Thread: Conrod swap question.

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I've wondered about this for quite some time, but never been sure who to ask. Looks like you guys are it.
Anyhoo, when fitting a rod to a motor which has the same size big end journal as the oem rod, but a narrower bearing width, does anything else need to be done?
Like does the rod move fore and aft, or do they just sit still?
Is there a danger of some oil pressure being lost through the extra side clearance?
Would it need spacers fitting either side of the small end (inside the pin bosses of the piston) to keep the rod from sliding about, or is it fine?

I'm not refering to using any rod in particular, in any particular motor, just a generic motor building question. I'm tempted by the prospect of shorter piston crown heights, with longer connnecting rods.

Generally speaking, on a steel (or cast iron) rod you would want to hold side clearance (the distance between the rods) to around .016 to .020

With alumunum rods, slightly more clearance would be preferred.

Yes, excessive side clearance can result in a lower (or complete loss of) oil pressure.

Thanks for the reply Geezer.
I've seen many rods with a similar bearing diameter, but narrower widths to some of the engines I monkey around with. And often wondered if they could be interchanged or not.

guess not.