Update - Head progress

Well - I phoned French Marine this morning - mainly as I wanted to pick their brains on Yanmar's recommendations these days on head gasket sealant.( the shop manual still says to coat both sides with Threebond 50)

I had chat with their tech man - and he persuaded me not to bother with new retainer caps and cotters - so I was ok with that. He also confirmed that Yanmar DO NOT use any sealant on their head haskets now !

" ...the new gaskets now are coated and don't need anything " - just clean. degreased and flat.

Now this really bugs me really - I buy the offical Yanmar workshop manual for the 1GM10 in 2002 - from Yanmar, as a part no. I do this because I want to know the specs for this engine. If you are going to make modifications to the specs - why not just say - " check with yanmar/addenda/ etc etc for any superceeded assembly instructions - over the years ?

They can't be bothered

Anyway - nice to hear a man selling parts telling you you don't need his parts ! I was only trying to stay with in specs - ie,
" the top of the retainer should be flush to the top of the collet - no recess"...
What other 'specs' am I supposed to ignore ! Gets me at times

I was close to getting a new exhaust valve - but reasoned it away. There is not much wrong with the old one - and with a touch of thin oil the guides are ok.

I have settled for just fitting new springs - along with the new stem seals. Stem seals are a must, but they are £11each ( yanmar ouch ) - yet the valve springs were only £10 - go figure that one ? I reckoned on the springs doing a lot of work over the years - and they were at the wear limit for 'off square'.

Again - in my sort of world, when they say check the spring for 'out of square' - and give a wear limit, I sort of expect a new spring to be 'spot on' 90 deg. They are not - in fact the two new Yanmar springs both measured about 0.7mm 'lean' off square on a glass plate !

So don't be too concerned over this - ok if they are way wonky change them. To be fair I have not tested their compressive strength - don't have a way to do it. For £20 the pair is a fair price for a hard working item. Having checked the new ones though - in hindsight I would not have bothered. They are the same length within a whisker.

I then thougth - well, I really ought to have got those new collets. So checked back with RibParts - and they are sold as 'a pair of one assembly' - ie you have to buy 4. The £6.60 price is each collet half - so the set for two valves is £26.00 plus vat @ 20% - !!!

I just looked at a Classic Mini site - 7mm collets. £1.90 a pair !! Yet - a mini valve is 26.00 - a Yanmar is 14.50 ? Someone is just playing with prices for a pastime !

Its going back in with the old collets.

I lapped the exhaust valve just a touch more today - then washed the entire head submerged in warm soapy water and brushed out the ports well with a small brush. I then drained it and dried it and blasted it all over with wd40. Let it drain off in the warm, then oiled the valve laps and the guides.

Re fitted all the fixing bolts in their threads with a bit a copper grease to offset any any trapped moisture. Blasted the inside of the waterways with wd40 as well.

I was going to get down the the boat today to check the block properly. I have cleaned up the old gasket graphite stuff - but need to check it for flat.

If its ok it needs thoroughly cleaning - and the studs wire brushed and oiled and torqued. The spec is to double nut and torque them to 44 ft lbs. ( head nuts on re-fitting 55 ft lbs )

Hopefully the block is ok - head was very good ( better than 0.02mm - spec is 0.07 )

Really - one has to use a bit of savvy here. You do not want any dip in the middle around the bore. So check it with a good straight edge. A cigarette paper is 0.02mm. Check your edge on a piece of glass if necessary - just check if the paper nips at all positions with little pressure.

Now check the head all around the bore ring - every half inch - to make sure there are no low spots. This is where the main pressure ring of the gasket is compressed. All the rest is just holding in water at no pressure at all - simply pumped through an open system - and there is no oil gallery.

But bear in mind what the block is doing in the middle at the same place - around the bore edge. You don't want both to be at max wear limit - you are asking for problems.

Their spec of 0.07 for the head I find way generous and would not trust that. On a head this size thats huge ! I'm happy to see it flat everywhere at 0.02mm. If I see the block like that as well I shall be happy.

Both faces have to be clean and degreased - ie white spirit, Meths then Acetone or 98% Alchohol.

This process needs to be attended to - careful cleaning and torqueing. Also - worth bearing in mind on these heads. Two of the studs are outside of the rocker cover - two are inside. Hence two exposed are corroded and two nicely oiled and fresh. Pay some attention to these exposed threads and their condition. All four nuts need an even troque.

In hindsight - this head needed nothing doing accept lapping a worn exhaust valve seat - and slight lapping on the inlet.

The valve seat would have progressively got worse as it leaked more - and then burned more, which would have started to pickle the valve edge. So I'm glad I have removed it for a look.

May get down this weekend - but bad gales and storms forecast, on top of a 14.5 metre tide here ! May stay in bed - or maybe I should be down on Lena for for the heck of it !

Geoff - Jan 2014

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