I bought a GSR longblock from my friend for pretty cheap because it was "knocking". He pulled it before I could ever hear the noise so im not really sure how bad the knock was. I got it with the intention of taking it apart, rebuild it and boost it. I figured the knock was a spun bearing.

I got it apart and none of the bearings had grooves or were black. The piston walls all look fine, so im kind of lost as to what the knock was...

My question is should I have a machine shop grind the bearing journals and get oversized bearings, just to be safe?

Also should I get the cylinders bored out to 81.5mm or just leave them stock?

What else could the knocking have been?

 

I personally, would send the block,head,and crank to the machine shop. Have th e crank inspected. micrpolished and balanced. Have the block decked and bored to atleast 81.5mm, and get the head decked as well. Then buy some forged pistons and rods and valvetrain. (dont forget oil & water pump , gaskets etc).

 

Knocking is what happens <U>BEFORE</U> you spin a bearing. Cars can have a rod knock for many miles before they spin a bearing. It just means that the clearances are too loose. You need to measure the bearing clearances to see if they are out of spec. It's relatively quick/easy with some plasti-guage strips to check it. If the ring seal is good and the valves are good (do compression and leakdown tests to determine if they are), then you could just replace the bearings and go, provided the crank hasn't been severely scored. Inspect the crank if any of the bearings were loose to make sure that it isn't damaged.

 

Well I already have the engine totally apart, so should I plasti-guage it with the old bearings, torque everything to spec, then if any of the clearances are too much I should get the journals grinded down and the crank micro-polished and new oversized bearings

 

Plasti-Guage: Yes

Grinding anything: No

Doing anything to the crank: No

Oversized Bearings: No

Bearings are soft metal. Generally if you catch them while they are just knocking you don't have damage to the crank or journals. Check your clearances and reassemble with correctly sized bearings. I generally like the Clevite bearings, they tend to run to the loose end of the acceptable range. Honda also makes bearings in a range of sizes.