Ok so I recently had my motor professionally rebuilt. Had the head sent out to a machine shop to run pressure test, have it hot tanked, and have all of the parts inspected and checked. I had new pistons put on my original rods and replaced the connecting rod bearings. My car makes a knocking noise at low throttle acceleration. It sounds like a rod knock but how can it be if the bearings were replaced with new bearings. I have seen posts where this can be possibly caused by an LMA. How can I be sure of this? I am running 98 itr cams, valves, inner/outer springs, and retainers. Please help me out. I am pretty much ready to throw the towel in on this bucket of **** and buy a b18b1 or b18c1 bottom end and call it a day.

 

What pistons? If you went with forged pistons you may or may not be aware they're always louder than OEM due to looser tolerences. They sound almost diesel like particularly when cold. Some are worse(noisier) than others.

 

OEM p30s. Stock bore not oversized. Keep the ideas comin guyz. Thank you for the responce TimoneX.

 

bump

 

the best thing to do, at least in my experience, is to listen to the valve train to see if the "knock" is coming from there. If you can tell that it's coming from the bottom end, then you may want to pull the pan and have a look at it.

 

To me it definitely sounds like it is coming from the vcalvetrain. It gets to its loudest point at approx 2500 rpm. It also goes away under hard acceleration(as far as I can hear) it seems to only make the noise when i am accelerating very lightly. Thank you for the input so far guys keep it coming.

 

<TABLE WIDTH="90%" CELLSPACING=0 CELLPADDING=0 ALIGN=CENTER><TR><TD>Quote, originally posted by sinatra &raquo;</TD></TR><TR><TD CLASS="quote">sounds like a rod knock but how can it be if the bearings were replaced with new bearings. </TD></TR></TABLE> someone used the right bearing on the wrong rod?
or you had a reworked crank that required an oversize bearing and nobody checked it an used the size suggested by the crank/rod labels?

good luck man, dont lose hope!
maybe its just a LMA. you should be able to check them easily enough! the one "bad" one will not spring back like the others, open your head and check it out!

 

Can you make the noise with the car in neutral and just revving it to 2500? If you can, just pull one spark plug wire at a time while revving the motor (don't shock yourself), if the noise goes away when one particular wire is pulled, that is the cylinder with the rod knock. If the noise does not change, the cause is more likely up top, but this test does not completely eliminate the bottom end as a possible cause. But, if the noise goes away during this test, you definitely have a bottom end problem.

 

noise goes away when #2 wire is pulled. Now how can this rule out the top end when the cam is still spinning and the LMA is still in the equation?

 

<TABLE WIDTH="90%" CELLSPACING=0 CELLPADDING=0 ALIGN=CENTER><TR><TD>Quote, originally posted by sinatra &raquo;</TD></TR><TR><TD CLASS="quote">noise goes away when #2 wire is pulled. Now how can this rule out the top end when the cam is still spinning and the LMA is still in the equation?</TD></TR></TABLE>
You answered your own question. The LMA is still operating with the wire pulled, so it is not the source of the noise. You are no longer putting a load on the rod bearing when the cylinder is not firing, so if the noise goes away, chances are the problem is the rod bearing of the cylinder that is not firing.

 

I just don't see how if the rod bearing is new. The rod bearings were done by the book.

 

they may have been done by the book, but they may not have been checked for tolerance. Did you plasitgauge the bearings?

 

The bearings were changed with the same color (brown) bearing that was in there before? Would that still call for platiguaging? Also, and what I now deem to be the problem, the cap was stamped backwards the number completes when put together but the stamp on the bottom that is supposed to go forward is actually at the back. This worries me because it was on like that when the first disassembly occured.