Help! Noisy BP!!!

[Pocket_Rocket]

My freshly swapped BP makes a loud noise, kinda like running an engine without oil, but slower than valvetrain noise, like some kind of knock or something. Any ideas? I checked my oil,and it's still full and crystal clear, with no metal shavings whatsoever.

[FB71]

kinda follows engine RPM? Sounds like one knock per revolution? Gonna guess its a rod knock, possibly piston pin. Oil would still be clear with either failure.

[Pocket_Rocket]

kinda follows engine RPM? Sounds like one knock per revolution? Gonna guess its a rod knock, possibly piston pin. Oil would still be clear with either failure.

Exactly, follows engine revs, like the sound is only coming from one piston. The sound is kind of irregular; sometimes it stops and comes back again after a few seconds. The engine also stalls occasionally with a sometimes rough, or lopey idle, but I figured it was because the ignition timing and idle settings are not perfect yet. A mechanic told me to check my oil for signs of metal shavings, that it would be a sure sign that something would've been wrong with the valvetrain or rods. Thing is, since I've filled my new engine up with oil, I only put like 10 miles on the BP, so of course, the oil is like brand new...If it's a piston pin, I'm done. I poured enough time and money on this, and I have none left of both; I'm gonna start to work full time again next week and I need a car, and I don't want to spend 500$ for someone to take all apart all I've done to fix it...If it's a rod bearing failure, do you think that the crank might be shot, or could I just get away with a bearing? Having the oil pan taken off to replace a rod bearing, I can afford. Having the engine taken out to replace the crank or head taken off to replace a piston pin is a big NO-NO, sez my wallet...

[jglutz]

If not a wrist pin...maybe a rod bearing.

[elcamino1]

Did you know the background of the engine befor you installed it?
Pull the oil pan you might get lucky.

[Pocket_Rocket]

From what I heard, the engine had been rebuilt, then bolted in a first gen Protege, the guy stacked 5000km on the freshly rebuilt engine, and then decided to go the BPT route. He sold it to another guy, complete with the G25M-R tranny. The new guy supposedly bought it because he already had a BPT in his 323, but kept blowing engines, so he bought it as a spare, just in case. His dad, who was the only one there when I came to pick up the engine, said his son only used the tranny, but never dropped that engine in his 323; he just blew his third BPT and just grew sick of swapping blocks, so he sold his 323 as is with a blown engine, and the spare BP separately, which I bought. The entire engine was really clean, inside and out, no sludge anywhere, and you can drain the old oil, put some new in, run the engine, and the oil won't even come a shade darker if you pour it again. I don't really have doubts about the claim that this engine has 5000km, maybe it was just machined incorrectly, with tolerances a bit too much on the tight side for the rod journals/bearings...Anyways, I just saw a 260 000km Protege GT (LX for you U.S. guys) for sale for 500$ that I might buy as a daily driver to go to work so I can make some cash, then I'll pull the BP out of my Festy and see what needs to be done, have all the time in the world, and if anything goes wrong I'll still have another BP in that Protege...

[Pocket_Rocket]

Jim, it sounds pretty much like this 240SX:http://www.youtube.com/watch?v=niHvQ-P00gA
Now, as I understand, you can't possibly tell if it's a wrist pin or rod bearings until you disassemble the engine, right? Either way, I found a couple of companies selling bearing sets on Ebay, but I can't find one that sells wrist pins for a BP. Do you know of any online company that does?

[FB71]

Here's the way I differentiate a rod bearing knock from a piston pin;

first, with the engine running, disconnect each spark plug, one at a time. The offending cylinder will quiet down when you disconnect it.

use a mechanics stethescope/piece of vacuum line/long handled screwdriver, and try to determine if the noise is loudest at the top of the block, or down at the skirt.

if it seems to be just under the head, it's most likely a piston pin.
if it seems to be near the oil pan, it's most likely a rod bearing.

also, if it sounds like a single knock per rev during a throttle blip, its most likely the bearing. A double knock during blip is usually a piston pin.

[FB71]

oh, and if that's what it sounds like, it's definately a rod/pin issue