engine valves

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normajay99
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engine valves

Post by normajay99 »

Back again,had problem with blue smoke and cut a long story short had head off and while this was off had head made for unleaded use with new valves springs etc etc this was carried out at engine repair centre the new head was replaced but the fly in the ointment now seems to be that I used a tube of non hardening gasket sealer when fitting the head back and I think it has somehow got into the valve chamber I can pick this off with my nail but do I need to grind in the valves or have to replace them I have only done over 100 miles since I fitted the head I thought the smoke was possibly due to worn or damaged rings iv,e put on some photos so I would be so pleased if you can give me any advice
les
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Re: engine valves

Post by les »

I don't see the stuff causing the valves any problems, however it would pay to remove any sealer from block and head. It is normal practice to assemble with a smear of grease on the head gasket, not sealer as such.

philthehill
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Re: engine valves

Post by philthehill »

What sealer did you apply to the head and block?
I agree with Les that the non hardening sealer should not effect the operation / sealing of the valves - any excess sealer should have been burnt off/away by now.
Whilst I would only recommend that a smear of grease is applied to either side of the gasket unless the manufacturer states otherwise - some engine manufactures i.e Rolls Royce state that a sealant for example 'Hylomar' http://hylomar.com/
is applied to the gasket and head/block faces - so to say do not put a sealant onto the gasket/head/block faces is not so clear cut as may be first thought.

normajay99
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Re: engine valves

Post by normajay99 »

Thanks for the advice about using gasket sealer ,I tried sending photos but could not upload (I think that's the term ) giving away my age now but my son is going to give me a lesson tomorrow so you may get to see them yet ,iv,e started removing the valves and the small diameter valve on number four cylinder is realy covered in a hard carbon deposit im sure its the gasket seeler further down the valve shank you can scrape it off with your nail the other valves don't appear to bad but just to add to the problem iv,e found no four cylinder is not gas tight ! so I think I,ll replace all piston rings if you think that's the best thing to do,on all pistons of course and can you tell me is there a particular type of grease to use to coat the head gasket thanks again Norma and co.
philthehill
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Re: engine valves

Post by philthehill »

Was the head de-carbonised and new valve seals fitted before the original fitment approx. 100 miles ago?
The hard carbon deposits found on the (small) exhaust valve(s) and stem is normal but can be compounded by the wear in the engine.
What is the condition of the bore when you run your finger nail up the bore - does it catch under a lip near the top of the bore?
If it catches in all probability the engine requires a re-bore and new pistons.
As regards what grease to use on the head gasket - Castrol LM or general purpose grease is more than satisfactory.

bmcecosse
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Re: engine valves

Post by bmcecosse »

ONLY ever use a light wipe of clean grease on a head gasket - unless you have an RR I suppose..... :roll: Clean up the valves - be sure to put them back in the same holes and lap them in again. Who did the head overhaul ? 'Unleaded' is a waste of money by the way... Hopefully they fitted the latest Mini type guides with the much better 'top hat' oil seals on the inlet valves. We really need to see pictures to be able to decide if rings will help - probably best to drop the sump and push the pistons out to inspect for broken rings and/or damaged lands on the pistons. Pictures should be reduced to 600x 400 or so to post on the thread.
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normajay99
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Re: engine valves

Post by normajay99 »

Some photos to see the current problem, as was unable to upload them yesterday.Realised they needed reducing in size! Hope they give a clue to the problem. Heres hoping![frame]Image[/frame][frame]Image[/frame][frame]Image[/frame][frame]Image[/frame]
bmcecosse
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Re: engine valves

Post by bmcecosse »

Just need cleaning up = but that amount of gunk would take many many miles of rich/oily running to build up. When the head came to you - was everything spotless? No sign of any gasket problem there.
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normajay99
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Re: engine valves

Post by normajay99 »

Picked up the refurbished unleaded head with new guides pistons top hat seals etc etc fitted everything back but used this blue gasket cement which I now believe has caused the problem after various comments from some well informed minor owners and dealers so have striped everything down again and awaiting new head and manifold gaskets from supplier No blue gasket cement !! have reground valves and cleaned everything down so theres no grinding paste left in there by the way can you tell me the pistons in the engine have a stamp on each of them with a no 40 also the no stamped on the engine block I was told it may have been a manufacturers stock no or has the engine had a rebore !
les
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Re: engine valves

Post by les »

If the combustion chambers and valves were spotless 100 miles ago, and when stripped, the condition is as the photos show, you must have used bucket loads of gasket goo for that to happen! If the Block has been bored the pistons may have 040 showing not usually 40. If you had new Pistons fitted no doubt you had a rebore. Ask the people who did the job.

