Just like the subject says!

What is the weak point? The stock rods, stock crank, stock pistons, stock block?

 

Most thin wall cast Ford blocks are good for 550hp+/- and depending upon rpm range. Higher the rpm the shorter the life. That said, a few years back there was a guy on here that ran a pull truck that was making 800hp. The truck was called Shazam and used a stock 400 block for several seasons. In all honesty, the stock rotating assembly is so heavy, you will have a hard time making the hp numbers and rpm to break it unless you turbo/supercharge/NOS the motor--IMHO. TMI kits use a much lighter forged crank for a reason. I used an Eagle 351W 4" stroker blank for my 408 and with the Oliver rods, Ross pistons, SFI balancer, and steel flywheel we reduced the rotating assembly by almost 40lbs.....that's a lot!

 

40lbs off the rotating assembly is saving an incredible amount of energy...that sounds like quite the build...with a stroker windsor crank it would lead to a lot of options.

I like a lot of options and think a 4" stroke is optimum for a street rig that you want to keep tires on. Have you checked out some of kits mustang depo has on ebay? I'm not up on the brands and quality.

 

Wow! (still impressed by 40# weight reduction!)

My answer to the question of how much power the 351M/400 can take is:


A whole lot more than the chebbie guys ever expected! heh heh

 

For a truck, your goal should not be maximum horsepower, rather it should be maximum torque.

 

Depending on application of course lol.

Take a look at a few of the builds from TMI, should give you a semi decent idea for a reliable build, if built properly (4 bolts mains, balanced lighten the rotating assembly, use of a girdle on the bottom end, etc) i think 600 would be bout the max i would feel safe with, but as with any high power motor i doubt that you're going to see any type of long term use just due to the fact that high performance motors are built to be driven and not babied.