Basic Metalurgy

[FelicityRebuild]

There are several bolts, nuts, etc. that will need replacing as I reasemble my engine. I know certain metals, when used together, cause oxidation, or fuse at higher temperatures. What type of bolt should I use: Zinc, Stainless, Other???

[hanleyclifford]

engine bolts

It is a mistake to upgrade nuts and bolts on your engine. The danger you alluded to is the galvanic cell. The engine is cast iron, primarily and the bolts and nuts are some grade of carbon steel. Remember, it is the basic castings that are most valuable and should not be endangered by the use of "noble" fasteners. You can probably find a galvanic series somewhere on the internet and note where cast iron lies in the order of things, as it were.

[thatch]

"In my humble opinion"

Matt,
I titled my responce IMHO for a good reason. The subject of fasteners can get as long as we will let it get. Having said this, I generally use grade 5 cad plated bolts for most external assembly accessories. This would include things like the oil pan, the bellhousing, the accessory drive and other similar parts that probably won't be removed for a long time. I install most of these bolts using anti-sieze so that when the time comes to take them out I will actually have a fair chance of doing that. For things like water pumps or the thermostat cover it is not a bad idea to spring for stainless along with anti-sieze to insure that the bolts or nuts will stay as fresh as possible. In the case of the accessory drive mounted water pump, using one of Don's SS extendo bolts in the lower hole will make pulling that part off a snap. I could go on and on but I won't. Bottom line, every time you install a nut or bolt just keep in mind that it will probably have to come back sometime.
Hope this helps, Tom

[hanleyclifford]

As long as we let it...

As you can see from the previous two posts, there is considerable range of opinion on this matter of fasteners. Note, however, that Thatch and I seem to concur on the use of some sort of steel for oil pan, housings, etc - things with the greatest liklihood of contact with some sort of water or bilge splashing. As you will see, the galvanic cell only occurs in the presence of an electrolyte (salt water, or any ionized water for that matter). You could bolt graphite to aluminum and as long as you kept it dry, there would be no problem(But remember the jet liner over Kennedy International Airport that lost its tailfeathers - aircraft fly in salt conditions too). It would seem, however, that in the case of the A4 some locations in the engine room would be less susceptible to "salt mist" - say, the lower water pump bolt. In fact a little oil leak in this area could do a lot to protect the metal. Having antifreeze cooling goes a long way toward mitigating this issue. If I were using salt water cooling, I positively would not put stainless fasteners near that thermostat housing. Finally, a word on the use of metallic based "never seize" type of products. Although it is satisfying to be able to disassemble an engine easily, may it not be at the price of deteriorated bolts and castings. Read the label. I'm sure that if this thread continues (someone is certain to jump on me) you will see that where 25 A4 owners get together, you will get at least 50 opinions. All the best to you and keep us posted!

[thatch]

"More thread on threads"

hanleyclifford,
Since I consider myself a nut and bolt "commoner" when it comes to the "noble" chart I'll defer to others who actually stayed awake in science class to cover that part of the discussion.
You and I both mentioned a particular bolt which gave me a chuckle and I'll explain why. Not long after acquiring my A4 equipped Catalina 30, I spent about 30 minutes lying on my side with hammer and drift in hand trying to coax a little rotation out of the now infamous lower water pump bolt. The bolt head over the years, because of leaky seals and improper tool techniques, had been reduced to a round nub. Finally, after a successful effort, I was able to remove the pump, rebuild it and re-install it using my own version of the extendo-bolt.
Cordially, Tom

[marthur]

Tom, what is your own version of the extended bolt?

[hanleyclifford]

nuts and bolts

hanleyclifford,
Since I consider myself a nut and bolt "commoner" when it comes to the "noble" chart I'll defer to others who actually stayed awake in science class to cover that part of the discussion.
You and I both mentioned a particular bolt which gave me a chuckle and I'll explain why. Not long after acquiring my A4 equipped Catalina 30, I spent about 30 minutes lying on my side with hammer and drift in hand trying to coax a little rotation out of the now infamous lower water pump bolt. The bolt head over the years, because of leaky seals and improper tool techniques, had been reduced to a round nub. Finally, after a successful effort, I was able to remove the pump, rebuild it and re-install it using my own version of the extendo-bolt.
Cordially, Tom

Tom, Actually the only thing I really remember from science class is one of the final exam questions - Identify the compound Ba Na 2. I only got involved in this "science" when I had to rebuild the foundation of my boat - fastened planks to frames with copper rivets, and frames to floors with iron bolts:eek. Since then I've become something of a "sophomore" OCD on the subject of galvanic cells. Confession - I have just purchased one of the MM ss extended lower water pump bolt which I will install with a six point socket. I want to be rid of this particular R&R aggravation once ond for all. (I will submerge the bolt in engine paint). BTW, I looked up your grade 5 capscrews, cadmium plated on the military galvanic series table. It seems that the cadmium offers some galvanic protection to the steel and iron! All the best, Hanley

