ANVIL

Looking to install my rods in my rb25 but i need the bearing clearances... anyone know or show me where to look it up ?

KAT-PWR

Factory service manual

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ANVIL

Mine must be missing pages or something cuz i cant find it in the fsm

ANVIL

Bizarre..
Haha

Redownloaded it and sure enough that page was missing. Lol found it.

hanzbrady

Around .002"

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ANVIL

I keep gettibg conflicting information though.

Where did u find that spec hanz?

Acl standard sizes use different clearances than oem?

From the fsm says .020 - .040

hanzbrady

Well, bearing clearances are all really up to a few factors,

1) Engines intended use
2) Hardware used
3) Oil viscosity

and assuming you're doing an OEM rebuild with oem hardware around 2 thou would be in the limit, and on the "tighter" side which is what you'd want in a daily driver. Rod bearing clearances are also always slightly smaller than mains in case you were wondering about those too.

I want to say in my SR my rods are around 2.5 thou and my mains are closer to 3 thou

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hanzbrady

Also a "standard" ACL bearing is not the same size as a standard OEM bearing, the ACL will be slightly tighter due to it being coated.

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hanzbrady

Sorry to keep bumping this, but I just wanted to back what I said with some tangible evidence. The bearing clearances we run on David Briggs SR20det are:

Rods .002x"
Mains .002x"

And this is fairly standard like I previously stated.

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ANVIL

Thanks for all the replies. The more the better.

Its intended to be a summer DD / weekend warrior

Cp pistons/ Manley h beams with acl main and rod bearings

ANVIL

My main bearings clearances were all right about at .003

hanzbrady

Then shoot for .0017-.002" for your rods and right around .002" for your mains. We run these on engines we build for a shop that specializes in Skylines. Also make sure to check your rod and piston manufacturers torque and clearance specs as those don't follow oem rules.

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ANVIL

Thanks for the tips! Appreciate it a bunch!

And i already checked the rods and pistons and they came with the information for the specs so im good there... its just these bearing clearances that confuse me but i think i got it now

You think .003 clearance from plasti gauge measurement is ok for mains?

hanzbrady

That's on the "looser" end of the spectrum, that's what my SR mains are and that's an engine I'm planning to drive harder and hotter, hence needing the room for expansion.

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ANVIL

Hmm. Well with time i think i will be pushing it harder and harder. What negatives can happen being on the looser end of the spec?

hanzbrady

Well it's not going to initiate any code red self destruction sequences, you're still in spec. Just run a thicker oil like 10w30 and do 3k oil changes and you'll be fine. The extra clearancee is a cushion for thermal expansion that occurs with harder driving.

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Sforteen

You guys need to specify what unit of measure you are using.. metric or standard. the factory manual is metric... Most people including myself refer to an Inchs measurement.

.0015-.002 inchs is right where i have mine...

500-800whp 9k RPM going on its 7th year.

hanzbrady

I've been giving measurements in standard hence the (")

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