Stainless steel bolts on cast iron motor B-RB?

[cj's mopar]

Question is there any reason to NOT use stainless steel bolts on cast iron specifically waterpump and housing on Big Block Chrysler?
Would this cause more or less corrosion?

 

[padam]

Typical stainless steel bolts are very soft, so not up to the task

 

[diesel_lv]

Water pump and housing would be just fine, just make sure to use anti-seize on the threads. The only load on those bolts is from the side load of turning the pump and fan.

 

[padam]

Well, there is the load from being torqued to the proper spec, so that needs to be taken into account.
I don't remember having a rust problem unless it was a junk yard motor.

 

[gkent]

I don't remember having a rust problem unless it was a junk yard motor

The issue isn't rust, its galling - which stainless likes to do. If you Google it you can probably find torque limits for stainless bolts. Keep in mind that stainless bolts are used exclusively in the food industry in all sorts of machinery. You wouldn't want to use them on your connecting rods or crank but they can be used just about anywhere else. One downside to stainless ... loctite doesn't work very well on them .

 

[chignikred]

RE ss bolts. Agree with comments. One other factor is that the correct lenght of stock bolts are often not available in ss, without special sourcing. So why bother for a bolt that has no water contact!

 

[Red63440]

Dis-similar metals can always cause a problem and as stated above SS bolts are not the strongest. You would do better using cadmium plated and using anti-seize.

 

[cj's mopar]

Thanks for the info !! I will take them off .

 

[Fran Blacker]

Don't use on exhaust manifold.

 

[old guys rule]

Thanks for the info !! I will take them off .

 

[Dajkzo]

As pointed out, stainless is prone to "galling" so anti-seize should be used. Here is my boat's engine. Everything is ARP stainless except for the main studs, damper bolt and flywheel bolts which are ARP chromoly.

Don't use the crap from retail stores.

I live near this outfit :https://www.fastener-warehouse.com/ The have everything and supply the Portsmouth Naval Shipyard (sub base)

 

[padam]

If they are ARP, I'm sure they are matched to the application.

 

[gkent]

I would not hesitate to use stainless bolts for: intake manifold, carb, Water pump, most accessories, valve covers, oil pan..

Where I would not use them: fan, crank pulleys, any internal fasteners, flywheel, clutch, heads, oil pump.

You don't buy ANY of these at Home Hardware and the like!

Not being hard is a myth. Stainless bolts will have a Rockwell core hardness hardness in the C32 range. By comparison a standard grade 5 is in the C34 range and grade 8 in the C33-39 range. The real difference is in the yield strength with stainless being about half that of a grade 8.

Where stainless is widely used, the sizes of the fasteners would be enlarged to compensate for the difference in strength.

 

[DeltaV]

Here's a nice article on bolt materials

https://www.boat-renovation.com/high-tensile-steel-vs-stainless-steel-bolts/#304_Stainless_Steel

 

[dvw]

My race motor and both my street cars have stainless water pump, intake, valve cove, timing chain, and header bolts. The race car is the newest build, 10years old. The street cars are 17 and 30 years. They have not corroded, broke or galled. Both street cars have iron heads.
Doug

 

[padam]

Here's a nice article on bolt materials

https://www.boat-renovation.com/high-tensile-steel-vs-stainless-steel-bolts/#304_Stainless_Steel

This is a good comment sense article. It's a little simple on the subject of tensile strength of different materials, but gets the point across.

 

[Nate S]

I’ve spent 30+ years designing machinery, sensors and lasers. There are often places where SS fasteners would be helpful due to their corrosion resistance. It’s been a collosal PITA to actually implement them because for the most part, beyond corrosion, they suck.

When it’s all boiled down, they work pretty well in low stress environments, essentially just sticking stuff together. When actual preload, cyclical stress, resistance to galling and stripping are important they are a poor choice. I would never select them for use on an engine or much of anything else critical on a vehicle.

As always, there will be people who tell us about how they did this. These are individual samples under unknown conditions. They probably work ok in the individual instances. They will not work the same over the same timespans, conditions, torques (both correct and wrong) as good factory spec hardware. They won’t rust though.

 

[Wietse]

Stainless steel thermal expansion properties are also not beneficial as SS expands more than Carbon steel types.
Therefore an SS bolt that is exposed to varying temperatures tends to have less clamping force when temperature increases, even until loose.
The extreme example, as mentioned above already, using them for exhaust manifold/headers is not recommended.
In tensile strength a stainless steel bolt is equal to a same size grade 5 UNC bolt and it doesn't rust, that's about the only benefits.

 

[padam]

I have attached sections from a torque chart from Fastenal for common screws, and highlighted a couple.
These are common variety stainless, of course better grades are available (aircraft, marine, ARP), but cost is high.

The full chart is linked to below, it's a pretty nice chart.
https://www.fastenal.com/content/me...nt-library/Torque-Tension Reference Guide.pdf