Help selection a stainless steel grade for a carburetor application

[viper]

I am working on a part for myself that will replace some brass internals in a carburetor. Methanol can react with brass and cause some problems so I want make some replacement parts in stainless. All the 300 series SSs are acceptable as well as a couple others for this so it really comes down to machinability. Because the OE parts were brass, these are obviously not structural parts and I would prefer a softer material to aid in machining. That being said, I know some of the 300 series pre-HT are pretty gummy so I really need something that is machinable.

I have some rather intricate areas that will require small tools so this could be tricky with stainless. I am also considering an anodize of a softer material for this application but concerned of the long term affect of Meth. SS is about the only metal that seems to do really well with it.


Ideas???

 

[Bobw]

My favorite SS, 17-4 in an H1150. Yeah its "hard" compared to the 300 series, but it machines much more like a non-stainless than the 300 series. You really have to screw up royally to make it workharden, and it can be machined dry quite easily. As for corrosion resistance, probably not as good as 300 series, but pretty close.

You can get it already heat treated in small quantities from McMaster Carr.

 

[3t3d]

303 Stainless Cuts like butter

 

[viper]

My favorite SS, 17-4 in an H1150. Yeah its "hard" compared to the 300 series, but it machines much more like a non-stainless than the 300 series. You really have to screw up royally to make it workharden, and it can be machined dry quite easily. As for corrosion resistance, probably not as good as 300 series, but pretty close.

You can get it already heat treated in small quantities from McMaster Carr.

Bob, I have 17-4 H900 in stock here but it is 3/8 round and I need 7/16 round. Damn it! I am going to upload a pic soon of the part because it presents a couple challenges in machining possibly. Well, I have turned anything this small before.....

 

[viper]

303 Stainless Cuts like butter

Is that frozen butter or melted butter??? ie, does butter mean good or bad? What condition 303 are you referring to? I have never cut it myself. Again, I have some small turning to do here so I am worried about breaking tools in stainless. What kind of hardness are we looking at?

 

[SDConcepts]

with carbide tooling and even hss, 303 is the easiest of the stainless materials to turn.

 

[Bobw]

303 Stainless Cuts like butter

Oh Damn, I didn't even think about 303, my brain was on 304/316/321.

I know 303 doesn't have the same corrosion resistance as the other 3xx's, I have no idea how that would react with alcohol. Is it sulfur they add???

 

[PixMan]

Oh Damn, I didn't even think about 303, my brain was on 304/316/321.

I know 303 doesn't have the same corrosion resistance as the other 3xx's, I have no idea how that would react with alcohol. Is it sulfur they add???

Yup. Avoid it for most chemical applications. I vote for 316SS.

 

[viper]

Yeah, 316 is what I had in mind but I have only cut 304, 15-5, and 17-4. 304 was a pain. How does 316 compare? I may have no choice but to do most of this part in a mill anyway which will end up being several open sided plunges with an end mill because I have some flats at the bottom of the inside of the part. Sure wish I could upload a pic but damn forum is messed up or I have been revoked.

 

[Limy Sami]

Just a thought,. what about some of the Ampco bronzes?........... you may find something methanol proof that's easier to m/c than 316.

http://www.ampcometal.com/en/index.php?page=home

Just a thought #2 if methanol is that nasty what will it do to zinc alloy / alu carbs

 

[viper]

Methanol is hard on everything and certainly will destroy carbs if given the chance. I am working with a key valving area that is known to leak and kill engines via hydrolocking. I am CERTAINLY open to other materials that will perform well against Meth and will machine like brass. That is why I was considering plating of other materials.

Funny for me to say but I am actually out of Meth in the shop. Usually have buckets of it everywhere but when you need it for testing, it is gone! I was going to throw some anodized Al, brasses, and SS in some of the goodness and see who does the best. I realize there are more scientific ways but I have learned that they are not always accurate due to the additives put in Meth like upper lubes.

 

[moonlight machine]

Having worked on Indy cars for about 25 years I have a fair amount of experience with methanol. Color anodized 6061t6 will last 1 season as long as it does not get scratched. Hard anodized and sealed lasts longer. most any ss is fine in methanol. What are you going to do to protect the carb? It will hold up in methanol for a short time. Each time you are finished running this engine you should run gasoline through it to clean out all traces of methanol. this is called "pickling" by Indy car mechanics. It won't run to well on gas as you will be jetted about 50% richer for methanol. Indy Cars have a map in the fuel injection that that leans the mixture when it is being pickled. The worst corrosion you see on the Indy cars is when some bright spark leaves 1 or 2 inches of methanol in a sealed fuel bladder over the winter. as bad as the methanol is I think the vapors are worse, you would be amazed at what looks like a ill conceived chemical experiment gone bad. Massive corrosion on all metal parts except the ss bits.

 

[viper]

Thanks for the tips. We call our process "purging" in the offroad world. Because these are carbureted, we just add the gas and let it bog out. Not the best for spark plugs but it works.

Do you guys run any brasses that have lower reactivity with Meth? We simply run the carb with the product and purge after and that seems to keep the carbs working good for the most part. I know what you are talking about with corrosion. Left some in a carb for a year. Carb was toast!

 

[Limy Sami]

In my late teens and early twenties (70's) we never bothered with special fittings on methanol fuelled grass bikes - JAP singles etc.
We drained the tank / ran the fuel out and drained the carb.