P-series or H-series bearings - Don Terrill’s Speed-Talk (2024)

P-series or H-series rod bearings for a 9000 rpm SBC?

The literature says the P-series is for really high revving engines where the big end may close up the bearing clearances more than normal at the parting line, with the greatest amount of eccentricity and high crush.

The H-series have medium eccentricity and high crush, and with the medium eccentricity that seems to mean they're maybe meant for lesser rpm?

The engine has 2.65/2.10 mains/rods with a 653 gram rod, 473 gram piston, and a 110 gram pin if any of that matters.

Thank you.

rickseeman wrote: ↑Sat Oct 21, 2023 6:09 pmH is supposed to be better

There is no "better". They are application specific.

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1972ho wrote: ↑Sun Oct 22, 2023 12:21 amOne thing that I know about both those series is the P is a softer bearing shell than the H series and is more forgiving if something happens,It basically won’t dig into the crankshaft and cause more damage (P) the H because it’s a harder shell will add to the crankshaft damage.

This. An old race engine (speedway and jetsprint boats) told me this years ago. His way was use the H series for mains to lock it all in and P series on the big ends for a bit of forgivenes. This is how I have done speedway motors for the last fifteen years.

1972ho wrote: ↑Sun Oct 22, 2023 12:17 pmDid you try reading the Clevite bearing instructions on there sight seems like remember something about the type crankshaft material that different bearings need to be used on also.Like nodular iron the H bearings they recommended not to used on they were mostly use the P bearings but that was something I read over 25 years ago when they had there full catalog of information available.

No sir, but I did see where if the crank is bending and flexing a lot that they did have a softer bearing to accommodate that situation also. That being the M-series intended for blown fuel engines.

Stranger wrote: ↑Mon Oct 23, 2023 11:35 pm

1972ho wrote: ↑Sun Oct 22, 2023 12:21 amOne thing that I know about both those series is the P is a softer bearing shell than the H series and is more forgiving if something happens,It basically won’t dig into the crankshaft and cause more damage (P) the H because it’s a harder shell will add to the crankshaft damage.

This. An old race engine (speedway and jetsprint boats) told me this years ago. His way was use the H series for mains to lock it all in and P series on the big ends for a bit of forgivenes. This is how I have done speedway motors for the last fifteen years.

This is good information right here.