Spark Plugs
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Discussion

190E Matt

Original Poster:

6,634 posts

235 months

Wednesday 26th November 2008
quotequote all
How easy is it for an inexperienced mechanic like myself to screw up when changing the spark plugs (e.g. cross threading them)

I want to do them (i will never learn if I don't) but I am really scared of fking up. Should I go for it?

Edited by 190E Matt on Wednesday 26th November 21:15

Boosted LS1

21,200 posts

281 months

Wednesday 26th November 2008
quotequote all
It's easy. Unscrew them carefully. Clean the threads on the plug befoore refitting and put a small amount of copper grease on the threads if you have some. When they go back into the engine you shoudn't need to use any force. They should go in a certain amount just using your fingers. If any of them go tight early then remove them and don't force anything. When they are in properly just nip them up hand tight and no more.

190E Matt

Original Poster:

6,634 posts

235 months

Wednesday 26th November 2008
quotequote all
Thanks Boosted, I think I will give it a go, being really really careful and gentle with my fingers smile

phumy

5,811 posts

258 months

Thursday 27th November 2008
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Boosted LS1 said:
It's easy. Unscrew them carefully. Clean the threads on the plug befoore refitting and put a small amount of copper grease on the threads if you have some. When they go back into the engine you shoudn't need to use any force. They should go in a certain amount just using your fingers. If any of them go tight early then remove them and don't force anything. When they are in properly just nip them up hand tight and no more.
I would normally screw the plug in hand tight until its at its seat, then get the plug spanner on it and turn a further 1/4 turn to "crush" the washer. To say only nip them up hand tight is a little misleading, i feel.

Boosted LS1

21,200 posts

281 months

Thursday 27th November 2008
quotequote all
^ Yes, he should use a spanner for the last bit. Doh.

eliot

11,986 posts

275 months

Thursday 27th November 2008
quotequote all
Probably got more chance of chewing the thread when removing them, due to carbon on the last few threads.
So when removing them, if it gets tight - go back in a little to clear the threads and reverse out again.

Steve_D

13,800 posts

279 months

Thursday 27th November 2008
quotequote all
When using the plug spanner/socket to either remove or refit make sure you keep it in line with the plug. As a lad, in a garage, I broke a number of plug ceramics in this way much to the disgust of the boss.

Steve

annodomini2

6,959 posts

272 months

Thursday 27th November 2008
quotequote all
phumy said:
Boosted LS1 said:
It's easy. Unscrew them carefully. Clean the threads on the plug befoore refitting and put a small amount of copper grease on the threads if you have some. When they go back into the engine you shoudn't need to use any force. They should go in a certain amount just using your fingers. If any of them go tight early then remove them and don't force anything. When they are in properly just nip them up hand tight and no more.
I would normally screw the plug in hand tight until its at its seat, then get the plug spanner on it and turn a further 1/4 turn to "crush" the washer. To say only nip them up hand tight is a little misleading, i feel.
Assuming its not a Twincam engine with the plugs deep in the head.

GreenV8S

30,996 posts

305 months

Thursday 27th November 2008
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The best way to get them started is to turn them *backwards* while holding them lightly in position. When you feel it drop off the end of the thread you turn it forwards and it should engage immediately.

It should screw in by hand all the way until the crush washer contacts the head, but it's very sensitive to side loads so it may need care to get it going all the way down. Plugs usually say how far you should turn them after they have been pinched up against the crush washer, 3/4 of a turn seems to be usual for new plugs, if you every reuse a plug then just give it a quarter of a turn. This last bit is the only part you should need a spanner for - and the same when you come to remove them. I do find it helps when turning them by hand to put the plug socket on to make it easier to grip.

jackal

11,250 posts

303 months

Thursday 27th November 2008
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a lot spark plug recesses seem to have a load of grit and sand and muck that seems to collect aroudn the perimeter of the base of the spark plug where its screwed in

when you pull them out, make sure none of that crud falls in


phumy

5,811 posts

258 months

Friday 28th November 2008
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jackal said:
a lot spark plug recesses seem to have a load of grit and sand and muck that seems to collect aroudn the perimeter of the base of the spark plug where its screwed in

when you pull them out, make sure none of that crud falls in
Best thing to do in this case is to clean, blow, brush the cr@p and dust out of the recess before you remove the plug, that way nothing will fall into the cylinder when the plug is removed.

freerange7

205 posts

209 months

Monday 8th December 2008
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Handy tip, do not wire brush plugs to clean and re use them,this will damage a lot of modern style plugs killing them quickly and the CAT if fitted, they are designed to last a long time and they may have metal coated tips.
They are cheap to buy so just replace them.

Good advice above on fitting the plugs, stories of cross threading and stripping of threads are mainly from heavy handedness.