Noob, just getting started on a 67 CL77

[e3steve]

So how do I measure the cylinder bore? What tool do I use?

Thanks,

Joel

Joel, get yourself a digital Vernier gauge; they're very cheap, nowadays, from most good tool stores or engineering suppliers (NOT Snap-On!). Also, a set of cheap dividers is good to have in the tool chest: straight (for simple measurements), convex (for External-Diameter tube measuring and concave (for Internal-Diameter measuring).

[e3steve]

Hi Steve,

I said the risk is over-torquing, in normal circumstances one uses a screwdriver for philips screws and an allen key for allen screws. The arm of the allen key is much longer, therefor the risk of over torquing much higher. I come across a lot of damage on old engine cases, and I noticed more damage on engines build with allen screws (steel or stainless).

Steve, can you please explain why the zinc of zinc plated bolts disappears in a few years, especially on the part what goes in the case (thread ) ?. If moister comes between a zinc plated bolt and a aluminum case the zinc will turn into a white dust, and is called zinc-oxide, and is a result of this oxidation reaction.

With a stainless bolt (allen or philips), you don't see the white dust but the thread will be weakened by oxidation, to the point where helicoils get necessary.

I agree, there are more products on the market with the same effect. But the copper grease is widely available and cheap, therefor I mentioned it.

Jensen

I take your point, Jensen, regarding the additional torque available from an Allen key; just needs commonsense to be applied when installing the screws.

The white dust is, as you say, aluminium oxide; it's being shed (sacrificed) from the aluminium (less noble) component to the more noble component (passive nickel plating, zinc plating or even stainless). With regular removal and lubrication with oil, silicone grease, copper grease or Tef-Gel there will be no cathodic transfer to speak of. Fresh water is worse than seawater in many cases as it contains more oxygen, therefore generates worse oxidisation.

[jensen]

Hi Steve,

Yes, taken off or out on a regular base and lubricate will make things less worse.

But with all respect, zinc is less noble then aluminum, also cast aluminum. The zinc acts as a anodic against the more cathodic aluminum, so the aluminum is saved. When using stainless steel, there is no protection for the aluminum to corrode (oxidize), so it will corrode.

You can read further here : http://en.wikipedia.org/wiki/Galvanic_corrosion
and here : http://en.wikipedia.org/wiki/Cathodic_p ... ized_steel

sometimes I wonder if people use oil or grease to assemble these old bikes. Most bolts I get out are bone dry and heavily corroded. I know Honda didn't do it,

Jensen

[Snakeoil]

There was a long discussion regarding stainless fasteners used on aluminum cases on another site. The key factor here is Oxygen. If you can keep the O2 out, then the chance of aluminum oxide forming and deteriorating the thread is slim. To that point the use of blue Loctite solve two problems, over torquing is not required and the O2 is sealed out.

regards,
Rob

[e3steve]

Hi Steve,

Yes, taken off or out on a regular base and lubricate will make things less worse.

But with all respect, zinc is less noble then aluminum, also cast aluminum. The zinc acts as a anodic against the more cathodic aluminum, so the aluminum is saved. When using stainless steel, there is no protection for the aluminum to corrode (oxidize), so it will corrode.

You can read further here : http://en.wikipedia.org/wiki/Galvanic_corrosion
and here : http://en.wikipedia.org/wiki/Cathodic_p ... ized_steel

sometimes I wonder if people use oil or grease to assemble these old bikes. Most bolts I get out are bone dry and heavily corroded. I know Honda didn't do it,

Jensen

You're quite right, J-man; zinc plating is less noble when associated with seawater, but I'm pretty certain, if my memory serves me correctly, that the Scale of Nobility is differently structured when referring to freshwater. I only deal with galvanic and cathodic issues on sea-borne vessels. However, I do know for a fact that sacrificial anodes are of the zinc persuasion in my particular field, but are magnesium for riverboats. I was referring to freshwater regarding our motors' casings fasteners.

Volvo, in particular, ceased using passivated-nickel fasteners in favour of the galvanised (zinced) type for their marinised engines because they couldn't be arsed to do the assembly properly by employing a corrosion inhibitor at the factory.

There was a long discussion regarding stainless fasteners used on aluminum cases on another site. The key factor here is Oxygen. If you can keep the O2 out, then the chance of aluminum oxide forming and deteriorating the thread is slim. To that point the use of blue Loctite solve two problems, over torquing is not required and the O2 is sealed out.

regards,
Rob

Bang on the money, Rob! Which is why I choose to use Tef-Gel or silicone grease on my casings' fasteners where there is a chance of dryness (i.e. no engine oil present). Copper grease is good but makes such a bloody mess.

15 years ago I wrote to the Volvo factory when, whilst working with Fairline & Sunseeker, we were inundated with removing all of the alternator bolts on KAD42 & KAD44 motors and applying Coppaslip. When the main hanger bolt seizes a tech has no alternative but to air-chisel the alt off and replace the front engine cover. Volvo's post-sales job creation scheme! They still use the fixings dry, and the alternator is still mounted beneath the 'flowerpot' seawater strainer! WOFTAM!

[jensen]

Hi Steve,

There you have a point, copaslip or copper grease make things messy, period.
I will look into the difference between seawater and fresh water in correlation to the Scale of Nobility.

Jensen

[e3steve]

J, zinc is definitely less noble than alu in seawater, which is why zinc anodes are used on sea-going vessels. I think zinc and alu are pretty close with the added oxygen of freshwater, which is why magnesium is used in such an environment.

Anyways, the up-shot is: exclude oxygen with a decent, non-melting inhibitor and you won't have a problem.