Would grinding down the rod journals to 1.850" significantly weaken the 215 crank? It's not like it's going to be making 600hp...maybe 200hp at best. Anyhow do you all think it would present any longevity problems/bad idea?
Wow, no opinions...So I bought some 6.2" Nascar rods that need 1.850" rod journals and want to install them into a Olds 215 block with Nissan KA24 Silv-O-LitePistons 9115.5MM. Is this a bad idea? I know the gains will probably not justify the cost but...will the smaller journals compromise the engine in a significant way?
Just based on simple section modulus formulas, a round "beam" has strength related to the cube of its diameter. Going from D=2" (d^3=8) to D=1.85" (D^3=6.3), you'll have about 80% (6.3 ÷ 8) of the crank's strength remaining. Up to you if that's "strong enough"!
Can't comment on the rest of the combination without more specifics - piston height and dish volume, block decking, gasket thickness, head volume, and whether you're offset grinding the crank to add stroke...
Hi Justin, many changes for little reward This weakens a cast crank, needlessly. 6.2" rod and 2.8" stroke = reduced rod angle.This is not good for your application. Better rod ratio is 1.7/1.8/1. Good Luck, Art.
That should be ok.
It would reduce the journal overlap only 0.15.
Rod/stroke from 2.02 to 2.21.
Less wear on the thust side of the block.
I always thought there was more to be gained from by a bigger rod/stroke ratio than just less wear on the thrust side of the block particularly with heads with small ports...like the Olds heads ¯\\_(ツ)_/¯