Ok so I took my car to a mechanic this past week because my 86 firebird with TPI died on my last saturday, anyways he ended up replacing the fuel pressure regulator because it was leaking and the timing chain and sprocket then he started it up and it was backfiring and missing like crazy so he replaced some of the push rods on one side of the engine and then it seemed to be running fairly well but when i got it back i noticed that there sounds like a rattling when im crusing about 45mph and on start up that same rattle occurs and then disappears so i was thinking maybe it needs to just get "broken in" or maybe its because he put in the wrong size timing chain or something like that... does anyone know anything about this?

 

Ok well the rattle sound is more like a ticking noise but now when i brake it feels like its trying to die and it squeaks/squeals along with the ticking and if it helps narrow down the possibilities it slows down when i brake, it cuts off when i accelerate, until 40-45mph and then about 55 it doesnt squeak/squeal or tick at all. the sound almost sounds like a more predominate ticking noise that my fuel injectors have made since i put new ones in... anyways if anyone has ANY ideas it would be greatly appreciated...

 

Is it detonation (ping)? If it sounds like marbles rolling around inside the engine then your timing is probably off. Otherwise, I would readjust the valves. Maybe this was done incorrectly.

To me it sounds like it could be much worse though. I can't think of a reason that push rods would need to be replaced if the timing chain was installed correctly. Sounds to me like the "mechanic" didn't have the cam timing correct after replacing the chain. Causing the pistons and valves to collide and bending the pushrods in the process.

What was the reasoning behind replacing the timing chain anyway?

 

Well when i asked him what would've caused the pushrods to bend he gave me a response like well maybe at one point when i was running the car hard the pistons would have bent the pushrods, how probable that is i dont know... he also said that he replaced them with pushrods from a nissan... im not sure if there the same length as the pushrods my 305 has in it... and the timing chain got replaced because it had broken on me.. how would you pinpoint if it was ping or if the valves were incorrectly adjusted?

 

Well, if your timing chain broke that could have caused your pistons to kiss the valves and bend push rods. If this is the case then you probably have more damage then what has been repaired. I would verify that the valves are adjusted correctly (Might not be possible if the push rods are the wrong ones). then do a compression test. You might have a bent valve. A bent valve can cause a noise like this.

I would possibly look to get a new mechanic. I don't know anything about Nissan push rods but there's a good chance that they are different. If they are different then you might not be getting the correct geometry on the rocker arms and valves. This can cause damage to the valve guides and possible break a rocker arm. I would consider getting a second opinion maybe.
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Oh, and a ping is like if you are driving a stick uphill in too high of a gear and you hear the engine struggling. It sound like someone dropped a handfull of marbles in the engine.

 

Oh, and pinging is the sound that you hear if you are driving up a hill in a stick shift in too high of a gear. Sounds like someone dropped a handfull of marbles in the engine.

 

Installing a new timing chain is exactly like advancing the cam, because your original timing chain was stretched, and thus your cam was running a few degrees late, which is also called retarded. This reduces cylinder pressures at lower rpm.
Detonation generally goes away with more rpm, it's more of a lower-rpm phenomenon. And too much cylinder pressure is a contributing factor.
Now, replacing a timing chain shouldn't be a problem, since the engine didn't have a detonation problem when it was new. Then again, you now have at least a little carbon buildup in the heads and on the pistons.
One, it could be a cheap chinese chain with inaccurate TDC marks.
Two, the mechanic could have installed it one tooth off. This could cause bent pushrods.
Three, good timing sets allow for advancing the cam 4 degrees. Your mechanic could have done this.
Four, your mechanic could have changed your initial spark advance.
At this point, I would immediately pour in a bottle of octane booster and see if it helps. Then post again.

 

What was wrong with your old timing chain? Did it break? If so, bent pushrods often means bent valves as well. Like was said above, there might have been more damage than what was repaired if your original chain broke.

You don't have to be turning a lot of RPMs for it to happen, either. When the chain breaks the valves STOP in whatever position they happen to be in at that moment the chain lets go. The crank, rods and pistons, however, still take a little while longer to spin down. If any valves happen to be far enough open that the piston can strike them (this is almost always the case), you get bent pushrods and/or valves.

 

sorry for taking so long to reply school is a pain. anyway quick question of why you recommended octane booster Atilla the Fun, and the original timing chain did break, and from what your saying damon is that the valves are more than likely bent? if thats the case does that mean i should be replacing the valves? and if im in that far im wondering if its just time that i get the whole engine rebuilt?

 

also my motors got about 165K miles on it and im positive it isnt that pinging noise

 

Oh man, 165k miles, timing chain broke (this should almost never happen on an engine like this, it's not an import 4 cyl with a mile long skinny timing chain), pushrods bent -- that engine is not long for this world. Like the guys said you probably have some valvetrain damage from when the valves were freewheeling for a few seconds and not indexed to the crank. I would start planning out the next engine for that car very shortly

 

thats a sad thought but i knew it was coming... is everyone else in agreement with that?

 

 

A stock engine is "non-interference". The valve can be wide open when the piston gets to TDC and it won't hit.

 

so what your saying is that my valves and pushrods couldnt have been damaged? if thats true how did the push rods get bent? are there other things that could cause that?

 

If you didn't damage any other parts, then what you're hearing is detonation, and octane booster is a quick and easy band-aid. If you do it, and you still hear the sound, then you know you have damaged parts.

 

do this first. pinpoint where it is knocking from. the front the back the top the left te right figure that out. then you can knock out some of these theories.

maybe he he just advanced it too much. check timing see if its off

 

well it definitly isnt detonation, put the octane booster in and it didnt change anything.. i suppose that it means that it isnt detonation and most likely is a lifter making that noise, is it possible that the valves just need an adjustment?

 

That is where I would start.

 

No it just means that octane booster didn't do anything.