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Discussion Starter · #1 ·
i have a 66 shovelhead, its setup for big bore jugs and heads. i think it was at 96 inches. i was wondering if anyone knows if i can go back to 74 inch jugs or 80inch jugs? im pretty sure the cases have been machined to fit the big bore jugs.

if it is not possible to go back to the stock size whats the smallest size big bore i can go with?
thanks
 

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I have run stock cylinders on big bore cases before, but I don't recommend it because it removes any support from the base area of the cases provided by the cylinder spigot. The spigot it self also stands a chance of breaking off, without the case there to shore it up. Also, you'll need new heads, as they have to be opened up to the new bore size as well. If you had a 96", that means the bore size was 3 5/8", and you could just run that size cylinders with a stock stroke and have 88". Shovels and earlier like stroke more than they like bore, because they are more low rpm biased. If i were you, I would build a low compression 93' with 4 1/2' stroke and the 3 5/8" bore. they are very happy long lived motors and still easy to start, IMO.
 

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Discussion Starter · #3 ·
thanks alot! that makes sense. i already have the heads to fit the big bore jugs i was worried about reliability and being able to kick it because im only having a kicker.
 

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Some time ago my dad bought a set of big bore STD cases, but didnt have big bore barrels so he machined a ring that pressed on to the barrels and was the same size as the big bore barrels would have been. Worked great!
 

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It's my opinion (worth every penny) that a Shovel that big with something like 7.5 - 8:1 compression would be a joy to ride. Loads of torque allowing fair high gearing; easy to start owing to low compression; less vibes from same; very flexible engine, pulling strong from down low making for less shifting and giving an easy-riding feel; bragging rights just due the size.
Put a small-ish carby on it to keep up mixture velocity and just ride.

Cosmo

P.S. Worried about performance?? Buy something fast, this one would be a rider. But, hey, I'm old and just like being in the wind, my prick's large enough that I don't need to compensate for anything.
 
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