Fitting head gaskets

[Nauti Fox]

Need a bit of advice please.
I'm soon going to fit new copper composite head gaskets to a GMC DH637 10.4 litre V8 diesel and wondered if any kind of sealant is recomended.I've had to get new ones made up as the previous owner had fitted two completley different ones(one good and one that was half the thickness and did'nt fit)
I've got experiance with petrol engines but have'nt worked on diesels before.
Any advice would be gladly received.
Al.

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[ccscott49]

No sealant, with copper asbestos head gaskets.

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[Nauti Fox]

Thanks Colin.
Al.

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[BarryH]

As Mr Scott says no sealant. I'll just add, torque wrench, use it use it use it. Do you know the settings and sequence. Does your lump use stretch bolts. If so get new ones. If not, run it and then re torque it. Oh and keep everything spotlesly clean.

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[ccscott49]

Like your logo! Very neat!

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[Nauti Fox]

Thanks Barry,I've managed to get a manual for it from Singapore with all the torque settings etc,although I've had to get a new torque wrench as none of mine go to such dizzy heights!
Setting the valve clearances looks a bit of a problem in that all markings are long gone.I was going to turn it over until I got TDC (compression) on each cylinder.Bit long winded I know,what do you reckon?
Al.

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[BarryH]

Hmm not making things easy then. I take it it won't be an ohc lump being a Vee config. Are you having the head/s skimmed at all. I only say this as theres been one or two engines that I've worked on that have VERY close valve/piston clearance at TDC. Turning over by hand shouldn't be a prob if valve contacts piston as long as your gentle.

What I've done in the past, mainly on jag V12's is to mark the tdc of each cylinder on the crank pulley. Takes a bit of fiddling with a dial gauge but saves time in the future. Just a thought!

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[BarryH]

Its about the only thing relating to me that is!!!

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[Nauti Fox]

No, not having them skimmed.I've checked that they are'nt warped and am just cleaning the faces with scotchbrite pads.Good idea about marking the pulley,unfortunatly you need to have the build of a racing snake to get in there!Think the valve/ piston clearances should be OK as the gaskets are being made by the guy that made the good one originally(the crap one being half this thickness)Testimony that it ran before with this set up although suffered from overheating which is also down to the rubbish gasket covering over 50% of the waterways!
Al.

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[ccscott49]

Dont put yourself down like that, theres plenty of peeps on hee will do that for you! By the way, I would have left all the valve clearances really slack, then they would have for sure not touched as you turn the engine over. But he is really going to have a problem, if theres no marks, when he comes to time the thing!! Love V12 jags, had a couple, worked on lots, did a lovely six downdraft conversion on a couple, that was really nice, a different engine! without all that dogs dinner of pipework everywhere!


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[Nauti Fox]

Dont need to time it Colin as its pushrod,aah old technology can be good!
Al.

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[ccscott49]

Good, because you do need timing marks for the ignition timing. But if you`ve not removed the distributor, then it should at least start, then you can adjust it by ear, or vacunm gauge.


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[Nauti Fox]

Its a diesel!
Al

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[tcm]

No, the valves will need readjusting imho. Barry's right, set the clearances very slack, tighten it up with a torque wrench in the correct order oppositely in turn as per the manual. Really, i think yoiu have to set the valves roughlyish or wide, run it a bit to warm up, then tighten the head again, then set the valves again. Tightening down the head will tighten those clearances. The thickness of the gasket isn't a fixed dimension, and it squishes down over time - it won't be exactlery the same as the last gasket at all, though nearish.


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[Wiggo]

Err, I would do the valve clearances anyway. Valve/cylinder clearances can be tiny on a diesel, and will need to be set correctly. Easy way to do them is to turn the engine over by hand till the chosen valve is wide open, then turn the crank another 180 degrees. This guarantees the valve is closed, at which point you can check the clearances and adjust as necessary. It's slightly more long winded than using the proper sequence of opening and closing, but idiot proof. Thanks to Tony Brooks and his diesel maintenance course for that one...

Timing should not be necessary unless you removed the injector pump.

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[ccscott49]

Just realised that! DooooooH! When I think V8 I think petrol, sorry.

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[Nauti Fox]

Yep,totally agree about clearances,what do you think about retightening the head,straight away or after a few hours/cycles?

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[ccscott49]

180 degrees is for in line engines.

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[BarryH]

Aye, tis true. For an eight it'll be nearer 45 degrees, depend on the engine config. Most vee's are of the 90 degree config, I think. Dunno hit "stop" on your browser while looking at my little avatar thing. Thats based on a 90 degree config.

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[BarryH]

No I may be wrong there, forget I said anything.

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