Some advice from the other LT1 guys please? MYSTERY SOLVED!

[DRIVEN]

Re: Some advice from the other LT1 guys please? NEW UPDATED

I currently have 2 LT1s myself and have owned a couple others plus worked on countless more so it's not my first rodeo either. That's what's wierding me out about this noise. I could have sworn it was a failed lifter because I've seen it a couple times and this noise sounded very similar. Apparently a previous owner thought the same thing because the lifters in this engine had been replaced recently. I replaced those with yet another set but it wasn't the problem. I realize that LT1s aren't a silky-smooth, silent engine but this particular tick is wayyy outside the normal range. I've spent hours and hours reading forums and asked probably a dozen builders/machinists/"guys who know" and none can seem to give me a straight answer. I'll get it figured out eventually. Like I said earlier -- it's a matter of spite now.

 

[DRIVEN]

Re: Some advice from the other LT1 guys please? NEW UPDATED

Well, it wasn't in the head. Letting the owner decide if he want's me to go deeper. At least the exhaust leak is fixed.

 

[Bonnewagon]

Re: Some advice from the other LT1 guys please? NEW UPDATED

I feel for you. My daughter's 95' LT1 has caused me more grief than I like to admit to.

 

[pontiacgp]

Re: Some advice from the other LT1 guys please? NEW UPDATED

It isn't an injector is it?

 

[DRIVEN]

Re: Some advice from the other LT1 guys please? NEW UPDATED

Nope, not an injector. One of my first tests was cylinder kill by unplugging injectors one at a time. I also did the same in the ignition side. The noise didn't get louder or quieter. It's more of a tick than a knock. That's why I was convinced it was valvetrain related. Now...I haven't got a clue.

 

[pontiacgp]

Re: Some advice from the other LT1 guys please? NEW UPDATED

sorry...I would have seen that you tested the injectors if I had read the complete post.. 😳

what about a valve spring that's broken?

 

[DRIVEN]

Re: Some advice from the other LT1 guys please? NEW UPDATED

All were checked early on. The heads were just rebuilt (new guides, surface, valve grind, seals) by the machine shop last week and installed earlier today. Rockers are new, lifters were swapped, pushrods are straight, cam lobes are good, oil pump drive was checked for damage and noise. The noise has remained constant since I started. Quiet when cold, starts at about 120* and gradually gets louder. Loudest at idle and gets quieter as you raise rpm. Can't hear it above 2000rpm. It's nuts!

 

[pontiacgp]

Re: Some advice from the other LT1 guys please? NEW UPDATED

if it's quiet at start then I think it has to be in the exhaust, a small hole or crack thats closed when cold and opens when expanded with the heat...

 

[DRIVEN]

Re: Some advice from the other LT1 guys please? NEW UPDATED

I promise it's not an exhaust leak. It did have a broken manifold bolt at the back of the pass side head but I fixed that. Besides, in my experience, exhaust leaks are usually louder cold and get quieter as heat constricts the opening from both sides. So there was two noises and one was obviously an exhaust leak. That one is gone. I have been thinking the other noise was valvetrain but that apparently isn't the case. The car belongs to my dad and I'm just helping out. He may decide to just dump it rather than waste any more time or money. If that's the case the mystery may never be solved. I REALLY just want to figure it out.

 

[DRIVEN]

Re: Some advice from the other LT1 guys please? NEW UPDATED

Just jumped on CL and guess what? He has it for sale. I haven't heard from him so maybe he's just testing the waters. I'll keep you posted.