SR20DET rebuild main bearing question. - Zilvia.net Forums | Nissan 240SX (Silvia) and Z (Fairlady) Car Forum

Garage Skidz · 11-19-2017, 12:24 PM

So i am rebuilding an s14 notchtop sr that had a spun #1 rod bearing, and i get to taking the crank out and find that on the block side of the main bearing journal the block is very slightly indented and discolored where the main bearing was. #1 and #4 mains are like this but #1 seems to be a little deeper.
the bearing didn't spin as i can see the lettering transcribed on the block from the back of the ACL race bearings it had. So is this a common thing? do i need to do anything about it, or does it not effect the bearing clearances enough to matter?
pics below of the #1 and #4 main bearing locations, crank and spun/destroyed rod.

PoorMans180SX · 11-19-2017, 12:47 PM

If you want to be safe, get the block line honed.

If you want to be informed, Bolt the mains down with the bearing shells in them, measure them with a good bore gauge, and compare those measurements against the OD of the crank journals (Measured with a micrometer). This will tell you the bearing clearances and if anything needs to be done to correct them.

These are the only two actions to take to be certain that clearances are absolutely correct and the engine will function properly. Plastigauge will not do it, a caliper is not accurate enough, and there is no sensory test that will tell you whether or not the clearances are right. Don't let people fool you with any of these methods.

Garage Skidz · 11-19-2017, 01:07 PM

thank you, and if i do need to get it line honed how do i get bearings that have a larger backing to fit? i know you can get oversize bearings but isn't that only for the crank journal side. i would think they would be lose after doing that.

PoorMans180SX · 11-19-2017, 03:07 PM

Quote:

Originally Posted by Garage Skidz

thank you, and if i do need to get it line honed how do i get bearings that have a larger backing to fit? i know you can get oversize bearings but isn't that only for the crank journal side. i would think they would be lose after doing that.

When they line hone, they actually surface the main caps so the bore is smaller, then hone the bore back out to factory size. So no larger bearing is needed.

11-19-2017, 12:47 PM	#2
PoorMans180SX Zilvia.net Advertiser Join Date: Nov 2005 Location: Michigan Age: 33 Posts: 5,431 Trader Rating: (16) Rides Gallery: PoorMans180SX Feedback Score: 16 reviews	If you want to be safe, get the block line honed. If you want to be informed, Bolt the mains down with the bearing shells in them, measure them with a good bore gauge, and compare those measurements against the OD of the crank journals (Measured with a micrometer). This will tell you the bearing clearances and if anything needs to be done to correct them. These are the only two actions to take to be certain that clearances are absolutely correct and the engine will function properly. Plastigauge will not do it, a caliper is not accurate enough, and there is no sensory test that will tell you whether or not the clearances are right. Don't let people fool you with any of these methods. __________________ Build: http://zilvia.net/f/showthread.php?t=643065 Friends don't let friends buy knock-offs.

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11-19-2017, 01:07 PM	#3
Garage Skidz Join Date: Nov 2017 Location: Charleston SC Posts: 15 Trader Rating: (0) Feedback Score: 0 reviews	thank you, and if i do need to get it line honed how do i get bearings that have a larger backing to fit? i know you can get oversize bearings but isn't that only for the crank journal side. i would think they would be lose after doing that.