BBC Rod Length?

What does a longer rod length do for a BBC blown engine and how significant is it. Say a .400 long rod verses a 6.700 or 6.800 rod length?

 

The rod is leverage, The longer the rod the easier the work!

Longer dwell time......

less piston side loading....

 

something I found

Here is something I found after my original post, of particular interest was the last paragraph.

http://www.rustpuppy.org/rodstudy.htm

 

Scary t-wrecks, I've been agreeing with all your posts (hope we don't get in trouble)........
Your motor will like the long rod. As a second opinion to the above.

 

I like the longer rod idea, I would run as long a rod as I could get. And as an extra benafit you can run a shorter compression hight piston. I dont really know if thats worth it either, thats just the way I like it.

 

long rods

Use to run 10.2 deck blocks 3.75 crank 400 long rod and a close to stnd. pin height. Then deck the block to what I wanted. Was injected on Alky. The motor was smooth, torque range was really nice and flat very little peaks and valleys. It was a 431 cu in and ran 7.80's all day.in the heat. Really pissed of a lot of 540 cu in guys. The piston skirts looked really good. no scuffs etc. I would never build another BB chevy with std. lenght rods again. even if they were free. Good luck, but you can,t go wrong with them. All the Pro Stock guys years ago ran long rods. Don

 

Don, today they will tell you to design your ring package, put the pin where it needs to be, then measure from the pin to the crank throw and that's how long the rod should be. Today rod length is way down on the important list.

Blessings...............Ron Clevenger.

 

Jm

It is well know on the internet that people that agree with me will be ousted....

 

The power makers are blowers and cylinder heads. Than you have to have good ignition to fire it and most of all, a properly tuned fuel system to make the most of your blower and heads.

I'm not saying the long rod is bad, I think it can only be good. If your looking for big gains, reread my first paragraph.

 

I too am a believer in a long rod engine.
The dwell time at TDC is the main reason.
Less side loading on the skirt means Less friction and improved ring seal.
A longer rod swings the pin less. Less friction
A longer aluminum rod is "said" to be easier on bearings. I personally have noticed no provable difference from this. But using less lead from the increased dwell time makes a huge difference,
Things to watch out for -
The higher the pin is in the piston = the hotter the pin hole is = so it needs more pin clearance.
Too tight of a ring stack reduces ring seal.
Top ring to close to the top is a major disaster.
All above personal preference opinions.