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Small Bore Head Gasket Reliability


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#1 unburntfuelinthemorning

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Posted 05 June 2019 - 09:49 AM

I've had to deal with a few small bore head gasket failures over the years.  No doubt some of these were down to mistakes on my part.

 

From the factory the head gaskets seemed to last well so what is the best belt and braces technique to ensure head gasket reliability particularly with the only choice now seemingly being copper gaskets?



#2 Dusky

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Posted 05 June 2019 - 10:19 AM

Belts and braces is skim both the block and head. I only ever use copper gaskets and haven't had one fail. ( tough wood)

#3 unburntfuelinthemorning

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Posted 05 June 2019 - 01:06 PM

Yes, the block and head are being skimmed this time.  In the past I didn't have the block skimmed and that was probably a mistake.

 

That'll be a copper Payen gasket going on there.  I've always used them if that is what Rover used to supply.

 

The workshop manual recommends 50 lbs/ft on the nuts, oiled.  I've seen differing opinions, some people say that's too much.

 

Most people say no sealant but some say Hylomar on copper gaskets.

 

Is it worth upgrading head studs or not?  I have the A+ type.



#4 Miniman Sam

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Posted 05 June 2019 - 09:25 PM

Hi, regarding sealer on the gasket, there is a special copper gasket sealing spray that you can get,
I have used this in past and haven’t had any issues.

https://www.ebay.co....m4383.l4275.c10

#5 dotmatrix

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Posted 06 June 2019 - 05:33 AM

I have used both Copper and composit with success

Edited by dotmatrix, 06 June 2019 - 05:34 AM.


#6 unburntfuelinthemorning

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Posted 06 June 2019 - 06:24 AM

Hi, regarding sealer on the gasket, there is a special copper gasket sealing spray that you can get,
I have used this in past and haven’t had any issues.

https://www.ebay.co....m4383.l4275.c10

Interesting stuff.  Anyone on here used it?



#7 unburntfuelinthemorning

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Posted 07 June 2019 - 07:30 PM

When is it worth upgrading the cylinder head studs to better quality ones?



#8 hhhh

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Posted 07 June 2019 - 07:40 PM

 

Hi, regarding sealer on the gasket, there is a special copper gasket sealing spray that you can get,
I have used this in past and haven’t had any issues.

https://www.ebay.co....m4383.l4275.c10

Interesting stuff.  Anyone on here used it?

 

I have and it seems to work. At least I haven't had issues with solid copper gaskets on bikes when I used it. 



#9 Moke Spider

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Posted 07 June 2019 - 08:40 PM

I feel that all head gaskets today are 'lesser' than they were since they removed asbestos from them. I'm not saying that's a bad thing though.

 

Copper Head Gaskets are great but only when everything else is perfect otherwise, they can be your worst nightmare.

 

When is it worth upgrading the cylinder head studs to better quality ones?

 

All the post 1968 Factory Head Studs and Nuts are brilliant and suitable for just about anything. Many of the new replacement Studs are inferior to these, I've had trouble with most of them in the past, so if I have to replace them, I now only use ARP.

 

One last point on the factory items. There were a few different types over the years and as mentioned, all are very good, however, don't mix and match types as some stretch different to others and while they may all be fitted up the same, a mixed set will produce different and uneven clamping of the head to the block.



#10 unburntfuelinthemorning

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Posted 07 June 2019 - 09:25 PM


When is it worth upgrading the cylinder head studs to better quality ones?

 

All the post 1968 Factory Head Studs and Nuts are brilliant and suitable for just about anything. Many of the new replacement Studs are inferior to these, I've had trouble with most of them in the past, so if I have to replace them, I now only use ARP.

 

One last point on the factory items. There were a few different types over the years and as mentioned, all are very good, however, don't mix and match types as some stretch different to others and while they may all be fitted up the same, a mixed set will produce different and uneven clamping of the head to the block.

So as mine are in good condition I may as well save some money in this area.



#11 unburntfuelinthemorning

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Posted 07 June 2019 - 09:37 PM

There seem to be many ideas on what the head nuts should be torqued to, for instance the workshop manual says 50 lb/ft, a lot of people say 40 or 45 lb/ft is plenty and David Vizard says if more than 10 lb of boost is used to torque the nuts to 60 lb/ft. 



#12 Moke Spider

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Posted 10 June 2019 - 07:47 AM

The later factory items I'm happy to take to 50 ft / lb (and that's the factory recommendation).

 

Those replacements presently on offer, I would only ever take to 45 when I have used them in the past.

 

It's important to get this right, as if the studs are over-stretched, the results are obvious, however, equally, if they are not stretched enough (by torquing up the nuts), then gasket failure is likely as the studs will be further stretched from combustion.

 

If going beyond 50 ft/lb, then the block has to be bored and honed with a torque plate in place or the bores will be quite out of shape.



#13 johnv

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Posted 10 June 2019 - 08:20 AM

My engine people (Bracknell Classic and Modern) insist that once you have torqued everything down, you run the engine until it reaches operating temperature, then turn it off and leave it to completely cool down (overnight)

Then undo each nut in turn a half turn and re-torque. I have followed these instructions and not had a problem



#14 unburntfuelinthemorning

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Posted 10 June 2019 - 09:11 AM

I've always re-torqued the head but I think I've been doing it wrong as I would loosen all the nuts 1/4 turn and then re-torque them instead of loosening and re-torquing them one at a time in turn.

 

Hope that makes sense. 



#15 johnv

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Posted 10 June 2019 - 09:38 AM

I've always re-torqued the head but I think I've been doing it wrong as I would loosen all the nuts 1/4 turn and then re-torque them instead of loosening and re-torquing them one at a time in turn.

 

Hope that makes sense. 

 

yes it does, I specifically asked them to clarify as it was not obvious from the statement 'undo each nut half a turn then re-torque' !






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