The purpose of grades of internal components?

[sil80drifter]

Does anyone know the exact purpose of grades of the OEM KA24E/DE engine components such as pistons and main/rod bearings? When I tried to order some aftermarket ones online and asked them about my respective grades retrieved from the block/crank/pistons, they said:

"Thats not how aftermarket suppliers work,they are all grade 1 you just order them by size and both in pistons and bearings(std,010,020 etc)Sincerely,PhilTech/Sales DeptFlatlander Racing/IPP(603) 378-0090"

What do you know about this? Please don't tell me to go measure my stuff and order what I need, as I will do that later, but right now I want to know what relation the grades have to the sizes of the components.Here is the odd thing: One of my spare blocks has the following piston grades (1 through 4): 1 1 2 2. The other has 2 2 2 2. What difference does it make?

sil80

[navysnail]

bearings are made to precice clearances, so when assembling the engine they use a micromiter and then select the proper bearing. yours should be stamped on the parts

[s13sr20chris]

i think some aftermarket companies prob use the grade sys. the rest just make one size and assume you will do any neccesary machine work.

[s13sr20chris]

oh, and the purpose of te grades is to get everything PERFECT.

[sil80drifter]

I looked at my block and pistons and I know what grade I need (from Nissan), but I'm wondering if I can get away without machine work if I just get all standard sized after market parts. I happened to e-mail a technician from Clevite and he said:

"The O.E. makes a ton of pistons at once, and they put a number (Grade) on each run. Those pistons are size and weight matched so that they don't put 2 different weight pistons in the same engine. It does not necessarily mean different size pistons. Sometimes it does though I know like in the case of the Chrylser 4.0L jeeps.

In the aftermarket you buy a piston first, then bore your block to fit the pistons, so there are no grades. So as long as you replace as a full sets, and you are not doing a high performance build, you will be fine."

All I really wanna know is, if I have this stock engine (with 70k miles on it), and I wanna replace pistons/rings/bearings, can I just order aftermarket ones that are standard sized, and not have to do any machine work?I really don't wanna spend time/money on machine work.... *sigh* stock is stock dammit.I hope.

sil80

[180fan]

Order from Nissan, and you will not have to do any of that mess. Just fiddle with the grades that are stamped on your pistons/crank/block and you'll be fine. Only work you'll need to do is fitting the rings picture perfect. Buying from aftermarket brands if you're using stock everything else just isn't worth it if you've gotta go through a machine shop, etc. It'll cost you alot more in the end. Besides, if the place you're trying to buy bearings from has been doing it long enough with a good knowledge of the particular motor that they're selling the bearings for, then they'd have the grade system as well. Another way to think of this, an engine rebuild is very critical. On very critical stuff, skimping is not a good idea. Also, if you're on a tight budget, the length of time it'll take to do the rebuild will also go up. Reason, you just don't got the cash to blow to make it happen in a short amount of time. My rebuild I figured would take about a month or so with my schedule of work and school. Guess what, I'm on month 3 going to 4 (but I'm getting some pretty snazzy parts though) to make it a monster when it rolls out. So take your time. You won't regret it.

[s13sr20chris]