philthehill
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Re: engine valves

Post by philthehill »

A good guide to whether the engine has had a re-bore is seeing if the engine number still in place on the O/S top front of the block.
It is virtually impossible to re-bore properly and accuratly with the engine number plate still in place.

normajay99
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Re: engine valves

Post by normajay99 »

Sorry about this but in my haste to get answers I wrote piston instead of valves :oops: so I did,nt have a rebore or new pistons fitted I can also say that the engine number plate is still where it should be on the front of the block as you said am still waiting for gaskets to arrive to reassemble and try it all again I was also told by someone to see if there was any movement side to side on the pistons while in the block I checked this and there was a small amount of play and I tried to fit a 4 thou feeler gauge in but it hit the top ring and was fairly tight is this ok!
oliver90owner
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Re: engine valves

Post by oliver90owner »

It is the compression rings which seal gases in the combustion chamber (combustion chamber to crankcase). There can be quite a bit of clearance between piston and bore, but, clearly, wear will increase if the pistons have too much clearance. Ring side clearance in the grooves is important, as is the ring gap. Aluminium expands more than cast iron, so sloppy pistons often exhibit 'piston slap' at cold start up. But that is another story.

Your problem would appear to be oil pouring down the guides. 100 miles and that sort of valve filth is indicative of a seriously worn out engine - if it was set up properly - or excessive oil running down the guides. It should be smoking profusely and using oil in fairly large quantities for valves like that after only 100 miles (of normal motoring). I suggest a compression test at some point would have been good, but now this engine needs someone with experience to investigate the simple reasons for failure.

Is the engine breathing heavily? Is it operating under crankcase pressure? (Some) inlet valves look OK, so the valve stem seals appear to be working. Are there seals on exhaust valves? What is the clearance between valves and guides?

As far as head gaskets are concerned, follow the gasket manufacturer's instructions. If there are none supplied, either enquire - or buy gaskets from a more reputable source. Simple as that.
normajay99
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Re: engine valves

Post by normajay99 »

Thanks Oliver90owner having the head made unleaded i also had new valve guides new hardened valves and seats in fact everything on the top end was replaced but how do you measure clearance between valve and guide or am I missing something ! even though I had this work carried out I still checked for any play when valve was sitting in the guide and they all seemed to be fine no slack or side play I fitted top hat seals on all the valves as per books iv,e read is this right or wrong also checked crankcase breather before engine head was removed and appeared to be fine even tried removing oil filler cap the compression tests before head was removed all plugs out was no1 160 no2 158 no3 162 no4 166 I added a small amount of oil to each cylinder to see if there was much change and got no1 177 no2 180 no3 175 no4 175 have bought copper cylinder head gasket and will wait and see if theres instructions with it thanks again all help is appriciated
bmcecosse
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Re: engine valves

Post by bmcecosse »

DO NOT fit top hat seals on the exhaust valves....only the inlets. The valves and chambers look very oily to me - I suggest that despite the reasonable compressions (and yes it is a 40 thou rebore) that there must be considerable amounts of oil getting in to the chambers. I can't see 'gunk' - blue or otherwise - causing all that mess..... The compression rings may be good - but the oil control rings may be broken - or even fitted upside down. May be worth popping the pistons out to inspect the rings and piston lands....Check the crankcase breathers are clear and connected properly when refitting the head.
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normajay99
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Re: engine valves

Post by normajay99 »

once again bmcecosse thanks for your suggestions got gaskets today but did,nt have time to fit them just as well I think! I,ll remove the top hat seals from the exhaust valves before fitting (they were fitted when i removed the head ) when I check the rings is it the gaps in each ring that will tell you if they need replacing and how do I tell if the ring or rings are upside down and to order them I would expect to order rings for engine block that's had a 40 thou rebore from standard size do you think it,s worthwhile just replacing all the rings when i,ve gone this far in stripping down the head also the copper gasket I had no instructions with it for fitting is the copper face up or down thanks PS as you may have guessed this is my first engine stripdown Well second time I,ve had the head off!!
bmcecosse
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Re: engine valves

Post by bmcecosse »

The check is to see if the oil rings are present and correct - and the piston lands not broken or seized up with 'gunk'. Yes - you would need +40 rings - but check if the pistons are ok first. The check for valve/guide clearance is simply to wobble them in the guide - there should only be the very slightest of movement and obviously no tightness. The exhaust valves need some lubrication -especially with hotter burning unleaded fuel - hence no seals should be fitted to their guides.
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