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NPT plug in combustion chamber?

Posted: Sun Nov 05, 2017 11:37 pm
by KnightEngines
Got some 2V Cleveland heads on the porting station, had a bit of a whoopsie - found a casting void in the corner of a short turn.
Of course it's the last intake port, just about done with the porting on this head when I broke through finalising the turns.

It's in a bitch of a spot, no access to the water jacket side.

My plan to save a days work is to drill down through the chamber in the quench area (closed chamber 2V 'aussie' heads) to get access to the water jacket side, clean it up with some acid to remove rust & epoxy it up, then fill the hole in the chamber with a 1/4" NPT plug coated on the threads with epoxy then milled flat.

I got no problem with the epoxy on the short turn lasting, done it plenty of times on other types of heads where access was easier, paint over it with glyptal after the epoxy has cured & it's a permanent fix.
But I haven't run an NPT plug in a chamber before, I can't think of a reason why I can't do it - anything I'm not considering before I go drill a hole in a head?

Re: NPT plug in combustion chamber?

Posted: Mon Nov 06, 2017 1:00 am
by Scotty
No diffrent to using a tapered stitch repair plug,they were availiable in different sizes ...a plug being the smallest it's harder to get the larger sizes now b & c plugs from memory. If you were to use a npt plug most plumbing fittings are cast iron not steel if you're wanting cast iron. The only consideration would be enough thread engagement in the parent metal to seal the threads.

Re: NPT plug in combustion chamber?

Posted: Mon Nov 06, 2017 1:06 am
by joe 90
Wouldn't you want a cast iron plug?
Then it's got the same coefficient of expansion as the head ........otherwise it'll come loose and fall out.


edit, beat me to it.

Re: NPT plug in combustion chamber?

Posted: Mon Nov 06, 2017 1:44 am
by cjperformance
I have seen diesel chambers repaired with screw in steel plugs before but using wet graphite powder as a sealant/installation lube. Graphite mixed into a paste with water, applied the both threads and screwed in tight. Apparently no leaks or comebacks when done like that.

Re: NPT plug in combustion chamber?

Posted: Mon Nov 06, 2017 5:32 am
by Cubic_Cleveland
I have repaired cracks in diesel chambers before and used this stuff on the threads of the ‘A-plugs’
https://www.seallock.com.au/products/fluid-weld
I think you have a very reasonable chance of success if you have enough parent material for good thread engagement.

Re: NPT plug in combustion chamber?

Posted: Mon Nov 06, 2017 5:38 am
by cjperformance
Cubic_Cleveland wrote:
Mon Nov 06, 2017 5:32 am
I have repaired cracks in diesel chambers before and used this stuff on the threads of the ‘A-plugs’
https://www.seallock.com.au/products/fluid-weld
I think you have a very reasonable chance of success if you have enough parent material for good thread engagement.
Interesting looking gear. I'd never heard of it before. Cheers

Re: NPT plug in combustion chamber?

Posted: Mon Nov 06, 2017 5:52 am
by Cubic_Cleveland
cjperformance wrote:
Mon Nov 06, 2017 5:38 am
Cubic_Cleveland wrote:
Mon Nov 06, 2017 5:32 am
I have repaired cracks in diesel chambers before and used this stuff on the threads of the ‘A-plugs’
https://www.seallock.com.au/products/fluid-weld
I think you have a very reasonable chance of success if you have enough parent material for good thread engagement.
Interesting looking gear. I'd never heard of it before. Cheers
No worries. It seems to work pretty good, I’ve used it with success to glue an insert in with a porosity hole in the aluminium behind it on a Hail Mary too.

Re: NPT plug in combustion chamber?

Posted: Mon Nov 06, 2017 6:40 am
by mag2555
I would use a Ciramic Epoxy from Coltronics on that plug, or heat the head in a BBQ and melt up some old Pistons and once you have the plug threaded in some pour on the Aluminum and ram the plug the rest of the way home, or however far you feel safe threading the plug in.

I have done repairs by these two methods more then a few times without a failure!

Re: NPT plug in combustion chamber?

Posted: Mon Nov 06, 2017 5:05 pm
by KnightEngines
Sorted - worked out well, I'll store that fix in the 'how to get out of the sh|t' memory file.

Now I just gotta finish porting.

Re: NPT plug in combustion chamber?

Posted: Mon Nov 06, 2017 6:09 pm
by cjperformance
KnightEngines wrote:
Mon Nov 06, 2017 5:05 pm
Sorted - worked out well, I'll store that fix in the 'how to get out of the sh|t' memory file.

Now I just gotta finish porting.
Easy does it ! :lol:

Re: NPT plug in combustion chamber?

Posted: Thu Nov 09, 2017 4:46 pm
by stealth
KnightEngines wrote:
Mon Nov 06, 2017 5:05 pm
Sorted - worked out well, I'll store that fix in the 'how to get out of the sh|t' memory file.

Now I just gotta finish porting.
A few pictures would have been cool...

Re: NPT plug in combustion chamber?

Posted: Thu Nov 09, 2017 7:47 pm
by peejay
Just plug the hole with a Ford 3v spark plug... it'll never come out :lol:

Re: NPT plug in combustion chamber?

Posted: Thu Nov 09, 2017 7:53 pm
by cjperformance
peejay wrote:
Thu Nov 09, 2017 7:47 pm
Just plug the hole with a Ford 3v spark plug... it'll never come out :lol:
:lol: ah so true !!