I have searched the forums and not heard this sound yet. So maybe someone can help me identify it.

http://www.youtube.com/watch?v=8WH2_urWlLM

Details
lt1, 1200 k on full rebuild
cc503 cam, ported heads.
New Water pump just installed with no change in sound
New Opti was installed just after engine was put back in car. ( gm opti from partsladi)
Sound is there with or with out Serp belt. ( not an accessory)

Sound is constant at about 1100 rpm.

Sound only come up when car is at operating temp. No sign of it when starting cold. But as soon as the engine gets heat soaked the sound comes alive.

From my search on the forums I read a post of someone with a similar sound that had to "Shim" the opti. i tried this with no change in the sound.
Engine builder wants me to pull engine back out so they can rip into it. i want to cover all my bases before I do that. Hate for it to be something stupid

Thanks

 

i dont know man

maybe the dowel is too long in the cam pushing the rotor into the cap on the opti

i would pull the opti and see what it looks like in there

 

I have taken the opti apart. I have an old opti here that i am going to swap the metal bearing assembly out to the new opti to see if the sound goes away. maybe i will shim that one as well. When i did the water pump a week ago I ripped apart the opti and found no issues in there at all

 

Take off the belt and see if the noise goes away. That way you can rule out the accessories and pullies.

 

Yea, as per the post. with out the serpentine belt the noise is there, it is not accessory.

 

do you have a mechanics stethoscope? Narrowing down the approximate area would help a lot. If you don't have one, try "listening" through a long 3/8" or 1/2" drive extension at various places on the motor. You should be able to narrow down the area the sound is coming from. Be very careful with moving parts, spark plug wires, etc. Did it make this sound from first startup? You say you have 1200k on it, if the sound wasn't there at startup, was there ANYTHING done to the motor prior to this sound appearing? It def sounds like something "spinning" is making the noise, but it doesn't sound like any main or rod bearing I've ever heard. Other possibilities would be water pump, opti, or maybe something related to the timing chain and/or sprockets. I've never heard a roller on a lifter go bad, but this sound doesn't seem to be that deep in the engine. What about fans? You said it only happens when the car warms up. Does the smog pump kick on when hot, or can heat affect it? You could try unplugging the fans and pump just to check. First though, see if you can narrow down the area the sound is coming from

 

That is the exact noise mine made and shimming the opti cured it.
Maybe you did not shim it enough, you'll need to determine how deep the dowl is sitting within the opti drive currently...us some puddy or some grease marker, then shim it out some more if there is room, don't remember the exact measurements, but I'd put the dowl at about 3/16-1/4 in in to the opti driver.
Mine too would only make the noise after getting up to op temp.
Just to verify, you can put a listening device, stephoscope or the old long steel rod to the ear and place it on the front of the opti and verify the noise is there..but thats just how mine sounded.....on/off/on/off kind of noise like that...not constant.

You may also look into the cam possibly walking forward causing it, may be why shimming didn't work..maybe the cam retainer is worn, not installed properly....when the opti is off, see if you can pull on the dowl any and slide the cam forward any excessive amount...just throwing out ideas

 

I am going to get a stethoscope tomorrow. I have tried to use an extension to find the sound. Could not narrow it down. Water Pump is replaced, with no change fans are not running when the sound is on.
I am going to swap in a different opti. See what that does.
When the engine was rebuilt. I put it into the car and drove for about 40 km and then the opti died. I replaced it. I noticed the sound about 100 km or so after that. So it might be the opti. I will know more in a few days when I get it in.

 

Thanks for this info. Maybe I didnt shim it enough. I found washers and put them as shims. I know it was a bit more then what you used. i am going to use a listening device and listen closer to the opti.
The cam retainer and all that stuff should be new. i would hope that would have been replaced when they did the new cam during the overhaul. But when i have the opti out I will pull on the cam and see what happens.

 

My new motor has been together for a couple weeks now and it's making the EXACT same noise!

I'ts only around idle, when you blip the throttle it goes away, then come back when rpm's drop back down to idle.

Sound it coming from the front cover area.
The waterpump is NOT causing it, Mine is electric and i shut it off.
It's NOT belt/accessory related, I've removed belt.
I replaced my Opti with a reman unit thinking it was the opti bearing, didn't fix it, so it's not a bad bearing.

I also have a Comp Cam. I'm leaning toward it having too long of a dowell. I guess I get to take the waterpump/opti off again and either grind the dowell down or put washers behind the 3 opti mounting bolts.

 

Well if you figure it out let me know. i am swapping the backing plate with the bearing from a different opti. Then i will check the depth of the dowel when I have it off. i did try to check it last time it was off. but its a *&^% to get an accurate measurement. I think i will put something like play doh in the opti to see how far the dowel goes into the opti itself. might be easier to gauge it that way.

 

Don't even bother, you'll never get them clocked Exactly the same (within half a degree) and your car will never run right. The low res track tells the computer where TDC is for each cylinder, so it Must be clocked precisely.

The piece that clocks/holds the optical wheel presses into the bearing from the front, and the round metal chunk/shaft (that goes into the timing cover seal) presses into the above mentioned piece from the rear of the distributor.

The way they reman them is by drilling like a 3/32" hole between where the 2 shafts meet (from the front side of the distributor), then they press in a roll pin upon re-assembly to ensure they are clocked correctly. Both pieces are hardened steel and don't drill (ask me how I know lol).

I'm gunna go out in the garage and see if I can shim the 3 opti mounts bolts with washers.

 

K, I've got my opti off and I've been poking around at it for a while. It definitely does not seem to be a cam dowel length issue. My dowel is over 1/8" away from bottoming out, I checked it with clay and a depth gauge. I'm pretty sure my cloyes 3145(?) double roller timing gear wouldn't allow for the cam to walk out 1/8" (at idle only?), so I don't think its the cam retainer either.

The dowel however is .010" undersized compared to the slot. And theres a pretty good waer mark on the drive side of the slot. There's no way the ~.241" diameter dowel would grow to nearly .251" diameter when heated to <250°. I'm thinking it might be too loose and is bouncing off the sides of the slot at constant RPM.

Synchro, do me a favor and get your engine hot so it starts making the noise. Hold it very steadily at a different RPM and see if it makes the noise (like maybe 1500rpm or 2000).

It's gotta either be related to the dowel or the timing set. I think I'm going to put some high temp wheel bearing grease in the dowel slot when I reassemble, I think this could fix it since it's dry.

 

With the engine hot, and at 1100 rpm the noise is constant. with a bit more rpm the noise get slightly higher pitched and then it goes away. or seems to go away.

 

Just a quick update,
Tonight I had the car on a lift, and using a mechanics stethoscope we started to poke around. I get no sign of the sound when touching oil pan, block, water pump,timing chain cover ( top or bottom).
BUT
as soon as we touched the opti the sound was very loud. So tomorrow i am taking the opti off and going to swap in a different backing plate off a bad opti I have. See if maybe that bearing in there is bad. i will measure my dowel length and I think I will shim the opti again as well.