Replaced LIM, now have noisy valve train

[Mitten Diver]

A buddy and I just replaced the lower intake manifold gasket due to a leak. We had to remove the pushrods to install the new gasket. We reinstalled the pushrods shorter for the intake and longer for the exhaust. My buddy torqued the rocker arms down with a 3/8" socket. We put the rest of the car back together including new fluids. When we started the car it runs fine, but the lifters are very noisy. This lifter noise was not there before the LIM replacement. My buddy thinks one of the lifters failed, I wonder if we needed to torque the rocker arms down to the specified 168 inch lbs or 14 ft lbs plus an additional 30 degree turn. If the rocker arms are to tight would they clatter? My buddy has more auto experience than me, but claims the rocker arms are designed to bottom out on the stud so the way they were tightened should not have an effect???

[Mitten Diver]

Sorry, should have included that this is the 3100 v6 motor.

[BNaylor]

Did you install the pushrods in the original locations? The length between exhaust and intake is correct. What figure was used or how were the rockers torqued?

On the VIN "M" 3.1L you should use the 14 lb-ft plus the additional 30 degrees or a range of 14-20 lb-ft which is acceptable and equates to about the same.

[Mitten Diver]

If you mean did the pushrods go in the exact same locations? I don't believe that they did, but the intake rods went in those locations and the exhaust rods went in their locations. Aren't all of the intake rods the same length as well as the exhaust rods the same length? I know they are about a 1/4-1/2" or so different from each other.

The torque was done by my buddy to a firm tight. He claimed that it was not overtight as a 3/8" inch drive socket would not overtighten these nuts. He claimed that the stud had a bottom out that the rocker arms should sit against. Do you think that the nuts need to be revisited? The motor had no valve train noise before the gasket was replaced.

[BNaylor]

The intake pushrods are 6 inches long (152mm) and exhaust 6 and 3/8 inches long (162mm). Whenever you do a valvetrain during disassembly the basic rule to follow is you mark or note the exact cylinder the rods came from and install them back in the same spot with the same lifters and rockers.

The best thing to do is redo the rockers and set the proper lifter pre-load per the factory specs as provided earlier.

[wafrederick]

If you put the push rods in the wrong spot,the valves bend.It could be a broken camshaft too,in half and this is a very common problem.It also washes out the cam bearings which the block is junk right away.If you want to know why it does this and it is NOT because the camshaft is hollow.The block was casted in China and the cam journals were casted offset and GM put in cheap,chincy cam bearings in.Jasper,a reman engine company found this out and fixed it right.They alighn bore the cam journals,Jasper is the only one that does this and put in updated cam bearings.I heard this from a Jasper rep I know

[tblake]

The noisy valvetrain is probably caused by one of two things....

1. The Rocker arms weren't torqued down correctly (retorque them)
2. The pushrods have to go back into the exact same spot they were taken out of for wear reasons. (sorry to tell you that after the fact)

You did change the oil before you started it, right? (just gotta ask)

Couple questions though... You say that the valve train is noisy? How long was the car ran to determine this? Sometimes the motor just needs to run for a few minutes to get the lifters pumped back up. Question number two, is the valvetrain noise rythmic, or do all the lifters seem to be making noise?

[Mitten Diver]

We will retorque the rocker arms and see what happens. At this point it would probably be impossible to put the pushrods back in the exact same spot unless they are marked. We are confident that we got the intakes in their location and the exhaust in there location. The motor has a steady tapping sound so we feel pretty confident that it is related to the lifetr/pushrod/rocker arms. The motor ran for at least 20 minutes and seem to have good power and ran very smooth no misses or anything.

We did install all new fluids when we changed the LIM.

[wafrederick]

Do not over torque them or the pedistals will break.I have seen this happen for the first time.My father walked away and heard a snapping noise,3 of the pedistals broke in half because someone reefed on them.

[Mitten Diver]

Does it matter what position the cam is in when you torque the rocker arms? should the engine be rotated so that there is some type of pressure being exerted by the valve springs? I.E. some valves are closed versus some of the valves being open.

[tblake]

if your talking about the 1999 grand prix in your signature, then no. Just torque them to spec.

[richtazz]

This engine is a zero lash design. That is why there is just a torque spec, and not a torque sequence/lash proceedure. As the previous posters have noted, it is imperitive to put everything back where it came from to get the engine quiet again in this design. As long as it's just a mild tick and not a loud clatter, don't be concerned (especially if it goes away after a couple of minutes). This is normal for this design engine, even when everything is put back where it came from.

[renoandkat]

replaced my LIM,put in 30 weight oil and primed engine. lots of noise in valve train. Added 1/3 can of seafoam and started engine--ran for 10 min and just when i was ready to say forget it, the lifter noise slowly subsided,little by little then no noise! Hooray--but not yet---started next morning --same noise let run and this time 5min--all noise stopped.Started engine total of 4 times with seafoam(guess could have used the entire can!. After 4th time, it would make noise for maybe 1 min then stop. Changed oil and put in 5w-30 and no noise since--not even for a min--maybe 15 sec if not started in few days.
I posted this to aid someone that may run into this. Initially, I found 1 rocker very loose (as if someone loosen the nut half way) when i pulled valve cover,so i disassembled that lifter and soaked in cleaner then in oil. Really thought would need to get new lifters but seafoam saved the day. 1996 buick regal 3100 V6 170000. Would like to thanks those that did the LIM Walkthrough on this site---really helped and also kept me from doing some things that would cause me to have to redo LIM. lol