Stock Rods

Post by **WDRacing** » Fri Nov 28, 2003 5:12 pm

I've looked at the stock rods, once they've been balanced and polished. They actually look pretty damn good. Has anyone actually broken a rod that wasn't from detonation or over revving?? Out of all the engine problems I've seen with all Nissan's it has always been a piston ring land or the piston itself that has been the problem. I haven't seen a rod snap yet.

I'm only wondering for the sake of comparison. Example, for the price of rods, I could have my head ported or a set of cams done up. The main goal for most enthusiats is obviously the most bang for the buck.

Please try to keep this thread on topic atleast a little guys...heh.

WD

Post by **robertwb70** » Fri Nov 28, 2003 5:12 pm

I don't think any engine has ever broken a rod from detonation

rods break from too much RPM-detonation destroys pistons and valves/heads

Post by **WDRacing** » Fri Nov 28, 2003 5:12 pm

My point was that 99% of all engine meltdowns result from detonation, without the user ever actually reaching the materials brake point from inertial stress.

WD

Post by **TrunkMonkey** » Fri Nov 28, 2003 5:12 pm

i've never heard of a 240 rod breaking just from too much stress.

sad to say, engine builders love it when people dump tons of money into their street cars so it can be "bullet proof", knowing very well that most of their customer's street cars will never produce enough power to warrant such aftermarket forged internals.

i've seen so called "bullet proof" bottom ends suffer the same disasterous demise as stock engines.

9 times out of 10, it's not the engine that fails, it's the tuner.

-demetrius

Post by **andrave** » Fri Nov 28, 2003 5:12 pm

I knew a guy that broke 2 sets of stock rods, first one stock, second ones were shot peened at a shop and all, and he was trying to rev to above 7000 rpm... so I *think* without ever actually seeing the rods or the engine that it was probably his rpm's that killed the rods.I also know several guys with NA engines that killed stock rods but they also use high power bands.everyone that I have seen break stuff on turbo ja's breaks pistons and ringlands and rings....

Post by **SingleCamSam** » Fri Nov 28, 2003 5:12 pm

It seems like most of the stress from making large amounts of torque would go to the rod bolts rather than the rod itself. In any case i'd trust the stock rods to over 400hp. They are forged an shot-peened from the factory just like those found in the SR20, which has been proven to hold that much on stock internals. Like you said our crapola pistons are the real weak link.

Checkered-Member · Post by **Checkered-Member** » Fri Nov 28, 2003 5:12 pm

there is a shop around here that specialize in Nissans, turbo and NA application, these people know what they are doing, and when building the engine they don’t replace the stock rods, only get some APR bolts for them. I guess KA rods are sturdy enough...

Post by **tapdeznutz** » Fri Nov 28, 2003 5:12 pm

sweet topic WD. so i know to keep my stock rods. now u mentioned getting the polished or sumthing. is there a benefit to having them cleaned up in that manner (e.i. lighter or whatnot)? also i remember hearing about having the piston/rods balanced. are they already balanced from factory and/or is there a benefit to having them balanced when sending them out to get cleaned up and checked?

thankx

jay

Post by **littlemilla3** » Fri Nov 28, 2003 5:12 pm

tapdeznutz wrote:sweet topic WD. so i know to keep my stock rods. now u mentioned getting the polished or sumthing. is there a benefit to having them cleaned up in that manner (e.i. lighter or whatnot)? also i remember hearing about having the piston/rods balanced. are they already balanced from factory and/or is there a benefit to having them balanced when sending them out to get cleaned up and checked?

thankx

jay

It would be a good idea to get them re-balanced. Over their lives they can probably get out of balance I would expect... A well balanced engine will rev higher and be much smoother. New pistons must be balanced too.

Post by **goldenchild** » Fri Nov 28, 2003 5:12 pm

i like what im seeing

Post by **SSS** » Fri Nov 28, 2003 5:12 pm

Plus on top of the shot peening/nitriding you might get done, cryogenic treatment is also cheap insurance.

Post by **machinehead** » Fri Nov 28, 2003 5:12 pm

SSS wrote:Plus on top of the shot peening/nitriding you might get done, cryogenic treatment is also cheap insurance.

I second this. cheap and will make the rods stronger then sr rods. But if there are any mircoscopic stress fractures on the rods, nothing will save them

but then again, thats unlikely unless the previous owner was a douche

Post by **ca240** » Fri Nov 28, 2003 5:12 pm

i remember hearing that since the stock rods were shotpeened from the factory you shouldn't shotpeen them again cause it'll weaken them or somethin...this true?

