Crankshaft ?

[434nova]

If a crank is cut for 2.100 rod journal does it mean it will use a regular small block chevy rod ? Or will it need a buick rod with a 2.100 journal if that is even possible. Also when using a 3.625 crank what is a good rod ratio to go with and still give you a good piston for compression height. How would a 6.000 rod work with this combo. This is on a 4.1 stage 2 motor.

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[earlbrown]

With a 2.100 journal that's SBC sized. I don't really understand the part about the rod ratio. It pretty much is what it is. Depending on your exact deck height and the thickness of the ring pack, that's going to limit what you can do as far as length and ratio.
The most common way would be to take your deck height, your stroke, factor in a 6" SBC rod then see what numbers that gets you for a CH.

Tomorrow or Monday I'll be announcing pricing on 'custom' off-the-shelf priced forged pistons for the 4.1. Part of it's selling point is a short ring pack that will allow room for long rods and strokers.

 

[David Husek]

If a crank is cut for 2.100 rod journal does it mean it will use a regular small block chevy rod ? Or will it need a buick rod with a 2.100 journal if that is even possible. Also when using a 3.625 crank what is a good rod ratio to go with and still give you a good piston for compression height. How would a 6.000 rod work with this combo. This is on a 4.1 stage 2 motor.

I don't recommend using a connecting rod shorter than a 6.300. The 6.350 length connecting rod is what I sell with my stroker kits. It will give you a 1.75 rod ratio. Same as the stock stroke setup. Many stage motors have been built with 6.5" rods without any issues. which will give you a 1.79 rod ratio. This is assuming that your stage block has the deck height to use a 6.5 rod.

As far as using a 2.100 journal, weber and dls both had Buick specific rods built for the 2.100 rod journal. Contact them, they may have a set for sale. Any questions, feel free to contact me.

 

[Nick Micale]

Rod length from stock to 6.300" will have no noticeable affect on wear or performance that you could see or measure with a typical turbo Buick build unless you plan to go way over 1000 HP, and this is from what we have experienced, and also what Kenny D. has published.

As far as a BMS or any Buick crank with rod journals turned to 2.10" means it has been damaged, and I keep this "reminder" to never go down that road again with any "worked" cranks.

I gave up at 3000 RPM during the break-in process.

 

[earlbrown]

I do find it odd when people grind down to SBC size. It would require less meat removal to go down to BBC size and have an even longer rod (giggty)

 

[750H.P.V6]

I wouldn't recommend running a 2.100" journal diameter with a 3.625" stroke. There is not enough overlapping material between the splayed rod journals. Nick is probably right that the crank was damaged at some time in the past and the rod journals were ground 2.100" in an effort to save it.

Neal

 

[WPP-Bill]

Back in the day, before 4340 3.625 stroker cranks were available, offset grinding a 3.400's rod journals from 2.2495 down to 2.100 was an "affordable" way to produce a stroker. We used custom rods for this combination and have a few individual rods left (no complete sets). Needless to say, the abundant availability of 3.625 cranks made that old offset stroker rotating assembly obsolete.