Valve preload adjustment on Chevy SB and 4.3

[Jinmajay]

I set the preload on the valves last night. I know there has been some discussion on this topic here before and I can say I have the proper procedure down. Researched this on the net, gm manual, Haynes manual and, How to build a Chevy small block book, cam manufacturer (Comp Cams) and Edelbrock. This is a brief summery of what I came up with:

• Assumed you have the heads mounted, lifters (hydraulic) installed and the proper length push rods. Mark all the intake lifters on the lifter valley. This will help you keep things straight when adjusting.
• Install your rockers. If roller, apply assembly lube to the roller tip and pushrod socket. If non-roller, apply lube to the pivot point too and liberal amounts to rocker tip.
• Set screw type rocker nuts- put a small amount of engine oil on the rocker stud and then screw the nut on but leave it loose (for all rockers)
• You should have the engine at TDC on #1 compression stroke. You will know this because #6 will slightly be opened on both the intake and exhaust (look at lifter top).
• Mark your crank damper in 1/8’s starting at TDC. My damper all ready had ¼ marks.
• Your first valve to adjust will be #8 exhaust (I think). The books say that you need to adjust the preload to .030 + or - .010. Let’s shoot for .030.
o To do this you need to get a dial caliper and set it on zero on the tip of the rocker. Rotate the rocker nut cw until the dial reads .070 (because it will be going backwards which =.030). Remember how much you turned the nut to achieve the .030. Go back to no load and try it a gain. Mine was a bit past ½ turn. I checked this on one other rocker/valve and it came out the same.
o Now remove the dial indicator and you can start your adjustments.
• Make first adjustment at TDC (just one valve), then rotate CW 1/8th turn. Make one adjustment and rotate 1/8 turn and so on until all are adjusted. This sets the lifter on the base circle and you should not be on the ramp of the cam ever by following this. If the lifter looks lifted, push it down with your finger, if it doesn’t move then you might not have started on #1 compression stroke. Go back and check.
• Remember to use a backer wrench when tightening the set screw and make sure it is tight.
• You will make two full rotations and come back to TDC on #1 compression and the adjustments will be complete.
• I know I’m leaving out the order of adjustment as I forgot to bring it with me today. I will try to up date later.
• You DO NOT NEED to pump up the lifters with a drill or old distributer before the adjustments! It is actually better if you don’t because it won’t hurt the cam as you rotate as the spring in the lifter will be allowed to compress causing less pressure on the cam.
• This will work on all Chevy SB’s which includes 4.3.

Let me know if you see someting else or if you have a better way.

and I will get the order by next week.

[lockdoc]

If I'm not mistaken the 4.3's (90's era) you just tighten the rockers down untill they stop. Unlike the small blocks of the same era.

On new engines I was able to adjust the lifters cold with the engine out. When I have done a cam change, etc. I was not able to set it properly without doing it the messy way. Running the engine, tighten rocker untill noise stops then another 1\4 to 1\2 turn.

[peter]

Yeah, that's usually the only way to be dead on....

[Jinmajay]

Here is the order.
Crank Position Adjust valve
TDC 8E
TDC+45* 2I
TDC+90* 4E
TDC+135* 1I
BDC 3E
BDC+45* 8I
BDC+90* 6E
BDC+135* 4I
TDC 5E
TDC+45* 3I
TDC+90* 7E
TDC+135* 6I
BDC 2E
BDC+45* 5I
BDC+90* 1E
BDC+135* 7I
TDC Complete

[Jinmajay]

If I'm not mistaken the 4.3's (90's era) you just tighten the rockers down untill they stop. Unlike the small blocks of the same era.

On new engines I was able to adjust the lifters cold with the engine out. When I have done a cam change, etc. I was not able to set it properly without doing it the messy way. Running the engine, tighten rocker untill noise stops then another 1\4 to 1\2 turn.

Anyone choosing to use this should do the research on their build. This can be used as a guideline. I have not started mine motor yet so it remains to be seen if I get lifter chatter. I have new GMPP roller lifters and a roller cam and I'm am trying to avoid the messy adjustment procedure as everything is "Reeeal Shinny".

Was yours a roller or flat tappet cam? Flat tappes have to "wear" or break in and that may have been the difference?

BTW, everything I read indicated 1/2 to 1 and 1/4 turn past resistance. Any thing to small could cause noise and decreased opening of the valves. Anything to great would increase your overlap and cause the valves to not seat as they should.

Not sure about the 90 4.3, just going by the items listed above but thanks for the correction as this was posted to help.

[91AWDAstro]

On the dry adjust procedure, you need to make sure your on the base circle of the cam lobe. To do this rotate the engine by hand until you see the exhaust valve start to open for the cylinder you are adjusting. You now can adjust the intake. slowly tighten the rocker down while rotating the push rod until you feel a slight resistance (zero lash), then go 1/2 turn. This should be about 0.030 preload.

For the exhaust, same procedure rotate until you see the intake open and then just before it's fully closed you adjust the exhaust.

I've done them dry and lifters pumped. If the lifters are pumped, you need to allow time for the lifter to bleed down before making the adjustment.

Same procedure for roller or flat tappet cams. Only solid lifters are done differently.

Also on stamped rockers make sure you use a thin wall socket so that it doesn't bind or is tight to the rocker. This can throw you adjustment out of whack.

To check preload:

Pick a cylinder that you are going to check. Hand rotate the engine in its normal direction of rotation until both valves are closed. You are on the compression cycle for that cylinder.
Wait a few minutes, allowing the lifters to bleed down. Now, lay a rigid straightedge across the cylinder head, supporting it on the surface of the head where the valve cover gasket would go. Using a metal scribe and the straightedge, carefully scribe a line on both pushrods. Now remove the torque from all valve train bolts, removing any pressure from the pushrods. Wait a few minutes for the pushrod seat in the hydraulic lifter to move back to the neutral position. Carefully scribe a new line on both pushrods.
Measure the distance between the two scribe marks, it represents the amount of lifter preload. If the lines are .020" to .060" apart you have proper lifter preload. If the lines are the same or less than .020" apart you have no, or insufficient, preload. If the lines are further apart than .060", you have excessive lifter preload.

Of course if you do this you will need to set the preload again as described earlier.

[Jinmajay]

[GEJ]

Jim-probably just me,but I like to "prime" hydro lifters in a pan of oil before installing them in the engine.The other element in setting the preload is to check for coil bind and rocker arm clearances.Here is some links that explains it better than I could.

http://www.lunatipower.com/Tech/Valvetr ... gTech.aspx

http://www.crankshaftcoalition.com/wiki ... ring_setup

[Jinmajay]

Where you been Gary?
Thanks 4 the info.