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

water is too "thick",petrol evaporates,we used to use parafin....if it leaks it will leak when it,s running.

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.

Engineers blue.

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Originally posted by PAUL FISHER
Engineers blue.

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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.

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.

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.

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.

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]

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.

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.

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

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

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

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

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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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....

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I was going to ask that too, as the valve pictured above looks spot on!

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.

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]

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.

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

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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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.

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