Originally Posted by coldknock
3-5cc is the norm for 2 relief pistons. It doesn't really matter anyway, except where valve clearance is concerned. Like I said, it's not enough to begin with. 252 degrees at 0.050" and 314 total, 110 LSA on a hydraulic roller cam is BIG. 11.5-1 will do but it's not optimal. I'd use a smaller cam, maybe one space up from the bottom of the page.
You can recite everything you've ever read in magazine articles and Smokey's books about long connecting rods, light weight pistons, dwell time, and decreased loads on the thrust side of the cylinder wall. That's all good stuff if we're talking about 500+ cubic inches, a difference of at least an inch in length, and we're shooting for 800+ horsepower over 7000rpms. Even then the results of using a longer rod would be less than you think.
In a 450-500hp small block Chevy, 0.300" of extra rod length ain't gonna amount to hill o' beans.
Been there and done it already.
I really dont think its all about performance from a engine builders standpoint, then again, it all has to do with how you look at it, durability? in some cases a longer rod will FREE up some power not only due to less weight to sling around, but also due to less friction.. and less friction means your also going to gain durability...
Most certainly, I would use a Small base circle cam, and you may need to have the rod bolts clearanced as well, people do this all the time on the long rod 406's.. Im building a 434 cid using 6" rods, 4.155x4.00x6.00" rods and there is no way, I can get by without using a small base circle cam..
some rod manufactuares have stroker clearanced profiled rods, all rods are not created equal... even with he so called stroker rods you always have to check, you can break a cam, I have seen this.. its not pretty, and you can bet more than just the cam and lifters will be damaged...