When i start up the car it makes this tap tap tap noise under the hood and i dont know what it is. my friend blew a bearing and had a piston knock...definantly not that. its failry quiet, and you can really only hear it at low rpms, like at idle. when you rev it it gets quiter until it fades away after about 1500. also it gets a tiny bit faster, and when the engine revs back down you can hear it again. it almost sounds like somethings banging that might not even be internal, like a bracket bouncing around or something. i have a feeling its not though. any help would be appreciated, thanks a lot.

 

could be the lifters

 

is that a serious problem, or would i just be able to replace em and go. also, if so, is that an expensive problem. i think somebody said it might be valve lash or something but they really had no idea. they said it might be a good idea to use Lucas oil on my next change and see if it helps.

 

Sounds to me like its just the oil not being pumped fast enough when its cold...

What weight oil are you using? Does the problem go away when its warmed up?

If so, then chances are that you are running a little bit too thick oil. The reason being is that when oil gets cold its viscosity becomes greater, thus, resisting flow. When it heats up, the viscosity becomes lower and it becomes easier to pump. When you rev your engine, you oil pump is spinning faster, therefor creating more pressure and it is able to pump the thicker oil. The noise is probably your rockers just clanging around due to lack of oil.

Try running a lighter oil and see if the problem goes away.

 

mhm. thanks for the tip. ill have to try it since i need a change soon anyhow.

 

lifters = valve lash. Just means you need to adjust your lash. What's your oil pressure at idle, when this problem is happening? What oil weight are you running right now?

If you rev it, and the problem disappears, sometimes you just can't hear it anymore (just throwing out ideas), so maybe don't discount that yet. Do you have a mechanics stethoscope? Best $10 I never spent (brother got it for me ). Or use a screwdriver, put your ear on the handle, blade onto what you want to listen to . I'd guess lifters, so try to liften to your valve covers, put your screwdriver against the valve cover bolts/studs, if one of them gives off more sound, that's near the lifter that's loose.

 

thanks for the tip. the oil pressure is usually spiked in my car. and bounces around a little, but is still generally spiked. should it be? if not theres my problem. i dno what weight oil im running, ive only had one change since i got the car, and it was the same time we had the mechanic do the checkup so he just did it. im saying when i rev up it cant be heard, but when it goes back down to idle, the sound is there again, so the sound isnt there at low rpms. this really isnt a bad problem is it?

 

my oil pressure is usually maxed out too, now that I can get a reliable 800RPM idle, it comes down to 45psi then. your car might have a high pressure pump in there or something. I forget what else could cause high oil pressure (well, overly thick oil...)
Might as well change the oil now, go to a nice 5w30 for the summer, see if the ticking is still there. If it is, adjust your rockers (your lash).

It's probably nothing serious, just some adjustment needed.

 

ok thank you soo much for the help. im just the body guy here, not the mechanic.

 

like the others have said sounds like noise coming from your valve train (rockers, lifters, pushrod, and valves). when rpm's build up the oil pressure builds up and is able to get oil to your valve train. I'm guessing that this motor has a few miles on it and that its old and warn. It is a common problem to hear this noise. Is is a bad noise yes and no. No in the sense that your not going to blow your motor and that it is a common noise that anyone will have with a pushrod motor and lifters . But yes since your valve lash is not in spec so that your intake and exhaust valves openings are not optimized. It is always a good idea to adjust the lash with your valves especially after 100k miles when you are suppose to change the timing chain.

 

um, i have a crate motor with around 25k on it. but on the other hand, it was installed in 1991. so yes its old, but it definantly isnt worn.

 

well in that case since the engine is brand new basically it has gone past the break in period. It is recomended to adjust your valve lash after the break in period. when a new motor is put in you should have break it in with so many miles and check everything, every bolt since parts expand and contract. So with my experience with new motors and new valve trains they recomend adjusting the lash again after the break in period.

 

well i just got the car a few thousand miles ago, maybe 3 or 4. but thanks for letting me know.