Cylinder Head Overhaul - Refitting

[ChrisH]

After 18 months idle, when I came to start Pearl the battery was flat and finished. Fitted new battery, but the solenoid coil would not pull in. As the solenoid is near enough inaccessible, you can't see it let alone reach it, and on a LH drive car the steering column gets in the way too, I thought I would take off the inlet/exhaust manifold to improve access and promptly sheared a stud on the manifold to exhaust pipe join. So, as I had a top end overhaul kit, I decided to take the whole head off, overhaul the head and drill out the broken stud in the exhaust manifold.

With the head off found that the inlet/exhaust manifold had been fitted somewhat unevenly, being tighter at the top than the bottom; there was evidence of exhaust gas leaking by all along the bottom. And, I thought to myself, probably an air leak on the inlet side which would explain poor running, lack of power, and difficulty in getting the emissions right - even the Reno garage here in France had problems when they did it for the last CT (The French MOT). Promptly then sheared one bolt off on the rear water blanking plate and one on the water pump. All three sheared bolts/studs sorted OK, and the valves lapped in - they were in very good shape which I found surprising. Also surprising, the head face was dead flat - I expected some bowing but there was none at all. I refitted the water pump and the exhaust manifold whilst the head was on the bench; not only was it easier to do so but I could ensure that the manifold was on flat and true, much easier than doing it when in the car - that may have been the problem with the manifold the last time it was refitted.

The problem with the solenoid came down to just a dodgy connection - the spade on the solenoid that the wire from the ignition switch fits was very "dirty" - so much so that there was absolutely no continuity through it anywhere. Once cleaned up all was 100%.

So all boxed up again, and once the fuel starvation problem was sorted - (see the post "No fuel supply - pump, filter problem?") she started and ran OK.

So, a Question. Ran for 20 minutes as suggested by Mr Haynes in his excellent workshop manual, where it then says let it cool down for at least 2 1/2 hours and then slacken each head bolt in turn in the correct seaquince for 1/2 a turn then re-torque it again to the specified torque (and readjust all the tappets again). Now, is this correct? I cannot recall slackening cylinder head bolts half a turn and re-torqueing before, but it was a long time ago. I think all I ever did, (if I did anything), was to just check the head bolts were still to the specified torque. Reason for the question is that I am not sure of this slackening off 1/2 a turn bit.

What does the team think?

Chris

 

[barnfind]

Steve Hennesey did a post on this recently.

 

[barnfind]

Here is Steve's post from last July (further back than I thought)

This is from an earlier post and it's worth following:

I've used my 'patented' method since the early 1980's. It was when I discovered the reasons why British Leyland 2200cc Princess models had tendencies to develop cracks in their cylinder heads.
Before fitting a second cylinder head on a customer's Princess in one year I prodded one of the bolt holes with an electrician's screwdriver and it was full of swarf from the manufacturing process. All other holes were equally as bad. A little light came on and I realised that the reason for the cracks was because the head could not be properly torqued down.

Since then, before I replace a head I do the following:

1) Stuff clean rag in all the orifices of the block except the bolt holes.
2) Thoroughly clean the surface of the block using a Stanley Knife blade, wet and dry paper lubed with WD40 or similar.
3) Stick a small screwdriver in each bolthole to check for swarf and crap.
4) Run the compressor up to 100psi, wrap the end of the airline nozzle with rag and blow out each hole. Keep a grip on the rag to prevent swarf and carbon going everywhere.
5) Repeat if necessary. Then run a tap down each hole to clean burnt carbon particles from the threads. Blow out all the holes again.
6) Remove the rag from the orifices and throughly clean the block surface and bores with thinners so everything is perfectly clean.
7) Fit the gasket without any sealant or grease (light greasing okay on copper asbestos gaskets). Carefully drop on an equally clean cylinder head that has been thoroughly overhauled and checked for straightness.
8) Apply a very light smear of copper grease to each cylinder head bolt and tighten them down by hand using an extension and socket.
9) Then nip them up using a bar, then tighten them in the correct sequence using half the recommended torque. Then 75% of the recommended torque, then 100%.
10) After 500 miles on a cold engine. Undo each bolt one turn and then torque to the recommended figure.

