Knocking on rebuilt engine

[StevenPH]

Hi all,

some of you may remember my lengthy issues last fall with a rough running engine, that ultimately turned out to be a spun crank bearing. That led to pulling, cleaning, and reinstalling the block, which led to low oil pressure that couldn't be solved, which led to buying a rebuilt engine from Jack.

I don't know how to link to another thread, but it was under the title Very Rough Running.

The new engine is in and running well, but needs a few adjustments. I had a horrible experience with the mechanic i used (much of the reason why i'm writing this 10 months later, but i won't go into that), and don't want to take my car any where near his shop, though he said he would make necessary adjustments for free.

----

To the issue at hand...

My main issue i'm having is with a consistent knocking coming from the engine. When he gave me the car back, he said there was a tapping follower (which it sounded like to me), but would hopefully 'settle down' in a few hundred miles. It didn't, so i ordered new followers and replaced them. The knocking was still there.

It's a pretty clear knock, and to me sounds closer to a tapping follower than the grumbling knock that comes from advanced timing. It's in time with the crank speed. It also takes about 30 seconds to start when the car is is first started cold, and then continues, regardless of load, engine temp, speed, etc.

My mileage is noticeable lower than it was with the previous engine, and i'm getting a fair amount of black smoke upon acceleration. Not an incredible amount, but more than i think is usual.

I have been playing with the IP timing to see if that helps, but so far it hasn't solved the problem.

My main concern is there is a piston and valve collision happening. Though that seems unlikely to me, as i am inclined to trust the clearances were correct on the rebuild, and since i re-adjusted the crank/cam timing and the sound was unchanged. I suppose i could have erred to the same degree that the mechanic did, but that seems unlikely.

I have an appointment to take it a new mechanic on thursday, but would prefer to solve the issue myself if possible.

Any thoughts? Maybe try reset the timing again?

Notable that while they didn't come with the rebuild, all four injectors were purchased very recently (rebuilt bosch), so i am inclined to trust them as well.

[StevenPH]

Here's a couple videos, the knocking is a little more audible when the hood is closed in the second video.

http://youtu.be/ThXRIgqxqpU

http://youtu.be/FBxQcfkdQAM



I wonder if it could be a rod knocking? Could explain why the sound is clearer from under the chassis.

[colby]

Sounds like a tappet to me. Its a hydraulic engine, yes? Also, your idle is far too high. It needs to come down a bit. Hard to tell how much without a tach, but its definitely idling too fast.

[TylerDurden]

was the engine completely warm when that recording with made?

It's hard enough to distinguish a rod knock even when you are right next to the engine, Let alone using an internet recording.

to start, I'd try using a mechanics stethoscope, to see if it can be isolated to one particular cylinder.

[StevenPH]

thanks for the replies.

The engine wasn't completely warm, maybe had been running for ten minutes prior, though the knock sounds the same whether or not the engine is warm or cold, the only time i don't hear it is in the 30 seconds or so after a cold start.

Suggestions on where on the head or block to place the stethoscope? I have one and have tried to locate the tapping, but can't detect a difference between the cylinders. It's a pretty cheapo harbor freight stetho though, so maybe a better one would yield some results.

[TylerDurden]

I'd put the probe near the base of each injector, since that's close to the action.

You could also try some really heavy engine oil as a test to see if it takes longer for the knock to emerge. That might exclude a combustion knock from an early injector. (I know you said they were new/rebuilt, but an early pop on one could get you a knock.)

Again, from the recording, it sounds mostly like lifter noise, but maybe the sound you are concerned about does not reproduce well. Do you think the sound is prominent in the video?

[Tac]

Our motor has just been rebuilt, and it's pretty loud. My millage is about 47, 48mpg. Do you have a oil pressure gauge in it? Usually with a bad rod the oil pressure is low. Ours is about 20 psi while idling running 5-40 synthetic. 85/90 psi when it first stars.

Tom