RB26 Main & Rod Bearing Clearances

[sickness14]

Hello.

I need some information regarding the Crankshaft bearing clearances and Rod bearing clearances. I have ordered ACL race bearings after having the crank machined and have 3 thousandths of an inch of clearance on the mains.

does anyone have documentation showing what the clearances are supposed to be so that i can give it to the machine shop? Any help would be greatly appreciated.

Thanks,John

PS: found this , but cant make any sense of it...

http://www.powerenterpriseusa.....html
Modified by sickness14 at 6:17 PM 10/19/2009

[krayton]

back of the fsm for your engine should have it.

i know r33 fsms have all the rbs specs and ish in the back of the fsm

[Darius]

That is normal for the mains.

Per the FSM page SD-9, the RB25/26 large end oil clearance is approximately 0.020-0.040 mm. Since I assume you used plastigauge to find the 0.003" value, you are golden. 0.003"=0.076mm. Divide that by two oil surfaces (0.076/2=0.038mm). That is on the bigger end of the range, but still within spec. Perfect for a higher hp application! Assemble away!

[sickness14]

That is normal for the mains.

Per the FSM page SD-9, the RB25/26 large end oil clearance is approximately 0.020-0.040 mm. Since I assume you used plastigauge to find the 0.003" value, you are golden. 0.003"=0.076mm. Divide that by two oil surfaces (0.076/2=0.038mm). That is on the bigger end of the range, but still within spec. Perfect for a higher hp application! Assemble away!

Darius,

I looked on pg SD-9 in the FSM for R34 and it talks about the manual trans gear specs but nothing about the engine. We used a feeler gauge to find the 0.003" value. I dont understand what you meant by dividing by two for the oil clearance. we measured the crank, and measured the block with caps assembled to get two numbers, subtracted them from one another to get the overall clearance. now we're trying to figure out how much of that clearance is for oil so we can figure out if the stock sized bearings will be sufficient. im not sure if i understand about the dividing by two thing. thanks for the help man! if possible, could you show me where in the manual those numbers are by posting a link to a pdf, or screen shot uploaded to like photobucket. i just want to see why my manual is different than yours. it is a R34 FSM right?

[Darius]

These measurements were taken from the R33 FSM. I didn't see anything in the R34 FSM, but I didn't search hard either. Either way, it doesn't matter since they're the same.

You can't measure bearing clearances very accurately with a feeler gauge. Pick up some plasti-gauge from the store for $0.25/ft and use that to measure the oil clearances on each journal.

You have to take the measurement of the plastigauge and divide by two because there is an oil film between the crank and bearing on each "side". So if you have an oil film of 0.020mm then the dry measurement between the crank journal and bearing surface should be twice that (0.040mm) since there is no oil film supporting the crank from underneath when its not running. You'll see what I'm trying to say when you get the plastigauge on there.

[sickness14]

These measurements were taken from the R33 FSM. I didn't see anything in the R34 FSM, but I didn't search hard either. Either way, it doesn't matter since they're the same.

You can't measure bearing clearances very accurately with a feeler gauge. Pick up some plasti-gauge from the store for $0.25/ft and use that to measure the oil clearances on each journal.

You have to take the measurement of the plastigauge and divide by two because there is an oil film between the crank and bearing on each "side". So if you have an oil film of 0.020mm then the dry measurement between the crank journal and bearing surface should be twice that (0.040mm) since there is no oil film supporting the crank from underneath when its not running. You'll see what I'm trying to say when you get the plastigauge on there.

Thanks Darius. i downloaded the R33 FSM and found all of the good stuff! The shop says they used a feeler , ill have to see if they can use a plastigauge too. They're saying the clearance they found with the feeler is .003" and the max i can run is .0035" within spec. I just want to be sure this is correct.

[Darius]

Technically, 0.0033" is the max clearance to stay within the FSM spec. 0.0035" is splitting hairs so it isn't a big deal. I just don't see how they could assemble the bottom end and get a feeler gauge in between the rod and crank journal and still get an accurate measurement.

Why aren't they using plastigauge anyways? It is fool-proof and absolutely dirt cheap insurance. I'd hate to have them feed you a line of BS just because they don't want to spend the 15 minutes to do it right and record the numbers for your piece of mind. No matter the machine shop, they have fuked up someone's motor at one point or another. No skin off their back. You have to keep on top of them to make sure they do a good job on your stuff.

[sickness14]

Technically, 0.0033" is the max clearance to stay within the FSM spec. 0.0035" is splitting hairs so it isn't a big deal. I just don't see how they could assemble the bottom end and get a feeler gauge in between the rod and crank journal and still get an accurate measurement.

Why aren't they using plastigauge anyways? It is fool-proof and absolutely dirt cheap insurance. I'd hate to have them feed you a line of BS just because they don't want to spend the 15 minutes to do it right and record the numbers for your piece of mind. No matter the machine shop, they have fuked up someone's motor at one point or another. No skin off their back. You have to keep on top of them to make sure they do a good job on your stuff.

Most definitely. I'll have to talk to them and see if i can get them to use a plastigauge and be sure. I would feel better about it as well. I dont need to rebuild it for a 4th time...

[sickness14]

The shop decided we're spot on with the clearances so we're moving to the next step!