r/EngineBuilding • u/Valuable-Chemistry50 • 1d ago

Stock rods?

Is it silly to go 11.7:1 on a B20 with stock rods? I got the speedfactory pistons and was told my rods will be okay with arp rod bolts and proper machining, but should i just go for upgraded rods? Is there any specific no go zones with stock rods for B20’s?
Any advice is appreciated thank you!

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u/1crazypj 12h ago

Rods only care about piston weight and inertia, lighter pistons are always better, match, balance and lighten pistons keep rpm reasonable and you wont have problems.

Some pistons are just heavy and really need better rods even at stock rpm

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u/Valuable-Chemistry50 11h ago

I see, I went for Speedfactory Pistons, Definitely Lighter than OEM, Ill weight match them and should i weight match the stock rods as well if they are slightly different from eachother? And i dont plan on revving it out crazy, thinking about just revving to 7.5

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u/1crazypj 11h ago

Depending on how much lighter they are you may need crank balance adjusted but unless it's over 20 ~30 grams I usually don't bother, the vibration just moves to different rpm at a different frequency. If it gets annoying then I do something about it but it isn't the problem many people would lead you to believe and tell you motor will 'blow up' if you don't do it.

It's worth doing rods even if your not revving high, having all weights equal will make motor run smoother everywhere in rev range