albertz
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| posted on 9/12/05 at 08:08 AM |
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Grinding valves
Whats the basic procedure for grinding/lapping in valves into an aluminium cylinder head?
I have just had the head skimmed and am hoping to get it re-assembled this weekend.
The last time i ground valves in i used a little wooden stick with a sucker thing on the end and some grinding paste. Is that still the way to go, or
is there a more efficient way of doing it now?
Any tips, tricks or advice appreciated.
Cheers
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britishtrident
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| posted on 9/12/05 at 08:54 AM |
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Yes unless you buy a valve lapping attachment for a slow speed drill.
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mike smith1
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| posted on 9/12/05 at 09:00 AM |
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People still use the lapping method as you discribed, but there are a few different ways, some engine reconditioners grind the seats with a valve seat
grinder that ossolates (sorry about spelling) around a pilot which goes into the valve guide and the grinder only makes contact with one part of the
valve seat at once,
others use a cutter which works on the same principle on a pilot, the cutter is the correct angle for the seat and is rotated by the hand, which cuts
the valve seat.
Just depends if you want to do it your self or have it done for you.
Lapping method is effective and cheap
Hope that helps
Mike
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Hammerhead
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| posted on 9/12/05 at 09:29 AM |
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I think you need the seats and valves grinding with the correct machine at the correct angle (about 30 degrees) then you use the stick to lap the
valves first with rough paste then smooth. As far as I can remember, but its been 14 years!
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Prez
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| posted on 9/12/05 at 09:46 AM |
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If you need to use the coarse grinding paste then chances are you need to have the seats re-cut and the valves re-cut or replaced. I would just stick
with the fine paste, you might be able to get the end of the valve stem into the chuck of a variable speed drill from the camshaft side of the
cylinder head, will save you a lot of hard work. Just be careful how much you grind away!!
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zzrpowerd-locost
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| posted on 9/12/05 at 10:03 AM |
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quote:
Originally posted by Prez
If you need to use the coarse grinding paste then chances are you need to have the seats re-cut and the valves re-cut or replaced. I would just stick
with the fine paste, you might be able to get the end of the valve stem into the chuck of a variable speed drill from the camshaft side of the
cylinder head, will save you a lot of hard work. Just be careful how much you grind away!!
Was going to say the same about the drill!
Dont just let it spin thou, let the valve lift off the seat every couple of seconds
When lapped correctly you are looking for a dull grey band around the seat and on the valve face, idealy in the middle of the seat/valve
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albertz
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| posted on 9/12/05 at 10:17 AM |
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The valves are going back into the same head, into the same guide as they are laid out in order. So hopefully they should not need much grinding and
should already be at the correct angle. I am basically just wanting to clean them up and make sure they are bedded 100%.
I was thinking along the lines of 5 mins with coarse paste and 5 mins with smooth paste per valve. Hopefully they should be not far off after that.
To be honest someone knocked over 3-4 valves and they are mixed up, so i will try and spend some extra time on them, just in case.
BritishTrident mentions a lapping attachment, would there be any catastrophic problems using the valve in the normal chuck and the drill on slow, i
cant see a major problem as long as i grab the valve above the groove for the retaining collets. Somebody might like to talk me out of that for a
reason i have overlooked though
EDIT: Couple of posts since i started typing my reply!! I will not bother with the coarse paste and will use the drill then
[Edited on 9/12/05 by albertz]
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mike smith1
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| posted on 9/12/05 at 10:30 AM |
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worth testing all the valves seal as well once you have put the head back together or your time preparing will be wasted and it will run awful!
place that skimmed your head should have a vac tester
Mike
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albertz
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| posted on 9/12/05 at 10:52 AM |
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Good idea Mike, i will try and do that.
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britishtrident
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| posted on 9/12/05 at 10:57 AM |
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**** IMPORTANT ****
On no account use a drill without a special attachment that oscillates as if the valve is allowed to rotate 360 degree it will score the valve seat.
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britishtrident
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| posted on 9/12/05 at 11:07 AM |
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Easy way to check if a valve is sealing is to lay the head on its side and pour a little kerosene into the ports, then direct a compresed air jet at
the combustion chamber side of the head working round the rim of the valve. If you get a steady stream of bubbles the seal isn't perfect.
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Peteff
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| posted on 9/12/05 at 11:10 AM |
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Get the sucker stick out, use plenty of paste and don't be idle. I always use the coarse then the fine then check that the seat on both
valve and head is a nice continuous grey circle with no eroded patches left in them
yours, Pete
I went into the RSPCA office the other day. It was so small you could hardly swing a cat in there.
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albertz
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| posted on 9/12/05 at 11:16 AM |
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Thats the end of the drill then....
Looks like its back to the hard graft method and blisters on my palms. How am i going to explain that to the wife
<Just as a thought, would the grinding paste not take away the scores on the seat? Maybe i am being really thick, but i thought that was the whole
point? Go easy on me, it was just a thought!>
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TL
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| posted on 9/12/05 at 01:01 PM |
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Don't be too put off about using the drill method. I do it this way: I use a variable speed reversible drill.
