an SPQR ? Lapping tool in an electric drill and various other mechanical methods but you can't beat
a good old fashioned valve stick
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mackei23b
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| posted on 21/2/15 at 02:51 PM |
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Thanks for all the updates....
I've tested with some diesel and.....there is a very small weep...I've also ordered some engineers blue for next week
I've redone one of the inlets and retested....remains dry for around 60 seconds and then there is evidence of a leak....
Here is a pic of the valve....
 
Valve
See what you think...?
Cheers
Ian
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pewe
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| posted on 21/2/15 at 06:25 PM |
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Looks good to me.
Adithorp's method ^^ of putting pencil lines at right angles to seat and rotating is a really good way of checking.
Cheers, Pewe10
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MikeRJ
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| posted on 24/2/15 at 06:07 PM |
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quote:
Originally posted by mackei23b
Thanks for all the updates....
I've tested with some diesel and.....there is a very small weep...I've also ordered some engineers blue for next week
I've redone one of the inlets and retested....remains dry for around 60 seconds and then there is evidence of a leak....
Just to check, did you have the valve spring and retainer fitted to the valve when you were testing for leaks?
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DIY Si
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| posted on 24/2/15 at 06:18 PM |
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I was going to ask that too, as the valve pictured above looks spot on!
Let your plans be dark and as impenetratable as night, and when you move, fall like a thunderbolt.
Sun Tzu, The Art of War
My new blog: http://spritecave.blogspot.co.uk/
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adithorp
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| posted on 24/2/15 at 06:45 PM |
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Looks good to me too... provided the bits around the other side look the same. Nice matt gary all around?
To be honest I don't think I've even done the paraffin/derv leak check on a valve I've lapped in; Just done it to see if they needed
doing in the first place.
"A witty saying proves nothing" Voltaire
http://jpsc.org.uk/forum/
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mackei23b
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| posted on 24/2/15 at 09:21 PM |
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Yes the spring was fitted with the collets.....I did a bit more lapping with a fine paste for another 5 minutes.....and there is no leakage for about
5 minutes.... I'll see what the engineers blue will show when it arrives....part of me thinks I've still got a bit of fluff from a rag
left on the valve....though I used new rags for the last clean and a blast with an air line.....
Thanks for the updates
Cheers
Ian
P.S meant to say the valve looks like that all the way round.
[Edited on 24/2/15 by mackei23b]
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ashg
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| posted on 25/2/15 at 04:00 AM |
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you don't need engineers blue. just use a marker pen, draw it on the valve seat and the valve and spin it round a few times with the lapping
stick all the low spots if there are any will still have marker pen in them 
the valve in the pic looks pretty good. did you use course and fine paste?
if it were my engine and the valve seat looked as good as that valve i would just stick it back together and run it. As soon as its been together a
while the valves will slowly start pitting again and that doesn't bother most engines until it gets really bad.
Anything With Tits or Wheels Will cost you MONEY!!
Haynes Roadster (Finished)
Exocet (Finished & Sold)
New Project (Started)
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Mr Whippy
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| posted on 25/2/15 at 12:09 PM |
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I just take the head to a local machine shop and they resurface the seats for around £50, then I always fit new valves as for most cars they are very
cheap Take's no time at all to then bed them in even just doing it by hand
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mark chandler
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| posted on 25/2/15 at 01:14 PM |
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I,ve always looked for the grey line and filled with petrol to check for leaks, maybe it's just me but soon get bored waggling the stick so grab
the valve stem in a cordless drill and pull it into the seat to grind.... Takes seconds.
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Oddified
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| posted on 25/2/15 at 01:37 PM |
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quote:
Originally posted by mark chandler
I,ve always looked for the grey line and filled with petrol to check for leaks, maybe it's just me but soon get bored waggling the stick so grab
the valve stem in a cordless drill and pull it into the seat to grind.... Takes seconds.
Cheating some would say, but that's what i do as well!
Ian
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