Anyone know about sr rod bearings???

[TheSnail]

My Sr block is at the machine shop, The guy said I needed new rod bearings, so I went to nissan and was about to order new rod and crank bearings, but there is like six different types, 0,1,2 grades, I was going to order the grade 2 thinking it is better material, but I stoped myself and went home to do reserch. It turns out that it is a matrix of number consisting of matching the numbers on the crank and the block. Does anyone know the stock grade rod bearing to use for a red top sr20det? Your help is greatly appriciated.-Voya

[gani]

You will need to check the 5 numbers on your block for the Main Bearings and add them to the 5 numbers on the crank, For the rods just order the ones that are on the crank, no math needed. sr20deTo determine the grade number without measuring add the numbers on the block to the numbers on the crank. Example: from Main#1 to Main #5Block = 11211Crank = 21121 Bearing grade numbers would be from main#1 to Main #5 "32332"

[TheSnail]

Okay I finally got it, that took me a two hours to figure out,lol. I was thinking there was more to it. Cool. But wouldnt all redtops share the same code, if so does anyone know it is? if not I will just go to the machine shop and pull out the TI-89,lol. Thanks, Gani.

[IvoryJ30t]

not all of the blocks/cranks are manufactured to the same exact spec.

the differences in grade are .0001 inch

[slow s13]

If you have the SR FSM downloaded its in engine mechanical EM-63

[TheSnail]

So what if a just get all grade 2's?

[TheSnail]

I have the fsm, I was looking at it, but it does not give the code, it just tells you how tog et it.

[slow s13]

yeah its on the crank and block because each one is a little different. The bearings arent allways the same size, It seems to me that the guy doing your rebuild should know how to do this. And the grade numbers arent how good they are its the size of the bearing, a grade 2 isnt better than a 1 its just a different size.

[TheSnail]

I know its the size, but since its by increments of .001" I will go on the safe side by getting all 2's, since I dont want rod knock in the near future.Thanks, Voya

[IvoryJ30t]

what is so hard about this. get the correct grade of bearing or it will wear out faster from the lack of oil or excessive clearance.

get the proper grade!!! unless the journals are worn and require machining, then you need to refigure the grade you need. DO NOT PICK A GRADE BECAUSE YOU LIKE THE NUMBER!!!!

[TheSnail]

I want to get 2's to make sure there is no clearence, I dont know if I should get the stock ones due to too much clearence, but I will see with the machine shop guy and get his opinion on the condition of the journals. I would rather be on the safe side getting 2's then getting bearings that are to small, which would create rod knock 5k down the road.

[IvoryJ30t]

if you get bearings with too little clearance, you will sieze the motor up or spin a bearing a few blocks after you start it.

measure the journals and choose the correct bearing. this is a VERY IMPORTANT procedure. you dont just guess on this.

[IvoryJ30t]

a bearing with too little clearance will die sooner than one with excessive clearance.

the crank rides on a film of oil, not the bearing. there must be a specific clearance maintaned for the oil film.

[TheSnail]

"if you get bearings with too little clearance, you will sieze the motor up or spin a bearing a few blocks after you start it."

Crap , I didnt think about that. I will get the two numbers and do the addition to get the right size. Sorry, I was kind of being lazzy and just letting the machine shop guy fit the two's. I will figure out the right size tomarrow. Thank's Ivory for not letting me do something stupid.-Voya

[IvoryJ30t]

yeah, its not as simple as it sounds. you need specific even clearance across the journals. have him measure, and get the correct sizes.

in the FSM, there should be a chart that you match the OD of the journal, to the chart, and it tells you the correct grade of bearing.

[TheSnail]

Hey Ivory, I got a question. You know how there are 5#'s, 1-5, I dont understand why there is five if there is four rod bearings. I orderd the crank bearings since there was only one grade, so what is the 5th one for? And Im guessing 1 is the first rod bearing and not the front crank bearing.

[TurboB15Sentra]

The way I do it when I blueprint a bottom end.... is use a micrometer to measure the main and rod pins on the crankshaft..I then buy the grade of bearing that the engine calls for.. and install them. Next, I bolt the girdle onto the block and TQ down to spec without the crankshaft in it. So, you would have the main bearings in place.. just no crankshaft in. Then, using a micrometer, measure the inside hole with the bearings in. Write that down for all 5 of them. Now, subtract the number from each main pin that you measured earlier from it's corresponding hole that you just measured. In other words... Pin one on the crank.. Subtract that number from the number you got when you measured hole number 1. This gives you the difference in size.. or the clearance. From there, you can determine if you need to go up or down in bearing size.. or stay the same. Do the same with the rods.. Put the bearings in, and Tq the caps down to 33ft lbs. Measure the rod pin on the crank.. and then the hole on the rod with the bearings in. Take the difference and that's your clearance. The reason I say to do this.. is because I have seen MANY motors off from factory spec. From heating/cooling the motor hundreds or thousands of times... the metal can shift/distort, throwing off the clearance. It takes a little longer to do.. but it's well worth if you want a long lasting, reliable motor.

Travis

[Nathan]

The way I do it when I blueprint a bottom end.... is use a micrometer to measure the main and rod pins on the crankshaft..I then buy the grade of bearing that the engine calls for.. and install them. Next, I bolt the girdle onto the block and TQ down to spec without the crankshaft in it. So, you would have the main bearings in place.. just no crankshaft in. Then, using a micrometer, measure the inside hole with the bearings in. Write that down for all 5 of them. Now, subtract the number from each main pin that you measured earlier from it's corresponding hole that you just measured. In other words... Pin one on the crank.. Subtract that number from the number you got when you measured hole number 1. This gives you the difference in size.. or the clearance. From there, you can determine if you need to go up or down in bearing size.. or stay the same. Do the same with the rods.. Put the bearings in, and Tq the caps down to 33ft lbs. Measure the rod pin on the crank.. and then the hole on the rod with the bearings in. Take the difference and that's your clearance. The reason I say to do this.. is because I have seen MANY motors off from factory spec. From heating/cooling the motor hundreds or thousands of times... the metal can shift/distort, throwing off the clearance. It takes a little longer to do.. but it's well worth if you want a long lasting, reliable motor.