Oil the valve stem then place it in drill chuck; apply a few dabs of paste to valve. run at slow speed, gently "pumping" the drill in
& out about every half second, i.e pulling the valve into the seat, then pushing the valve away from the seat (to allow the paste to redistribute
itself, to avoid the same bit of grit staying in the same place, wearing a groove). do this about 20 cycles, then reverse the drill direction and do
it again.
A few minutes of this on each valve usually works. Clean off all the paste with parafin and check that the valve / seat is dull grey all round. If
not, repeat.
A note for the purists (before you get on my case!!): This may not be the "book" way of doing it, but I have never had a problem with it.
I don't leak check with parafin etc. I'm not saying you don't need to, it's just that I can't be arsed to. If it looks
good and dull grey, it probably is OK. I repeat, I've never had a hint of a poor compression or overheating, etc. I've only done it on
road cars, so I accept that maybe if you are looking for the last half a bhp for a race engine you might look down your noses at the "drill
method".
You pays your money, you takes your choice.
Grind a couple in with the wooden stick, and I bet you'll do the last 6 with a drill!!
Good Luck!
Cheers,
Terry
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MikeRJ
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| posted on 9/12/05 at 01:44 PM |
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There really should be no need to use the coarse paste. As said before, if the seats are in a bad state you need to get them recut properly.
Simply grinding the valve down with coarse paste to restore a badly pitted seat recesses the valve, causing a surprisingly large (negative) impact on
performance.
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rusty nuts
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| posted on 9/12/05 at 06:47 PM |
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Chances are that with modern unleaded valve seats they may be in good condition, having spent years lapping valves in by hand I rarely use coarse
grinding paste try just a couple of minutes with fine , using parafin or WD40 to lubricate stem and paste , clean and put a tiny dab of engineers blue
onto valve , put valve back into head and using grinding stick rotate a couple of times. What you are trying to do is get an unbroken line of blue on
both the seat and the valve . Very relaxing job I find. HTH
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NS Dev
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| posted on 11/12/05 at 12:06 PM |
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quote:
Originally posted by TL
Don't be too put off about using the drill method. I do it this way: I use a variable speed reversible drill.
Oil the valve stem then place it in drill chuck; apply a few dabs of paste to valve. run at slow speed, gently "pumping" the drill in
& out about every half second, i.e pulling the valve into the seat, then pushing the valve away from the seat (to allow the paste to redistribute
itself, to avoid the same bit of grit staying in the same place, wearing a groove). do this about 20 cycles, then reverse the drill direction and do
it again.
A few minutes of this on each valve usually works. Clean off all the paste with parafin and check that the valve / seat is dull grey all round. If
not, repeat.
A note for the purists (before you get on my case!!): This may not be the "book" way of doing it, but I have never had a problem with it.
I don't leak check with parafin etc. I'm not saying you don't need to, it's just that I can't be arsed to. If it looks
good and dull grey, it probably is OK. I repeat, I've never had a hint of a poor compression or overheating, etc. I've only done it on
road cars, so I accept that maybe if you are looking for the last half a bhp for a race engine you might look down your noses at the "drill
method".
You pays your money, you takes your choice.
Grind a couple in with the wooden stick, and I bet you'll do the last 6 with a drill!!
Good Luck!
I use the drill too, cordless reversing one. I have an old cut in half sucker stick, put that in the chuck and do it that way. I just lift the drill
in and out and keep reversing it as well. The sucker stays on the valve and lifts it with it.
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02GF74
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| posted on 12/12/05 at 12:36 PM |
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quote:
Originally posted by MikeRJ
There really should be no need to use the coarse paste. As said before, if the seats are in a bad state you need to get them recut properly.
Simply grinding the valve down with coarse paste to restore a badly pitted seat recesses the valve, causing a surprisingly large (negative) impact on
performance.
I used a cordless drill on a pair of new heads and valves and jewelleers rouge (very fine paste). As mentioned use a finger to push on the valve and
lift if off the seat often.
Wrap a piece of bicycle inner tube or similar so the drill does not mark the valve stem, no prizes for how I found that out. 
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Danozeman
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| posted on 13/12/05 at 07:59 PM |
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I always use the sucker stick. i find it much easier to control than a drill. I have apot of both coarse and fine paste. The coarse has never been
opened.
If the valves are excessively pitted they need renewing/ regrinding.
Dan
Built the purple peril!! Let the modifications begin!!
http://www.eastangliankitcars.co.uk
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Jeffers_S13
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| posted on 14/12/05 at 08:30 AM |
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Sucker stick for me  with literally one drop of thinners on the edge of the valve just before starting to do the twidling, it capillaries around the
whole thing and thins the paste a bit, makes the whole job so mush easier, especially now its a bit colder, was doing it just last weekend.
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