les wrote:You only need to leave a 'ring' of carbon around the crown of a piston when decoking, the rest can be removed.
did my first de coke about 50 years ago,and done more than I can remember since,was given the above advice by my father,who used to do a de coke every year,regardless of the condition of the engine.I have left a ring on , and taken all the carbon off, and also left it all on. I have never seen any difference after. No one in all that time has ever been able to explain to me how a ring of carbon,on top of the piston could stop oil from getting up the bore. Anyone out there now who can give a logical explanation.
I'm going to try and put it all back together at the weekend and will let you know how it goes.
Still a few questions...
1. The bores are nice can clean, no scoring, just the tiniest of lips ay the top, presumably where the piston doesn't quite travel to. Presumably that's quite normal and therfore ok. I don't understand what people are saying about carbon deposits. The seem to be none. The bores are some of the nices shiniest metal I have ever seen. No carbon.
2. I still don't understand quite why claning the cr@p off the top of the piston (did it with oily rag) was such a bad thing. This rusty flakey material on top of the pistons would surely have knackered up the bores upon running the engine again.
3. Can anyone tell me how to remove the last water elbow stud from the old head. Simply will not move. (shall i just get a new stud)
4. Should I use the black gasket glue stuff on re-assembly. Some say do, some do not. The block is nice and clean to receive the copper head gasket.
5. What order to tighten up the head bolts? When you do tighten, do you do 1/2 pressure 1st and then re-tighten.
6. should I check again after some miles?
7. Would tappit gaps be done engine hot or cold.
Thanks for your help - this is the 1st time I've tried this. keepiing my fingers crossed just means I keep dropping spanners and sockets!
NO GASKET GOO - EVER !! Just get a new stud - it's going to snap..... Wipe the gasket with grease both sides - nip the head down evenly all round - with the rocker gear fitted, but DO NOT tighten the 1/2" AF rocker pedestal at this stage - just nip them down. Tighten in steps - with a torque wrench - following the order in the workshop manual up to 40 ft lbf. Then tighten the 1/2" AF rocker nuts - to 25 ft lbf. Set the valve gaps (12 thou inlets and 15 thou exhausts) and run the engine up to temperature. Switch off and let it cool - retighten the head nuts to 45 ft lbf and reset the valve gaps. Don't touch the head nuts again!! PM me if you don't have a manual.
Last edited by bmcecosse on Thu Oct 18, 2012 7:48 pm, edited 1 time in total.
Update - got the head back on, but waiting for a few parts to arrive before I can tighten it all up and fire up the engine.
Found several bodged up jobs on vaious gaskets which were blue sealant rather than gaskets. From at least 25 years ago.
They'll be done properly this time.
Will be next weekend before I finish it now. It's left all nipped up just as the nuts start to bite + a tiny bit.
Amusingly got the long and the short studs mixed up. They're correct now.
Thanks again for the advice. Will let you know next weekend. Is there a "running in" period as I would quite like to take her on a 250 mile trip within a few days of next weekend.
Well it's all together.
Cured the water leak from the heather tap - it just wasn't flat. It could have been letting water out, hense I was using some!
Now it just refuses to start. Have sparks on all plugs. I have checked and rechecked the firing order. The leads are in the correct order. The leads are in the same order I took them off.
There is petrol. I'm "floating" the distributor to see if I've done horrible timeing things by accidentally moving it round.
No water in the bores when I put it together. Possibly a trickle down no1 (nearest car) when I spotted the leak. We're taking a spoonfull at most. All other bores definitley dry. I did put a little oil on tip of each piston, perhaps size of 1p piece.
Did you check the tappets after it was put back together?
Chuck about an egg cup of petrol down the carb and see what that does.
If the carb wasn't kept upright silt can find it's way into the jet tube and block it.
Does it spin over any differently to how it did before?
"Once you break something you will see how it was put together"
Ah, now that's interesting. No The carb assembly was not kept upright.
It smells of petrol when turned over - that is trying to start it in bursts doe 30 - 45 seconds.
The pump clicks lots and then settles.
The actual turn over feels quite normal.
When you say tip the petrol down the carb, exactly where do you mean? There is a the reservoir - that's full anyway.
There's where the air intake is, where else is there?
No BRRMM, nothing. Put some petrol down the air intake.
There is the suck of air when turning over (put my hand over intake, blocking it and felt suction.
Worryingly, there appears to be absolutely no conpression at all. Tested by turning the engine over on the handle. I'd expect a little kick back at least -nothing. It's like having no plugs in it at all.
No valve setting yet. I have slackened things of slightly. Valves all seem to be going up and down properly. I'm convinced I have torqued down the head properly.
I'll set some vavles tomorrow. I'm familiar how, having done it on a straight 6 many times.
It the valve nearest the radiator inlet or outlet, I've got that wrong before. I assume they then just alternate.
She Lives!!!
Yes it was th valve clearances. It became obvious as I did the 1st one. It was so far out. Then I turned the engine on the handle for the next one and felt a bit of compression.
Part of me thinks that valve clearances could have been the original problem on cylinders 2 and 3 - there was hardly any difference in the engine note when taking those leads off originally. If effectively they were not sealing on the valves, then 2 cylinders and a bit of the others working may have explained why i had such a lumpy engine with no power.
At least I've learned to change a head gasket!
Thank you so much for your help. Much appreciated.
