Long Rod 2V? Opinions wanted

GMISJUNK

New Member
Jul 31, 2008
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I have 21cc probe stroker pistons and a cobra crank that I have been told will work with a 6.125" rod. The crank is not a stroker crank but it has been to the machine shop, the radai on the crank have been re-worked and balanced but I dont know what has been done to the journals. My engine builder says the piston and rod set-up seems like it would work. Does anyone have info on this set-up? I am thinking comp. ratio would be around 9:1? any info is appreciated! is this worth my time? Seems like a long rod for a 2V.
 
What is the intended use for the engine? Often, long rod combinations end up with the ring pack getting squished together and/or putting the oil rings in the wrist pins. These can result in a little bit higher oil consumption, but the bigger issue is a much weaker piston and ring pack if you want to run boost. That's why I ask the intended use. If it's NA, that might be fine, but why stop at 9:1? If it's boosted, be aware that the ring pack and piston may not be as strong as the factory setup.
 
A stock 4.6l engine has bore = 3.552" stroke = 3.543" rod = 5.933" This give a rod stroke ratio of 1.675:1. Going to a 6.125" rod reduces the piston compression height by 0.192" which should not be a problem and which give a rod stroke ratio of 1.729:1 which should not be a problem either. Just get all of the specs to make sure that compression ratio will be OK.