I'm about to write a book, but bear with me... <img border="0" title="" alt="[Smile]" src="gr_stretch.gif" />
I just installed a set of good heads on the car, with the same 918 springs & Ti retainers that were on the heads before it, using larger (2.02/1.575), stainless Ferrea valves.
Now--here's the deal-- These heads were bought off of Ebay, and had been milled an unknown amount--and milled poorly--my machinist hd to take .015 off just to true the surface properly...
We measured a total of 40 thousanths had been milled--
as I said in a months-ago post, we had P/V clearance issues w/ the Ferrea exhaust valves,(using a 226/.591/112 cam, btw) and not having fly-cutting tools available (or the $ to buy them) I recessed the valves 30 thou. instead, in addition to putting on a set of Cometic .078 multi layer steel head gaskets, in order to rectify all clearance issues.
To correct geometry we shimmed the rocker shaft 30 thousanths.
I'm still using 7.4 ChMoly PR's.
All the rockers are torqued to the proper 22lbs, and the car runs fine--no DIC codes or lights indicating a problem...(I do not have a laptop, so I can't run Atap on it or anything--there is Ed Wright programming done as well)
---
This brings me to my problem--why the hell does the car sound like a sewing machine?
It literally sounds like that---a "tap-tap-tap-tap-tap"
(about 5-6 times a second at Idle of 1K), following rpm.
It is not coming from one point of the VT--it's on both sides.
The sound is present at all times--from cold start & idle though the point that it blends into the rest of the noise at high rpm.
It doesn't seem to affect power at all--which is magnificent straight up to 7000RPM--absolutely pins you to the seat the whole way.

Before you ask, I've read about collapsed lifters here, and I'm questioning that only because the sound is coming from both sides--not just one piston.
It sounds like mechanical noise, not the "tick" of an exhaust leak--and so far, I can see no leaks at the headers.
Yes, the sound is audible around the wheel well too, though the sound seems to emanate directly from under the valve covers....
So...do you have any suggestions?
What the hell could this be?--I'm not thinking it's a catastrophic thing at this point, because like I said--there's no apparant impact on the car's functioning--but I really need to get it figured out--it's very embarassing, to say the least, to have a 2001 Corvette that sounds like a damned Diesel truck!! <img border="0" alt="[judgement]" title="" src="graemlins/gr_judge.gif" />
<img border="0" alt="[cheers]" title="" src="graemlins/gr_cheers.gif" />

 

Aftermarket valvetrains aren't geared towards how quiet they should be.

I ran 918's on the stock cam, and there was a noticeable increase in valvetrain noise. Add a high-lift / quick-ramp cam, and you are going to get a noisy valvetrain.

A collapsed lifter is a very discernable noise. It doesn't blend in with the rest of the valvetrain noise, and it is VERY loud. Sounds like an exhaust leak on crack.

Certain valvtrain combinations are very noisy. If you ever hear me go by, you'll think I'm packing a diesel.

Double Springs / CM PR / Crane Lifters / Lunati 226/226 .554

 

I'm just puzzled, because I had the exact same springs/retainer combo on the other set of minorly polished, stock-valved heads--and had just a very slight increase in noise--almost unnoticeable....
<img border="0" title="" alt="[Confused]" src="images/icons/confused.gif" /> <img border="0" alt="[Fluffy]" title="" src="graemlins/fluffy.gif" />

 

Ditto <img border="0" title="" alt="[Sad]" src="gr_sad.gif" /> Here's a link to how mine sounds http://home.attbi.com/~cdcastle1/TR220idle.mpg (just listen for the engine instead of the exhaust). It's been running fine for 10k miles like that,although it is heavy on oil consumption

 

It's pretty tough to hear the engine over that( sweet-***) exhaust...but that does remind me somewhat of how the car sounds...
I wish there were a way to record my engine and post the sound...it'd make this a lot easier to explain <img border="0" title="" alt="[Big Grin]" src="gr_grin.gif" /> ...

 

How did your valve guides look? I just replaced mine recently (along with some other work) and my "mysterious tick" went away. They were very loose to say the least. Are you using oil? That'd be another symptom. Anyway, I originally pulled the heads looking for a bad lifter and the guides were the only problem I found (everything else checked out fine).

