400B Schrader core issue. Final boil tests

Post your tech questions here, lots of knowledge available.
Post Reply
logo-3x1-48-Inches-1
TwoCanoes
Super Colemanaholic
Posts: 1886
Joined: Mon Feb 25, 2019 10:27 pm

400B Schrader core issue. Final boil tests

#1

Post by TwoCanoes »

400B valve assemblies apparently come in two versions – one that takes a short-stemmed Schrader core with a stem length of about 0.164 inch and the other, a long-stemmed core, with a stem length of about 0.209 inch. If a short-stemmed core goes bad, replacements are readily available from OCP (# R510 for $5.15). But a source of long-stemmed cores has yet to be found. So, if you have a stove that came with the valve assembly requiring the long-stemmed core, it looks like you'll need to buy the entire valve assembly (OCP # C036 for $33.45). What about mixing parts, that is, putting a short-stemmed core into a valve assembly designed for a long-stemmed core? I did some swapping of parts on a 400B. The test stove is a 400B (3-’90) in which the original valve assembly took the short-stemmed core. For the test, I bought both a R510 core (stem length = 0.169 in.) and a C036 assembly from OCP. The C036 assembly required a long-stemmed core (stem length = 0.210). I did boil tests of three treatments:

Treatment 1: Replace the original Schrader core with the OCP core, R510.
Treatment 2: Replace the original valve assembly with the complete assembly from OCP, C036.
Treatment 3. Replace the long-stemmed core in the OCP C036 assembly with the short-stemmed R510 core.

The logical fourth treatment, putting a long-stemmed core into a valve assembly designed for a short-stemmed core, wouldn’t work because the valve would be unable to close. Anyhow, here are the boil times for the 3 treatments. The stove was lit strictly according to the instructions on the tank, and was allowed to warm up with the valve wide open for 90 seconds prior to putting the pot on to boil. The pot was covered and contained 500 ml water with water temperature at the start of the test of 57 to 59 F.

Treatment 1 boil time: 2 minutes 49 seconds
Treatment 2 boil time: 2 minutes 58 seconds
Treatment 3 boil time: 4 minutes 19 seconds
Stewart in
Eastern Washington State
Majicwrench
Super Colemanaholic
Posts: 6064
Joined: Mon Jul 30, 2012 9:33 pm

Re: 400B Schrader core issue. Final boil tests

#2

Post by Majicwrench »

Always fun to see these tests.

Just curious, did you do a boil time before you started swapping parts?
Keith
TwoCanoes
Super Colemanaholic
Posts: 1886
Joined: Mon Feb 25, 2019 10:27 pm

Re: 400B Schrader core issue. Final boil tests

#3

Post by TwoCanoes »

Majicwrench wrote: Sun Feb 11, 2024 7:34 pm Just curious, did you do a boil time before you started swapping parts?
No, but I checked the stove out to make sure it was behaving normally, which it was. However, I did the same boil tests on 2 other 400Bs that I bought new 25 and 30 years ago. Under the same conditions a couple weeks ago, their boil times were 2:50 and 2:46, respectively.
Stewart in
Eastern Washington State
Majicwrench
Super Colemanaholic
Posts: 6064
Joined: Mon Jul 30, 2012 9:33 pm

Re: 400B Schrader core issue. Final boil tests

#4

Post by Majicwrench »

Like I have mentioned before, the only stove of this style I have is a very well loved 576.
And I replace core maybe 12? years ago?
Might try to recreate your test with mine and see how it does.
It has been so long I do not recall if I change just core or what
Keith
TwoCanoes
Super Colemanaholic
Posts: 1886
Joined: Mon Feb 25, 2019 10:27 pm

Re: 400B Schrader core issue. Final boil tests

#5

Post by TwoCanoes »

Majicwrench wrote: Sun Feb 11, 2024 8:22 pm Like I have mentioned before, the only stove of this style I have is a very well loved 576.
And I replace core maybe 12? years ago?
Might try to recreate your test with mine and see how it does.
It has been so long I do not recall if I change just core or what
The 576 looks like it has a brass F&A tube and would most likely take the short-stemmed Schrader core like the 400. My next project is to reassemble a 400 that I've been working on for some time. I had to replace the core on it, and I used the OCP core. I should know in a day or two how it does.
Stewart in
Eastern Washington State
Flint
Member
Posts: 21
Joined: Fri Jan 14, 2022 12:42 am

Re: 400B Schrader core issue. Final boil tests

#6

Post by Flint »

TwoCanoes wrote: Sun Feb 11, 2024 6:46 pm Treatment 1: Replace the original Schrader core with the OCP core, R510.
Treatment 2: Replace the original valve assembly with the complete assembly from OCP, C036.
Treatment 3. Replace the long-stemmed core in the OCP C036 assembly with the short-stemmed R510 core.
Stewart,

Thanks for sharing what you found with these combinations.

I'm curious if you happened to note how the low flame setting compared between the three treatments in terms of lowest steady flame capability, and ease of adjusting the fuel lever angle to get a low simmer? Some people describe the low flame being too sensitive to fuel lever angle on these single lever stoves.

