Hi there.... Looking to build a 451 stroker with 440 factory crank and .30 over pistons ..Will 7.100 rods work ?? Thanks guys !!! Or do I need a different crank ??

You can use any rod but most all 7.1 rods are 2.20 rod journal which would require turning factory crank down to 2.2 from 2.375. If you do that you may as well offset grind for more stroke 3.90 at the same time as custom pistons are needed anyways. There may be shelf pistons for 3.9 stroke with 7.10 rods

I'm (slowly) doing a 451 (440 steel crank/400 block) with KB 280 pistons (OE 6.768" rods). On initiaL mockup the pistons are .019" below the deck and the plateau is .139" above the deck. that is alot of cubes in the lighter B block & the only real exorbitent expense is the pistons & they ain't that bad (still need milling then balancing). OE 440 pistons can have a CH of 2" 2.03" 1.920" and for on paper math workings, a 7.1 rod is going to be .332" taller than the std 440 rod. EDIT had the counterweights turned to 7.250 in the very beginning. balancing later

There is absolutely no reason to use a 7.1" rod on a 3.75 stroke unless you are talking about 10,000 rpm.

There is, though, a very good reason to use a 2.200" rod journal, which lets the crank stroke go to 3.90 or 3.91. Then a 6.535 rod will be easy and cheap and most of the major manufacturers of forged pistons have lightweight slugs as shelf stock that will fill out the rest of the setup.

Or use the 3.75 stroke, a decent set of 440 length rods (those pistons are really light so even the stockers will probably do) and the KB pistons mentioned above.

Check out the last several years of EngineMasters and you'll see that many of the winning combos used really short rods compared to the strokes, and they made the most average power and torque between 3000 and say 6500 rpm.

I used to be a long rod believer but time and again it has proven to be incorrect for street engines.

R.

The other variable is piston height. The 451 B block engine with 440 rods uses (from memory) a ~1.3" piston which does not normally need an oil support ring and also is stable in the bore. Also, I believe there are shelf stock pistons that can work in this application.

The longer rod would likely put the pin in the lower oil ring and need the need the ring support. This adds complexity to the build and maybe some reliability risk.

The 6.76" rod seems to work really well with 451".