- Third Gear
- Posts: 405
- Joined: 04 Apr 2008
- Location: Dunmow, Essex, UK
nigelrbfurness wrote:Just as a follow up to the head gasket problem and for interest, when I was cleaning the block surface I found that farthest bolt hole, inlet side number 4 cylinder, had a slight raised edge to it just at one side. I recall that the bolt in that hole felt tight as I undid it, however trying head bolts in it now the thread seems fine so I'm wondering if this ridge was there all the time and caused the gasket to fail by preventing the head from seating properly. Clearly, removal of said ridge is necessary but I am perplexed as to what caused it in the first place and why it was not noticed when the block was new in 1994. If the bolt had been over-tight to the point where the thread became stretched then it would be tight again now when I put a bolt in. This is only the second time the head has been off since the engine was built. The block surface is straight, no signs of warping.
That sounds like someone has tightened or overtghtened a bolt that was too short and only engaging by a couple of threads and it has deformed the top couple of threads in the block, probably nadgered the bolt as well.
Its been close to 40 years since I removed a Lotus Twink head, are some bolts shorter then others, could the above have happened with the wrong bolt in the wrong hole? If so then check all the bolts for deformed threads at the end, you can simply dress down the block surface with a engineers whetstone.
I can also see why running a bolt through the hole a few times will have freed it up, might be worth running a plug tap down all of them as a precaution.
- Coveted Fifth Gear
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