408W or 427W

[Dana E.]

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For the amount of horsepower that you're wanting, I really see no reason to spend the extra $2000-2500 for the Dart based engine. The block is more expensive right off the bat and the forged SVO crankshafts are more expensive than what you could use on a 408.

Good 351 blocks are hard to find in my area. Roller block motors last about one day, when they arrive, in the wrecking yards here. The going rate is $750 for a complete motor. If you're lucky, it'll clean up with a .030 bore. By the time you add in machine work on the factory block, I can upgrade and machine a Dart block for well under a grand.

somethings to think about, the shp block will put an additional 40# on the nose.

It looks like it's about 30# heavier.

If you do decide to go with the Dart based engine, I wouldn't stop at a 4.000" stroke, I would go with a 4.100" or 4.250" stroke for 445 or 460 cubic inches.

I like your thinking. I had thought about a 438, but I don't have enough intake or exhaust for a high HP 460 cubic inch motor.

[blykins]

Like I said, it's your choice on what the budget will allow. I was just trying to give you some food for thought as I do these kinds of combinations all the time and I'm familiar with what machining needs to be done, what kind of power is expected, etc.

The difference in price that I was talking about was not only the additional cost of the block, but the fact that you have to use an SVO style crankshaft, which in turn requires H series bearings. With only a 500hp requirement, a production block and a Scat cast crankshaft will suffice with tons of room to spare. Also, keep in mind that a Dart block doesn't come fully machined. They need square decked to fit your rotating assembly, cylinders finish honed to fit the pistons, and the mains checked. I treat them like I do any other block when it comes to the machine work.

If you have an RPM Airgap, you're not necessarily working with an intake that won't flow. These can be made to flow very well and if your focus is on torque with some great mid range power, then I don't see anything against using it.

The pricing for any cubic inch displacement is pretty much the same when dealing with the forged rotating assemblies. So if a 445 or 460 is the same price as a 427, then in my opinion, it's better to get more for your money. You can always upgrade intake manifolds later. Your sidepipes are going to be a bottleneck no matter what displacement you go with, but a header that will support a 393W will not support a 427W that makes considerably more horsepower.