Post by **TrunkMonkey** » Fri Nov 28, 2003 5:12 pm

ca240 wrote:i remember hearing that since the stock rods were shotpeened from the factory you shouldn't shotpeen them again cause it'll weaken them or somethin...this true?

not true. it won't weaken them, but unless you have work done to your rods (have them polished) there's no need to have them done again.

-demetrius

Post by **BREEZY240SX** » Fri Nov 28, 2003 5:12 pm

SingleCamSam wrote:It seems like most of the stress from making large amounts of torque would go to the rod bolts rather than the rod itself. In any case i'd trust the stock rods to over 400hp. They are forged an shot-peened from the factory just like those found in the SR20, which has been proven to hold that much on stock internals. Like you said our crapola pistons are the real weak link.

Sorry to dig this thread up again, but I think it might answer the very question that I have been searching these forums for. You say that the stock pistons are forged and shot-peened? Are you sure about that? Until now, I hadn't heard anything to confirm it, but I knew that it had been rumored. The reason I ask, is that I have a '91 KA completely torn down to the block right now. I am going to turbo it and I bought the forged pistons already, but I was unsure of the rods. I had heard somewhere else before that the crank and the rods were forged, but couldn't find any definate info to back that up.

To make a short story long....... (Just kidding!), is this true and if you don't know for sure, are there any other useful sites that you can direct me to?

Thanks!

-BREEZY240sx

Post by **SingleCamSam** » Fri Nov 28, 2003 5:12 pm

Crank and rods are both forged.

Post by **andrave** » Fri Nov 28, 2003 5:12 pm

not pistons though.

Post by **SSS** » Fri Nov 28, 2003 5:12 pm

Damn straight. If the pistons were forged stock, i wouldn't be pulling down the spare block i've got sitting here.

Post by **andrave** » Fri Nov 28, 2003 5:12 pm

BREEZY240SX wrote:Sorry to dig this thread up again, but I think it might answer the very question that I have been searching these forums for. You say that the stock pistons are forged and shot-peened? Are you sure about that?

thats what I was referring to...

Post by **02_silver_wagon** » Fri Nov 28, 2003 5:12 pm

how much whp would you guys say re shotpeened rods with arp bolts would be able to handle?

Post by **hayato kazami** » Fri Nov 28, 2003 5:12 pm

my friend driving a 93 240sx with 200km, still in good condition! he still try to race with it and still fine, he just have to replace the water pump.....

Nissan engine, like a rock...... ^-^

Post by **02_silver_wagon** » Fri Nov 28, 2003 5:12 pm

Do you guys think reshotpeened rods with arp bolts could handle 400 crank hp?

Post by **LarryStooge** » Fri Nov 28, 2003 5:12 pm

im responding to this since i have experience in the matter of shot peening and polishing. I work for http://www.ccwheel.com and we shot peen the centers of our 3 piece wheels. Shot peening is a process (im explaining it for those that dont know) that takes a peice of metal and throws tiny tiny little beeds of iron at it at high speeds. Its done with a blow through system, sort of a vacuum effect. It pounds the surface down and hardens it (the surface). To acheive best results, polishing the surface before shotpeening is best. You polish a surface to smooth it out and to clear any scratches/uneven surface, this makes it stronger (not by much) because there isnt anything to pull the metal apart by, jsut smooth surface. Basically, think of magnifying a surface, the tiny scratch or uneven surface becomes a canyon, this is a surface that will cause pull on the metal, and eventually make a crack (if exposed to enough stress). We have found best results with our wheels (we put them through extensive testing, and the numbers that show the strength prove it!) by having a smooth polished surface on the metal before shot peening, this allows shot peening to do its job better, therefor making the surface as dense as possible. As far as weakening a surface by shot peening it more than once, we shot peen our centers 2-3 times to make sure the entire surface is exposed, and the test results show no ill-effects. Also, if any local guys need a shot peen job on anything (susp parts, etc), just let me know, I'll do it for ya as a service to the 240.

Post by **McAdam** » Fri Nov 28, 2003 5:12 pm

I;ll toss in what I;'ve heard... all nissan cranks are forged from the factory. only real crappy cranks were the VG30E's out of the first gen 300zx. I have seen one snap in half. Most nissan rods are forged (if not all) from the factory. There is a guy on AZ240sx.org that has a 505rwhp, T66 powered KA24DE. he said he regrets getting forged rods, because he beleives the stockers could do the job AS LONG AS YOU DON'T REV THEM! keep it under 6500 to 7000 and you should be fine. I have no reason to doubt this guy, 505rwhp on a KA speaks for itself. and yes, I saw the dyno chart and the underside of his hood.

McAdam

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