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'41 Slow Cranking


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My '41 is experiencing slow cranking... again. When I first purchased the car 2.5 years ago, I went through this. The car had sat for about 5 years, so I installed a new battery. I replaced it with what was in the car, a NAPA 7024 Commercial 6 volt. Although the cables looked new, I replaced them with #1 gauge. I cleaned all the connections including the ground strap. I had the starter professionally rebuilt. I have never driven the car, and have worked on the car about once every six months. This has alowed the battery to sit for months with inactivity. The battery was charged and the engine was cranking fine six months ago. Fast forward to today: the same battery holds a charge, I cleaned all of the battery and cable connections, and the engine will get a few revolutions of cranking and then stops. Then after a few more tries, the engine will not crank at all, only the solenoid clicks and an effort from the starter to turn like the battery is dead. There is a slight and I mean slight bit heat from the solenoid to starter cable but nothing like the heat generated from the cables that originally came with the car. I hooked a volt meter to the battery cables during cranking to load test and the voltage drops to 4.7 volts during the cranking efforts. I am suspecting the battery has become sulfated enough to get weak and not handle a load. Even when things were working "good", it was not great compared to 12 volt systems. My questions: What is the failing load test voltage on a 6 volt battery? Is it half of a 12 volt system? Those are 80% of 12 volts which is 9.6 volts? This would mean a 6 volt failing mark is 4.8 volts. If so, I guess I just need a new battery but I want to get something better if it is available. Any suggestions to fit the original battery tray or proven modifications to offer better cranking ? Anyone using those Optima or gel batteries, 8 volt batteries, etc? Thank you!

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Have you run the car since all the degreasing the tops of pistons and other?? Have you charged the battery since all the compressions tests?? If so, the batt is weak..starter bushings may be worn...or..engine is tight from the cleaning...run it ..get it hot..let the lifters pump back up..Dont panic if they clatter for a little bit when u start it..lifters have collapsed and will pump up momentarily..

I would suggest to refrain from lots of decarbing the engine..the stuff you stir up can be lots more trouble than the slightly increased compression from carbon on the piston...

Edited by Mssr. Bwatoe (see edit history)
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Yes. The engine was fully warmed up, and barely any valve clatter. The battery is fully charged, and has been slow charged for days, I have a charger on the car when cranking, rebuilt starter, connections cleaned, cranks better with the plugs out but still not as good 2 years ago when the battery was brand new. I think the battery has just gotten sulfated from sitting and cannot create enough power. I am considering a stronger battery that is the same size, there are a few good comments in previous discussions about the Optima battery. Any comments on putting in an 8 volt?

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An 8 Volt battery only masks the real trouble. Clean the battery connections (both ends of the cable) to make sure of a clean positive connection, maybe even add a ground strap from engine to frame. Try a known good battery. If it fails to improve you need to have the starter and solinoid checked.

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A new Optima battery took care of my slow cranking. Still not great but but similar to other 6 volt cars. I would never buy another NAPA battery. This is the second or third time I have experienced them lasting only 2 years.

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I have had good luck with Interstate batteries.

My 1941 Continental had one in it when I got the car. It has always cranked vigorously so I bought one for the 1939 Zephyr. The '39 cranked vigorously at first, but now is a little slow.

I suspect that the charging system on the '39 is not quite up to snuff. It's hard to tell on '39s because they don't have an ammeter. You DO have to keep the terminals clean as they tend to corrode during extended idle periods.

Be sure to get the heavy-duty battery: "2-XHD 600 CCA 750 CA"

post-31768-143138097834_thumb.jpg

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