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+--- Thread: M7 Bolts for engine (/showthread.php?tid=1878)
M7 Bolts for engine - richard - 16 Sep 2008
Hi Guys,
Just in the process of playing engines. Need to get hold of the M7 surrounding the engine in the De.
I would like to go for stainless ones, but have had mixed comments regarding self-welding and corrosion. Would anti-seize work if used with Stainless bolts?
Look forward to hearing from the wealth of information out there.
Cheers guys
Richard
Re: M7 Bolts for engine - Daniel Shane - 17 Sep 2008
Hi Richard,
To be honest your going to get some degree of self-welding as the engine is Ali and the bolts are steel so the two dissimilar metals will react.
However stainless might react abit quicker. I've always used copper slip on all the bolts I have every used on any engine, not just the PRV and I've never had a problem so far
Dan
Re: M7 Bolts for engine - Darren C - 17 Sep 2008
Hi Richard,
Stainless only "self or cold welds" to stainless. All other seizures are "galvanic". If you remember your galvanic table in chemistry at school, you'll realise that the further apart chemicals are on the table the more aggressive they will react. They'll need a catalyst to corrode, but this can be simply air or moisture in the air. The effect is increased with temperature change.
So in real english the exhaust studs will be fine, but the engine block they're threaded into will corrode. This will long term either seize the stud, strip the thread or turn the threaded hole into white powder (aluminium oxide). However this is not at all any reason not to change to stainless as the original studs are steel too. The best advice I can give is to use a good anti seize lubricant or a loctite product on all your stainless threads. This should eliminate air/moisure ingress and prolong the life of the fixing. Even if you don't use stainless it's advisable on just plain steel too
Be aware though that Stainless steel has a lower shear point than mild/carbon steel and shouldn't really be used for suspension bolts where a high tensile steel is needed.
Anywhere else is fine
Cosmetically though it'll look the dogs dangly bits
Trouble is one yer start you wont stop...I've just about changed all my cars fixings to stainless, and even made specially sized stainless washers (to match the originals) on my lathe. :roll:
Good Luck
D
Re: M7 Bolts for engine - Rich Hanlon - 23 Sep 2008
Yep, as Darren says, the strenght of stainless versus standad stuff would be the major problem I'd say...