Lhorn

My recently rebuilt 350 starts to make a chirping noise about 1 minute after it is started up. It does not sound like a knock to me. It varies with engine speed. If I drive around for a while, it becomes MUCH less noticable. I can't seem to figure out where it is coming from but wouldn't be surprised if it is coming from inside the engine. I don't have a lot of miles on the engine but it hasn't gotten worse at all. I've taken off the belts so thats not it. I've also checked the flexplate and everything looks good. The oil pressure is between 35-60 depending on temp and rpm. The car runs well. Any thought about what could be causing this? Thanks




350 block with cast bottom end. Flattops. Performer RPM heads (64cc). Comp cam (magnum 280H I believe), Carter 600cfm, Weiand X-celerator intake, Hedman headers and TH350 trans.

Stekman

chirping? sounds like a belt issue. Make sure all your belts are tight and what not. do the free-play test, how easily can you push them off to the side? try some belt spray, see if that does anything. Make sure nothing is rubbing against he belt. If all the free-play is normal (i think its like .25" per foot or something) and nothing is rubbing, see if you can get an engine stethoscope. Basically, check the belts before other issues.

rjmcgee

Sounds like a pushrod rubbing against a guide plate.

Nixon1

I had all 16 pushrods rubbing for 10,000 miles and it never chirped once. This was stock pushrods, so they were destroyed. It just made a light metallic scraping noise.

It might be a bearing in one of the pulleys. My Camaro squealed and chirped REAL bad and it wasn't the belt....finally narrowed it down to one of the pulleys, but I don't remember which one. I sold it with the squeak (didn't do it the day of the sale. )

Lhorn

It's not a belt because I ran the engine with the belts off for a few seconds. I'll check under the valve covers today. Could there be something wrong with a lifter? It really isn't the clattering noise I would expect from a lifter but I did have to replace one recently. I didn't mention, but this is a Chevelle (sorry).

formula350_87

Distributor? Worn out cap/rotor.

Stekman

Like Nixon said, it could be a bearing on one of the pulleys.

Lhorn

I don't have serpentine belts. This is on a Chevelle - old school. It is definitely not belts and pulleys.

Lhorn

Update. I thought that perhaps the noise was a little louder on the driver side. I pulled the valve cover and ran the engine with it off. Not much difference. The rockers looked good. A couple of pushrods looked like they were touching a guideplate (no real wear seen however) and a pushrod or two looked like they might be real close where they entered the head. With the engine running, I used an oilcan to lubricate basically everything that moved under the valvecover. There was absolutely no change. After running the car around the block a couple of times, it becomes much more quiet. Anyone else with a similar problem or suggestions? I guess my main concern is that a bearing is getting eaten, but as I've said, I check all my oilfilters and they are real clean.

Nixon1

It's normal for the pushrods to make contact with the guideplates from what I've been told. Mine does, and they rub all the time. The guideplate slots are so thin that it's impossible for them to NOT make contact. As long as the pushrods are HARDENED and not the stock, soft-metal ones, it should be fine. That's where my mistake happened.

Put an engine stethoscope on it... With a sound as odd as that, I dont know if you'll be able to find the exact source of it without one.

rjmcgee

A pushrod will chirp like that if the guide plate is too far over to one side. There is a differance between the guide plate guiding the pushrod, or having the guide plate forcing the push rod over too far. Mine did this and after loosening a couple rocker studs and moving the guide plate around a bit the chirping stopped. Might have to play with a couple of them until you find the one that is making noise.

BTW, You can use a crow's foot wrench and reach the rocker studs and not have to re adjust the valves when your done.

RB83L69

Does one valve seem to move less than the rest? Have you had to re-adjust the valves? Does adjusting the valves affect it?

Get a piece of heater hose, and stick it in your ear (I love telling people to do that!!!) and use it to listen to everything on top of the motor; rocker seats, push rods in guide plates, etc. etc. Other than a rocker ball, I doubt you'll find it up there though.

88IROC350TPI

My old engine would "chirp" ...well it was more like a ear hurting metallic screech. Pulled it apart and all my cam bearings were trashed

Stekman

THANK YOU ! ! ! Like stated above, a stethascope (but heater hose works too) is great. As dorky as it may sound, it works like a charm. Just dont take it out before you walk into the house.

Im sure thats the LAST thing he wanted to hear. But its happened to me before, needless to say "Ear hurting metallic screech" doesnt do the sound justice. Well only my front went bad.

Lhorn

Definitely wouldn't call it ear hurting screech. It's just a gentle but very noticeable chirp. My worst fear its that it's a bad bearing but I kinda don't think so. I've tried the hose to the ear thing without luck. It seems where ever I put the hose I hear the sounds your supposed to hear Like the hum of the valvetrain or bottom end, but with the chirping sound in the background. Haven't really identified an area where the chirping is much louder. I've taken it to a couple of mechanics to look over. One guy did the stethoscope thing and couldn't find the source. Another guy admitted he had no idea but wanted to charge me over a thousand bucks to pull it see what shows up. I"m gonna do some more looking - I heard guys on another Camaro board talk about an exhaust leak making a chirp. If I find nothing, I may just watch it and see what happens.

Stekman

If it sounds like a hum with the chirp in the back ground that could mean that merely 1 bearing is going bad, whether that be a cam, crank, or a rod. It could very well be a case of you go some piece of dirt or something in your oil system and it got lodged between the bearing and the surface or the cam, rods, or main. But like i said, it IS possible that only 1 bearing is going bad, and is in the very early stages.

Air_Adam

Is it possible the timing chain is rubbing on the timing cover? I noticed a nice worn-in groove on the inside of my cover when i pulled my 305 apart.

Lhorn

I hope it's not a bearing, but could be. I've done a lot of reading about bad bearings on message boards. I don't have the classic "knock" and bad oil pressure and the car runs great. Oil and filters are clean (NO metal). Of course, that doesn't rule it out.
I thought about the timing chain thing. Pulled the cover and everything looked kosher. No evidence of wear.
My problem is that I don't have any friends interested in cars to help me pull the engine. It's a real PIA to rent a engine hoist and stand, pull this beast by myself, tear it down and put it back together and reinstall it. That's why I'm inclined to just run it as is if it's running good. If I do some damage from letting a bearing go and end up having to pull the engine, I'd probably rebuilt it with a forged bottom end so it wouldn't be the worse thing in the world to sacrifice a few internal parts. That's kinda the predicament I'm in. Thanks for all the replies. Any others are eagerly welcomed.

Poncho Villa

Ever figure it out? I've got a similar thing going on, weird chirping sound when cold, put it in D though, and it goes away, making me think it's tranny related. New motor mounts, still does it. Yes, the stethascope is the answer. Taking my car back to the shop to see if we can find the problem...

Lhorn

No I still haven't figured it out yet. I haven't had much time to look however. Been busy with other projects. I'll probably get after it pretty soon however. I'll probably just end up pulling the engine. It's been a real pain in the A@@. Maybe I'll end up getting a crate engine or shortblock.

Poncho Villa

Pretty sure mine is tranny/driveshaft related, when I put it in gear there is an audible squeak, and the chirping is intermittent, sounds like something rubbing somewhere.

There are a couple of other threads on this too--mention checking torque arm bolts, bell housing bolts, exhaust hangers, anything that could be loose. Chances are it's not your motor. Good luck.

Will post when I figure mine out. Motor runs sweet, and I guess a little squeak is no big deal when you consider my friend's brand new truck makes all kinds of weird sounds. My car is 13 yrs old and runs like a dream.