Grease for head gasket and bolts??

[sparkie]

Hi all, just rebuilding my little Yamaha 2hp after cleaning waterways etc, was lucky to get the head bolts out without damage, lot of white corrosion, so intend to grease them before putting them back. Was thinking of using copper grease, any thoughts on this?? Also head gasket had bonded firmly to head and block, so having to replace same at enormous expense, so thinking of a smear of ??? thickish oil or grease both sides of this also before re-assembling so as to avoid future problems. Any thoughts?? Cheers.

 

[Old Harry]

copper/alloy is not a good idea

 

[sparkie]

copper/alloy is not a good idea

Yes that was one of my reservations. Options are copper, white (calcium), or LM (petroleum). Did think about zinc chromate paste but have found this tends to set very hard over time.

 

[RivalRedwing]

I don't know the engine so don't have the torque setting to hand but... head bolt torque settings are usually defined on the basis of dry threads, greasing the threads is likely to increase the thread pressure before the torque wrench goes 'click' - more of an issue on alloy blocks but if you have a torque range then aim for the bottom of the range. A little bit of ordinary grease if you must, but first clean out the threads in the block with a thread chaser. Re the head gasket - as per the suppliers recommendation, usually they recommend 'dry'.

 

[Trundlebug]

I agree on the head gasket, always assemble dry without any sealant or lubrication. Hopefully it's not a regular maintenance item so the inconvenience of cleaning it when taken apart is just one of those things that has to be endured I'm afraid.

On the threads I share the nominal concerns re differential metals and copper grease, so it would be worth researching a bit or talking to the (grease) manufacturers to see what they say before proceeding.
But it's an ideal application for copper grease in some respects as you're using it as an anti corrosion agent rather than lubricant.
In that respect, and from practical experience copper grease will only have a slight effect on the assembly friction for the torque settings. Other greases much more so as they're much better lubricants.

 

[sparkie]

Thanks both. Interesting.

 

[VicS]

Hi all, just rebuilding my little Yamaha 2hp after cleaning waterways etc, was lucky to get the head bolts out without damage, lot of white corrosion, so intend to grease them before putting them back. Was thinking of using copper grease, any thoughts on this?? Also head gasket had bonded firmly to head and block, so having to replace same at enormous expense, so thinking of a smear of ??? thickish oil or grease both sides of this also before re-assembling so as to avoid future problems. Any thoughts?? Cheers.

You should be able to find the correct answers to your questions ( or verify mine) in the relevant manual at Boatinfo - The library, containing manuals, brochures and other technical documents from the last hundred years!

ITYWF that the bolt torque is 10 Nm ( 7 lbs.ft), that they should be coated with Loctite 572 and that the gasket should be installed without any coating . (the bolt torque may be marked on the head .)

 

[sparkie]

Hi Vic, thanks for the link, all v.useful stuff, and I've bookmarked it for future reference. Dry assembly for the gasket then, and Loctite 572 (whatever that may be) for the bolts. Interestingly, for the 3 hp model, clean engine oil is specified..... Can't think what the difference could be. Anyway, I assume the Loctite will provide some corrosion protection as well as security for the bolts, so that seems to be the way to go. Cheers!

 

[RichardS]

Hi Vic, thanks for the link, all v.useful stuff, and I've bookmarked it for future reference. Dry assembly for the gasket then, and Loctite 572 (whatever that may be) for the bolts. Interestingly, for the 3 hp model, clean engine oil is specified..... Can't think what the difference could be. Anyway, I assume the Loctite will provide some corrosion protection as well as security for the bolts, so that seems to be the way to go. Cheers!

I always use copper grease on all bolts, as do all the car restorers that I talk to. I've been using it into aluminium castings for 50 years now and have never had a problem when disassembling at a later date. However, if you have any concerns, you can use aluminium grease rather than copper grease. I tend to use the ally grease on alloy wheels studs because it is not so messy.

Richard

 

[Poignard]

I would not use any lubricant on the gasket and normally I would simply oil the bolt threads unless, as VicS has pointed out (post #7), the engine manufacturer specifies something different.

 

[Daydream believer]

In the days when had a Humber Sceptre I was told dry, but I do know that some mechanics used knotting, which contains shellac. The gaskets used to have a sticky coating of it when supplied which was usually considered sufficient

 

[sparkie]

Thanks for the contributions. All very welcome and of interest. Cheers!

 

[V1701]

In the days when had a Humber Sceptre I was told dry, but I do know that some mechanics used knotting, which contains shellac. The gaskets used to have a sticky coating of it when supplied which was usually considered sufficient

Yamabond or hylomar I guess would be more modern equivalents. I've used this one successfully on motorbikes and also used it on a new exhaust elbow (to augment the gasket) for the boat, haven't used for head gasket but I don't see why you shouldn't...

 

[DownWest]

Usually head bolts (and others) are torqued up with some lub on the threads. Otherwise, the friction can vary and give different settings. Certainly was required on assembly of aircraft engines when I was involved and in the Yanmar manual for the 2GM20 that was on the bench recently.

 

[Boathook]

I've always used a bit of keenol? grease on the threads to aid future removal. It also hopefully reduces corrosion between the aluminium and s/s bolts. I have also used a smear of it on gaskets for the same reason including the cylinder head one on the Malta. The use on gaskets (especially carbs) was shown to me by a marine mechanic many years ago.

 

[VicS]

Usually head bolts (and others) are torqued up with some lub on the threads. Otherwise, the friction can vary and give different settings. Certainly was required on assembly of aircraft engines when I was involved and in the Yanmar manual for the 2GM20 that was on the bench recently.

Use the torque specified for the condition of the threads. If the specified torque is for dry unlubricated thread s a bit of Googling will find a reduction figure for lubricated threads

I've always used a bit of keenol? grease on the threads to aid future removal. It also hopefully reduces corrosion between the aluminium and s/s bolts. I have also used a smear of it on gaskets for the same reason including the cylinder head one on the Malta. The use on gaskets (especially carbs) was shown to me by a marine mechanic many years ago.

These days gaskets such as head gaskets are usually coated and should be installed as supplied. "Many years ago " gaskets were not coated.

 

[sparkie]

Yamabond or hylomar I guess would be more modern equivalents. I've used this one successfully on motorbikes and also used it on a new exhaust elbow (to augment the gasket) for the boat, haven't used for head gasket but I don't see why you shouldn't...

Looks like useful stuff. I need a new tube of silicon so will give this a go instead. Cheers!

 

[gordmac]

I would be surprised if the head bolts were fitted without lubrication, torquing is pretty innacurate at the best of times! I used to put Hylomar on head gaskets.

 

[sparkie]

All been very interesting and informative this. Decided to go with the service manual recommendation - Loctite 572 on bolt threads and then torque to 10Nm, and the general consensus on here which is a dry gasket head joint. Thanks to all contributors.!

 

[RichardS]

All been very interesting and informative this. Decided to go with the service manual recommendation - Loctite 572 on bolt threads and then torque to 10Nm, and the general consensus on here which is a dry gasket head joint. Thanks to all contributors.!

I'm amazed that the cylinder head bolts are only torqued up to 10 Nm. That's much less than a spark plug and one could do easily achieve it with a 10mm ring spanner.

Richard