So I am building a new 383 lunati forged crank and callies rods. I have heard mixed thoughts on rod length. I have heard 6.0 rods motors knocking like crazy and some have not. I need longevity and I dont want to sound like a diesle. I am looking at JE pistons or Mahle. this is a low boost application and a daily driver.

Thoughts ?

 

6" rods decrease the side force on the pistons. This creates less friction and I've read it releases about 5hp over 5.7 rods. The rings should also last longer. The only problem with 6" rods that I know of is less parts availability and can be an issue when shooting for the perfect compression ratio.

Not sure what the benefit of using 5.7 rods is.

I don't know what the heck the knocking is your talking about.

 

i have two 383 stroker motors both with 6" rods, and they both make the same sound, its not a loud/bad sound, its normal for 6" rods. if you are looking to squeeze every last bit of power out of the engine go with 6" rods, if you want longevity go with 5.7". not saying 6" rods won't last, but 5.7" is better for a street vehicle.

 

Whats the knocking?

 

I've been running a 6 inch rod 350 for over 5 years now, what's this knocking you speak of because I don't hear a thing out of mine.

 

i have a 406 with 6" rods.no noise .clearanced the block.i have even had 6 1/8" inch rod in race engine with no problem.and all the 355's i've had in the race car,never a problem with the 6" rods.but i know a fellow that put the wrong piston in(not knowing any better)and it sounded like a diesel

 

Are you guys sure that the knocking your hearing is rods??? There has been alot of issues with forged pistons and incorrect bore finish/specs that will cause piston knock when cold for a few minutes. This will generally happen when the machine shop does not have the pistons when doing the overbore and hone or if they just didnt pay attention to detail. Just my 2c's

 

its not really a knock, its more of just a faint sound if you listen closely on the plenum.

 

I don't see what possibly could knock if they are installed correctly. My motor doesn't have any noise.

 

All I can really hear out of mine is the rockers tapping away like a sewing machine.