reliability of stainless bolts in engine

[timothymoore]

i didnt want to hijack the other users previous thread on stainless bolts. but my question is : are the stainless steel bolts safe to use in the delorean's engine block? because ive heard that they can bond or what not to the block causing the bolt to seize up and you could break a bolt. i used anti-seize when i installed my new water pump , then heard stainless bolts were bad for the D. am i good with the stainless bolts as long as i use anti seize? thanks

[Bitsyncmaster]

I use them a lot on my engine and have not had any problems.

[1batt4u]

People use anti-seize lubricant on the bolts. Should be no problem.

[DCUK Martin]

Stainless is seen as a gateway to never having corrosion issues. In aluminium, it can cause accellerated corrosion of the Al and also has another characteristic which is a royal pita to deal with - that of galling. I'll post a link for additional reading, but once you've fought a stainless steel bolt that has failed due to galling, you'll never want to use them again. To my mind, going stainless is replacing one potential issue (bolt corrosion) with two more that are potentially even worse. My 2p is to use decent quality Yellow zinc plated steel fasteners and if you want the finish to live on, give it a light coat of clear lacquer. Use anti-sieze either way.

http://www.estainlesssteel.com/gallingofstainless.html

[Bitsyncmaster]

http://www.estainlesssteel.com/gallingofstainless.html

This is more about using stainless bolt with stainless nuts. Also it's more of a problem in production assembly lines that use air tools to assemble. I have yet to have any problems with stainless in aluminum even with no anti-seize.

[jmettee]

This is more about using stainless bolt with stainless nuts. Also it's more of a problem in production assembly lines that use air tools to assemble. I have yet to have any problems with stainless in aluminum even with no anti-seize.

+1

I use SS & anti-seize wherever I can. However, most of the new bolts in my engine are Zinc-plated as 7mm SS is VERY hard to some by, but nuts are more common to find & I've used them.....also not much of a problem is a nut seizes.

Galling, as far as I've ever hears is ONLY a stainless-on-stainless issue....& that's not an issue on the DMC or PRV. When using SS-on-SS, anti-seize is recommended for this reason.

[DMCMW Dave]

Martin's point is that with stainless bolts into aluminum you move the corrosion problem to the aluminum side of the dis-similar metal contact. Much harder to replace a corroded hole in the engine than a rusty screw. Anti-sieze will slow it down but that applies to steel bolts as well.

The people reporting "no problem" have probably not tried to take something back apart after a few years of exposure to weather. If your car is a garage queen and seldom wet this problem isn't likely to show up for a long time.

[content22207]

Electrolysis (galvanic corrosion) can't happen without an electrolyte present (moisture). Stainless screws in aluminum that rarely see moisture may be OK. Stainless screws in aluminum that are constantly exposed to moisture (IE: cooling system and exhaust system) will readily weld themselves together, anti-seize notwithstanding.

Stainless galling is not a problem if you go slow. Also stay away from fine threads whenever possible (not much choice with metric fasteners, but something to remember when using fractional bolts in other applications).

Remember also that most stainless fasteners have only slightly more tensile strength than Grade 2 fasteners. 18-8 stainless (most common) is 70,000 PSI. Grade 2 (hardware store bolts) is 60,000 PSI. Metric 8.8 is 116,000 PSI and Grade 5 is 120,000 PSI. Do not use stainless fasteners in strength dependent applications.

Bill Robertson
#5939

[DCUK Martin]

Martin's point is that with stainless bolts into aluminum you move the corrosion problem to the aluminum side of the dis-similar metal contact.

Yes - but my general point is that if you're going to stainless because you want fastners to not get stuck over time, stainless is actually more likely to get stuck than plated steel.

The only valid reason to go stainless on the engine is so it stays shiny forever, IMO.

I've had trouble in the past with stainless studs on a factory exhaust system (Nissan). if they'd just used steel, it'd have snapped off and I could attack what remained with a stud extractor. As it was, I had a nut that would have turned till the cows came home but never unscrewed and I had to figure a way of removing the stud with the exhaust still present. I've also had issues using M10 stainless bolts with steel nuts on the DeLorean cat bypass. As Bill says, it's an application where a higher level of torque is required and upon attempted removal, the nut just shears the threads at that point, though tensile strength and galling resistance is largely unrelated.

[Bitsyncmaster]

Yes - but my general point is that if you're going to stainless because you want fastners to not get stuck over time, stainless is actually more likely to get stuck than plated steel.

The only valid reason to go stainless on the engine is so it stays shiny forever, IMO.

I've had trouble in the past with stainless studs on a factory exhaust system (Nissan). if they'd just used steel, it'd have snapped off and I could attack what remained with a stud extractor. As it was, I had a nut that would have turned till the cows came home but never unscrewed and I had to figure a way of removing the stud with the exhaust still present. I've also had issues using M10 stainless bolts with steel nuts on the DeLorean cat bypass. As Bill says, it's an application where a higher level of torque is required and upon attempted removal, the nut just shears the threads at that point, though tensile strength and galling resistance is largely unrelated.

Yes shiny forever is a major reason. For exhaust I would use stainless studs and brass nuts. Steel plated bolts usually strip the plating off the threads when installed so you start getting corrosion the first time it gets wet. Take an AN cadmium plated bolt and torque it into your application. Remove it and you can see where the yellow plating is gone.

[content22207]

Stainless doesn't stay shiny unless you polish it -- every DeLorean owner should know that. It will accumulate a white powdery coating as it reacts with the aluminum (in the presence of moisture).

Bill Robertson
#5939

[DCUK Martin]

Steel plated bolts usually strip the plating off the threads when installed so you start getting corrosion the first time it gets wet.


In the case of Zn, it is meant to be a sacrificial anode. It's not meant as a coating but a finish. The original Cd plating is ideal for steel-in-aluminium.


Stainless ... will accumulate a white powdery coating as it reacts with the aluminum (in the presence of moisture).


No it won't, unless it is aluminium oxide from the neighboring metalwork which -is- a white powder.

[1batt4u]

I'm in the process of working on my engine. I am slowly takng off parts. I started to take off the bolts on the passenger side valve cover. One at a time, putting each one back. Did that to see if they come out with out any problems and not get stuck, which all was good, they came out with out any problems!!!
I also started measuring each bolt for accurate measurements.

I want to buy Polished Stainless Steel bolts. 2 questions:

1. Is it necessary to have the bolts as they are, not threaded at the top, and the bottoms threaded. Or is it ok to buy full threaded S/S bolts?

2. Using anti-seize on the bolts. People recommend using anti-seize on the S/S bolts. I noticed some bolts or I think it was just one bolt, when I took it out it had oil on it, as it is exposed inside and oil gets to it. I guess no anti-seize goes there.
How many bolts are exposed to oil??

I tried polished-stainless.com they don't carry a few that I need. Anyone know any good places. Looking the Polished stainless steel, not natural finish.