3.1l rocker lash help!

[mtownfiero]

My fiero with a 2nd gen swapped 3.1l is sitting at a friends shop since it was running rough and dieing at idle. The guy who owns the shop did some test's for me to find that it wasnt getting hardly any vacuum. After checking all the lines i figured that something in the lim or uim didnt set right and decided to redo those gaskets. After i had the uim back on the owner of the shop told me that tq. ing down the rockers to 18ft lbs. like i had read on here wouldn't be the right way to get a good valve adjustment since some are open and some are closed. He also said the way i had it couldve been causing my vac prob because some valves were stuck open when they shouldn't be and after i get a base setting while rotating the motor i should adjust them further while its running.

My question is what is the best way to do the valve adjustment so that they will be tq.d equally and open and close as they should. Consdidering ive never done this correctly by getting it at TDC some how and adjusting them. Thanks for any tips/ help if i could get an answer by friday thatd be great.

[torq455]

assuming you have stock rocker arms, there is no adjustment. they are torque to spec only. it won't matter if the valves are open or closed. i don't remember if 18 ft/lbs is correct. i know GM likes the torque to ## and add 90 degrees.

[WrathOfSocrus]

If the cam was holding a valve open it could cause an incorrect torque reading. However the way the net-lash system works it would be impossible to torque it down to the point that it holds the valve open with all stock parts. If anything having improper torque would cause a loose rocker condition. A compression test would confirm whether or not the issue is in the combustion chamber.

If you are using aftermarket parts such as a cam, 1.6:1 rockers, custom pushrods, different rocker studs, or any combination of those then it could be possible they were over tightened. The manufacturer of an aftermarket cam should have details on how to properly install their product on their website. I'm pretty sure a lot of people refer to the instructions that Comp Cams has on their site.

From what I understand if there are stock parts there should be no need to re adjust the rockers once it is running because there is no adjustment to the stock setup. If you have the lower intake off you should check the area around the intake valves for oil residue or any kind of excessive wear or damage. It could be pulling air in past a bad valve guide. Otherwise it was more likely a leak in the intake area.

[mtownfiero]

These are all stock parts but tq.ing them even when all the rockers are at different points wont mess them up at all? I have had to losen the rocker arms to take them out when doing the lim. I just dont want to be told again that im doing it wrong and want to be able to explain it. These are the gen II heads not gen III 3100 heads.

[turboD]

The pushrods for the intake are a different length than the exhaust (going by memory, the exhaust pushrod are the longer set). If you crossed the two differrent lenghts, you may have bent valves.
The 3.1 are a torque to set/spec - I've seen specs at 18 ft lbs, and up to 24 ft lbs. depending on year and model. Any lobe that is up and opening the valve, will move the valve to an open position as you tighten the rocker. Since the "preload" is only .020 to .040" the lifter will compensate for the lash. D

[torq455]

Agreed. i'd torque mine down to 24 ft/lbs.

[mtownfiero]

so the reason i dont have to put the motor at TDC and tighten some then rotate it and tighten the others is because the pushrods are a different legth and the lifters will compensate for the lash no matther where that particular valve is in its cycle? Thanks this is helping me understand a lot better.

[torq455]

yeah, as you tighten, the springs will compress. you have hydraulic (self adjusting) lifters. lash is factory set. if you had solid lifters, then you'd have to make sure the lifter base is on the base circle of the lobe. that ensures the valve spring is unloaded so you may set the proper lash.

[mtownfiero]

Alright thanks again. Also should i re tq. them to 24 ftlbs. because i had tq.d htem to 18 before?

[torq455]

i would. just don't go over that.