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Original Message
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| RE: Tough question. |
| By Gerry Proctor - 01/28/2005 12:46:43 PM; IP 207.133.188.254 |
Here's a little nugget of knowledge about the real vs. perceived difference.
Many real Shelby 427 Cobras are really 428 Cobras regardless of what the badge says on the fender.
The 427 was designed as a racing block. It is as different from a 428 in just about any way you can think of. The 427 blocks were stress relieved in manufacturing. Many used alloys not used in regular production manufacturing. Then there is the crossbolts and the custom assembly.
The 428 was designed as an economical lever to push big Thunderbirds and Galaxy wagons around. It uses standard production line casting and assembly techniques. It's just a big-inch FE. There's not even much difference between a 428 T-bird block and a 428SCJ block.
If a 427 and a 428 block cost the same, you and probably everyone else would pick the 427 block. But they don't cost the same so that's where you have to decide. If you can get a good 428 block for $600 or pay $3,000 for a 427 block, which do you choose? Depends on what you're going to do with it. If you're going to be spinning the engine regularly to 7,000 rpm, you'd better get the 427. If you don't need the more robust endurance features of the 427, then from an economical standpoint the 428 makes a lot more sense. Carrol Shelby thought so.
As for which makes more torque...depends entirely on how the engine is built. The torque peak always occurs at max VE. If both engines have the same VE curve, then they'll make the same torque, statistically speaking. Theoretically, the 428, with the longer arm should make more torque or, if you will, the 427 should make more torque due to the move favorable rod/stroke ratio. Either of these falls withing a dyno's margin of error so the difference would be inconsequential as far as being a factor in your choice.
As far as horsepower. It's a bit of a different side of the same coin as torque. The 427, with the potential for a higher redline, could make more horsepower than the 428. But, again, only if it were built that way. If you use the same parts (cam, heads, intake, exhaust) on both engines, they'll perform about the same. Theoretically, again, the 427 should make more horsepower due to a slightly lower piston speed which equates to less friction. Again, within the dyno's margin of error.
Now, obviously, if there is no similarity between the two engines (428 using C8AE-H heads, mild hydraulic cam, iron intake and log exhaust manifolds) and a dressed medium riser 427 you have nothing fairly compared. The 427 would unmercilessly kick the 428's ass.
So, in my opinion, get the 427 if you need the extra endurance and durability for those 7,000+ rpm adventures. If you don't need to spin it that tight, the 428 makes more sense.
Things like very high compression ratios, supercharging, and big shots of nitrous demand upgrades regardless of rpm ceilings so if you're contemplating those, you might end up needing the 427's strength(along with the forged, lightweight pistons, forged crank, worked rods). |
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