I picked up a GM 4" stroke forged crank for my 454. Got it for $400. It was standard/standard, and just needed a polish to clean up. Getting hard to find those now.

The engine builder I'm using suggested I run a 6.385" rod. He was telling me it takes some of the steepness out of the angle of entry into the hole, and takes stress off the crank. He mentioned the compression I want to run would exert more force on the reciprocating assembly. What's the deal with this? Can anyone explain whether I need to bother with longer rods, or stick with the stock rods and 3/8" bolts?

I believe he may be concerned about the rod length because I'm going to run a 12-13:1 compression motor with a UD 255/263 .612/.639 107 solid, and looking at a shift of somewhere around 6500-6800 (depending on how things work out at the top end/gearing/tires/etc.)

The thing that's a bit confusing is that a L88, and LS-6's were rating at 425 and 450 HP, but produced more HP than rated (some say as high as 525 HP). Granted, I'm looking at around 550-600 HP at the crank, but that's a factor. As I said, he seemed concerned about the compression exerting force on the reciprocating assembly, but the L88 and LS-6 were also rated at 11:1 (or maybe it was 12:1...I forget). So, this leaves me a little baffled.

The one thing I can say is that he was NOT trying to sell me parts. In fact, he suggested I buy the parts since he couldn't get them any cheaper than Summit or Jegs. He just mentioned I should consult with him before laying out any cash, to make sure I got what I needed.

Anyone like to chime in here?

Anyone have an opinion on this?

Sean,
I had the same question about 2 weeks ago and there are some other similar posts on this board, but all basically give the same response. Look here>>>> Longer rod advantage (http://www.chevelles.com/cgi-bin/forum/ultimatebb.cgi?ubb=get_topic;f=4;t=019615)
And then read page #2 of this post>>> More info on the longer rod (http://www.chevelles.com/forum/ultimatebb.php?ubb=get_topic;f=4;t=019847;p=1)

Missed those posts, thanks. Unfortunately they didn't clear things up much! :D

You mentioned you're going with +.25 length rod. Why did you decide to?

Originally posted by SS_Sean:
Missed those posts, thanks. Unfortunately they didn't clear things up much! :D

You mentioned you're going with +.25 length rod. Why did you decide to? =
Sean,
Here is another post for you to read.
Balancing & Rod length (http://www.chevelles.com/forum/ultimatebb.php?ubb=get_topic;f=4;t=019847)

Technically speaking your machinist is right. There is slightly less initial loading on the crank with a longer rod but the key word is slightly :D
This is just not a good reason to change rod lengths.
The differences are negligible,, almost to the point of being immeasurable.
There are valid reasons to use both short & long rods but the difference in crank loading would be pretty much on the bottom of my list.
I can & have discussed some of the so called advantages & disadvantages of both before but the bottom line I feel is,, unless you have a very valid reason to change the length of your rod leave it alone ;)
Again,,, in my opinion it is just not that big of a deal,,, but fun to ramble on about :D

Thanks for the info, Mike. I sent you an email with some more questions...

If you are buying all new parts go with the longer rod, if you already have pistons or the shorter rods then use them.