Lite knock after rebuild???

[Jus10dun]

I just finished my 86.5 7m-ge and i finally got it to run right.

But when i get above 2000 it knocks but not like it knocked with rod knock it sounds exactly the same but it doesnt do it consistently and it is not quiet it is like as loud as the day before i parked it.

It does it when i get back on the throttle after shifting or letting off. and at idle when i give it gas.

It sounds like it is coming from the middle of the motor but i sounds like it moves from cylinder to cylinder.

Any ideas, experiences, or advice

Thanks Justin

 

[oscolivar1]

did u rebuild it or did a shop.

 

[Adjuster]

What type of pistons did you use, and what clearance was set for them?

Have you fully warmed up the motor?

Could be piston slap? (Generally only a problem on forged pistons where 6k clearance is run, but if the shop put your engine together really loose, it would be a problem on any engine.)

 

[Big Wang Bandit]

I know multiple people who have rebuilt 7m's and right after they fire it up, they tear it down again, only to find the bearings are completely fine, Only next to realize it IS piston slap.

Let the engine warm up to operating temperatures and get back to us.

 

[Jus10dun]

i rebuilt the motor myself.

The only thing that i didn't do was the machining.

also i let the motor run for like 10 minutes and still heard the noise

But i did figure out what is wrong with it last night i broke a injector sensor and i guess it wasn't geting a good conection and the injector wassn't working so the lit knock ior pinging was from it leaning out. i still haven't fixed the sensor so i am not a 100% sure but the motor ran exactly the same when i toke the sensor entirely out. so after i fix it i will let you guys know

thanks Justin

 

[Jus10dun]

also i have stock pistons(or OEM .020 over) But, i havn't seated the rings by doing the 30-50 full throttle break in. Will that make that noise if i havn't done that?

I also fixed the injector sensor and at first it ran good and didn't knock and then when i test drove it did it right after i shifted and got back on the gas again.

I also thought that it was ba gas so i put 93 in it and it still did it.

 

[Jus10dun]

do you think it is still piston slap.

 

[supramacist]

I am wondering if your exhaust is totally tightened down. It sounds like that pipe could be moving and or thumping a bit under neath that car. My pipe used to do that but I would be in traffic sitting still and it would start vibrating. This may not help but it may be worth checking, especially if you have rubber hangers.

I'm not totally sure but I had a van once that had rod knock. You can take a broom handle and cut to a few feet long and touch it to the engine and touch it to your temple and hear the engine working. Just follow down the block if it's rod knock or piston slap, you'll know it for sure. Ofcourse I mean a wooden handle before someone lashes out about this doesn't work well with a metal handle.

It could be valve spring chatter.

 

[Jus10dun]

well i know it isn't the exhaust because i can here it coming from the motor and to me it sounds like it is coming from the no.1 cylinder and even after i warm it up it does the same thing.

So do you guys think that it could be because i didn't break the motor in yet, I really don't want to do the initial break in if it is rod knock or piston slap. but i really don't know what piston slap is.

can i get it with oem pistons?

Is it because i havn't broke the motor in yet?

 

[cuel]

Some where in IJ's build thread on mkiiitech, he talks about how over torquing the timing belt idler pulley bolt will pull #1 cylinder outta round, and how he found that out. Retorque that bolt to exactly 36 ft. lbs., and see if the knock goes away.

 

[supramacist]

Well..., That's a plus. He's a smart man.

 

[Jus10dun]

that acually might be it because i had to torque it down more because it was too loose and every time i fired it up and checked it and it was off so i had to tighten a little much to keep it tight.

But what is the knock or loud tap that i am hearing is that valve on piston. or is that something else????

 

[supramacist]

Ya that could be it so stop rinning the engine. because it could be the piston and the valve or the valve and the piston, you decide. See I'm just being an ass. If Ij said it..., you could damn near trace it back to the beginning. B.C.

 

[cuel]

If the problem is the bolt pulling the cylinder out of round, the tap your hearing could very well be piston slap. The cylinder is out of round just enough that the piston is moving side to side. Think about how fast that piston is going up and down at 800 r.p.m.'s(revolutions per minute). Thats just at an idle. It would be a good reason why it(the knock) seems to move, and why sometimes it disappears. The piston is intermitantly moving from side to side with each stroke.

However, if that's not the problem, and it dropped a valve, you have to pull the head back off, replace the valve, inspect the valve seat, combustion chamber, piston, and cylinder wall for damage, fix any of that you find, and put it back together. Lets hope the first answer fixes the problem.

