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Some guidance needed
https://www.ausmini.com/forums/viewtopic.php?f=2&t=51463		 Page 1 of 1
Author:  NAV [ Sun Mar 22, 2009 7:02 pm ]
Post subject:  Some guidance needed
I have the head off NAV at the moment and am wanting to put in new valve stem seals while it's off as the engine was a bit smoky. I know I'll need a valve spring compressor.
Besides the seals what should I look at to ensure my head is in good order and ready to be put back on? I had unleaded seats put in already when it was rebuilt.
I'm not sure what a good valve & seat look like once they have been in the car for some time. Is it a good idea to lap the valves at all if it looks ok to the casual observer? Or can I do more harm than good?

How much carbon build up would people think is acceptable? Is this bad?
Please ignore the oil as it's from when i pulled the head off. Click on pics for bigger ones
Image Image Image Image

I have removed the carbon buildup now. And can anyone see any signs of gasket failure in those pics?
Author:  sgc [ Sun Mar 22, 2009 7:07 pm ]
Post subject:  Re: Some guidance needed
NAV wrote:
And can anyone see any signs of gasket failure in those pics?


None whatsoever to these eyes..
Author:  gafmo [ Sun Mar 22, 2009 7:13 pm ]
Post subject: 
I dont have the trained Eye as others do but I would be saying the exhaust seats would need doing.
While I dont see any sign of gasket leak I would still check it flat and possible take a little more off the pointy section also
Author:  sitnlo62 [ Sun Mar 22, 2009 7:27 pm ]
Post subject:  Re: Some guidance needed
NAV wrote:
I Besides the seals what should I look at to ensure my head is in good order and ready to be put back on?


Nav,
A series engines have a tendancy to suck huge amounts of oil down the valve guides.
If the valve guides and valve stems are worn you will have a problem with oil consumption even with new stem seals so check they are within tollerance.
You may need new guides and valves as well.
Remember if you fit new valve guides you will also need to have the seats recut.

Things to look for on a valve seat that has been run are seat recession especially on the exhaust and pitting. Also look for a telltale groove on the valve face.

Dave
Author:  BALLISTIC [ Sun Mar 22, 2009 9:16 pm ]
Post subject:  Re: Some guidance needed
sgc wrote:
NAV wrote:
And can anyone see any signs of gasket failure in those pics?


None whatsoever to these eyes..

Same ....... get the head surfaced and get the head shop to check your guides and valves stems etc.........if it needs new guides, replace them all, fit the bullet nose type and fit the mushroom type valve stem seals.
Author:  Tombo [ Sun Mar 22, 2009 10:09 pm ]
Post subject: 
Where the gasket seals looks fine.
That sort of carbon build up is pretty typical of any older carby engine. Be more concerned about what is on the backs of the valves if it's loosing oil.
Like sitnlo said, guide wear is common. Once the spring is removed wobble the valve stem, o.k. play is tiny.
Lapping valves won't do any harm.
Heres a pic of a simple valve spring compressor i made due to necessity.
I put the small hole over a rocker tower bolt, wind a nut down over it then lever it down against the spring retainer, this releases the valve collets, then i let it back and turn it to the side to get the spring out.
Image
Author:  sgc [ Sun Mar 22, 2009 10:11 pm ]
Post subject: 
Tombo wrote:
Heres a pic of a simple valve spring compressor i made due to necessity.


I use my thumbs to get them off :shock:

Getting them back on is more of a challenge, though..
Author:  Tombo [ Sun Mar 22, 2009 10:14 pm ]
Post subject: 
sgc wrote:
Tombo wrote:
Heres a pic of a simple valve spring compressor i made due to necessity.


I use my thumbs to get them off :shock:

Getting them back on is more of a challenge, though..

The compression weight of those spring is more that i weigh :oops:
Author:  Leighton [ Sun Mar 22, 2009 10:36 pm ]
Post subject: 
I made somehting similar too, that GR told me :wink:

just a metal rod with a tube, cut to size welded onto it.

if you want ill get some pics tommorow?

