Author Topic: Cylinder head damage  (Read 394 times)

Online Minto

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Cylinder head damage
« on: 13.05. 2021 01:09 »
Just realised that some damage to my iron cylinder head is possibly worse than I first thought. The damage seems to be  fairly common as I've seen a few on eBay damaged in the same place, the timing side inlet rocker cover screw thread part has cracked. It's been welded by a previous owner though not very well. My concern is that it may have internal damage extending into the inlet port and thus effecting induction. I poured some brake cleaner into the hole which leaked straight out onto the fins, the corresponding hole on the drive side held the brake cleaner.
I've wedged and modged some chemical metal into the voids in the crack and the weld and it now seems to hold tight, but am I hoping against odds that this is the extent of the damage?
Opinions or advice as always, very much appreciated.
Jase
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Online Greybeard

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Re: Cylinder head damage
« Reply #1 on: 13.05. 2021 09:38 »
'Modged' not heard that one before.

Online Minto

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Re: Cylinder head damage
« Reply #2 on: 13.05. 2021 11:15 »
Hey GB
The Oxford dictionary definition:
Verb; to modge.  To stuff down into a hole with a knackered old drill bit until it squidges out the sides.
Apparently an amalgam of the two old English verbs mush and bodge.
Jase
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Re: Cylinder head damage
« Reply #3 on: 13.05. 2021 15:03 »
Thank you for the clarification Minto.

What about the word 'wonged', pronounced 'wonjd'. That is, to squeeze the tea bag with a spoon to extract the most strength from it; "Give my teabag a good wonging please".

Online Minto

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Re: Cylinder head damage
« Reply #4 on: 13.05. 2021 15:47 »
Thanks for that morcel of enlightenment Neil.
There should be separate thread for obscure terminologies and colloquialisms.
Jase
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Online berger

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Re: Cylinder head damage
« Reply #5 on: 13.05. 2021 19:48 »
two wongs don't make a right. can you imagine being in the pub and asking a mate if he wonjs his bag *lol*

Online Minto

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Re: Cylinder head damage
« Reply #6 on: 13.05. 2021 21:17 »
Struggling to imagine being in the pub at all. He'd better be a good mate..
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Offline Swarfcut

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Re: Cylinder head damage
« Reply #7 on: 23.06. 2021 20:11 »
 I got to considering why so many heads suffer from these awkward to repair cracks to the threads securing the 4 central rocker box bolts.

  I thought these bolts were all BSF, like the cylinder head bolts. But no, early ones are Cycle, later ones are indeed BSF and so forcing the wrong bolt down the hole is a possible reason for the damage and cracks. You can bet the head you have is the one on the change or someone used the wrong bolts.
 
  So there you are, check the thread type on any unknown head and basket case bolts before reaching for the breaker bar. They should be a nice free running fit into the head.....and nip up easily. As usual with a blind hole, clean out the crap and check the bolt does not bottom out.

 Today there are new repro's  of the different types on ebay so if you're in the market for new ones check that thread type. The head you have may not be contemporary with the original model year so choose the thread that fits, not what the book says. I'd also add that if you do buy new its worth making sure they sent the right ones if you find "That thread's a bit tight"

 Swarfy.

Online JulianS

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Re: Cylinder head damage
« Reply #8 on: 23.06. 2021 22:45 »
All the swinging arm heads I have had  , iron and alloy had 5/16 x 26 tpi rocker box bolts.