 

[Jus10dun]

well if that is making the no.1 cylinder of and the valve is hitting the piston wouldn't that make any of the other cylinders off?

but luckally it doesn't do it constintly so it probly isn't a droped valve.

Thanks a lot i am going to check to see if that is it tonight.

 

[Jus10dun]

if it was valve spring chatter like supramacist said. than how can I verify this?

BTW I took the timing belt pully tensioner off and retorqued it down to 36 ft lbs and it still knocked.

 

[Junior]

it's a non-interference motor, it can't be valve to piston contact.

out of round cylinder will allow the piston to jostle along the longitudinal axis, however your wrist pin circlips should prevent that from being too bad. Depends entirely on the tolerance of the piston I suppose.

Piston slap explanation: Imagine you're holding an assembled piston/connecting rod assembly in your hand (hopefully you've done this) now imagine you hold the conrod vertically with your left hand, then in your right, you spin the piston on the front to back axis (spinning it around the wrist-pin) now the piston will basicly spin until the piston skirt touches the connecting rod. What piston slap is, is the forces inside the cylinder pushing down on one side of the piston more than the other, and this forces one side of the piston to "kick sideways" and make contact with the cylinder wall, while the other side is not in contact, it comes out as a "tick" or a "clack" sound.

forged pistons are more susceptible because the coefficient of thermal expansion is higher on forged metals than on cast ones. Meaning the expand more as they got to operating temperature. This in turn means that there needs to be a greater clearance between the piston and the cylinder wall, so that it'll fit tightly once it's up to operating temperature.

all in all, it means that the thing will clack like a diesel when it's cold.


as far as what the problem is, it could also be pre-ignition, if your ignition timing isn't correct.

 

[cuel]

Honestly, its hard to verify what a "knock" is without atually being there, and finding it. Was really hoping the tensioner was it. Is this an auto or standard? If its an auto, maybe you might have a torque converter bolt loose, and its hitting the back of the block. Did you have the block and rods checked for out of round? Did you plastigauge the rods and mains when you put it back together? Were they all in spec? Are you sure you torqued them all correctly? Hate to say it, but you need to take your car to someone with enough experience to listen to it and point you in the right direction.

 

[Jus10dun]

Honestly, its hard to verify what a "knock" is without atually being there, and finding it. Was really hoping the tensioner was it. Is this an auto or standard? If its an auto, maybe you might have a torque converter bolt loose, and its hitting the back of the block. Did you have the block and rods checked for out of round? Did you plastigauge the rods and mains when you put it back together? Were they all in spec? Are you sure you torqued them all correctly? Hate to say it, but you need to take your car to someone with enough experience to listen to it and point you in the right direction.

no it is not auto.

And i double checked all of my torque specifications.

also i have all brand new internals. oem .20 over pistons, stock factory rods, new crank from advanced auto parts.

Also it only knocks or pings or taps after the motor warms up after it has been running for 2 minutes. also when i rev up past 2k and when i feather the gas to shift.

i also fixed the idle pully with a brand new one. because the old on looked to have bent somehow so when i put the new one in. i thought for sure it was going to be it.

I also checked my timing like 500 times.

then i decided to check my exhaust manifold bolt to see if they were in spec and i had to tighten all of then down at least a 1/2 turn and some a full turn. but ihave not fired it up after that. Because i decided to check under the valve covers for problems. and thought that the exhaust leak would make the noise all the time and would go away after the car has warmesd up do to the gaskets expanding.

I have only checked my exhaust side and it seems to me that every thing i fine and there isn't and exessive ware or any thing damaged

also i bought a jdm motor to fix my rod knock problem when i bought the car but that motor seemed to be more far off with rod knock than mine so i proceded to rebuilt my origanal motor.

although i used the cams form the jdm motor becasue they seemed to have less ware then mine but, had slight rust or scaaring on the area of the lobes that don't push the valve. And the cams still have that ware and look to have not been touched by the retaners

Does that part touch the retainers?

Should i put in my original cams?

Or do you think that it was the exhaust leak?

 

[cuel]

Did you check the cam clearances on each lobe? If one of the shims was off by enough, that could cause a similar symptom. Usually, I try to put the shims and buckets back on the same valves they came off of. I usually number them. As far as the wear on the jdm cams, I'll have to take a peek in my parts car motor tomarrow, I thought the shims and buckets were as wide as the lobes... not sure though. An exhaust leak can have different sounds. It is possible... Start it up and see if the knock went away. IF not, check the clearances on the cam lobes. It should be in the TSRM.