rod length?
rod length? Building a 4.075 bore 3.31 stroke 346.
How long of a rod is too long? better to have longer rod and shorter piston?
At 6.25 piston is 1.315c.h. rod ratio is 1.88(great)
At 6.315 piston is 1.25 c.h. rod ratio is 1.90(even better)
Motor is going to be alum rods so i can get them any size i want.
which is a better combo? im leaning towards 6.315 rod, but the 6.25 is a shelf piece should something happen!
thanks for the input
Dave
How long of a rod is too long? better to have longer rod and shorter piston?
At 6.25 piston is 1.315c.h. rod ratio is 1.88(great)
At 6.315 piston is 1.25 c.h. rod ratio is 1.90(even better)
Motor is going to be alum rods so i can get them any size i want.
which is a better combo? im leaning towards 6.315 rod, but the 6.25 is a shelf piece should something happen!
thanks for the input
Dave
Smokey Yunick always said to put the longest rod in there and go win races, but that was back in the 60's. Nowdays, Pro stock racers don't care how long the rod is, they use a real short deck block to get the heads at a better angle to win races. Me personally, like a long rod (so does my wife 
).
). 
TECH Apprentice
Joined: Dec 2008
Posts: 372
Likes: 1
From: Kinston North Carolina
Boy has this been beat to death over the years. I think looking at it from engine longevity standpoint the longer rod would be optimal for a few reasons. The longer rod of course puts less load on the piston skirts and the Cyl wall, and also will be more friendly to the rings due to the pin being located further up the piston making it much more stable in the bore. But looking at it from a power standpoint the rod just needs to be long enough to connect the piston and the crank. lol. The power differences are to small to justify. But if your going to be whizzing it i would recommend the longer rod.
Smokey Yunick always said to put the longest rod in there and go win races, but that was back in the 60's. Nowdays, Pro stock racers don't care how long the rod is, they use a real short deck block to get the heads at a better angle to win races. Me personally, like a long rod (so does my wife ).
).
Dave, talk to whoever it is designing your piston and settle on what will fit your application best. The designers will be able to recommend a ring pack and compression height in the piston that will work well, while keeping weight down. Then, whatever length that connects the crankshaft to the piston pin is the one to go with.
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3.310 stroke for class rules.
2.0 pins, alum. rods,4.08max bore,flat top,350cuin max.
sounds like 1.250 is the way to go. just wanted more input before i call for the pistons. If i can modify a "in stock" piston it is cheaper.
2.0 pins, alum. rods,4.08max bore,flat top,350cuin max.
sounds like 1.250 is the way to go. just wanted more input before i call for the pistons. If i can modify a "in stock" piston it is cheaper.
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I would go with the longest rod you can without running an oil support rail. Its highly adventagous to keep the pin out of the ring lands. There's just about no way around it, you'll always have better oil control. In your case, the 6.250" rod with the 1.315cd would give plenty of room for a nice metric ring pack and a great R/S ratio for reduced side loading. The difference between the two 1.88 and 1.90 is negligible.
Shane
Shane
Longer is better,My old lady agrees!
Started build
4.07(6.2 block) x 3.350
With 6.430 rod 1.115 c.h. Flat top
Stock unported 243 cast heads fitted with super victor and a Braswell 750 Carb. Be ready for April 30 in Bowling green(NMCA). Cant wait should be a blast.
Started build
4.07(6.2 block) x 3.350
With 6.430 rod 1.115 c.h. Flat top
Stock unported 243 cast heads fitted with super victor and a Braswell 750 Carb. Be ready for April 30 in Bowling green(NMCA). Cant wait should be a blast.