Travis

This is exactly what I was about to suggest, this should NOT be a problem for the machine shop to do for you, if it is...find a new machine shop. It might cost you a little extra in labor to go through the steps to mic the bore of the mains and the rod pins etc. but it is WELL worth it to get the right size bearings in there. You COULD just buy thick bearings and have the rod machined to fit it perfectly, but its better to just start with the right grade.

[VitaminT]

Is this method recomended over plasti-gauging? Especially for a home user that might not have a nice mic gauge.

[Nathan]

Well, its much more accurate than plasti-gauge, but its also very expensive to buy a GOOD bore mic. I've seen them go for about 170 and those were only accurate to .0005 inches. The really good ones can be closer to 500 or more dollars. Plasti-gauging can still be effective, this is just the ideal way You could take the block and crank to the machine shop to JUST have it measured, shouldn't be too ridiculously expensive

[TheSnail]

This crap is indepth, I thought I was just going to pick up some rod bearings at Nissan, and hand them to the machine shop guy, but Im having trouble doing that. I am supprised that people would ever need to be as accurate as .0005, thats crazy. Dont get me wrong, I put am the one that assembles the motor but I do + or - 1-2 foot pound of torque and you guys are talking about a fraction of a mm, screw that, I am not going to mess with that crap, I dont trust myself to that accuracy, I will let the machine shop guy do his thing. I hope all this bearing stuff works out and I dont pick the wrong one. Thanks for all of your responces.-Voya

[Nathan]

Well, when the entire crank rides on an EXTREMELY thin layer of oil measureable in microns....0005 inches is enough to matter

[TurboB15Sentra]

We (import guys) always rave about how our little 4 bangers hold up so well making big HP. The reason why is because of things like what we are talking here. Precision and attention to detail have to be paid in order for it to work right and last. Old Chevy smallblock's... hell.. 3 thousanths clearance on the rods.. and they're fine. 3 thousanths clearance on an SR pumping out 400whp.. and I promise you.. it won't last very long.

I don't even allow plastiguage in my shop... If you don't have the right tools to assemble your engine... take it to a competant machine shop that can. Not saying this to be mean or anything... but you'll be kicking yourself in the *** if in 5000 miles, you've got a nice hole in the side of your block and your SR20 is now a SR15. :-p Do it right the first time!Travis

[IvoryJ30t]

Hey Ivory, I got a question. You know how there are 5#'s, 1-5, I dont understand why there is five if there is four rod bearings. I orderd the crank bearings since there was only one grade, so what is the 5th one for? And Im guessing 1 is the first rod bearing and not the front crank bearing.

because there are 4 sets of rod bearings and 5 sets of main bearings.

since your machine shop guy most likely does not have documentation on an sr20det motor, download the FSM from somewhere and and pay very close attention to the oil clearance.

thats why i dont like to open a motor if i dont have to. ill get extremely obsessive about the specs and it will take me forever to put the scales and the micrometers away and put the thing back together.

[IvoryJ30t]

you know your obsessed when you have things like wrist pins, bearing halves, and rod bolts on the digital drug scale.

[Nathan]

since your machine shop guy most likely does not have documentation on an sr20det motor, download the FSM from somewhere and and pay very close attention to the oil clearance.

A good suggestion here, I went so far as to download the entire engine mechanical section and gave it to my machine shop. When I got it back it was nice and worn looking with grease all over it, I was most pleased they used it

[TheSnail]

Wait the machine shop guy told me to get rod bearings, so would I not have to match anything up since the 5 number thing is for the main bearings? The thing is, the guy at nissan said when I orderd the main bearing set, that there is only one kind, but there is 6 dif kinds of rod bearings. He might not know what he was talking about, since he admited he did no know.

[Nathan]

Without looking at the FSM, I can tell you with 99% certainty that there ARE different grades for both rod AND main bearings. Nissan is anal retentive about clearances (thank you Nissan!) so I'm certain that there are different rod bearing grades offered by Nissan. If you cant find them, then you could order up a set of Clevite 77's, they are most likely made for SR20DE's too. I KNOW Clevites offer different grades. Also, if you get a grade that is too thick, its not too hard for the machine shop to hone out the rods to fit the new bearings perfectly. My recommendation to you at this point is to print out the engine mechanical section of the FSM, take it to the machine shop, explain you are having a hard time figuring out the bearings that you need and want them to do it, and order them for you. Give them free liscense to hone out the big ends of the rods, align hone the mains etc. to fit the bearings in with proper clearances. It might cost more but trust me, a perfectly rebuilt motor is worth every penny.

[s13sr20chris]

plastigauge is ok for just a turd beater that you want another 100k out of, but do it right on a performance motor. i see a lot of guys not even measureing the stuff. they just get the bearings in the grade indicated and slap em in there. one time a guy built a motor that way and one was too tight. after a 15 minute drive the oil was solid white. the bearing babbit(sp?) broke down. he had to do it all over again.

[TheSnail]

I think im just going to give nissans number along with 120$ for all bearings to the machine shop guy and let him figure it out, he's the profesional, It's to much for me.