How do you adjust valves on a Chevy 4.3 v6?

Answer 1

this info is only accurate for 88-94 4.3 v6 engines. otherwise, check a repair manual.

disconnect the battery and coil pack (for safety...really, do it), chock the wheels, and put the transmission in neutral.

pull the valve covers. there will be other stuff to remove before you can get the valve covers off. have plenty of shop rags in place at the bottom of each valve cover to catch the oil that will leak out (maybe 1/3 a quart under each cover).

inspect the rocker arm studs first thing. Chevrolet used pressed in rocker arm studs, which can rise out of the stud boss holes. if you had what sounded like excessive rocker arm/lifter noise, there's a good chance that a stud or two has risen. if any of the rocker arms are loose enough to shake freely, it's very likely that a rocker arm stud is on it's way out. take a good look at the overall height of each stud in comparison to the others. a pulled stud will be fairly obvious. if this is the case, see the marked section below on installing screw-in replacement studs before proceeding. *

get the engine at top dead center for piston one. first, note the position of the number one spark plug wire on the distributor cap and lay the cap aside, wires still attached if possible. align the timing mark on the crank damper to 0 by rotating the engine clockwise using the longest ratchet wrench you have or a breaker bar. if you can't see the marks on the toothed timing marker, clean it up with a wire brush first. when your damper timing mark (there could be two marks on the damper. if so, use the furthest right mark) is at 0, take a look at the distributor rotor position. if it's pointing in the general direction of spark plug wire one, the engine is on the compression stroke. if it's pointing the opposite direction, it's on the exhaust stroke. the rotor probably won't point exactly toward the number one position, which is fine.

adjust lash. back off the rocker arm stud nut a full turn. rotate the pushrud between your fingers as you (very slowly) tighten the nut. the pushrod will first turn very freely, but eventually you'll feel a slight drag. if you're unsure, do it again and wiggle the rocker arm a bit as you go. when you're satisfied, tighten the nut an additional 3/4 of a turn. an easy way to do this is to mark your socket with a permanent marker for a visual reference (it will wipe off easily).

if you're at tdc on the compression stroke, adjust lash on these valves:

1 intake

1 exhaust

2 intake

3 intake

5 exhaust

6 exhaust

if you're at tdc on the exhaust stroke, adjust lash on these valves:

2 exhaust

3 exhaust

4 intake

4 exhaust

5 intake

6 intake

to identify the exhaust valves, look at the exhaust manifolds. the exhaust ports will be directly under the exhaust valves.

the cylinder order when standing at the front of the vehicle is like this:

firewall

6 5

4 3

2 1

front of engine

the distributor cap plug wire order is like this:

firewall

1 2 3 4 5 6 (counter-clockwise)

front of engine

install the valve covers, replacing gaskets if necessary. remember to pour plenty of fresh oil over your rocker arms and pushrods so that they aren't running dry at startup.

* you can either pull the head(s) and have all new replacement screw in studs installed at a machine shop (around $100-125 for a set of v6 heads + cost of gasket set + time of pulling heads)......or......diy, replacing only the pulled studs, which isn't the easiest task to do, but is definitely easier and cheaper. if you diy, you'll be pulling the raised studs out, and tapping those stud boss holes for screw-in studs. a few different companies make a tool called a rocker arm stud remover / tap alignment tool. there are a few problems here though. first, the tool might not be aligned to your rocker arm stud holes (i tried the summit brand and it was off). how ironic is that?....tap alignment tool huh? you can check this by trying to place the tool over two adjacent rocker arm studs (intake and exhaust for one cylinder). if it doesn't slip on over both studs, it won't work as is. if your tool isn't aligned, the solution is to modify it. you'll want to notch out the unthreaded hole of the tool so that it looks like a 'U' from top to bottom rather than an 'O'. this will allow you to adjust the distance between the rocker arm studs for correct tap alignment. you can do this with a hacksaw and file if you're a handy person (which i did). a bandsaw would be much easier. after that, the tool is straight forward to use. another problem is having enough room to turn a tapping wrench (t handle). if the raised stud is on the backside of the head, you might run into the firewall. otherwise, you might have to remove some accessories to have room for turning the tap wrench. the last problem is dealing with chips from tapping. you don't want any metal chips in your engine. you can cover the top side of the head in plastic and poke holes to get to the rocker arm stud boss holes. use a thick grease when tapping to catch chips in the hole, which will get stuck in the grease in the tap flutes. definitely do tap by hand (no drills) and go slow, cutting only a couple of threads at a time, before backing the tap out to clean off the chips. what you'll need to complete this diy job: stud remover / alignment tool modified (around $20 plus sweat), screw in 3/8" studs for a Chevrolet v8/v6 (nut end is 3/8" diameter, boss end is 7/16" diameter....check eBay, $25 for a two head set), tap wrench and 7/16"-14 tap (a whole sae tap set is fairly cheap, $15-20, harbor freight, ace hardware), thick grease (a few bucks), plastic (bag or otherwise). to tap a stud boss hole, first pull the raised stud using the tool. bolt down your alignment tool to the adjacent rocker arm stud. insert the tool's pin in the tool / empty boss hole. tighten the stud nut just enough to keep the tool from moving around. you don't want to accidentally pull a non-raised stud, so take it easy. remove the pin making sure that the tool hasn't moved. apply grease to your tap and start slowly into the tool. the tool is partially threaded and some chips will come from running the tap through the tool (don't worry about it). continue on into the stud boss (remember only a couple of threads at a time). when you eventually feel the tap turning freely, you're done tapping. insert your screw-in stud and tighten it down using double nuts and a wrench or two (two rocker arm stud nuts will work). the stud is tight enough when you can remove the nuts without also backing out the stud that you just installed. put your rocker arms back on and adjust lash as instructed above.

don't listen to internet naysayers about the possibility of installing cock eyed rocker arm studs when diy'ing. i did this myself and alignment was perfect. follow these directions and you'll be fine. just remember to go slow, and clean those chips out often. btw, i don't think it is even possible to install screw-in studs crooked in the existing stud boss holes. once the tap cuts the first threads, the tap can only follow the hole. if tapping was started crooked, the tap could get in a bind and stop cutting or possibly break, but not cut misaligned threads all the way down the stud boss hole.

p.s. - summit should be ashamed for selling a defective tool, repeatedly (search some forums for complaints). try the proform or comp cams brand but don't cross out the possibility of needing to modify the tool if it isn't properly spec'ed. if i had time to order another tool, i wouldn't have modified the summit brand tool.

p.s. 2 - using a rocker arm stud 'pinning kit', as suggested by a local parts house sounds like bad advice to me. attempting this with the heads in the vehicle, i predict a broken drill bit in a stud boss. think about it - tiny drill bit, hand held drill, drilling through steel in an awkward position....I'll pass. with the heads out of the vehicle, screw-in studs would be just as easy or easier and would give me more peace of mind.

i hope this info helps someone out.

travis