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Registered
Join Date: Dec 2009
Posts: 306
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Correct group size battery for my 911
Anyone know the correct group size battery for my 77 911. Someone has put the wrong smaller size low cold cranking amp battery in it. I had a 78 3.0 911 sc years ago that had a very large heavy high cold cranking amp battery in it which I think was the correct group size but don't remember it.
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10-30-2019, 11:09 AM
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Registered
Join Date: Oct 2018
Posts: 1,018
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I recently went through this for my 911 SC; thread here
However, I do NOT know if a 1977 uses the same size. |
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10-30-2019, 11:20 AM
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Registered
Join Date: Jun 2017
Location: doylestown, pa
Posts: 699
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jack olsen has a whole thread about small batteries.
i ran a SMALL <10lb battery for a while with no issues on my 76.. im not running a pc680 and its fine. drop the boat anchor and save some weight |
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10-30-2019, 11:55 AM
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Registered
Join Date: Oct 2008
Location: Denver, CO
Posts: 3,494
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LCOX -- seems there are 3 schools of thought here -- 1) stick with the stock (boat anchor) group 49/h8 battery, 2) go with the slightly smaller group 48/h6 battery that will fit in the standard battery tray w/o modification, or 3) go with a much smaller battery (eg oddest pc680).
On my cold weather-driven 86 targa, I went with the second option several years ago and have no regrets -- plenty of power to crank start in sub-zero weather and a fair bit easier to install than the group 49 battery it replaced. What size is currently in place in your '77? Regardless of size, STRONGLY recommend going with an AGM-type battery to avoid issues associated with outgassing on std lead acid batteries |
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10-30-2019, 12:16 PM
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Registered
Join Date: Nov 2017
Location: Houston, TX
Posts: 870
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I put a group 51R in to start my 78 SC motor and it's been fine for over 2 years. Needs a trickle charger if not started for about a month (same as my 993, which has a huge battery).
I've had one in a 300zx with no issue for 4 years, no trickle charger needed. That same size battery is used in Honda Civic, Toyota mr2, small Nissans. I live quite a ways South of the Mason Dixon line, here batteries die from heat not cold. Ymmv. |
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10-30-2019, 12:58 PM
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Speed Metal Army General
Join Date: Apr 2012
Posts: 457
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The odyssey pc925 is a great option. Smaller lighter and still has tons of CCA. Not one of the super small ones mentioned, but a good in between. Mine has been working great.
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10-30-2019, 09:19 PM
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__________________
1983 911SC 1977 930 Turbo (again) 2018 GTS 2023 Audi A4 '74 914 '76 911S '72 911T '73 1/2 911T '77 930 Turbo (all gone) |
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10-31-2019, 07:36 AM
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2018 Porsche 991.2 GTS
1983 Porsche 911SC
