stainless water pump bolts

[Bowbender]

I'm thinking I'll replace the bolts I broke off while replacing my water pump with stainless bolts. They are 1/4" bolts, 20 tpi, so should be easy to source.
Two questions ; good idea or bad? How much torque should I apply when installing?

 

[CJ]

Stainless an iron have a pretty big problem with galvanic corrosion. Unless you are sure you can insulate the stainless bolts from the iron block I would use normal steel bolts with a good thread sealant.

Galvanic corrosion is erosion of one metal by another due to contact. -->> Galvanic corrosion - Wikipedia, the free encyclopedia

-->> Marine Fasteners

-->> Galvanic and Corrosion Compatibility Dissimilar Metal Corrosion - Engineers Edge

 

[IOPort51]

Stainless hardware is generally a bit softer than steel and likes to "gall" the threads. I agree with CJ on this, it would be hard to beat grade 5 hardware and a torque wrench for this job.

running a tap through the holes would not hurt anything.

 

[Bowbender]

Thank you, gentlemen, grade 5 bolts it will be. With anti sieze on the side.
My water pump bolts onto an alum housing (timing cover?) On the front of my Dauntless Buick 225 V6 v6. Could this same galvanic action be the reason the original bolts were rusted in so solid? I figured it might have something to do with not being turned in 45 years.
Thanks for the links CJ, I appreciate the education. IO, any recommendation on torque setting, I'd hate to strip the threads out on that alum.

 

[thiswontbetooexpensive]

Thank you, gentlemen, grade 5 bolts it will be. With anti sieze on the side.
My water pump bolts onto an alum housing (timing cover?) On the front of my Dauntless Buick 225 V6 v6. Could this same galvanic action be the reason the original bolts were rusted in so solid? I figured it might have something to do with not being turned in 45 years.
Thanks for the links CJ, I appreciate the education. IO, any recommendation on torque setting, I'd hate to strip the threads out on that alum.

That was the culprit. Chevy had a bad problem with this on v-6 engines as well. (My brother has had two of them and both rotted out)

Try your best to keep them all the same. The softer metal will always be the one to rot out, it's just chemistry!


This won't be too expensive Dear! That's what I keep saying. Over and over again.

 

[IOPort51]

I maybe would think about re drilling and a Helicoil??

 

[csuengr]

SS bolts are more than strong enough for a water pump. I have never torqued water pump bolts and have never had leaks. If you use SS bolts, just put some anti-seize on them. I have used SS hardware with anti-seize on exhaust systems that routinely reached 600+ *C and never had one gall or break.

 

[Petescj]

I maybe would think about re drilling and a Helicoil??

Thats what I did in that aluminum timing cover on my 360. It works.

 

[73CJ]

CJ you are correct about galvanic corrosion. It is a fact of life. The key here ish salt to kick off the reaction.

But even by the chart for cast iron and 303 -

"B - The corrosion of the base metal is marginally increased by the fastener"

I use AMC 304 SS all over my CJ. They all get spun at least every decade. And boy do we have salt up here. I just don't like rusty bolts. The key is immersion.

Helicoils are actually stronger than the original threads because there is more surface area for the Helicoil OD thread. Check it out. I had to prove that to a Gov Inspector once.

The helicoils I use are AMC 304 SS. I also have lots of helicoils on my aluminum tub with SS bolts. None in high stress areas though like tranny to bell housing or motor mounts. And yes the torque values are lower reducing clamp load. http://www.conoflow.com/pdf/products/Bolt.pdf

Galling generally occurs when you use an air wrench on a SS nut and a SS bolt, but can occur elsewhere too.

(I am a degreed Mechanical Engineer and a ASQ Certified Quality Engineer )

bowbender if you want SS on your water pump housing, go for it.

 

[Bowbender]

Thanks for all the replys, not sure which way I'll go now. I won't get parts'til Monday or later. Stay tuned...

 

[IOPort51]

I don't think you can make a wrong decision.

but you damn sure know a bunch of stuff you didn't before.

Thanks for all the replys, not sure which way I'll go now. I won't get parts'til Monday or later. Stay tuned...

 

[mstar]

Don't want to ad to this debate so take this as strictly informational.Check out ARP (automotive racing products) line of high strength stainless steel fasteners. I have used the engine kit that supplys all the bolts for my 427 ford sideoiler and also on a Dauntless Buick 225 V6 V-6.The main thing with stainless bolts and AN fittings for that matter is to lubricate the threads with oil,anti-seize,permatex,whatever is appropriate.And NEVER use a impact wrench! As a general rule I usually run a tap in the threaded holes after beadblasting a part and wash before assembly. Hili-coils are a life saver on these old aluminum parts.I had to put a few in my timing cover on the v-6 motor last month. mike

 

[Bowbender]

I've decided to go with grade 5 bolts and anti seize. I'll run a tap through all the threads to make sure they're clean and get bolts long enough to use all the threads available. I'll reserve the helicoil option in case things get ugly in the future.
I appreciate the feedback from all of you, the collective knowledge and experience is very helpful.