Long Rod 2V? Opinions wanted

G

GMISJUNK

New Member

Jul 31, 2008

1

0

0

Mar 21, 2009

#1

• Mar 21, 2009

• #1

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.

 

bhuff30

Founding Member

Dec 11, 2001

6,037

35

129

Olathe KS

Mar 21, 2009

#2

• Mar 21, 2009

• #2

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.

 

Stan Weiss

Member

Dec 8, 2006

347

2

16

Philadelphia, PA

Mar 21, 2009

#3

• Mar 21, 2009

• #3

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.

 

billfisher

Active Member

Jul 17, 2005

1,296

4

38

huntsville, AL

Mar 22, 2009

#4

• Mar 22, 2009

• #4

improving rod to stroke ratios can only help torque, and the side benefit of reduced rod angles. and quieter operation and less thrust loading of ur pistons.

 

billfisher

Active Member

Jul 17, 2005

1,296

4

38

huntsville, AL

Mar 22, 2009

#5

• Mar 22, 2009

• #5

mock assemble it and check piston deck height. if it's good use it.