engine bearing questions???

[sunnys14]

after reading about engine rod failures from FIZNAT and MARKEMARK, my dreams of 300rwhp of stock rods have come to an end... i decided to get some wiseco pistons 9:1 comp ratio .20 over, crower rods, cosmetic headgasket, toda main bearings and rod bearings. i was shopping on horsepowerfreaks.com and i saw that the main bearings and rod bearings have oversizes ranging from 10 and 20 over. does this mean i have to get 20 over main bearings and rod bearings since i am getting 20 over pistons??

[sunnys14]

also, horsepowerfreaks.com sells 2 types of connecting rods.... bushed fit and pressed fit? what does that mean? which one is better?

[sunnys14]

anyone?

[:: orion ::]

300rwhp is EASY on stock internals...if that's your goal, don't bother building the motor.

I've been running ~12psi and making ~300rwhp for over a year now...all stock motor. I shift at ~7000, run autocross and road course HPDE's as much as possible...it'll withstand that low of a HP level.

Now, if you want ~350 and above, build it.

- Brian

[PapaSmurf2k3]

after an interesting and very informative conversation with fiznat last night, I can actually answer this question. No, you dont need oversized bearings just beacuse your getting oversized pistons. You will need to "plastiguage" your bearings in order to find out if they are in spec, and then determine if you need to hone your block, in which case youd need oversized bearings. This is all pretty new to me so I might have something wrong. after learning about all this plastiguage crap, I now know why so many people just let the machine shop take care of the fine details.

[sunnys14]

i have to get pistons for sure because my rings blew... so youre saying i dont need rods at all? the most i was going to do was 14psi on a t04e daily driven. what about engine bearings and rod bearings? what size? or i shouldnt need to replace them?

[eh?]

You need to measure your rod and main journals to determine what size you need, if you don't do that you'll be replacing the engine in no time.

[sil80drifter]

after an interesting and very informative conversation with fiznat last night, I can actually answer this question. No, you dont need oversized bearings just beacuse your getting oversized pistons. You will need to "plastiguage" your bearings in order to find out if they are in spec, and then determine if you need to hone your block, in which case youd need oversized bearings. This is all pretty new to me so I might have something wrong. after learning about all this plastiguage crap, I now know why so many people just let the machine shop take care of the fine details.

aaaaaaaaaaaaaa! papa smurf!!! what are you saying?! :

Here is the deal:Your stock bearings are matched to your crank. If your crank is worn or is out of spec (which can be measured by plastigauge), you'll need to "cut" the crank, and get accordingly larger (thicker) bearings. This goes both for rod and for main bearings. Otherwise, if you get new stock size bearings and the plastiguage shows they are in spec, you can use them.

The honing of the block (or the cylinders to be exact) occurs for the sake of the pistons (or piston rings to be exact). When you get new pistons, it is advised to get them one size larger than the old ones (unless you cannot oversize anymore due to the largest possible size already being in there), which means you'll have to first bore the block to the larger size and then hone it for the sake of breaking in the new piston rings.

don't mix terms and definitions. It could drive someone to misconception.

sil80
Modified by sil80drifter at 11:23 AM 8/18/2005

[sunnys14]

well damn! i wanted to order everything first and not have to wait till later to get them ordered.

[DjPantsSpecR]

i just replaced all my bearings, and i used my own copy of Nissan Fast to get my part numbers, and then i handed them that sheet and demanded a large discount, which since i'm always in there, i got. Sorry, on to the point.

Using plastigage to measure the clearance you already have is a great idea. Now if you have the block upside down adn the oil pan is off there will be a number stamped to the side of each bearing cap (even though it is technicall only one cap). This number tells you what clearance you need for you main bearings.

The rod bearings grade are stamped onto the first balance weight on the crakshaft in order.

to give you an idea, my main bearings were: 1-2-3-2-1 and my crank bearings were 1-2-2-1

those are the numbers, now you have a little more research ahead of you to figure out the size bearing you need, so bust out that FSM!

[sil80drifter]

no.

those numbers on the crank and block (and top of the block for pistons) really don't mean anything unless you're using OEM Nissan bearings. They have their own grades and numbers, and those only go for WHAT IS ALREADY INSTALLED. When you install new bearings, you cannot order them individually "by size", you can only get all 4 rod (or 5 for mains) sets stock size, 1 over and 2 over (sometimes even 3). They will all be the same size. When you have them, you can put them into the block, use plastiguage, bolt the rods and main girdle up, unbolt it and see if the plastiguage shows the bearings to be within spec. If they are in spec, you install them. If not you'll have to have the crank machined to fit them. This is why you can never go wrong with oversized rings, because you'll just machine the crank to them once and they will be a perect fit. When you (like me) take a risk, and get stock sized bearings hoping that they will fit, you are on your own. Thankfully mine did fit and were in spec so I installe them.

My reasoning was that since my old stock sized bearings didn't wear (if they did that would be really bad) then aftermarket stock sized ones should be just as good, since they are made to be the same size, but new.

I've made an entire post about the numbers on the crank and block, and even attached an XML spreadsheet to put in your numbers and see what you need to get from the dealer, but that is for dealer bearings and pistons and rings only.

this link should help you out:

zerothread?id=101885

sil80

[DjPantsSpecR]

yes, but like i said if you have the numbers and you have an FSM you can figure out the clearances, but thanks for telling me i was wrong anyway.

why would you have to machine the crank to put in new rings?

I also had zero problems putting stock sized bearings on my mains and rods and this was on one of the dirtiest engines i've ever seen.

[sil80drifter]

sory i typed rings instead of bearings.You MAY have to machine the crank to put in new BEARINGS. If they are oversized and your crank is stock.

I have put stock bearings (non OEM) into stock block as well, and it seems to be fine. What I said is that those numbers don't mean anythig to us because unless a Nissan mechanic replaces the bearings, you will not be able to get a separately graded bearings from them. All the numbers tell you is what the bearing grades were when they assembled it. What you put into the engine when you replace them is something different. You always go with one "grade." It's either stock or oversized (+1, +2, etc).

sil80
Modified by sil80drifter at 4:22 PM 8/18/2005

[DjPantsSpecR]

i think you need to read what you typed guy: "This is why you cant go wrong with oversized rings, because you'll just machine the crank to them..."

so take it easy guy

[sil80drifter]

hey come on, what's a typo between KA-T enthusiasts?

sil80

[DjPantsSpecR]

i know, i'm sorry i was just being an *** cuz i felt the advice you gave was the same i give, but after thinking about it for a while, if i werent using OEM bearings i would use plastigage FIRST, to get a good average of where my bearings would sit in, rather than relying on stock grades and wasting a bunch of time calculating.

you gotta plastigage anyway afterwards, i was just biased toward using stock bearings, but thats clearly not whats being asked so i am, in fact, the ***. good day