Flint
TwoCanoes
Super Colemanaholic
Posts: 1886
Joined: Mon Feb 25, 2019 10:27 pm

Re: 400B Schrader core issue. Final boil tests

#7

Post by TwoCanoes »

Flint wrote: Sun Feb 11, 2024 9:06 pm I'm curious if you happened to note how the low flame setting compared between the three treatments in terms of lowest steady flame capability, and ease of adjusting the fuel lever angle to get a low simmer? Some people describe the low flame being too sensitive to fuel lever angle on these single lever stoves.
I couldn't come up with what I considered to be a reliable objective measure of flame control. But I did play with the flame control after the boil test was done and before I shut the stove off. Treatment 1 had excellent flame control - as good as the two 400Bs I bought new and which have never had their valve assemblies messed with. Treatment 2 had just as good flame control, but the lever was more difficult to adjust. On the new, long-stemmed valve assembly, the top end of the eccentric block stuck up higher than on the other valve body, and I suspect the hook on the generator wire was rubbing on the generator tube. Also, with the new valve assembly, getting the generator wire hooked to the hole in the eccentric block was (let's see, how should I put this . . .) a delicate chore. Treatment 3 had okay flame control, but with only a very short throw on the control lever. Full flame on Treatment 3 was pretty low to start with. If a Treatment 3 stove were the only 400B that was available to me, I'd be using a different stove. Bottom line: I think the 400B flame control in Treatment 1 is nearly as good as on the 400 and 400As. The biggest advantage of the older models is that the control lever has a much longer arm, so it's easier to control. Just my opinion, which may be biased by the fact that I have more experience with the 400Bs.
Stewart in
Eastern Washington State
Flint
Member
Posts: 21
Joined: Fri Jan 14, 2022 12:42 am

Re: 400B Schrader core issue. Final boil tests

#8

Post by Flint »

TwoCanoes wrote: Sun Feb 11, 2024 9:44 pm Full flame on Treatment 3 was pretty low to start with.
Stewart,

Any guess on why full flame was lower on Treatment 3? Seems like it would have to be that the Schrader valve wasn't opening all the way. Either that or the generator wire isn't fully retracting out of the generator orifice, but that doesn't seem likely since it was the same setup as Treatment 2 in that regard, which had good full flame.

Flint
TwoCanoes
Super Colemanaholic
Posts: 1886
Joined: Mon Feb 25, 2019 10:27 pm

Re: 400B Schrader core issue. Final boil tests

#9

Post by TwoCanoes »

Flint wrote: Tue Feb 13, 2024 12:35 am
TwoCanoes wrote: Sun Feb 11, 2024 9:44 pm Full flame on Treatment 3 was pretty low to start with.
Stewart,

Any guess on why full flame was lower on Treatment 3? Seems like it would have to be that the Schrader valve wasn't opening all the way. Either that or the generator wire isn't fully retracting out of the generator orifice, but that doesn't seem likely since it was the same setup as Treatment 2 in that regard, which had good full flame.

Flint
You're correct, the Schrader core wasn't opening all the way. Stem length of the OCP core is about 0.040 less than the stem length of the NIB core. When the OCP core is put into the NIB valve assembly, that 0.04 is effectively added onto the clearance between the core and the eccentric block. The NIB core in the NIB valve body opens essentially as far as is possible for that core, which is 0.140. The OCP core is also capable of opening 0.140, however, it only opens to about 0.109 when installed in the NIB assembly. Personally, I didn't think the restricted valve opening would have such a large effect.
Last edited by TwoCanoes on Tue Feb 13, 2024 6:58 am, edited 1 time in total.
Stewart in
Eastern Washington State
User avatar
Gasman64
Super Colemanaholic
Posts: 7405
Joined: Fri Nov 19, 2010 12:26 am
Title: Gaseous Maximus

Re: 400B Schrader core issue. Final boil tests

#10

Post by Gasman64 »

Thanks again, Stewart, for your research and experimentation; this is quite in depth, and I'm going to save the info. somehow.
I think this information you've compiled would be good for the archives.
Steve
Pennsylvania
ПТН ХЛО
T4P
Flint
Member
Posts: 21
Joined: Fri Jan 14, 2022 12:42 am

Re: 400B Schrader core issue. Final boil tests

#11

Post by Flint »

TwoCanoes wrote: Tue Feb 13, 2024 5:09 am The OCP core is also capable of opening 0.140, however, it only opens to about 0.109 when installed in the NIB assembly. Personally, I didn't think the restricted valve opening would have such a large effect.
Stewart,

Thinking about this some more, I also would not expect the reduced Schrader valve actuation to have this effect. The fuel inlet orifice at the bottom end of the plastic fuel air tube looks to be around 0.020” diameter. If the Schrader valve stem was moving 0.109”, it seems that the area of that Schrader valve opening will be many times larger than the area of fuel inlet orifice. It seems like something else must have been preventing a full flame. Any additional thoughts?

Flint
logo-3x1-48-Inches-1
Post Reply

Return to “Technical Assistance”