stroking a 427 so

[Anthony]

ENTDOC (Chuck) You have to understand the history of the engines, and why they were developed.

The bore and stroke of 427's and 428's is really not that much different (4.23 X 3.78 vs. 4.13 X 3.98). The reason why ford came out with the 427 was for NASCAR racing, as 7 liters was the limit, which is why Chevy had the 427, chyrsler the 426, Pontiac the 421. The Ford 427 grew out of the 406 (4.13 X 3.78). I guess Ford figured to get the maximum advantage for nascar racing, they had to increase the displacement of the 406 near to the limit of 427, and rather by stroking it, they enlarged the bore to 4.23", probably knowing that the largest bore and smallest stroke at a displacement of 427 " was the best option for sustained high (7000+) rpm racing. Unfortunately, there wasn't much more room to increase the bore, because of the fixed bore spacing designed into the engine casting, so they had to have a special (expensive) casting line to guarantee the bores were aligned more closely than on standard production FE blocks such as the 406, 390, 428. Early 427 racing cranks were cast nodular iron, and later ones were forged. The 428 block was more of a standard production block. I guess with Ford knowing they could not mass produce 427's for standard production cars, they instead decided to increase the stroke of the 406 to 3.98" to come up with the 428, of which all had cast nodular cranks. All the other manufacturers were producing passenger car engines in the 7 liter range, Mopar the 426 wedge, Pontiac the 421 and 428, chevy the 427, oldsmobile the 425, buick the 425 and 430. Other than the 406, ford didn't have a production 7 liter motor, and they weren't going to put expensive 427's in grocery getters. It was the easiest way to increase the displacement of the 406.

Actually, all of the above engines are slightly oversquare, with the ford 427, mopar 426, chevy 427 all around a 4.25" bore. If you really want to see a torque motor, look at the current Ford truck gas motors, all undersquare design, with the bore less than the stroke, designed purposely to deliever max torque at low rpms for hauling heavy loads.

The 428 was more of a torque motor not because of the bore/stroke, but because of the tamer hydraulic cams, lower compression, moderate sized heads. Actually, if you compared the factory rated max torque output of a 427 vs. a 428, you will find that the 427 as delivered in the cobra was rated at 480, and the 428 as delivered in the cobra was rated at 475, both at 3700 rpm, and the 428 police interceptor was rated at 460 @ 3200 rpms. The 428, as delivered in most cars developed max torque at lower rpms, thus better suited for passenger cars. You can take a 428, and with high compression, high rpm cam, and high flow heads make a lot of horsepower, close to a 427.

A 428 CJ crank is good to 7000 rpms, and 750 hp, as I have been told. Ford cast cranks are better than chevy cast cranks. AS far as destroking for an advantage, I would guess that in most racing, it would be beneficial to be at the limit in displacement, with the best bore/stroke ratio. I have never heard of any winston cup cars running a destroked 351, to 320 " or so. I think they all run 358". I know Smokey talked about running a destroked 427 chevy to 410", to get an extra 200 rpms, but I would think if it was that great, everybody else would be doing it as well.

If you have to buy a crank anyway, I would buy the 428 crank instead of the 427 crank, as it is cheaper, will increase the displacement and torque output, and it is still very durable. In fact, some drag racers primarily use cast 427 (390) cranks, not forged 427's, as some think they are more forgiving and they don't spin as many bearings. If you are going to turn down the rod journal, to offset grind the crank, then you may want a forged crank for the increased strength at the location of the rod journal.

I actually know Eric Oldham, the guy who is selling the 361 truck crank, 427 destroked set up. He is a serious drag racer, and runs a T-Bolt clone. He is fast. I actually bought a tunnel port fuel injection system off of him, maybe someday for a GT40 MkIIB