Plug port repair

[Andrew Evans]

I have recently aquired a silver century. The spark plug is an NGK Ab6 which I think is 18mm. However the spark plug port could do with repair. I was thinking of in situ. Any advice and where i can buy a reasonably priced repair kit? Andy

[Charles uk]

Andrew

Are you talking about a cylinder head with damaged spark plug threads?

Your right, the thread size is 18mm.

If it's damaged threads your talking about, & the thread will not retaing the sparkplug properly, a 18mm sparkplug helicoil will have to be fitted.

In the UK this could cost you £15 to £25 & they still might want the cylinder head removed, it might be cheaper depending on where your located, to buy a replacement head from John Williams on this site & replace the faulty one.

[Andrew Evans]

Andrew

Are you talking about a cylinder head with damaged spark plug threads?

Your right, the thread size is 18mm.

If it's damaged threads your talking about, & the thread will not retaing the sparkplug properly, a 18mm sparkplug helicoil will have to be fitted.

In the UK this could cost you £15 to £25 & they still might want the cylinder head removed, it might be cheaper depending on where your located, to buy a replacement head from John Williams on this site & replace the faulty one.

Thank you for your reply, both a local garage and a local engineering co have said that they can repair in situ. I am obviously trying to steer clear of a head removal as there will probably be gaskets, broken bolts, drills and taps involved. There are plenty of repair kits for 14mm and cheap as well. I also thought that there might be someone with a kit and then all that is required is the insert as it must be a common problem. It is well catered for in the automotive field and some repairs have solid inserts not heli-coils.

[Charles uk]

My local tool supplier don,t list 18mm sparkplug kits, but the 14 mm kit is £83.00.

Your might be best off, going to one of the locals who will install one for you, it will be the cheapest way to do it, when 18mm inserts are not a standard stock item.

As long as they clean all the swarf out of the cylinder you will be OK, if any gets in the ring groove it might get stuck & force a piston out job.

[Andrew Evans]

Hi again, On ebay -spark plug repair you will see some kits and they are a lot cheaper than that. One of them is some form of cement (permatex i think). I find it odd that an engine of this background should have a metric measurement spark plug. Yes I know where you are coming from regards the swarf but i read a forum about some guy at a garage he said they shoved a rag down and when they pulled it out the swarf came with it however using plenty of tapping lubricant (like grease we used to use rocol the swarf sticks to the tap). The engine is useable but I lke peace of mind. I do trust the garage and the engineering co, they both do marine work and the garage owner has 3 seagull engines they both said that they had done this repair in situ before. The garage owner looked for the tap but could't find it. I think i shall ask permatex some questions.

[Charles uk]

Spark plug threads have been metric since before the 1st war.
Avoid the cement I don't know anyone that's used it, so can't comment on how good it is.
There is not much compression in a Seagull, so if the plug tightens up to 20lbs torque, it ain't broke so don't fix it.

Good luck

[Andrew Evans]

Thanks

[charlesp]

I've watched this thread for a couple of days. I have to say that the obvious answer - replace the head - is the cheapest, most likely to work, and the one that gives you the opportunity to clean the waterways.

One on the Bay as I type.

[Andrew Evans]

I have obtained a WSPCL head 1973, from the local free ads, am I right in interpreting John's writeup in concluding that it will fit OK?

[pistnbroke]

To stop the swarf apply compressed air continuously through the carb inlet and ass you drill the hole out it blows out the swarf ...same when you tap ..use greased tap and drill as well.....

[Charles uk]

I've never looked, is there a inlet/transfer port overlap on Seagulls, I've allways assumed no reeds no overlap, Wrong again.