well i finally scored a 400 and i got some questions. what's the advantage of using 5.7" or 6.0" rods versus the standard size rod? if one does choose a 5.7" rod, does the rotating assembly need to be balanced? i plan on using my vortec heads and rpm intake, and considering the rpm cam:

http://store.summitracing.com/partdetail.asp?part=EDL%2D7102&autoview=sku

will the rpm cam be too big? have heard that a larger cam on a 350 will behave like a smaller cam in the 400, that being said, i currently have the xe268 on my 350 and i don't want a bigger cam. what if i just used the xe268 in the 400??
i don't plan on going to the track much, just cruising around town and driving to work once in a while.

you should balance the rotating assmebly for any engine imho. A longer rod will give you a better rod to stroke ratio which will make it rev alot smoother and be safe in higher rpms. If its a pure street motor I doubt you will get a big enough gain to justify the price though.

Longer rods will put less side-to-side load on the cylinder walls, though I can't recall exactly why this is - although it involves the angle the rods go to when the crank is in certain positions.

well i finally scored a 400 and i got some questions. what's the advantage of using 5.7" or 6.0" rods versus the standard size rod? if one does choose a 5.7" rod, does the rotating assembly need to be balanced? i plan on using my vortec heads and rpm intake, and considering the rpm cam:

http://store.summitracing.com/partdetail.asp?part=EDL%2D7102&autoview=sku

will the rpm cam be too big? have heard that a larger cam on a 350 will behave like a smaller cam in the 400, that being said, i currently have the xe268 on my 350 and i don't want a bigger cam. what if i just used the xe268 in the 400??
i don't plan on going to the track much, just cruising around town and driving to work once in a while.

Look at the "Definitive Guide to Vortec Heads" sticky in Engine Topic, I outline my Vortec/400 build in a post there. I used a Crane cam with the same specs as the Performer RPM cam, Vortec heads, RPM intake and ran a 12.15@ 110.52 on worn drag radials, weighing 3760+ lbs race ready. That was with an off-idle launch and 2800 stall cheap B&M converter. With some RPM at launch and maybe a little more tuning, that combo would have hit the 11.90-.80 range with ease. That cam works very well with Vortec heads in a 400 in my personal opinion. I really enjoyed that old Vortec combo and wish I would have stayed with it. For the $ it was very tough to beat. Just one thing I would add -- I would either use the Crane 234/244 or Elgin 234/244 over the Edelbrock RPM cam, because from what I've seen all Edelbrock did was rebox the Elgin grind. You can buy this cam from Summit as one of their 'house' grinds.

:cool:

If you're rebuilding a stock 400 shortblock with stock replacement pistons that are within 30 grams in weight, there is no need to balance a mild engine. The difference between the 400 rod and the 5.7 rod is nothing, other than a better selection of replacement pistons. Now if you plan to buy an aftermarket crankshaft, then there are many more options, which will be determined by budget, intended use, and RPM requirements.
If you're buying an aftermarket crank, it only makes sense to buy the one designed for 6" rods since it will internal balance with little or no mallory metal, allowing increased RPM without fear of damaging bearings. If you never plan to go past 6000 RPM, there is no gain to the longer rod/internal balanced crank combination.

By what you've described of your intended operation, rebuild it stock, crank, rods, rod bolts, etc and bolt your Vortec heads on, you'll be a happy camper. ;) I would strongly recommend having the block decked and the cylinders torque plate honed.

The way I understand it, rod length is the last thing to consider when building an engine. The advantages of a longer rod are usually too small to be concerned with. So, don't sweat it. Look at the overall picture and go with what your budget allows.
I don't have anything to compare to, but the 268 is a good cruising cam for the 400, lots of power, starting at under 2,000 rpm and pulling to around 5,000 before it drops off. Of course those are not exact numbers and the rest of the combo has a big effect, but it should be nice.