ive been searching for threads on this and couldnt find much info, so im wondering whats involved and what are the exact benifits of using a longer rod. im planning on building this for drag racing purposes, not competition just a weekend warrior. thanks appreciate any info guys

 

The idea behind a long rod design is to keep the piston at TDC longer which will build a little more pressure and produce a little more TQ. And when I say "a little" that's exactly what it is.. barely enough to measure. The rod ratio is but one thing to consider when building a motor, for racing purposes there are all sorts of other factors that have a bigger impact on power production.

 

That works well with a power adder. You may also want to look into using 93/race fuel mix, or even alcohol, and go with a custom grind cam.

 

I couldn't agree any more, don't worry about a long rod build.

 

The longer rod reduces friction.

 

I asked my machine shop guy about this last week. His opinion was that my truck motor (which will never, ever, see above 3500rpm) wouldn't benefit at all from longer rods. That doesn't make him an expert but I know him well enough to trust his opinions.

 

shorter rods actually increase piston speed during the up and down time in the cylinder, this will increase air velocity (int & exh) at lower rpm, so its beneficial. Shorter rods also decrease dwell time near TDC & BDC. So they start the piston on the down stroke earlier than long rods, they also travel down the cylinder faster. So this is all indicative that lower octane fuel be run. Lower octane ignites and burns faster than high octane.


heres a rod vs stroke thread i did a few years ago
https://www.ford-trucks.com/forums/5...od-stroke.html

 

For naturally aspirated engines, I have seen many people use a longer rod to decrease of the compression distance of the piston. By forcing the pin up, it makes for a shorter and lighter part. Typically I've seen this in engines that are going to run over 8k though.