Wanted Century head

[THCL500J8]

Need a head for an LLS, Head has had plug thread repaired with a threaded insert, and plug no longer protrudes into the combustion chamber.

Please Pm me if you can help. Thanks.

[Stelios_Rjk]

If you find a spark plug that can fit in the new threads you will solve the problem. You just need a plug with no resistance, same temperature like the normal (D16 or AB6) and the same length of the threaded part. On NGK I know that 6 is the temperature indication.

So you either check on the web to do the matching or you find a seller with knowledge or a book (not that easy as you could think on the second occasion).

You go this was by the time the repair made, resulted in a smaller spark plug thread size.

I have used an equivalence on a forty which came with M14 thread size I think.

[Hugz]

Here is a photo of a head that came of a century villiers block with original thread. The plug is a Champion D16. The anode is flush with the top of the firing chamber.

I have a slightly different spare head that also fits a villiers block but does have a helicoil repair on the thread. The plug is in the same position.

The helicoil head is yours if you wish it. Surface not great.... some gasket goo would be needed.

I'm assuming all century blocks with villiers carb are the same? (apart from the ports)

[headdownarseup]

unless it has the "high compression" head which is different again!

hang on and i will try and get some pics!
bear with

jon

[headdownarseup]

here we go then, found it!

[Charles uk]

Keep going Jon there are at least 3 more versions of the of the LLS/CPC heads.

[headdownarseup]

i have got another cylinder head kicking about somewhere that is also "high compression" but has a bit more "protrusion" (smaller combustion chamber) with squarer edges to it, but its dropped down the back of my bench and i cant quite reach it otherwise i'd have a pic of that as well.

perhaps CHARLES could help with any others!

jon

[THCL500J8]

Sorry all for not getting back to you all, we lost mums brother this week so its been a little hectic.

The idea of a longer plug is a good one and would be it, But i cannot find an 18mm plug with a 7/8ths to 1 inch reach as the whole is 18mm. if it were 14mm half the car plugs in the world would fit. And all would be good.

What type of head is it? its a standard head dish shaped not hemispheric, even had a good head gasket.
If the "High compression" head is the way go, sign me up.

[Charles uk]

Your head was designed to run an 18mm 1/2" reach plug, as were the vast majority of Seagulls, if it's not broke it doesn't need fixing.
Moving the spark plug electrode closer to the piston crown often will produce a hot spot that can burn through the piston, & increasing the compression on an engine with 40+ year old bearings, might also hasten it's demise.

Jon fit your 3 heads to an LLS & measure the compression, how much difference did that make? very little is the answer.

The shape changes in these heads were Seagull trying to increase the incoming charge's ability to remove more of the spent exhaust gas.

I'm not sure which of these heads came first, but the dished one was the last version.

Only the 170/125 had an hemispheric type cylinder head & domed piston, as they were the only looped charged powerheads.

[THCL500J8]

I think we could be a crossed purposes, I dont want to change the plug position i just want it were it should be but my head has been Fix if thats the word.
Pictures should explain, this head is for the junk bin.

As you can see the sleeve that has replaced the damaged thread is as long as the reach of the plug, so the plug wont protrude into the cylinder.
What a great repair this was.

So time for a head, hope that clears it all up. Sorry for the confusion.

Also sorry for the multiple pictures but i can't seam to upload more than one at a time.

[Charles uk]

The plug doesn't protrude into the cylinder on any Seagulls.

[headdownarseup]

i've just looked through all the previous pics.
i would use the head you've got there. as long as the plug can be tightened enough so there are no leaks, then it should be good to go as is.
some helicoil repairs do look a bit ugly but that's how they are!
i've just tried to upload some new pics but my camera has gone on the "blink"
what i can tell you is that both the standard and high compression heads (with spark plugs inserted) there is no protrusion into the combustion chamber by the plug. if anything, they are slightly recessed!

jon

[Adrian Dale]

I understand your frustration with this, I can see from the photos that you need a new head not a half arsed repair job.. seems straight forward. If I had one I would have it in the post to you by now, but I don't; surly some one has the correct spec head laying around? Cant any one help this guy get his gull closer to original... he just wants a head


AJ Tasmania

[Seagullrestorer]

A

[bikerboyfife]

Hi that head you have undo it from the block take it outside spin it around yer heed 3 time,s let it go and wait for one arriving in post asap sorted