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Original Message
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| WHy not drop in some 360 pistons instead. |
| By Dave Shoe - 01/21/2004 6:59:02 PM; IP 12.2.11.190 |
360 pistons are a 390-4V piston design, just as 390 pickup pistons are 410 pistons. Both were used to drop compression in pickups to around 8.5:1 to prevent detonation during long-term heavy lugging.
If you prefer spirited performance over long distance hauling, you should do well with 360 pistons, 390 rods, and 390 crank.
I seem to recall 390 piston/pin combos weigh the same as 410 piston/pin combos. Typically, oversized pistons are balanced to stock bore specs, sometimes using a lighter weight piston pin as the coarse adjustment. If so, you could swap pistons without rebalancing.
Since 360 rods are lighter in weight than 390 rods, you'd have to rebalance the assembly to use the long rods. The piston swap is easier, though you'll have to deal with ridge issues with either swap, which means boring the cylinders to get rid of the ridge. A bore job means oversized pistons - no big deal but something to think about.
The C1AE heads have slightly larger chambers than truck heads, so it sounds like 390-4V car pistons might make about 9.5:1 or 10.0:1 compression with a Felpro head gasket. You'll likely need to recalibrate the distributor and might benefit from a slightly hotter cam kit, as it'd reduce the dynamic compression ratio.
390-2V car pistons would drop that to about 9.0:1 with Felpro head gaskets, maybe 9.5:1 with steel shim head gaskets.
JMO,
Shoe. |
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