Engine cranking with high compression head

Smokedtires

Smokedtires

Senior Member
Hello all, I have my new Snyder 6.0 head installed. I don't know how old the 6v battery is. I bought my car last June. I've had a battery tender on all winter long while it sat.

My question is about how slow it cranks with the new head. Is this common with high compression heads? While it does start, I feel one day there just won't be enough there to turn it over. Is there a recommended battery upgrade, or just a new fresh battery recommended?
 
Smokedtires said:
Hello all, I have my new Snyder 6.0 head installed. I don't know how old the 6v battery is. I bought my car last June. I've had a battery tender on all winter long while it sat.

My question is about how slow it cranks with the new head. Is this common with high compression heads? While it does start, I feel one day there just won't be enough there to turn it over. Is there a recommended battery upgrade, or just a new fresh battery recommended?
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First I would check all grounds and connections. Add a second ground from battery to engine in addition to the one to the frame.These old girls like to be grounded. Ensure you retard the timing when cranking.
 
Higher compression will require more grunt to rotate the engine. As noted above make sure your battery is up to snuff and the terminals are clean. Also use the battery with the highest CCA (Cold Cranking Amps) that will fit.
 
I can assure you that if you had an 11 to 1 compression head, your stock starter wouuld spin it easily as long as the electrical system was in good shape.
 
In addition to grounds and connections I would rebuild the nstarter if you have not yet. I ran a brumfield 5.9 for years and now a 6.0 on a burtz. Starter has always spun the engine just fine. Would not even know it was high compression.⁵
 
X2 about the starter. If you don't want to rebuild it now. Take the band off and look at the commutator, cleaning it will make a huge difference in how your starter will perform.
 
I have a 7:1 head with a stock starter, and it turns over just fine using 155A from the battery, which is well within what any 6V battery will deliver.

I went to see a friend a couple weeks ago who was in a similar situation – very slow cranking after he'd left the battery on a maintenance tender for a month. When we hooked up a 4A charger, the battery read as mostly depleted! So I guess sometimes those tenders aren't good for recharging.
 
Check the size of the cable to the starter. When my car started cranking badly, my cable turned out to be sort of a 4.5 Ga., based on diameter. A 1 Ga cable fixed things right up.
 
The Les Andrews Blue book, "Diagnosis and Troubleshooting" has excellent instructions for voltage testing of the Model A's 6 volt starting system with an inexpensive VOM in Chapter II.

Using a reliable hydrometer, check the specific gravity of each cell of the battery. A specific gravity of 1.275 – 1.285, even 1.30 is considered a full charge. A reading less than 1.260 indicates insufficient charge. If any of the 3 cells continue to fail this test after charging the battery, the battery is defective.

Also, I've overheard a conversation at a club meeting where the flange on the starter had been painted and was hindering a good ground to the engine.
 
As Y-Blockhead mentioned, these slides may help you:
 

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Are you comparing the starting speed to 12 volt starter as compared to a 6 volt? The 6 volt turns much slower than a 12 volt system.
 
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Fullraceflathead said:
Are you comparing the starting speed to 12 volt starter as compared to a 6 volt? The 6 volt turns much slower than a 12 volt system.
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Especially if the starter hasn't been converted to 12 volts. If that is the case, the fan will nearly pull the car along just on the starter.
 
So I pulled my battery and found 2 of 3 cells dry. Bought a hydrometer and have it on charge. Might see if I can find a new battery tomorrow if the specific gravity doesn't improve. Impressed it was even capable of turning over the engine at all.
 
If I don’t know absolutely the age and condition of the battery (in other words, if it came in a car I bought) I replace it, period. Also, set your timing if your points rubbing block has worn a bit this will retard the timing (which would not hurt starting) but if the pint gap is too big, that will advance the timing (which can make it more difficult for the starter to crank the motor). I recently removed the starter of a car that my friend was having trouble and the surface on the engine side had been painted.
 
Engine is turning over much better now. I did reset the points gap to 0.020 when reinstalling the distributor. Thanks everyone for the suggestions.
 
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