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Rectifying a mistake in a cylinder head.

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bricky16/05/2021 07:21:06
584 forum posts
72 photos

Having compleated the main machining on the cylinder head of the Brian Rupnow Rockerthump engine I was about to start the vave cages and noticed that they would protude into the combustion chamber.I found that the two step bore was to deep by 0.092" as I had read the drawing wrong and made the second bore the total depth of 0.196". I have made a washer 0.092 and propose to glue into place with J-B weld and drill and tap with a BA countersunk screw will this work as I have made a decent job of the cylinder head so far.


David George 116/05/2021 07:35:15
1874 forum posts
505 photos

Hi Frank have you a picture of problem as it may help us to have more information.


JasonB16/05/2021 07:56:25
23088 forum posts
2774 photos
1 articles

Are you talking about the cylinder side of the head with it's double depth recesses? and your "washer" will actually have 3 holes for valve and spark plug?

If so it's worth giving it a go, the JBW should take the heat and the screw which could be smaller will keep it in place if the adhesive does fail.

From Brian's build thread

bricky16/05/2021 10:42:43
584 forum posts
72 photos

Hi David I am sorry but I can't upload into my album from my photographs .It's not that I have not in the past but I had three quick power cuts in 15 minutes a while back and as my computer was carrying iphoto which no longer exists,when we manages to get the router back to normal the computer had put the present photo package on which I am having difficulty in working.


bricky16/05/2021 10:45:17
584 forum posts
72 photos

HI Jason,That is exactley what I have and after your advice I will proceed.Thanks.


Oily Rag17/05/2021 14:11:28
540 forum posts
184 photos


As good as JB Weld is I would recommend Devcon HP Titanium putty. This, I believe, has a far higher temperature rating, I think it is the highest of all the 2 part epoxy glues as well has the highest pressure rating. I have used it to successfully repair blow holes in cylinder heads on air cooled motorcycle engines.



JasonB17/05/2021 15:17:23
23088 forum posts
2774 photos
1 articles

You could actually do it without any filler/adhesive as it's not sealing anything just filling the space so the compression ratio does not drop.

JDWeld is said to be OK upto 287deg C. looks like the Devcon is only 177deg C

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