[thatch]

Re: marthur question

Mike,
Thank's for asking. My version of the bottom water pump bolt is nothing more than a 3/8" coarse thread SS hex head bolt 4" long on to which I have firmly bottomed out a 3/8" SS nut. The nut now becomes what was the head of the bolt in the old system with the majority of the new bolt now allowed to extend slightly beyond the water pump cover. The threads left exposed are about 7/8" long which is just about perfect considering the thickness of the WP flange and the thickness of the accessory drive in that area. Just in case you're wondering, the two WP mounting holes are positioned to miss the idler and accessory drive gears, if someone were to install a bolt that was longer than needed.
Tom

[sastanley]

awesome

Tom,
Brilliantly simple!

[thatch]

I belong in jail!

Shawn,
Don should get all of the credit for the "long bolt concept. I should only get credit for stealing his idea.

[67c&ccorv]

Mike,
Thank's for asking. My version of the bottom water pump bolt is nothing more than a 3/8" coarse thread SS hex head bolt 4" long on to which I have firmly bottomed out a 3/8" SS nut. The nut now becomes what was the head of the bolt in the old system with the majority of the new bolt now allowed to extend slightly beyond the water pump cover. The threads left exposed are about 7/8" long which is just about perfect considering the thickness of the WP flange and the thickness of the accessory drive in that area. Just in case you're wondering, the two WP mounting holes are positioned to miss the idler and accessory drive gears, if someone were to install a bolt that was longer than needed.
Tom

Wrong - see my post and picture in General Maintenence, ("Don't be a Bodger") of a PO's "home-made" extended bolt that nearly contacted my acessory drive gears.

I would be very cautious with this one fellows and measure the length of the threaded portion of the housing before installing a "home-made" extended bolt.

Cheers!

[thatch]

sorry to have to disagree

67c&ccorv,
Before I gave my answer to marthur I went through the process of mocking up the components involved. These parts are the idler gear, the water pump and the accessory drive unit. After carefully checking for any possibility of bolt interference it was obvious to me that Universal was very careful to make sure that a longer bolt than necessary could not contact the gears. After your post, I recreated my mock up but this time I used all thread and ran it in until it bottomed out on the housing on the opposite side. I'm sure you know the answer by now, no interference at all. I did find your post on this subject and I think if you look at the photo a little closer and visualize the position of the accessory drive gear, you will see how the bolts will clear.
Tom

[67c&ccorv]

It is a mistake to upgrade nuts and bolts on your engine. The danger you alluded to is the galvanic cell. The engine is cast iron, primarily and the bolts and nuts are some grade of carbon steel. Remember, it is the basic castings that are most valuable and should not be endangered by the use of "noble" fasteners. You can probably find a galvanic series somewhere on the internet and note where cast iron lies in the order of things, as it were.

The engine block and castings are indeed cast - but they are not cast iron. Universal's own adverstising states the block is a "high nickel-chromium casting" in order to forestall corrosion in a marine environment.

I won't go so far as to say the block and associated castings are "stainless steel", but they are certainly not the kind of pot steel one would find in a automobile engine.

I would say if you want to improve your fasteners with S/S and are worried about galvanic corrosion then use blue loctite (which can be removed with hand tools) which will form a barrier between the threads or body of the fastener and surrounding engine components.

[hanleyclifford]

Claims by Universal of "high nickel-chromium" notwithstanding, the empirical evidence clearly shows that these engines are highly subject to corrosion in the marine environment, both galvanic and otherwise. The engine castings are indeed mostly ferrous - containing alloys of nickel and chromium, but not enough to move them up significantly on the galvanic series so that they might be electrochemically immune from attack by more noble metals!

[67c&ccorv]

67c&ccorv,
Before I gave my answer to marthur I went through the process of mocking up the components involved. These parts are the idler gear, the water pump and the accessory drive unit. After carefully checking for any possibility of bolt interference it was obvious to me that Universal was very careful to make sure that a longer bolt than necessary could not contact the gears. After your post, I recreated my mock up but this time I used all thread and ran it in until it bottomed out on the housing on the opposite side. I'm sure you know the answer by now, no interference at all. I did find your post on this subject and I think if you look at the photo a little closer and visualize the position of the accessory drive gear, you will see how the bolts will clear.
Tom

Thanks thatch - I never tried extending the bolt all the way. If, after your test you say it the bolt won't contact the idler/aux drive gears after running it through to the other side then I will believe it.

Just don't be bodgers!