Thinking of this combo, the rod to stroke ratio would be 1.44. Would this be to low? Ok? Will be a somewhat drag truck with some street use.

What engine family ?

You can probably go with a little longer rod because you'll most likely be using a .927 piston pin. Talk to the piston vendor and see what they can do. I used 6.200 rods in the 427 small block that we just finished up. That was with a 4.125 stroke.

Even if you can't use a longer rod that ratio is okay. You'll eat some power with ring friction but you'll make some torque with the extra displacement so it is a trade off.

This is going to be going in a 360 based Magnum race block. Mostly strip, but some street. Going to be going with a smaller solid roller setup. Real question is will a turbo be able to be used well with this stroke and bore. Compression will be trying to be kept low, but have to make sure the ring land is thick enough. Thanks for the replys.

Normally aspirated short rod ratios are typically fine....even at 1.45:1 or so, I'm not a big fan of short rods in a boosted motor, if the motor gets into any kind of lean-out detonation issue that slug will start rattling...with a short rod ratio kicking more to the side and with the piston under pressure it's going to tend to be harder on everything you can imagine.

Don't they make a 6.25" rod? it may be a SBC journal though, I would run a 3.55 or 3.79" crank for boost and just turn the wick up a bit to make up for the loss of N/A cubes, in a well set-up boost motor you'll NEVER miss them and your bottom end will be a fair amount more stress resistant and spin more freely at all RPM's and loads. I'd even do a 4" but not a 4.25" unless it was a big block (that has longer rods) and even then i'd prefer a shorter stroke there too.

There's reason a lot of the heavy hitters with turbo motors tend to run shorter strokes and wind them tighter, part of it is that a turbo naturally raises the peak RPM that peak torque and power is made, you're taking a long stroke short rod combo out of it's element and making it run hardest at the point where the natural/inherent frictional rotation losses (= more heat being transferred into the block) are rising at a rate much faster (per say 100 rpm) than a shorter stoke motor.


Opinions vary though...

Who makes that 4.25 crank, Ohio Crankshaft? A 6.00 rod would almost have the same piston, right?

K1 makes a 4.25 crank.

Might look into a 4.18 crank and a longer rod. Will see. I am in a way limited to the boost at 14 psi unless I go standalone. Going to try and get into the single digits with the Factory PCM and an SCT custom flash. The resolution is sketchy when trying to use a 3 bar map sensor. The highest octane I will put in it at the track is going to be 108 unleaded.