Omega Owners Forum
Chat Area => General Car Chat => Topic started by: JamesV6CDX on 12 March 2017, 16:06:22
-
So I have lapped all of the 24 valves in my cylinder head. And have refitted them all.
To test that they are seating correctly, I have filled the ports with paraffin, and have left it some time.
All of the valves are sealed correctly, apart from the no1 exhaust valve. I've tried a couple of times now carefully lapping again with some fine paste, but when I refit it and fill the port, the fluid gently drips out from the valve seat.
There is a nice clean ring around the valve from lapping as expected. There is also one in the seat, although less so - the seat is more shiny.
I can't refit it in this condition, as it would lose compression (and being a diesel it relies on this more than a petrol) - and also might cause it to burn out early.
Any ideas? I'm just off to Halfords to buy some more paste ::)
I guess in reality I could take it to the machine shop, I doubt it'd be too expensive just to fit one new seat.... but I've got 23 of them to seat properly... surely I can sort the last one?
Had to walk away for a bit, back aches from leaning over it and I'm getting fed up with it ;D
-
Is it possible that you might have got a slightly larger particle of carborundum in the first coarse grind and the fine paste hasn't yet polished it out? You would need an eyemaker's watch glass to inspect it closely, to check.....
Ron.
-
Are you testing it with the valve spring in place?
-
Good point well presented...
-
Are you testing it with the valve spring in place?
I can see James' point, if the others, spring loaded or not, seal OK, why doesn't this one? :y
Knowing James, he will have numbered the valves and used the same ones. Just a thought James, could there be any possible distortion in either the valve or guide, allowing the valve to sit slightly askew on its seat, and yet, because of rotation while lapping, both valve and seat have the correct polished ring? :-\
-
could be the vaive itself is very slightly bent, only takes a few thou, grinding it in gives the impression all is well due to the circular motion, proof of the pudding would be to fit the valve on another position and retest.
-
To answer the questions
- yes, testing with valve spring installed
- i would always number valves during a rebuild. But I'm this instance (I won't bore you with why) the valves being installed in this head are all known good valves from my old head. So they are all "foreign" which I know is why it's taken a while to seat some.
Coarse paste is usually a no no on modern heads. I tried it on this valve and it made it WORSE. So fine paste only......
-
Then the options I can think of are :
- Valve stem is bent
- Valve guide is misaligned (unlikely I would suspect)
- Valve head isn't perfectly circular
- Valve seat isn't perfectly circular
- Valve seat isn't flat
- You haven't ground it far enough
- any combination of the above
-
Is "ground too far" an option?
-
Is "ground too far" an option?
I doubt it. Unless you have the patience of a saint.
Seriously though, unless you've worn completely through the seating areas to find a piece of metal that is no longer round, or even more unlikely, ground it to the point that something else binds up before the surfaces mate... then I very much doubt it. :-\
Edit : Oh yeah, the other one I missed is cracked valve seat/head
-
I did another careful grind with fine paste for a bit.
So far ten minutes and drip free.
Trying to decide if I can see a slight shine of fluid around the circumference but you could go around the bend looking too closely.
I think if it's still drip free in an hour I will take the "fit and forget" approach with this head :y
-
To be fair when I first tested it, before starting work, it resembled a sprinkler system - and still ran on all 6 ;D
-
James, I do know what a perfectionist you are, but there comes a time when even you have to stop! 8) :y
Ron.
-
You can use coarse paste, no issues but the valves need to seal properly
-
Still fluid tight :y
-
Is it running yet? ;)
-
Is it running yet? ;)
Under normal circumstances, it would have been by the end of tomorrow - but, I need to wait for someone to come over and help me lift the head on :y
-
Pop the valve in a power drill. Vastly speeds up the lapping process ,)
-
Pop the valve in a power drill. Vastly speeds up the lapping process ,)
I tried that on one of the others and had an absolute mare with it afterwards.
I find that doing that, you don't hear / feel it cutting, and can't get the pressure as correct :y
-
Continual rotation in one direction doesn't work - so I was told in my earlier years, but I cannot remember the reason why. I was also told of an accessory for a power drill that mimicked the alternating-direction action of hand grinding but it's unlikely to be available still as so few people lap valves in nowadays.
Ron.
