s14 sr knock - help me narrow it down

[yoozef]

Over the summer I put a new s14 sr20 long block in my 240. The engine started and sounded good. But it would break up past 2k rpms. I tried to set the timing on it and followed the procedure. I unplugged the TPS, went inside the car to rev the car to 3k rpms, but around 2300 rpms it started knocking. I saw the check engine light come on and immediately shut the car off. FML.


I then tried to start the car and it started and ran (still knocking). I changed the rod bearings first, because I should’ve done it before so I just went for it. Started the car up, still knocking. So I pulled the head today and the valves show no sign of apparent damage. The tops of the pistons have some detonation damage.
#1
http://i29.photobucket.com/albums/c276/dzerek/1.jpg

#2
http://i29.photobucket.com/albums/c276/dzerek/2.jpg

#3
http://i29.photobucket.com/albums/c276/dzerek/3.jpg

#4
http://i29.photobucket.com/albums/c276/dzerek/4.jpg
I ran the engine for a total of maybe 15-20 minutes before it started knocking, so i'm pretty sure the damage is from previous owner? My question is, what would cause the car to immediately start knocking after unplugging the tps and going to 2k rpms other than bearings/bent valves? i'm stumped, the gas in the car is old mixed with 2 gallons of fresh 93 (my gas gauge doesn't work, so don't know how much old gas), but how would that cause an audible knock appear and stay after an attempt at setting timing? Chime in if you have any idea
My previous longblock had forged pistons in it and after a 1000 miles it had a lot of gunk on top of the JE pistons. Not sure if that’s related.

[fliprayzin240sx]

Fuck, those pistons look pretty bad...all the pits on it are detonation. Also, look at the top of the cylinder on the exhaust side. Looks like somebody got a chissel and went to town on it. Thats your detonation right there. Shit got hot enough it ate the block...

I can't tell you if it was fucked already before, but you said it wasnt knocking before you attempted to set the timing? You were supposed to get the car up to temp, then unplug the TPS and then shoot it with a gun while its idling. You don't rev it to 3k and hold it after unplugging the TPS...atleast I've never done it. Timing could have been so out of whack and it was advanced like crazy.

[yoozef]

yeah, i tried doing it without ravving it up at first, but it was "jumping" back and forth... so i went on zilvia to look it up, and the instructions said to rev it to 3k rpms 3 times to lock it into "timing mode". But i didnt even get to 3k, and i wasnt holding it by any means... and the cylinder walls are good, i think it's just a reflection or something, but they don't look damaged...

[Kingtal0n]

You generally wont see that kind of damage just from idle situations. It usually takes heat, boost, improper timing and or bad gas while driving under load (hence boost). Knocking is a relative term; Knocking where? Anything can knock, and I doubt the knocking you heard at idle was detonation. Although, if it was detonation occuring, that could indicate a much more serious problem such as coolant blockage (and thus overheated cylinders) or very very bad gas quality... But very unlikely right?

Start simple. SR20's have a track record of knocking because of a spun bearing (from some kind of abuse) And if you have the engine out with the head off already might as well pull some caps and try to find which one it is.

If they all look good you are still faced with the problem of messed up pistons. I Would either invest in another known good OEM longblock and utilize good hardware for a new install, OR, rebuild to OEM spec that long block with obviously replacement parts where necessary (such as pistons...)

I recommend in a case like this that you take your time on the rebuild, do it right, slowly, read the FSM three times before you even start. If you are in need of a vehicle ASAP then just buy another engine (even if its a KA) temporary and run that while you rebuild your other engine. IN other words its better to run a junk engine while you fix your real deal engine SLOWLY and CAREFULLY only do it once.