My mechanic is talking about using the 6.535 inch big block chevy rods on an offset ground crank. What is the plus and minuses of this. I would like to know before I go and purchase the rods.
Well, the off set grind will give you more stroke, and by going to a BBC rod, it would cheaper and have more options of rods to choose from, than a BBB rod. And pretty sure you'd also have a better selection of rod bearing. Those are the "pluses", but the "minus" may be that you would need to purchase a piston with a lower compression height than a "stock" type piston.If that's true that would kill the "savings" from the rods and end up spending it on the pistons..... Maybe someone else will chime in, I could be wrong about the compression height. Gary G.
I was thinking about what I posted, I should have said Pin Height instead of Compression height. Is a 6.535 a BBC rod length? I know for my 470ci, I have aluminum 7 inch BBC rods, and the pin height i'm pretty sure is lower than a stock BBB piston. Gary G.
A stock length big block rod is 6.135 center to center length so a 6.535 would be an aftermarket .400 longer than stock length rod. The stock big block Buick rod length is 6.600 and it is made to fit the larger Buick rod journal. Compression height is the distance from the center of the wrist pin bore to the top of the piston deck. Your 7 inch Buick rods would be .400 longer than stock requiring a .400 shorter compression height piston. A stock compression height piston would protrude .400 out of the bore. The primary advantage of a shorter compression height piston is much lighter weight.
Typically, more stroke should be followed by longer rods. Otherwise, you may run the risk of the piston skirt hitting the crankshaft counterweights. I realize you're not talking about a huge amount (.080-.090" or so), but it's something to consider.
I had that combination for a while. I forget the math right now, but if you turn down a Buick crank to a BBC rod journal and offset grind it, you can use a 6.535" rod with a stock compression height Buick piston. Then you have to mill about .040" off the block deck (I think). That set-up didn't live in my motor, but it was because of the yahoo that put it together. Don't get me started on that ... BTW, I still have the rods ... 7 are good and one has a blackened big end. They are Eagle H-beams that have been narrowed to fit on a Buick crank pin. I would sell them real cheap.
With an offset ground crank( 3.95) you would have to deck the block about .025 to have a zero deck with a Wiseco piston. The compression height differes fron brand to brand on off the shelf pistons.
Jeff What was the final displacement of your engine with a 3.95" stroke? Also, what bore size were the Weisco pistons?
