Thought I recently was on a thread and there was a comment about detonation with a long rod?

I always have zilcho luck with the search.

Gracias!

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'72 Duster 198 stock cam, 3:23's Hookers on jack stands for 8 years in the driveway
'79 Maxivan 360 Offy Qjet Comp RV cam/rusting in the driveway.
93 D350 160HP Cummins Auto Dually Clubcab needs a injector pump
2005 Golden Couch Buick

I'm not having any issues with a 7" rod.

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11.02 @ 120.56
http://www.youtube.com/watch?v=EAxRmoDgsdY
Chassis dyno
http://www.youtube.com/watch?v=wd6hFGzLJMc

There was a mention of Doc not recommending using the long rods.

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'72 Duster 198 stock cam, 3:23's Hookers on jack stands for 8 years in the driveway
'79 Maxivan 360 Offy Qjet Comp RV cam/rusting in the driveway.
93 D350 160HP Cummins Auto Dually Clubcab needs a injector pump
2005 Golden Couch Buick

The only issue would be getting pistons with the right comp height to allow choice of 8 - 9:1 comp.

Lou

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Home of Slant6-powered fun machines since 1988

The rod ratio thing is way over blown. Getting the reciprocating weight down and using thinner rings of superior materials are much more important than rod ratio. I'd much rather have a quench combustion chamber than change the rod ratio .073.

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Joshua

I run the k1/weisco no problems so far.

Kev

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I agree, there has been much debate over this topic for years, and several well known engine builders have thoroughly tested this "theory" both in dyno testing and actual track testing to conclude that it is a "theory" and nothng more. David Reher of Reher-Morrison says "the rod connects the piston to the crank, nothing more". They dyno tested dozens of rod length combos in their same Pro Stock engine mule in .050 thousandths increments and ended up with a rod length almost .750 longer than when they started, and saw no measureable increases at all in either torque or HP.
Ed Iskenderian also has done tons of research in this area, and has even created a graph of a SBC engine with a 5.700" length rod and the same engine with a 6.000" length rod. He plotted the piston height of each engine relative to a 0 deck height in 1° increments for the entire 360° of crank rotation and found that the piston heigths of each engine were virtually the same for each degree of measure for the entire 360°.

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There's no such thing as too much cam....only not enough engine!

It's all in the tune.

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11.02 @ 120.56
http://www.youtube.com/watch?v=EAxRmoDgsdY
Chassis dyno
http://www.youtube.com/watch?v=wd6hFGzLJMc

The long rod combo works fine... if you get the needed static compression for the boost level you plan to run.

But...

Most of the long rod combos give you 10 to 1, right out of the box.

And...

High boost levels tend to "over-stress" light, short, "slipper-skirt" pistons with thin ring packs.

Can the long rod combo be made to work with boost, likely - yes
Would a combo using a longer, heavier piston, with thicker rings hold-up better... ??
DD

Heck, go "whole hog!" 262in stroker etc.

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'72 Duster 198 stock cam, 3:23's Hookers on jack stands for 8 years in the driveway
'79 Maxivan 360 Offy Qjet Comp RV cam/rusting in the driveway.
93 D350 160HP Cummins Auto Dually Clubcab needs a injector pump
2005 Golden Couch Buick

I have built many NMCA engines that have made over 1000 HP with either nitrous or superchargers, and you'll find that at some point along the way the lightweight components begin to fail frequently. For any type of forced induction engine you need to design the piston first with the right ring pack, top ring heigth, piston material, crown thickness, wrist pin length and thickness, and compression. Then make the rod fit the gap between the piston and crank. Rod length to stroke ratios are less important on forced induction engines, but you still want to get away from cylinder wall loading with really poor ratios, but it isn't a tragedy if you cant. But like Doc said earlier, basically you need to tailor your components for the build you are trying to accomplish. The long rod isn't what causes the detonation, its the increase in compression you gain from it. You can get away with higher compression in a nitrous engine, but turbos and supercharged engines are more sensitive and require a lower static compression in the 8.5-9:1 range or detonation will be a constant problem.

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There's no such thing as too much cam....only not enough engine!