CHP 347: Difference between 5.4" and 5.315" rods

[68RustBucket]

their least expensive kit/shortblock has 5.4" rods, and all the others have 5.315" rods. should this lead me to believe that the shorter rods are better in some way or what? i'm planning on ordering one of these shortblocks, but would like to know the reasons that there are 2 different lengths for the 347's rods. thanks fellas

~jake

 

[mustangdave]

The one with 5.4" rod may use a diferrent(cheaper) piston that is shorter. Since that kit is less expensive, it could be because they are using some off the shelf parts from another application.

 

[hrspwrjunkie]

The 5.4" rod pushes the piston pin into the oil ring which can lead to poor oil control or shortened ring life if the rings aren't fitted to the shortblock correctly. The 5.315 rod brings the piston pin out of the ring landing which can make for a better seal and longer ring life in most applications. The only problem is a reduced rod to stroke ratio which can still shorten the life of the motor. Six to one, half-dozen to another. Your call. I can honestly say I wasn't impressed with the quality of the stroker kit I got from CHP. I was much more pleased with the kit I got from DSS...but other people have said the exact opposite.

 

[68RustBucket]

i've been considering DSS as well due to the included main support system (windage tray, i believe). the only thing that turns me off is the 5.4" rods, which cause the increased possibility of oil burnoff and whatnot.

i'm not going to be driving this motor real hard 90% of the time, as it will be a weekend/summer cruiser. i know i've heard good and bad things about both kits, but i'll have to find out for myself.

 

[cougar694u]

The included main support is probably a main girdle.

As for the difference, it's going to come down to preference.

The longer rod will provide a longer piston dwell at TDC, providing more torque. It is also a better rod lenght to stroke ratio, which means the angles pushed on the cylinder walls & rod are less extreme. It's basically less strain on the motor, and may provide a little more torque at the cost of the oil ring difference. However, I've seen tons of people run the long rod kits in their import cars (same piston design with the extra support ring), and haven't had a problem. It also will allow you to turn higher RPM's safely.

 

[Bullitt]

i have a DSS shortblock (306) and have nothing but good things to say about their quality of work.

despite only having the "base bullet", the motor has lived up extremely well to 25k HARD miles and 6800 RPM.

i have a friend who got one of their 331 stroker shortblocks and was also extremely pleased with the quality of the parts and work.