motor started knocking, but not rod knock

a compression test will tell you if you have a leaking or bent valve...no compression

the coil pack test will get rid of the knock confirming which cylinder has a spun bearing. or possibly bent rod. but more common and what your explaining its another sr with a spun bearing.

let me explain. pistons are in each cylinder. compression fuel and spark explode causing piston to be shot down with a metric shit ton of force. those pistons are connected to rods. those rods are connected to a crankshaft. that crank moves the flywheel clutch etc making your car go. basic engine mechanics.

a spun bearing is where the rod meets the crankshaft. there should be oil between the two. if there is not then its metal on metal with again, shit ton of force. that causes a spun bearing. as you drive the car you are just making the gap between rod and crank larger.

coil pack test... with no explosion the rod is pulled down by the crank and then pushed back up. no knock.

WITH explosion the rod is FORCED down turning the crank and still has downward momentum. when the crank tries to push the rod up you get knock. because of the downward inertia of the rod and the gap between rod and crank. the crank actually hits the rod and thats what you hear.

so unplug spark and you take away the downward force allowing the crank to move the rod up and down freely
 
ok i guess i should try that then, unless i could risk fucking something up by doing that lol

is it like unplugging an injector where i can just do it while the engines running, or would i havce to turn the engine off, unplug the coil, and then turn it back on?
 
You didn't listen. Take out injector, take out coil pack same thing it gets rid of explosion in cylinder.

You need to have the car running. One hand gives throttle till you hear knock. When engine is knocking disable each cylinder one by one. When you hear knock and unplug it and no more knock then you know what cylinder it is
 
crayZwhiteboy said:
a compression test will tell you if you have a leaking or bent valve...no compression

the coil pack test will get rid of the knock confirming which cylinder has a spun bearing. or possibly bent rod. but more common and what your explaining its another sr with a spun bearing.

let me explain. pistons are in each cylinder. compression fuel and spark explode causing piston to be shot down with a metric shit ton of force. those pistons are connected to rods. those rods are connected to a crankshaft. that crank moves the flywheel clutch etc making your car go. basic engine mechanics.

a spun bearing is where the rod meets the crankshaft. there should be oil between the two. if there is not then its metal on metal with again, shit ton of force. that causes a spun bearing. as you drive the car you are just making the gap between rod and crank larger.

coil pack test... with no explosion the rod is pulled down by the crank and then pushed back up. no knock.

WITH explosion the rod is FORCED down turning the crank and still has downward momentum. when the crank tries to push the rod up you get knock. because of the downward inertia of the rod and the gap between rod and crank. the crank actually hits the rod and thats what you hear.

so unplug spark and you take away the downward force allowing the crank to move the rod up and down freely
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Unplugged the injectors one by one while reving it to the rpm that i would hear knocking. seems like its cylinder 4 thats messed up
 
spun bearing on rod number 4. im in the same exact situation man. i hardparked my car until i can get the funds to do a longblock swap. im not even risking the costs that it will take to rebuild. since i cant do it myself.

rebuild: IF its ONLY the bearing that needs to be changed. your looking at $100 fix. take out bearing put new bearing in. done. that working only has like a .0001% chance lol. dont qoute me on that number

option 2, replace bearing with an oversized bearing to accommodate for the gap between the rod and the crankshaft. not recommended for revving engines over 6000 rpm. chance of working past 6 months= around 1% lol again.

option 3, here is where i give up since i dont trust myself to rebuild an engine that ill need to rely on. if it was a track only car ill try but not on my daily. remove crank, remove rods, take rod that was banging against crankshaft and the crank to a machine shop so they can either turn the crank or grind it smooth, same with the rod. using measurements get a bearing that will accommodate for the gap. might as well replace all the bearings since everything is out. and one spun already.
replace everything hope for the best. if you can do this yourself its an option with less than a 40% failure rating. however, if you cant do this yourself (my feelings of my situation) the cost of someone else doing this plus the cost of the machine shop would BY FAR outweigh the $1000 longblock, $100 gasket set, $100 in fluids and new hoses. and thats only if everything works and is done right and nothing goes wrong.


good luck on your decision man.
and again, i pulled all the %'s out of my ass so dont hold me to them
 
he has a rebuilt sr20 0 miles waiting to be swapped jst needs money i guess

that motor was tits before you fucked it up lol
 
he stated that he wanted to keep his block and just switch the head...

i was trying to convince him to just swap out the whole longblock

hopefully him doing that test changed his mind
 
benarovi said:
he has a rebuilt sr20 0 miles waiting to be swapped jst needs money i guess

that motor was tits before you fucked it up lol
Click to expand...

Its not rebuilt, i guess you could say its 'reconditioned'. It has resurfaced cylinder walls, new piston rings, front and rear main seals, and new seals and gaskets all around. The reason im waiting for it to be swapped is cause i need to take the head off and take it to a machine shop, have them check the valve shims and the valve lash to make sure its all correct. Whoever put that motor back together did something wrong on the head, probably as simple as that. At this point since im not giving up on the car and planning on keeping it, i might as well throw on a cometic head gasket and some ARP head studs. I want this "next" SR to last me a long time without any BS problems

and that SR wasnt exactly tits, it always had low compression, it just ran hard. What really fucked it up in the begining was running 20psi (not my fault lol) with no tune, and when the motor got flooded with fuel, as somebody earlyer said. Oil mixed with fuel = no lubrication. Even though i changed the oil twice since the fuel problem (1k miles each time), i never changed the oil filter, cause i never had an oil wrench at the time of oil change, and that shits on there TIGHT

but anyways thats the end of that motor i guess. Just waiting on my tax return so i can hurry up and put this new one in. Probably gonna swap the turbo while im at it too

crayZwhiteboy said:
he stated that he wanted to keep his block and just switch the head...

i was trying to convince him to just swap out the whole longblock

hopefully him doing that test changed his mind
Click to expand...


Nah what i meant was i wanted to keep the other long block i had (the clean "new" one out of the car) and switch the head on it since that motor's head was making wierd noises, but like i said, what im gonna do is just take the head off and send it to a machine shop to have everything done, and have it prepped for a new head gasket as well


anybody know of any good machine shops anywhere from ft lauderdale to west palm beach that can do this to an SR20 head and not charge me out the ass?
 
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ok how about u get a video of your motor making this sound....it would make everyones life easier
 
Roly D Sauce said:
ok how about u get a video of your motor making this sound....it would make everyones life easier
Click to expand...


this would have been done already if i had a video camera. that being said, i dont have a video camera to take a video, which is why im asking if i can drive to somebody for them to take a listen
 
Sketchy564 said:
this would have been done already if i had a video camera. that being said, i dont have a video camera to take a video, which is why im asking if i can drive to somebody for them to take a listen
Click to expand...

I'm sure you have a friend with a camera.
 
well heres an update

chris jackson listened to it last night and he thinks it sounds like its a rocker arm

im pretty sure its coming from cylinder 4, because when i unplug that injector at the "knocking rpm", it doesnt really knock, but if i unplug any other injector, it will still knock just as loud

so when i have the chacne im going to pop the valve cover off and see what i can find

but what im wondering is, is the problem as simple as just replacing the rocker arm? or is there more damage like a bent valve that could be done?
 
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