Is it easy to crack a housing by doing the spark plugs up too tight? How would you know if you cracked it, apart from if you could actually see the crack? Would there be an noticeable difference in the engine's performance?

heb.

 

itll useually strip first

but a crak there on the aluminum would leak coolant

 

You would get some blowby too I would imagine.

 

Is it neccessary to do up the plugs tighter then on a normal engine? I did them up fairly tight and a bloke I know reckons they could be done up a bit tighter?

 

Just snug, not really tight.

 

Plugs in a rotary engine are no different than any other engine type. Specifically, you should only be torqueing these to between 15-20 ft/lbs - and that is a very light pressure.

Basically, you only need to compress the pressure ring between the spark plug body and the mounting hole so that there is no gas leakage here. The compression ring is the part that is like a washer with a slot in the middle all the way around. As you tighten it down, the slot compresses, sealing against gas blowby.

You should also ALWAYS use an anti-seize compound on the threads to ensure that they do not gall (molecular reaction between steel plug threads and aluminum housing) which will lead to an engine housing that gets damaged on plug installation, or removal. Usually, what will happen is that you'll NOT add the anti-seize, the plug will seem to go in fine, and then get 'stiff' halfway through the tightening process - this is because miniscule slivers of metal are in the threads and the more you tighten it, the more metal gets stripped off until you no longer have threads in the housing.

There is no simple fix once you get to this point.

My simple method of ensuring that I have enough, but not too much, is to take your forefinger and thumb and apply pressure to the ratchet wrench with these 2 fingers, ONLY. If you only use your 2 fingers to tighten it (and are using anti-sieze compound), you'll never have to worry about overtightening plugs.

Going great guns on the plugs is going to seriously screw up your engine housings. Tell your friend to mind his own business...

 

cool, thanks for the feedback. Very much apreciated. Nice car btw longduck!

 

The only thing you could do for stripped spark plug threads would be to helicoil it, but then you run the risk of spilling metal flakes inside the housing. and that would be shitty

 

there were some really nice threads on salvaging a stripped spark plug hole a while back. very ingeneous and successful solutions with the motor still in the car.

Do a search!

 

I havnt stripped it, or cracked it. I searched for symptons or signs of a cracked housing and found nothing except this post. Didnt search for fixing a stripped spark plug hole because I dont need to!