-
If it makes you feel reassured, I didn't put nearly as much effort or scrutiny into grinding the valves on my V8 as you have already and it passed it's emissions test with flying colours last week. :D
-
. I was also told of an accessory for a power drill that mimicked the alternating-direction action of hand grinding but it's unlikely to be available still as so few people lap valves in nowadays.
Ron.
Like this? ;)
http://www.ebay.co.uk/itm/BGS-Werkzeug-22-28-mm-Valve-Lapping-Grinding-Tool-Pro-Range-1738-/271211992150?hash=item3f257e9456:g:mbUAAOSwBLlU1nhh
-
Exactly what I was thinking of, Andy - it has gone up a bit! :o
Ron.
-
Continual rotation in one direction doesn't work - so I was told in my earlier years, but I cannot remember the reason why. I was also told of an accessory for a power drill that mimicked the alternating-direction action of hand grinding but it's unlikely to be available still as so few people lap valves in nowadays.
Ron.
Can cause twist marks or scoring of the seats / valves rather than a nice flat surface where they meet.
Seem to remember something like dont go past the 360 degree rotation, and 1 foward 1/2 back then 1 foward again, but that was a loooong time ago.
-
Yes Zirk; now you say it, I remember! I used to rub the rod between my palms (NO, dirty minded lot!) back and forth like chafing your hands on a cold day with the same sort of light pressure until I got p*ssed off with it and had coffee..... 8)
Ron.
-
It's still fluid tight - not lost a drop - so Job Jobbed. A Jetwash / final clean just in case there are any traces of valve paste, and it's good to drop on.
The timing chain procedure looks reasonably simple on paper, but watch this space ;D
-
Funny how something as simple as getting a valve to seat can make me so happy :D
I've spent most of the day "rubbing the rod back and forth" in order to achieve this result, so I'm now sat back in the bath with a cold G+T (no beer in the fridge, fail >:( )
-
Continual rotation in one direction doesn't work - so I was told in my earlier years, but I cannot remember the reason why. I was also told of an accessory for a power drill that mimicked the alternating-direction action of hand grinding but it's unlikely to be available still as so few people lap valves in nowadays.
As unavailable as Amazon? LINK (https://www.amazon.co.uk/Gunson-G4095-Eezilap-Valve-Lapper/dp/B0012MCW06)
What James has done here(put valves from one used head into another) shows just how well the seats are machined on modern engines/equipment: you wouldn't have even considered doing that on an old engine with just grinding paste - you would've had both the seat and the valve reground and then lapped(which even with coarse paste is a final finishing operation) them to match each other.
-
.....
As unavailable as Amazon? LINK (https://www.amazon.co.uk/Gunson-G4095-Eezilap-Valve-Lapper/dp/B0012MCW06)
.....
see my post above ..... ::) ::) ;)
-
Yes, Nick, and there is a major difference in durability in modern engines nowadays, too. In my austin A30, it was considered time for a rebore and new piston rings, etc., after 40k miles!
My Omega has done more than three times that mileage already.
Slightly off topic, but when I eventually get around to rebuilding my Sunbeam S8 motorbike, I will need to have harder valve seats installed to cope with unleaded petrol - unless anyone has experience of the lead supplement that I hear you can get for the petrol?
Or maybe there is a petrochemical expert in the forum who can tell me how to treat the petrol to be like leaded?
Ron.
-
....
Slightly off topic, but when I eventually get around to rebuilding my Sunbeam S8 motorbike, I will need to have harder valve seats installed to cope with unleaded petrol ....
IMHO that is a task that can be done if the head ever comes off for some other reason. I assume the bike will have limited use, so valve seat recession will be a longtime in happening. :y
-
Tee hee - the head is already off, as are most other things! The bike is in its component parts and buried in my garage, waiting for my loving care and attention..... :-[
Ron.
-
Well worth doing if the heads off, we pay about 200 notes for the likes of a land rover engine but that includes all the labour and a complete rebuild
-
I would be doing the rebuilding myself and I don't charge me Land Rover prices! It's only a 500cc twin cylinder engine - any idea of cost just for new, hardened seats?
Ron.
-
Tee hee - the head is already off, as are most other things! The bike is in its component parts and buried in my garage, waiting for my loving care and attention..... :-[
Ron.
I had a Bond Bug like that. After it'd sat in my garage for 'a long time' I decided it was never going to happen & got rid. :-X
-
Oh no, I am DEFINITELY going to rebuild the bike.....when I get a Round Tuit! ::)
Ron.