By using these simple rules I never had any failures at all and I urge any of you who are carrying out any top end work to use these rules. There is nothing worse than a head gasket failure when you're miles from home and you had forgotten to renew your AA subscription [/I][/I]

 

[Steve Hennessey]

Thanks Bryan - I'm glad that someone reads my posts

 

[ChrisH]

Thanks guys for the response - I guess I will go for the "slacken off and re-torque" bit now. Interestingly, Mr Haynes says run for 300 miles for the earlier engine and recheck, but only 20 minutes for the 1100 engine. I think I will go for Steve's 500 miles, or thereabouts, then do it, sounds sensible.

Chris

 

[angel]

You can't check tightening torque accurately enough if you don't slacken the bolts 1/4 to 1/2 turns, that's why all the manuals state this. Actually this process is used to take into account initial head gasket squashing (and thus lowering head bolt tension).
You can probably continue like this until the 500 miles that you will need to re-torque the head bolts, but to be 100% sure, I would suggest that you go over the bolts once again (1/2 turn off, then tighten to the correct torque, one-by-one). You will not do any harm for sure.

 

[mike4gtl]

If you use a composite gasket i wouldn't recommend re-torquing the head. Plus R4's (1108) are listed in our books as using a stretch type head bolt which you just "do up".

I must admit the 1108 engine is so easy to put a gasket on, i am surprised more people didn't do their own.

 

[malcolm]

My 1108s have always needed torquing up after a bit of running. I generally drive gently for a few hundred miles and then re-torque. Haven't read the Haynes manual.

The re-torque does seem to move the bolt position around a fair bit from where it was previously. What are composite gaskets?

 

[Steve Hennessey]

Composite gaskets are 'man made' using a variety of materials as opposed to copper asbestos which was asbestos sandwiched between two thin sheets of copper.Some engines used a single copper sheet that had to be annealed each time you used it. My Rover V8 used to have pressed sheet steel head gaskets - there are many different varieties out there. I always liked to play safe and retorque - it's like adding an extra bit of insurance to your policy!!

 

[ChrisH]

Just done the re-torque after about 20 mins running. Was surprised how 'slack' the head bolts seemed to be even though they were tight. Also, as noted above, they seemed to turn round far more on re-torquing. I think I will run the car for a few hundred miles and then give it another re-torque.

Chris

 

[alewis]

Interesting discussion about re-torquing, I just did the head on an old V8 which has studs and nuts and it says nothing about re-torquing it in the manual. which is good as it would require dismantling the full carb setup, coolant system, brake pump assembly not to mention the power steering pump etc to get the rocker covers off and get to the bolts!

The R4 is nice and accessible!

 

[angel]

If you use a composite gasket i wouldn't recommend re-torquing the head. Plus R4's (1108) are listed in our books as using a stretch type head bolt which you just "do up".

All workshop manuals (Renault, Haynes, Autodata etc) recommend two retightening processes, one immediately after the gasket replacement after the engine has run for 15 minutes then left to cool, the other after the first 500-800 kilometers.
I have never seen a copper/asbestos gasket on such engines, all are composite ones.
Our head bolts are not of the "stretch over the yield limit" as used on most modern engines. Therefore, they can be retorqued and used almost infinitely. You always see a "torque and angle" tightening process on modern cars, and this serves to bring the bolt to its yield limit (you can feel the bolt stretching at the final stage of tightening!)

 

[Steve Hennessey]

I have never seen a copper/asbestos gasket on such engines, all are composite ones.

Yes Angel, I referred to Copper/asbestos as a comparison between different types of head gaskets, not meaning that they were ever used on R4's, which of course, they were not.