I purchased a 99 Trans Am Collectors a few weeks ago.

It had some valvetrain ticking so I figured bent pushrod or something simple. The owner said he broke a rocker and had it replaced. He said his mechanic told him it was a bent pushrod. Weird he wouldn't have changed them but OK I believe him.

I start getting an issue under WOT where the motor dies and backfires. I kind of feel like it is fuel or ignition problems. It started during hard acceleration and began doing it even in neutral not moving.

I am running a data log while reving the car yesterday and it starts getting extremely loud ticking. The exhaust has been blowing chunks of the old cat out so I am thinking maybe the exhaust was getting plugged.

I decided to test fuel pressure this morning and get 58-60 psi which is normal but the noise is really bad. I rev the engine from the TB and no backfiring or dying but the engine was cold and air temp was cool. Other people have reported their fuel pressure dropping after it got hot so I figure I will re-check it after I get this noise figured out.

I wanted to open her up in case something broke. I get in and not only do all the rockers look good and almost new, the pushrods are all aftermarket 7.35" (seems short) and straight as an arrow.

The only thing that looked weird was the fact that torque on each rocker seemed to be all over the place. Maybe they were not torqued right? On the Driver's side of the car the rocker guide was supposed to have 8 rectangle spacers and I only found four whole and one half. The other 3 1/2 vanished. On the passenger side all of them were present.

I got some pretty mixed information from him. I am not sure he ever involved a mechanic as his dad and him seemed to do all their own work.

I also found one of the passenger side valve cover tubes disconnected which I imagine would make valvetrain noise worse.

The springs look stock and to be in good shape at 173k miles.

Anyone think any of this stuff could cause that noise? It kind of almost sounds like an exhaust leak too? I have attached a YouTube video for the sound.

Thanks in advance.

Engine noise: http://youtu.be/dPifDTV-SEU

 

whats the oil pressure looking like? and ur saying the rocker plates where missing on one side ? or a third of them where missing ?

 

My oil pressure is reading low which I know can be a symptom of a bad lifter. I really hope it isn't a bad lifter because I don't want to pull the heads. I guess at this point I am pretty much there anyway.

I was hoping it was a bad oil pressure sensor. During the data log the oil pressure sensor read a constant .20mv and never changed.

Rocker plates under the guide bar were all there on the Passenger side. 3.5 were missing on the Driver's side.

You think the valve springs chewed them up and spit them into the cylinder and lifter holes? That would definitely suck because then I am sure the cam would be chewed up too. :/

 

Yeah if oil pressure is that low that's a problem . That means no or hardly any oil is being pump to the lifters and there on the verge of collapseing or your gonna wear out if you having yet the cam bearings . Check all the rockers for play see if you can spin the pushrod on the ones that still have the rocker guides. They shouldn't spin . that's another things the rockers should have them guides that's a problem all in its own . Check back when you do those things .

 

I already pulled all the rockers and pushrods out. Should I replace those rocker plates, put some longer pushrods back in and check for play? What else could cause that low oil pressure?

A bad oil pump?

 

Yeah bad oil pump or bad oil pump o ring. You said it had 175k on if and yeah you can replace the rocker plates and put stock length push rods 7.4 I don't know why the had them shorter unless the did a cam sawp are all the PR the same length or are the ones that didn't have the guides shorter ?

 

Cam bearings destroyed can cause noise and low oil pressure as well

 

Yeah 175k and all the PR were the shorter size. I really have no clue if they swapped cams. I am thinking not since they look like stock springs and they are 241 castings. I would think if they were going through the hassle of a can swap they would at least throw some 243s on it.

Should I just rebuild the whole damn motor? I knew I was going to have to do it soon anyway? It seems like it would be cheaper than throwing money at it in its current condition. I was just hoping to be able to drive it more before replacing the motor.

I guess I could replace the pump since it would be part of a rebuild anyway.

 

Ugh it just occurred to me it should have 853 heads.

On further research I guess it is possible for a 99 to have 241s.

 

Your talking about heads man those have nothing to do with the springs . I wouldn't drive it anymore ur just increaseing your chances of really messing something up .

 

My point in the heads was if they were 241s then they could have been swapped so I really have no clue what has been done to this car. For all I know the block doesn't even match the Vin on the car.

I am going to pull the engine and rebuild it. No sense in playing this chase down the internal gremlins game. Probably why the guy sold it to me because his mechanic told him it was a ticking time bomb.

 

To the OP...don't pull the engine out YET! Please take my advice: replace with 7.4 rods, ..and torque each rocker down properly to 22ft pounds....make sure your lash is correct. ..then button it back up and she what she'll do....that's minimal work...nominal time and minimized headache....i really feel that whoever put that valvetrain together had NO clue on proper torque specs...take the advice as a fellow LS1 owner...you may be very happy with the results. ..

 

That's not a valve train noise, sounds like a spun rod bearing. And the squeaking noise is due to the piston hitting the cylinder head.

Get a video of the engine at 1500-2000 rpm. Also drain the oil and or cut open the oil filter, it will be full of metallic flakes.

Russ Kemp

 

She has been running for at least 200 miles with low oil pressure. The previous owner probably drove it more. That was my bad for assuming it was a bad sensor. No oil is going to trash it I am sure.

I will get some 7.4" pushrods and put them in since I don't want to fix the car in my driveway. I need to move it into my garage and doubt we will be able to push it.

The oil pump looks like it is probably as much work as pulling the engine. If I can drop the engine in 2-3 hours it just makes more sense.

The oil level itself was never low so I am not thinking that would be a spun rod bearing unless it had the worst timing ever. It makes more sense that it would be something in the top of the motor.

If it ran that long without oil I am doubting it won't be damaged.

 

That my friend is a flat lifter roller that has worn through a cam lobes hardened surface. Happened to me and was the reason I did this. Its happening too fast relative to the idle speed to be a single piston or rod.

https://ls1tech.com/forums/generatio...-swap-top.html

 

Either way OP...take your time and I hope your issue isn't too severe. ..last week I installed a SNS stage 2 cam with .650 springs...All torque specs were spot on...i turn the engine on..everything seemed good...After a few minutes the car starts making a ticking noise that very similar to your original post...it sounded like it could have been a lifter, bearing etc...However I had 3 or so rockers that needed readjustment. ..that's was all it was...hopefully your case isn't too much worse...

 

They had shimmed the rockers and installed shorter pushrods. All weird. It would be so much easier if I knew what the heck they did.

That in itself is an issue. If a lifter had collapsed I would think with a raised rocker and shorter pushrod it wouldn't even touch the rocker.

Maybe they had the heads milled. No clue at this point and no real way to tell without tearing it all down. I may pull the heads once I get it in the garage before I pull the motor to see what I can see.

I would probably be pretty mad if I pulled the engine only to find everything mechanically good.

 

Well said....i agree 100%! Keep us posted on how this turns out.