 

The valve guides looked to be in excellent shape...and there wasn't any detectable play in the valves inside them...

 

i ust finished putting my motor together and after i start it and drive it a bit , i find out i have a very loud valvetrain!!!
i put new crane lifters and a big *** cam, i also have adjustable rockers.
it's so loud that people next to me on the highway notice it. the only difference form what you are describing is that the noise goes for a while after i flore it and comes back after a few seconds. this could be attributed to a lifter or two bleeding down too fast.
i changed the lifters with comp camsones today and will finish it up tomorow. i'll tell you how it goes. ( and yes , i did check my lifter preload , six times in 10 days)

the cool thing about cometic gaskets is that they're reusable.

 

with my 918 and XR-E lobe combo, this thing is loud as well! LOL - at least i have my noisy rear and loud exhast to make everything worse! <img border="0" title="" alt="[Smile]" src="gr_stretch.gif" />

 

Maybe I should mention that I have stock lifters and rockers-- I have heard that the aftermarket's are sometimes loud, but that doesn't apply to me... <img border="0" title="" alt="[Sad]" src="gr_sad.gif" />

 

my valvetrain is also very loud, sounds pretty much like you described. Or like a pack of typewriters at idle or low rpm. I have ARE doublesprings, I dont know if those are louder or what.

 

Well-- I just got done changing the oil form 5w to 10w30, and haven't really noticed any change--
damn, the car's strong, though... <img border="0" alt="[judgement]" title="" src="graemlins/gr_judge.gif" /> <img border="0" alt="[Burnout]" title="" src="graemlins/burnout.gif" />
Keep those ideas coming--I appreciate all the input from you guys <img border="0" alt="[cheers]" title="" src="graemlins/gr_cheers.gif" />

 

Aftermarket valvetrains are just noisy. Mine sounds like that too. I have Comp 977 double valve springs. It certainly is not a noise that is 100% in synch with the RPM, meaning you don't hear a click with every revolution on every cylinder. I think that the harmonics are such that you can only hear it a couple times a second if that.

Just tell the guy in the other traffic lane that your car has some bad spark knock and you're going to fix it later.

 

It's not the guys that I'm worried about <img border="0" title="" alt="[Wink]" src="gr_images/icons/wink.gif" />

 

Any other Idea's?
<img border="0" alt="[cheers]" title="" src="graemlins/gr_cheers.gif" />

 

I jsut completed a cam swap and my vavletrain sounded like a clam factory. Due to the cam circle being a bit smaller on the new cam , the vavletrain was sloppier. I just sent a set of rocker peddestals to a machine shop in Mobile to have them machined .025 My partner who is a mechanic for the localChevy dealer has done this during a few cam swaps and it has worked great.

topfig
MGySgt USMC

 

Thanks top--that was actually one of the things I was considering doing myself...de-shimming the rocker shaft .005 at a time until the noise went down...
<img border="0" alt="[cheers]" title="" src="graemlins/gr_cheers.gif" />

 

Well, some of the heads/cam guys may be OK with lifter preload.

Case in point:

One of the folks here measured the base circle on his .561" lift Comp Cams cam. The base circle measured .060" less than his stock LS1 cam. That works out to be actually .030" less (1/2 that distance) from the Comp Cams centerline to the heal of the lobe. BTW, thats the important number since that .030" is what effects lifter preload.

That in itself would require .030" longer pushrods to regain the preload.

Well, many folks have there heads milled .030"
That in itself would require .030" shorter rods.

So, with the Comp Cams [and] the heads milled .030", it all works out to just what the preload was before anything was changed (kinda "Tit for Tat")

Food for thought..... <img border="0" alt="[cheers]" title="" src="graemlins/gr_cheers.gif" />

Ron,

 

Check your oil pressure, if it's not >40psi at idle then your oil pump oring is not seated correctly or torn. Andy from A & A corvette and I had the same problem, the same day, with the same results a tapping motor.
Phillip

 

What kind of tires you running?
If you've got drags, you're shooting way low on that '60--they're easily capable of 1.7x's
If you can get 1.9's out of street tires, though--I'lll be very impressed <img border="0" alt="[hail]" title="" src="graemlins/gr_hail.gif" />
<img border="0" alt="[cheers]" title="" src="graemlins/gr_cheers.gif" />