after exhausting most of my resources to no avail, i'm hoping someone here might be able to help me out in diagnosing a random mystery noise in my engine...

background: i had a motor built by a very reputable shop in september, and ever since day1 it has made this really weird ticking noise that i, nor my builder, nor my friends, nor a shop that builds nhra race cars can figure out... i drove it 4,000+ miles already (cross country "break in") and the noise hasn't gotten better or worse...

specs on the motor: US-Spec SR20DE block 1mm overbored (86mm stroke x 87mm bore), milled and acid washed US-Spec highport head, Wiseco 9.0:1 87mm pistons, Eagle H-beam rods, U12 DET balanced and micropolished crankshaft, ARP Head/Main studs, Cometic head gasket, Jim Wolf Technology S4 Cams (0.464" lift, 266* duration), HKS Rocker Arm Stoppers, 1mm oversized Manley valves, 3-angle valve job, bowl port/blend, JWT Titanium valve springs, JWT Bronze valve guides. Garrett GT2860RS .86a/r at .5bar boost (for now...)

problem: it's a metal on metal ticking noise, similar to a bad lifter. however, it *only* does it at certain rpm and throttle positions. from a dead stop, it'll start making the noise at about 2800-3000 rpm. at normal cruising (under almost no load) at any speed, it'll do it. weird thing is, if i give it even 3% more throttle, it stops completely. if i back off the throttle as little as 3%, it also stops. it's weird as hell, it doesn't fade away slowly, but totally stops. it's either on or off. i can control it and make it happen (or stop) by modulating the throttle, it'll do it if the car is in neutral and revved, and i seriously can't figure out what's going on.

so far i've checked the HVLAs thinking maybe there was air trapped in one/some of them. they're fine. checked the valve clearances, they're fine. the timing chain tensioner was brand new at the time of the build, removed last week with 4k miles on it, installed another new timing chain tensioner. no luck. timing chain itself is brand new with only 4k miles on it now. it's not detonating. timing has been checked and rechecked. there's no metal in the oil. ran the car with no valve cover (plastic bag over the head) and the noise got MUCH louder (so i know it's not something outside the engine that just sounds like it's coming from the motor). it's not an exhaust leak. it sounds like it's coming from the head, but listening with a stethoscope, it seems to be coming from the lower timing chain area. i suspect chain guides, but where the noise (seems to be) coming from there really isn't anything that could make (that) noise. the motor runs hard and pulls strong as hell. i seriously can't figure it out. i'm hoping someone here might have an idea...

please help guys, this is really scaring me considering i paid for this engine with student loans and it is #4 in two years, i really don't want it to wind up in the pooper like the past engines... i'm really nervous driving it since i have no idea what this noise is, but i don't have a choice at this point...

 

*bump*


...anyone?

 

That sounds very familiar to when my buddy scorched his sleeve. It sounded like a light tap, but only at certain RPMS and would fadein/out very quickly. Other than that the car ran fine......until it blew two months later.

 

it's a pretty loud tap, and it doesn't fade at all. it's like a lightswitch, on or off, that's it... it's been running for two months already, 4,000 miles on it total, and it pulls hard as crap...

 

Try using a stethescope. Those things are so unbelievably sensitive that you'll have no problem pin-pointing the noise. I have a brand new motor that's also making wierd noises. After weeks of trouble-shooting, I finally bought a stethescope and immediately traced the problem to my tranny.

<TABLE WIDTH="90%" CELLSPACING=0 CELLPADDING=0 ALIGN=CENTER><TR><TD>Quote, originally posted by SR20DETg20girl &raquo;</TD></TR><TR><TD CLASS="quote">i paid for this engine with student loans</TD></TR></TABLE>

Heh, that's what I did too. I'm already regretting it though seeing as I'm working full time now to get out of debt

 

the stethescope is great advice, however, that led me to the lower timing chain guide area... but there's nothing down there that could be making that noise... it's back at a shop now with a professional race team, they're still trying to figure it out and came to the same conclusion using the stethescope...

the student loans thing was kind of a do-or-die situation. i had to drive cross-country and the motor that used to be in my car had terrible compression and burned 2 quarts of oil a week... i figured it was time to build a *real* motor and use either a credit card or student loans which i'd have to pay back eventually but would be interest free meanwhile