Ok, i readjusted my valves and still at low idle I hear a knocking noise, not terribly loud and it seems to be coming from high in the block by putting a stethoscope (long socket extension) on the engine. Its the same whether the car is hot or cold.

It is not noticeable as i up the rpms even just past 1000 and at high rpms engine is smooth and no real noise,

is this the forged pistons i am hearing at the very low rpms?

do i worry?

 

it could be a few things but if your motor was put together right and you know there isnt say problems with the bore diameter and the pistons size then.....i would have to say yes its your pistons. because they are forged they have a later heat expansion, so thats why in the first start up you hear more rattling, because the pistons havent warmed up yet...

as long as it goes away after about 10 minutes and it doesnt continue as you drive then you should be ok.

 

Anytime there is a noise like you are describing that you would not normally hear from a normal engine, then I would worry. One thing you may want to check are the tolerances of the rods to your crank. Sometimes there can be a minor defect where the rods don't properly fit on the journals of your crank. Another thing I would check on is your valve adjustment. I know you said that you adjusted them, but just make sure that you used the metric measuerment rather than the standard. I know that sounds stupid but.............mistakes do happen. Good luck man


[Modified by armrslr, 11:44 PM 8/26/2002]

 

only hear it at LOW idle. can't hear it as engine starts to rev. its there even with very hot engine.

and valves are adjusted right. Car wouldn't run probably if you adjusted based on metric vs sae measurements and feelers.

 

If the noise goes away or is quieter when the car is warmed up then it must be the pistons. I have JE's and they are quiet on start up. Arias pistons on the other hand, are quite noisy on start up.

 

I have JE and they are noisy on start up and when warm Yea they are the noisiest upon start up but it never goes away unless im cruising then I dont hear it.

 

yea, i hear mine when cold or warm. i only hear it at low idle then when i hit the throttle even a little, i don't hear it anymore!

 

your gonna say, no, but i know what it is, this is a b series motor correct?
its the plastic behind the timing belt, take off the outer plastic and look.
its starts to melt and the sound goes away once its hot. i built a b16 and the first time i started it, that was the prob, i thought the motor was seizing or something, then i found. let me know if that was it...........

 

hmmm
I have my upper timing belt cover off anyway. there is no plastic behind the timing belt. i don't hear it coming from there anyway.
I wish that was the case. I am less concerned because the noise pretty much goes away as i pick up the rpms. i suppose it could still be one of the bearings? I used acl std size but the plastigauge all fell within the specs for the motor.

it is b18c1 engine.

 

well ok, you have verified alot of things that could be it....

is the sound loud or do you just think its loud because your worried about it....i thought the same thing when i first started my engine, and i have weisco pistons.....they were pretty loud....but you get used to it and understand why they do it

if it doesnt get louder when you get on the gas then its not a rod knock.....usually rod knocks get worse when you get on it a bit....

i would drive it and dont be hard on it but dont be to soft on it either.... see what happens, if the motors gona let go and blow it will do it withing the forst 500-1000 miles of being rebuilt

i know thats not what you want to hear but thats what i was told when i built mine, and so im spreading the knowledge to you.

as far as the timing cover thing...i dont know never seen that.

 

it really isn't all that loud.
I have about 1300miles on it now and I am pushing 12-14psi on it without any signs of a problem.

I guess i'm just worried about it

 

it's piston slap dude. It doesn't really hurt the motor that bad. On some forged pistons at initial start it will slap for a little bit. Does it should like a diseal motor? Because if it does then yes it's piston slap. The old batch of Arias pistons were nosey, but not the new batch of pistons. They changed their metalgury to reduce piston slap.

 

i have 8to1 wiseco's and they are supadupa loud at startup. and the noise is from the area where the head meets the block. and its not as loud when the motor warms up but it is definetly still there, however the secont the rmps pass 800rpm it goes away. This i have been told by many builders is piston slap as mentioned before. I totally know why your worring, evertime i open my hood with the morot running at idle i hear that damn noise. but if i ask my normal non motor friends they cant hear it at all. Also 10 to 1 odds are that if it goes away with just a few hundred rpm then it is piston slap. and the other guy is right about the rod knock. that **** gets louder with rpm. your fine dude.!

 

its the pistons, the silicone needs to heat up and the piston expands. But in my case, it was doing the same thing u explained, one of my cylinder was bigger than the rest and the #4 piston was slapping pretty hard. when i opened my motor, the bottom skirt of the #4 piston was all scarred/scraped up from all the slapping. Not trying to scare u or anything, just giving u ideas of what it could be.

 

Thank you!! i guess i'm fine then cause thats exactly what it is....
been pushin the car to to 14psi without any probs.
dyno friday!!

 

...

oops

 

Piston slappity slap slap !

Sounds familiar... kinda similar to mal-adjusted valves, but not exactly. I have JE's and they sound 'clackity' until the engine is at operating temp for a minute or two. From then, the motor sounds like a truck, but fine at high rpm, right ?

Forged pistons... gotta love 'em.

X2

 

How's your oil pressure at idle? At 1500 rpm? At 2000 rpm? New pump?

 

pressure at idle at the turbo is 15psi,
at 2000rpm its about 25psi and at 4000 rpm its about 45 psi and thats after going through a -3an line. stock pump original

 

if its after market piston then its piston slap. every built motor has it and it wont go away. weather its cold or hot. its normal to hear.

 

Too low on that presssure. You may want to try an .050 shim on your spring.
If that pump has a lot of miles on it, might be time for a new stock one.


[Modified by earl, 9:12 PM 8/27/2002]

 

Yes I also have it. The new clearenses on the sleves create all the noise, once the pistons expand the noise goes away in my case 2000rpm. Can you say diesel


[Modified by fast[R], 11:20 PM 8/28/2002]

 

Pistons dont expand because of rpm, they expand because of heat. You just dont hear your engine beating itself to death above 2000 rpm.

 

With RPM comes heat right

 

Yes, but once warmed up and expanded, they do not cool off at idle and retract.