Good advice needed - head damage at spark plug

Good advice needed - head damage at spark plug

Author
Discussion

Olf

Original Poster:

11,945 posts

155 months

Friday 27th May 2011
quotequote all
Hello,

I'm trying to get an old engine going but have found there is some damage to the head on the flat mating face around the spark plug port. See picture. It's not really worth spending money on so any bright ideas for dealing with this? When you turn the engine over compressed air and fuel vapour escape from the damaged area.


paolow

3,051 posts

195 months

Friday 27th May 2011
quotequote all
ooof - if there are gases escaping when you turn the engine over then you are in for problems when it's acutally running! Really odd damage - how does that happen? Also, if a plug were tight in the hole and the rest of the threads etc were in good order I would have thought that you might have at leat a REASONABLE seal at cranking pressure; suggests you have worse problems than are visible...
What engine is it? Do you actually have the head off?

Olf

Original Poster:

11,945 posts

155 months

Friday 27th May 2011
quotequote all
paolow said:
ooof - if there are gases escaping when you turn the engine over then you are in for problems when it's acutally running! Really odd damage - how does that happen? Also, if a plug were tight in the hole and the rest of the threads etc were in good order I would have thought that you might have at leat a REASONABLE seal at cranking pressure; suggests you have worse problems than are visible...
What engine is it? Do you actually have the head off?
Lord alone knows how the damage happened.

I thought you'd get half a seal two but was hoping it was a sigh of good compression wink No I haven't got the head off yet... Didn't like the idea of jumping in with a thread sealant - do they make them for that temp?

It's a 1950's Ferguson engine.

Classic Grad 98

15,552 posts

97 months

Friday 27th May 2011
quotequote all
Perhaps you can turn a copper washer on a Lathe which fits the external diameter of the spark plug thread and has a larger external diameter than the standard crush washer which comes with the spark plug. Clean up the plug recess with some 1500 grit wet & dry.
So long as the thread allows sufficient torque to be applied, this may just work- and will be practically free and won't require further disassembly. Pretty much any other solution will require head removal.

garagewidow

718 posts

107 months

Friday 27th May 2011
quotequote all
apply some chemical metal around the threads before reinstalling the plug,allow to harden and it should seal ok.it will resist the high temperatures no problem.

but you may not get the plug back out though.if you do it will scrap the thread for sure.could always helicoil it too.
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seagrey

385 posts

102 months

Saturday 28th May 2011
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There are spark plug seat repair tools available,
I have a Sykes Pickavant kit but they are no longer available.
Try Timesert,they sell them also.

wildoliver

8,027 posts

153 months

Saturday 28th May 2011
quotequote all
Is the thread ok?

Have you considered a tap seat cutter (as in house water tap), should clean that up ok, you will need to bung the hole up with something you can get back out again though.

Steve_D

11,997 posts

195 months

Saturday 28th May 2011
quotequote all
Here is a link to the Timsert seat repair instructions.
http://www.timesert.com/images/sparkplug/SeatRecon...

Steve

Olf

Original Poster:

11,945 posts

155 months

Saturday 28th May 2011
quotequote all
Thank very much all - some great help here, especially seagrey and Steve. Think I'll try the Timsert. I'll let you know how I get on.

Pumaracing

2,089 posts

144 months

Monday 30th May 2011
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If the thread is fine then it justs needs the washer seating to be recut. The tools to shape this are part of thread inserting systems so if you can find someone who has one of those. Even a well equipped general engineering firm could cut a 45 degree seat and a flat for you. I can't believe an old engine like this will mind the spark plug being sat a bit lower in the combustion chamber.

jm autoservices

15 posts

128 months

Monday 30th May 2011
quotequote all
Timesert will solve your problems, they are the only thread repair I have found to be 100% reliable far better than the cheaper helicoils in my opinion. A copper washer would seal but If it was a job I was putting my name to I'd timesert it at least it means easy replacement of plugs in future.