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B31 cylinder head interchangability? #761725
01/06/19 2:03 pm
01/06/19 2:03 pm
Joined: Nov 2015
Posts: 127
boerne texas
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dean toensing Offline OP
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dean toensing  Offline OP
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Joined: Nov 2015
Posts: 127
boerne texas
In an effort to broaden my search for a nice rebuildable cylinder head for my 49' B31 I'm hoping to find out if some or all B31 heads will fit and function. Not to concerned with numbers originality. The casting number on my head is 65-1157. There seems to be other b31 heads out there that look the same with a different casting number.
Thank you,
Dean

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Re: B31 cylinder head interchangability? [Re: dean toensing] #761765
01/06/19 7:59 pm
01/06/19 7:59 pm
Joined: Sep 2001
Posts: 2,918
Comox BC Canada
Gordo in Comox Online content
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Gordo in Comox  Online Content
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Posts: 2,918
Comox BC Canada
Dean

According to the Roy Bacon books the B31 only had one change, larger fins in 1953 on both barrel and head. I would expect that both would fit. The early head part number is 65-1156. In 1953 the part number changed to 65-1700. The cast number was normally one digit different from the part number.

Gordo


The roadside repairs make for the best post ride stories.
Re: B31 cylinder head interchangability? [Re: dean toensing] #761769
01/06/19 9:14 pm
01/06/19 9:14 pm
Joined: Nov 2015
Posts: 127
boerne texas
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dean toensing Offline OP
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dean toensing  Offline OP
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Posts: 127
boerne texas
Thank you Gordo, great info!

Re: B31 cylinder head interchangability? [Re: dean toensing] #761773
01/06/19 10:28 pm
01/06/19 10:28 pm
Joined: Nov 2011
Posts: 5,202
U.S.
Magnetoman Online content

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Magnetoman  Online Content

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Posts: 5,202
U.S.
Originally Posted by dean toensing
my search for a nice rebuildable cylinder head for my 49' B31 ...The casting number on my head is 65-1157.
I have two iron heads within easy reach, neither with this casting number nor the one in Gordo's previous email. However, in digging around for fork tubes today I "discovered" my index of items on the same shelf shows two ZB heads. From the side of the shelving unit I can barely see them in the most inaccessible far corner of the shelf, basically trapped by at least 100 lbs. of BSA parts that would have to be moved to get to them.

I have no idea if either of these trapped heads has the casting number(s) you are looking for. But, my question for you is, what is the very most you would be willing to pay for a head if, after I moved 100 lbs. of parts, at least one of them turned out to be the head you need?

In considering your response, if any, (which you can do by PM) keep in mind that I 'never' sell anything, I hate haggling, it would take a lot of time and effort to move everything off that shelf and then back on again, and there's no guarantee I would find what you're looking for after all that work. So, it would have to be a take-it-or-leave-it offer I can't refuse to make the possibly-futile work worth considering.



Re: B31 cylinder head interchangability? [Re: dean toensing] #761780
01/06/19 11:46 pm
01/06/19 11:46 pm
Joined: Sep 2001
Posts: 2,918
Comox BC Canada
Gordo in Comox Online content
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Gordo in Comox  Online Content
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Posts: 2,918
Comox BC Canada
MM: the numbers posted come out of a 'BSA SPARES 1949 to 1952-3' parts book MC574-3. It covers B31/33 and GS models.

Gordo


The roadside repairs make for the best post ride stories.
Re: B31 cylinder head interchangability? [Re: dean toensing] #761783
01/07/19 12:00 am
01/07/19 12:00 am
Joined: Nov 2011
Posts: 5,202
U.S.
Magnetoman Online content

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Magnetoman  Online Content

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Joined: Nov 2011
Posts: 5,202
U.S.
Gordo, I didn't mean to imply the numbers you gave were wrong, only that neither of the two heads I have easy access to have those numbers on them so they're for some other ZB. I don't know what numbers are on the two heads trapped on the back of one of the shelves.. I realize now that I should have written those numbers down somewhere accessible when I placed them on the shelf, but I thought then that that's where they would live out the rest of their lives (which they still may do).

Re: B31 cylinder head interchangability? [Re: Magnetoman] #762026
01/09/19 6:06 am
01/09/19 6:06 am
Joined: Jan 2019
Posts: 41
Christchurch NZ
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devon Offline
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devon  Offline
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Joined: Jan 2019
Posts: 41
Christchurch NZ
Hello MM, was the B31 far less common than the B33 in the US?


I've wondered and ought to try placing the B31 head on the B33 cyl, and running it.

Last edited by devon; 01/15/19 5:55 am. Reason: Extra details




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