Repairing Mating Faces

Helpful information and requests for assitance and advice
Locked
Mick D
Posts: 2886
Joined: Mon Mar 24, 2014 5:44 pm
Location: Aberdeenshire

Repairing Mating Faces

Post by Mick D »

Hi

I have a couple of minor dings in the mating face of my cylinder head to rocker cover joint:
Dings.png
I've dressed them back to flat but am wondering what the best way to achieve a leak free joint would be.

I'm considering:

Epoxy based structural adhesive flatted back plus gasket, (not sure it would cope with the repeated expansion/contraction).

Silicon plus the gasket, (leaning towards this option).

Fabricating a thicker gasket.

Does anyone have any thoughts on the above or alternative suggestions?

Regards Mick
You do not have the required permissions to view the files attached to this post.
Andy51
Member
Posts: 742
Joined: Thu Mar 31, 2005 1:00 am
Location: BERKS UK

Re: Repairing Mating Faces

Post by Andy51 »

Silicon is cheap and normally pretty good. Andy
User avatar
Group Leader
Member
Posts: 538
Joined: Tue Nov 29, 2005 8:51 pm
Location: Herts UK

Re: Repairing Mating Faces

Post by Group Leader »

If you wanted to restore it "back to metal" you could fill the depressions with Alutite and carefully dress the surface back to flat. However I suggest you would need to consider the following points:

1) You'd need to remove the cover and all of the associated "gubbins"
2) You would need to be well practiced at "Alutiting" - if you've never used it before get plenty of practice on representative scrap beforehand
3) You would need to make sure that you used the Alutite sparingly as it is relatively expensive and harder than the parent metal so difficult to dress back perfectly flat

Using Alutite would score on other methods though in as much as it would be much closer to a proper engineering job and thus far less of a bodge

Alan
1953 AJS 16MS, 1939 BSA 250 and a 1/3 scale Sopwith Triplane but that's another story ..... :lol:
User avatar
clive
Member
Posts: 5657
Joined: Mon Jan 01, 1990 12:00 am
Location: LONDON UK

Re: Repairing Mating Faces

Post by clive »

Well I would use silicon and a gasket and see if it seals. Not too much mind to ensure it does not get somewhere it should not be. But it is not a fix (and might even be called a bodge :o ;) ).
Locally we have a specialist ally welder who could certainly fix with it with some weld and flat it back. Do you have such a specialist near you? Its going to need disassembly and perhaps you could try the silicon solution until you need to pull the engine down.
clive
if it ain't broke don't fix
User avatar
Duncan
Member
Posts: 2118
Joined: Thu Jul 10, 2003 1:00 am
Location: HAMPSHIRE UK

Re: Repairing Mating Faces

Post by Duncan »

Assuming it is not visible once the gasket is on I would prep it and use JB weld but not the rapid stuff.
Mick D
Posts: 2886
Joined: Mon Mar 24, 2014 5:44 pm
Location: Aberdeenshire

Re: Repairing Mating Faces

Post by Mick D »

Cheers Chaps :D

The head is staying put for now so welding and Alutite are not options thanks.

Duncan, JB Weld looks interesting, particularly their HighHeat putty, do you have any experience of how to store the product once opened and what sort of shelf life to expect? (or am I looking at a one job fix?)

Regards Mick
User avatar
ajscomboman
Member
Posts: 3963
Joined: Mon Jan 01, 1990 12:00 am
Location: HAMPSHIRE UK

Re: Repairing Mating Faces

Post by ajscomboman »

I've just had the same problem on a Tiger 100 head that came in. I took it to the local machine shop to have the seats and valve guides done. When It came back I noticed a small indentation that wasn't obvious till they cleaned the head. They advised that the best option would be laser welding as it doesn't involve heat. Very bloody expensive though! I enquired about normal ali welding to which they replied that the dent was so small it'd need opening up to get a good hold. I opted for a small bit of JB weld and it's been perfect so far. As Duncan has mentioned use the slow cure and not the rapid, might be the same name but it's totally different in how it reacts to heat.
Reynard24
Member
Posts: 362
Joined: Mon Dec 16, 2013 2:27 pm
Location: CAMBRIDGESHIRE UK

Re: Repairing Mating Faces

Post by Reynard24 »

The trick with silicon is to use the smallest bead and to let it almost completely cure before assembling the joint then the bead should spread rather than ooze under pressure. The temptation ,however, is to use a great glob of the stuff and assemble immediately with the resultant mess breaking away from the joint and causing all sorts of mayhem. Apologies to Grandma in advance.
User avatar
Duncan
Member
Posts: 2118
Joined: Thu Jul 10, 2003 1:00 am
Location: HAMPSHIRE UK

Re: Repairing Mating Faces

Post by Duncan »

Mick D wrote: Mon Jul 05, 2021 7:53 am Cheers Chaps :D

The head is staying put for now so welding and Alutite are not options thanks.

Duncan, JB Weld looks interesting, particularly their HighHeat putty, do you have any experience of how to store the product once opened and what sort of shelf life to expect? (or am I looking at a one job fix?)

Regards Mick
Hi Mick, I just use the two tube variety, I have not seen their putty but have used similar usually the core is one material and the outer another you cut off what you want and kneed them together to start the reaction which is usually quick setting, the ones I have used come in a stoppered tube and have a disc of plastic on the either end , I just put the plastic back on and pop it back in the tube and it has kept okay, usual disclaimer that it was a different type.
laxy
Member
Posts: 790
Joined: Sat Jan 01, 1994 12:00 am
Location: LINCOLNSHIRE UK

Re: Repairing Mating Faces

Post by laxy »

I have had excellent results with this type of repair using a product called chemical metal by plastic padding
Simple to use , dries in ten minutes and sands down easily. Fit new gasket with light smear of well seal.
Locked