I had a slow day at work yesterday and was doing some research on the stroker for my Cougar when I stumbled across a rod that might make a stroker 300 with 302 pistons a relatively easy deal. The stroker part depends on how far the crank can be ground. The deck height of the 300 is 10". The rod I measured out of a 300 today was 6.22" long and 0.993" wide. The rod I found is out of a Jeep 258. It's 6.125" long, uses a 2.095 bearing, a 0.912" pin diameter and 1.063" wide. With a 302 piston that leaves you 0.285" at the top of the bore. Eagle makes a rod that is 0.025" longer (6.15"), weighs only 660 grams (stock is ~750!), and cost $479/set. With the Eagle rods and 302 pistons a 4.5" stroke would fit for 344 cubes, but the rod ratio would be only 1.36. With a 351W piston a 4.25 stroke would fit for 325 cubes and a ratio of 1.45. Piston to counterweight clearance might be an issue with either combination. With the std. Jeep bearing you can also only get at 0.1" extra stroke from offset grinding the crank, but there are stroker cranks out there.

One issue that might be present with this rod is the absence of an oiling hole. I had never noticed this little hole in the side of the rod before, but it looks like it sprays oil under the piston. Are all the 300 rods like this? Is the oil spray really needed? It looks like it just sprays extra oil on the wrist pin or something.

 

What is the optimum rod ratio?
I am sure that the oil hole in the rod is for cooling the piston as well as Lubrication for the wrist pin.
Larger diesels have nozzles in the oil galley (Installed through the outside of the block) that spray LOTS of oil to the underside of the piston(s).

ftwfred

 

I believe the optimum rod ratio is considerably greater than 1.45 or 1.56 (stock) for less side loading. But then again the 300 throws that theory out the window by running forever. I was thinking more along the lines of a long rod 300 using 240 rods. A really big six is definately cool.

 

There really isn't an optimum rod ratio. It's been said for decades that the higher the ratio is the better the engine will run, but recent research has shown that lower rod ratios can produce more power if the engine, and more specifically the cam profile, is optimized for the lower ratio. The drawback to a lower ratio is increased piston side loading, but since the 300 doesn't spin a lot of revs that is probably not a factor. FWIW, a good rule of thumb for decent life span on a street engine is at or above 1.5.

 

"What is the optimum rod ratio?"
I've been told it's 1.65....
the 400 had a perfect rod ratio of 1.645.

 

1.75 is considered optimum. Above that the reduction in side loading and in acc/dec loads at end of stroke are very minimal; below 1.75 both become progressively worse

 

In case anybody's still interested, you can buy small block Chevrolet connecting rods off the shelf that are 6.20" or 6.25" long. They come in either 2.00" [283 & 327] bearing sizes, or the later 2.10" [305 & 350] size. They're 0.940 inches wide on the big end.

Cheap enough; A set of 8 [2 spares?] forged rods with ARP bolts for under $300.

 

The stock 300 rods, as well as all other stock rods other than newer powdered metal ones, are forged. The Eagle rods I'm talking about are either I beam or H beam (don't remember, it's been a while) steel.