Leighton
Author:  NAV [ Mon Mar 23, 2009 9:31 am ]
Post subject: 
Thanks for the advice guys.
I'll check the seats and guides once I get a valve spring compressor sometime this week.
From older photo's I have of my head it doesn't appear that my valves have recessed at all but that's just going by the eyeball.
How much movement is acceptable for the valves in the guides? 3/4 of bugger all or a couple thousanths of an inch?

From what I've been told it wasn't a lot of smoke (like a mobile smoke screen) as I've never noticed oil smoke while driving. While getting it skimmed and checked by a pro is a good idea, I:
A) Don't have the spare cash. and
B) Want to spend as little money as possible on this engine as there is another waiting to be rebuilt for NAV so i just want to get it running again.
Author:  simon k [ Mon Mar 23, 2009 10:43 am ]
Post subject: 
don't get it checked by a pro, they'll look at the backs of your valves and say they're on their way to burning and need recutting - the backs of the valves take a beating against the hardened seats. When you pop the exhaust valves out, clean the backs of them and you'll notice that there is a ridge where they contact the seats.

When I asked my machinist about lapping valves, he said the $56k machine he has to cut the seats and backs of the valves does a much better job of getting the angles right than a lapping tool. They don't cut the 2 angles exactly the same, they cut them so that they start off sealing at the top edge, then as they wear they seal further down the face - makes them last longer

I guess lapping them will take the ridges off the backs of the valves, but it'll need doing regularly, as the angles are the same from the start

now, that's my limited understanding, and it's probably all rubbish, so Camp Freddy can tell me to shut up
Author:  NAV [ Mon Mar 23, 2009 11:11 am ]
Post subject: 
simon k wrote:
now, that's my limited understanding, and it's probably all rubbish

Cheers Simon, it sounds like you've got some knowledge in that area, and sounds like good advice. The trick is here that you've been advised by someone who should know what they are on about. My seats may have been cut at the same angles, i guess i'll find out when pull the valves out.


simon k wrote:
so Camp Freddy can tell me to shut up

:roll: :lol: :wink:
Author:  drmini in aust [ Mon Mar 23, 2009 1:15 pm ]
Post subject: 
NAV wrote:
simon k wrote:
now, that's my limited understanding, and it's probably all rubbish

Cheers Simon, it sounds like you've got some knowledge in that area, and sounds like good advice. The trick is here that you've been advised by someone who should know what they are on about. My seats may have been cut at the same angles, i guess i'll find out when pull the valves out.


simon k wrote:
so Camp Freddy can tell me to shut up

:roll: :lol: :wink:

I face my own valves here at 45 deg and then get the seats in the head cut to the same angle. I always lap them in lightly afterwards, I have seen many valve seats cut not quite right. Most small shops do not have a $squillion machine for this work unless they are in the business of fitting new valve seats. :wink:
Author:  NAV [ Mon Mar 23, 2009 2:04 pm ]
Post subject: 
drmini in aust wrote:
I face my own valves here at 45 deg and then get the seats in the head cut to the same angle. I always lap them in lightly afterwards, I have seen many valve seats cut not quite right. Most small shops do not have a $squillion machine for this work unless they are in the business of fitting new valve seats. :wink:


Cheers Doc, It was done by morwood motors (possibly had the machining sent out) in Fyshwick (ACT) about 5 years ago when I had the whole engine done and unleaded seats and new valves put in.
How much movement can the valve have in the guide before it's time for new guides?
Author:  drmini in aust [ Mon Mar 23, 2009 2:28 pm ]
Post subject: 
Measure the valve stem and compare to size at top, if it's worn .001" or more replace the valve.
Try a new valve in the guides, if it rocks more than a few thou it's new guide time. You can also see wear in guides if you put a light behind and look inside. They wear oval at top and bottom.

If you fit new standard guides, get them reamed with a 9/32" solid reamer. This is MOST important with currently available bronze guides, these close up when fitted depending how tight they are in the head..
:x

You can also send the head out and get bronze `K-lines' fitted into your old guides. These let you run with less stem clearance than stock guides. They are good, but of course cost more.... :roll:
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