RE-adjusted rockers. Worse problems now...

[Jon89LE]

Alright, well awhile ago i posted this and some of you had mentioned to tighten the rocker nuts a full one-turn to set preload. Well on the rear bank one of the rockers i couldnt get to since the damn manifold was in the way so to even things out, the center cylinder has a preload of 1/4 turn and all the others have a full turn. The car has a horrible tick now. It sounds like its coming from the back but i cant see that cylinder with the less preload causing that much noise since before today, they all had 1/4 turn of preload. Can anyone add some input here? The motor feels "tighter" so i think one-full turn is too much since its obviously louder. Thanks for any help. The motor is a 3.1mpfi with CompCams rockers.

[Rhedalert]

Were the valves "closed" when you adjusted them?

[geoffinbc]

You need to adjust while on the base circle of the cam. By the discription you gave I do not think you did it right. You didn't just add a turn to what it was already sitting at did you? You need to back them off completley and the re adjust them.

[614streets]

What does your cam call for , i bet its 3/4 turn after zero lash.

[xxrollin]

If there fully adjustable rocker arms with the Jam Nut, then you need to get on the base circle and tighten till you cant spin the pushrod anymore, then the rule of thumb is 1/4 turn for preload. I've always been told that and even the shops I deal with say that. 1 full turn is way to much, and you cant set them properly on the cam... Also, if this was a re-built engine, I've also herd its a good idea to soak the lifters with oil and even use the end of the pushrod to pump the plunger side to get it full of oil before install......

[v6h.o.]

the Stock GM rocker arms used to be set at 1 and a half turns... yeah...

for my rockers i always turn them 1/2 turn to set preload.

easiest way to set them is do it without having to pull the lower intake to check the pushrods while adjusting, is this:

pull the valve cover off, and start with one rocker at a time, have the engine running, back off the rocker nut untill you hear ticking from that valve, its now loose, start to tighten the nut untill the tick goes away, youve now taken out all slack in the lifter/pushrod/rocker. now turn in your lifter preload for whatever turn in you do. the engine will sorta change rpm as you turn in the lifter preload, this is normal.
go onto the next rocker ect ect. very simple quick. it helps to have an assistant who works the ignition to turn on the car when your ready and turn it off when your done. saves getting so much mess all over the place. you will get some oil squirting out. not a huge amount.

[geoffinbc]

Wow. Backyard mechanic or what.
On stock studs the spec is 1 1/2 turns past zero lash. The amount of turns depends ONLY on the thread pitch of the stud you are using. The finer the thread the more turns you have to add. If you did 1 1/2 turns on say a SBC or Crane stud then it would be WAY too much.

You should read this.

http://www.cranecams.com/?show=faq&id=3

[Jon89LE]

The threads are ironhead 2.8 studs which i was told needed one turn of preload. The paperwork that came with my rockers said for only 1/4turn of preload which is what i did but noticed a big difference at the track. I ran a little over half a second slower so i know they were too loose. I thought i could get away with just tightening them without going back to zero lash first but i thougt wrong . I was at a friends house since im away at school and his dad was getting impatient so i had no choice but to leave it like that. Im going to have to take the intake manifold off to adjust them so it may become a day project. One rocker in the front and one in the back dont allow room for the socket, hits the manifold. So with the Iron head studs, should i preload them to 1/2 or 3/4 turn? Thanks for all the responces guys...

[geoffinbc]

At LEAST 3/4 turns. Can you not get a wrench in there? Just mark the adjusting nut with nail polish or whiteout and turn it until the mark has made 3/4 turn.

[Jon89LE]

The wrench was the first thing i tryed with no luck. It was one of those "offset" wrenches. Atleast thats what i think they are called. I wouldnt have such a huge problem with this if it werent for that damn one rocker in the back. Taking the manifold off is going to be a major pain in the ass. With the pitch of the iron head 2.8 studs, how much preload will 3/4s of a turn equate too?

[XLR8ING]

With my rockers, I use a universal adapter to get to the rear rockers when I adjust them, and adjust them about 0.5 turn preload.

[geoffinbc]

The wrench was the first thing i tryed with no luck. It was one of those "offset" wrenches. Atleast thats what i think they are called. I wouldnt have such a huge problem with this if it werent for that damn one rocker in the back. Taking the manifold off is going to be a major pain in the ass. With the pitch of the iron head 2.8 studs, how much preload will 3/4s of a turn equate too?

I cannot remember the pitch anymore. I calculated it before. I will pull them out and do it again.