Rod Length? Short Stroke
 

I am curious. Lets say someone had a standard deck dart block. And they used a 4.00 stroke, 4.560 bore, to make 522CI. And then they used a long rod, say like a 6.535 or 6.700 or whatever works. Why would someone do this setup, vs. say a 4.25 stroke setup and make a 555/557ci? Given the cranks cost the same? A friend of mine has this 522 setup, brand new shortblocks, callies cranks, oliver rods, dart blocks. He did not build them, someone else did. I am curious why someone would choose this combo? I can't see it being "its what they had laying around" given brand new callies and oliver pieces, and new dart blocks.

Is it for High RPM with the short stroke?

Better rod angle with the longer rods?

How does the longer rod affect it with a blower? I thought the longer rod keeps the piston at tdc longer or something like that?

Better rod angle ratio.

According to some of the top engine guys here, Young ect. you really should use a tall deck for the strokers, to keep your ratio a or above 1.5.

I'm not an engine expert, but this is what I've been taught.

You would prolly not use a 6.700 rod. Already with a 6.535 your compression hight is pretty low at ca. 1.25. A 6.385 with a 1.4 comp hight. would be better I think. A more "stable" piston. Besides, yuo could go to 4.600 and make a 532 cid.:coolcowboy:

Most people overthink the rod angle thing. 540's are very popular at 4.25 stroke, 6.385 rod and a 1.502 angle. Pretty close to a 454 with a 6.135 and 4.00 stroke, 1.533 angle.

What's the deal with a long rod setup keeping the piston at tdc longer? Does this have a effect on cylinder pressure? I thought I read it creates more cylinder pressure, and more prone to detonation? :bigbird:

Less push on the cylinder wall .

long rod = more torque

From what I understand, the long rods will, as stated above in post #5, create less pressure on the cylinder wall, where as a short rod will create a higher pressure on the cylinder wall, and possibly deform it. Pistons with sort compression hights will also "slap" more and then create more wear.

I've never heard about longer tdc. times and detonation issues because of long rods. But I see your point.

Long rod does NOT = more torque. Talk to RM Builder on this!

fixx
 

+ 1 and less scuffing on the piston,,but you must internally ballance the engine and run the smaller ballancer (396/427) style..and yes a longer rod will make the engine think it has a bigger stick in it..

Over on Speedtalk, Darrin Morgan says that he's never seen any hp increase going from a short rod to a long rod. Supposedly there is a slight reduction in cylinder pressure at tdc with a short rod resulting in less detonation. Also, a short rod results in a longer piston which can be good for stability and ring sealing. On the other hand, a long rod results in a shorter, lighter piston which is better at high revs. As far as cylinder scuffing, I'd be more worried about proper bore finish, proper clearence and avoiding over rich mixtures that wash down the bores.