Author Topic: Crank case matching numbers  (Read 1001 times)

Offline Russ

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Crank case matching numbers
« on: 17.08. 2009 12:13 »
Hi all,
This is my first experience with this type of forum so not sure if I am doing it right! If I'm not please let me know? I am just starting to restore a 1951 A10 Plunger and need information. Can you tell me what the matching numbers on a set of crankcases refer to and is it important to have a matched pair. I have a set with the number 380. What does this particular number mean?
Thanks Russ
1951 A10 Plunger.

Offline a10gf

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Re: Crank case matching numbers
« Reply #1 on: 17.08. 2009 13:39 »
Welcome, no worry, this is a perfect 1st post.

1st crankcase thoughts, it's very good, chances are you'll have an oil tight engine at the case joint, internals will line up properly + probably many more good features, someone here surely knows.

 Later (after 5 posts) post some pictures? (+ the small ever returning request, where are you situated... see topic=419. Thanks.


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Online RichardL

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Re: Crank case matching numbers
« Reply #2 on: 17.08. 2009 14:07 »

Welcome. We look forward to pictures of that '51.

Matching numbers means machined at the factory as a set. As A10gf has said, better sealing, plus: cam tunnel and crankshaft in their best respective alignments (Oops. Actually, A10gf said that, also.) ; landing for cylinder base with no step between halves.

Richard L.
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Offline Rusty nuts

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Re: Crank case matching numbers
« Reply #3 on: 17.08. 2009 20:32 »
I think the number means very little except to indicate they are a matched pair.
I have a 1949 set of cases which are also stamped 380.
Maybe matched by the same guy!
1949 A7 Plunger
1947 A7 Rigid Star Twin
1969 Triumph T120R
1972 Triumph T120V

Offline MikeN

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Re: Crank case matching numbers
« Reply #4 on: 18.08. 2009 00:00 »
The crank case numbers on my A10 engine are a matched pair, and yet when i was building up my engine and going through the alignment checks I found that although the cylinder base joint face was nice and flat it was 3 thou out of paralell to the crankshaft main bearings. It took me many hours to scrape it true.
 having said that, it had been running that way for the last 50 odd years so maybe we worry to much about these things