Zac, you mentioned earlier you own a similar snowblower with the same engine. Can you check to see what spark plug and belt you are using? Thanks.
I found a service manual for the H70 on the Tecumseh website, http://www.tecumsehpower.com/CustomerService/BSI.pdf
, which identifies the recommended spark plug as a Tecumseh # 33636 and cross-references with a Champion RJ17LM or Autolite 245 (superceded by 456).
This manual was published in 2009, so I'd still like to get a vintage manual to see what the recommended spark plug was in 1971. Some third-party vendors (e.g., http://www.outdoordistributors.com/pdf/Tecumseh/TECUMSEH-MODEL-H70-130025-PARTS-LIST.pdf
), list Champion RJ8C as a suitable replacement.
Also, the parts manual I got on the Yahoo Groups site identifies the belt as Hahn # 308452, which cross-references with a Dayco 3VX335. My used snowblower came with a Dayco 15335 belt, which is similar but not a direct replacement. The 15335 belt is stocked by my local auto stores, but the 3VX335 is a special order which might be why it was installed by the previous owner.