OK guys, I've started shopping for parts to build a 420A Turbo. I wanna strengthen the internals to push 350HP+. I have a question about the Eagle Rods. I have the choice between these 2: stock 5.472" length rods or 5.608" length (+.136 longer than stock). I know that longer rods decrease the r/s ratio. I need your knowledge on that one. I wanna know what should I go with for my project? Is lowering the r/s ratio only a matter of reliability or is there any considerable performance gain? Thx for your inputs guys!
#80678, "RE: Startin' My 420A Turbo Project..." In response to Reply # 0
whats an r/s ratio?
just FYI - i have the long rod kit from howell, which is the same as the long rod in your post, and i have no issue with it at all. very torquey...
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#80679, "RE: Startin' My 420A Turbo Project..." In response to Reply # 1
Yes, I'd like to know what an r/s ratio is too.
Beyond that, a longer rod will give you a longer stroke. (whatever the difference between that and stock x 2). Longer strokes generally mean more torque, but a more limited RPM top end.
The thing I would be curious about is what is the effect on the compression ratio? Would you have to compensate for the increased compression given by a longer rod with even lower compression pistons, or does it make that much of a difference? You'd like to see compression ratios of anywhere from 8.0 to about 8.8 IMO. I know there's guys out there that are running higher compression to get the turbo to spool quickly and for more power, but you run closer to the edge of detonation to do it.
If it were me, I would go with a longer rod and like an 8.5 compression piston. That way, even if it does bump it up a tad, you'll still be safe.
Just my 2 cents. Good luck with your project!! Brian
#80686, "RE: Startin' My 420A Turbo Project..." In response to Reply # 2
R/S ratio = Rod/Stroke ratio. What does this mean? It is the amount of force that is everted on the cylinder walls. Horizontal pressure on cylinder walls.
#80687, "RE: Startin' My 420A Turbo Project..." In response to Reply # 2
Originally posted by ForceFed420a The thing I would be curious about is what is the effect on the compression ratio?
None. You use a piston with the wrist pin location moved up by the same amount. The whole package stays the same length, but the rod is longer than stock. Helps cut down on side loads on the pistons and skirts, allows higher RPM, and more torque transfer to the crank.
There was a nice, long thread about these things in Advanced Tuning a while back. Go read it.
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