-
Oh no, I am DEFINITELY going to rebuild the bike.....when I get a Round Tuit! ::)
Ron.
Here you are ..
(http://www.stosyth.gov.uk/images/editor/Sep03a-round-tuit.jpeg)
Your Wish is granted .. now get on with it .... :) :)
-
Thanks Nige - I knew somebody would oblige! :y 8)
Ron.
-
Slightly off topic, but when I eventually get around to rebuilding my Sunbeam S8 motorbike, I will need to have harder valve seats installed to cope with unleaded petrol - unless anyone has experience of the lead supplement that I hear you can get for the petrol?
Or maybe there is a petrochemical expert in the forum who can tell me how to treat the petrol to be like leaded?
If the head is aluminium, then it must have hardened valve seats. These will be good enough for unleaded fuel. A good solvent cleaner will show the edges if you have doubts. Simple.
If it's cast iron, then it might be good enough. I put 50,000 miles on a Pinto without hardened seats without a problem. 4,000 miles on a Cologne V6 created such valve seat recession that it barely ran. Neither case is unusual. Lead replacement additives are still available, and considering that you're unlikely to do more than a few thousand miles on an old motorbike(for the rest of your life ;) ) will be all you need.
-
Tee hee - the head is already off, as are most other things! The bike is in its component parts and buried in my garage, waiting for my loving care and attention..... :-[
Ron.
I had a Bond Bug like that. After it'd sat in my garage for 'a long time' I decided it was never going to happen & got rid. :-X
Good looking car for a 'plastic pig'
A young stud about town was far more likely to pull in a bright orange Bug than a Reliant Regal. :y
-
The head IS aluminium, Nick, as is the block. So the seats will already be hardened. That's good to know; saves a few pennies on replacement.
I don't anticipate marathon coast-to-coast rides on it, likely just gentlemanly pottering about - it's hardly a boy-racer's bike! ::)
Ron.
-
Aluminium heads on an engine do not in anyway guarantee hardened exhaust valve seats sadly.....as many Rover V8 owners will be able to confirm sadly
-
Is there an easy way to tell for sure if they are hardened or not? Mind you, as Nick has said, my likely annual mileage means that it won't be a big worry.....
Ron.
-
Aluminium heads on an engine do not in anyway guarantee hardened exhaust valve seats sadly.....as many Rover V8 owners will be able to confirm sadly
That is not what the many Rover V8 owners I know say: you'll be suffering from knackered cams/followers/bores/ other low oil pressure related faults long before the valve seats fail. I read a letter from a manufacturer of valve seats some years ago, he reckoned that they had never(since the thirties!) sold a valve seat that wasn't suitable for unleaded fuel.
-
You do know how to confuse me! :-\ ???
Ron.
-
Continual rotation in one direction doesn't work - so I was told in my earlier years, but I cannot remember the reason why. I was also told of an accessory for a power drill that mimicked the alternating-direction action of hand grinding but it's unlikely to be available still as so few people lap valves in nowadays.
As unavailable as Amazon? LINK (https://www.amazon.co.uk/Gunson-G4095-Eezilap-Valve-Lapper/dp/B0012MCW06)
What James has done here(put valves from one used head into another) shows just how well the seats are machined on modern engines/equipment: you wouldn't have even considered doing that on an old engine with just grinding paste - you would've had both the seat and the valve reground and then lapped(which even with coarse paste is a final finishing operation) them to match each other.
I'm glad I didn't know this when I hand lapped valves on my Mk1 Consul, M2 Zephyr, Renault16 and Beetle engines all those years ago. ;D
-
Aluminium heads on an engine do not in anyway guarantee hardened exhaust valve seats sadly.....as many Rover V8 owners will be able to confirm sadly
That is not what the many Rover V8 owners I know say: you'll be suffering from knackered cams/followers/bores/ other low oil pressure related faults long before the valve seats fail. I read a letter from a manufacturer of valve seats some years ago, he reckoned that they had never(since the thirties!) sold a valve seat that wasn't suitable for unleaded fuel.
Pre 85 engines are well known for valve recession as they had a basic chilled Iron seat, this vastly increased if they operate on load for any period (so smaller cars not such an issue, Land Rovers etc, bigger problem).
There was always some confusion as Rover stated they were ok from the early seventies (they weren't but the recession was considered small.....), its when they finally opened the inlets up with EFi that they truly had to swap over to a proper hardened seat. Easy enough to track with the valve seat part numbers.