Okay, I was told that maybe I set the valve lash wrong on my car when I did the cam swap, so I decided to do it again. I pulled off the driver's side valve cover and got the engine to the #1 firing position and adjusted the valves that I could on that side. They were: 1E, 1I, 3E, 5I, 7I. Then I rotated the engine another 360* and before I went to set the lash on the remaining valves on the driver's side, I noticed 2 things. 1)The #5 exhaust valve appears as if its being pushed down, and its one I am supposed to adjust, I thought the valves you are adjusting are supposed to be closed? and 2) The #7 intake rocker is totally loose, and it feels like it could just about lift right off of the stud, I have no idea why, I has just lashed it like 10 minutes ago. So, as you can see, I need help.

Another question I have about valve lash is how tight are the rockers supposed to be, should you be able to move them at all after you set the lash?

Thanks!

------------------
1987 Chevy Camaro IROC-Z
L98 TPI 350 (5.7L)
TH 700R-4 Transmission
Borg Warner 7.75" 9 Bolt Rear End

Current Mods: LT4 Hot Cam, Comp Cams 1.52:1 Roller Rocker Arms, Edelbrock TES 1 5/8" Headers, Hooker 3" Aerochamber Cat-Back System, Performance Resource Chip, Accel Ignition Coil, Cap, Rotor, 8.8mm Wires, K&N Filters, JET TPI Air Foil, All Free Mods, Falken ZIEX Z-Rated Tires.

Best ET (w/o LT4 cam): 14.32 @ 97.7mph
(corrected for elevation)

7.5" 10 Bolt with 3.42s soon to come!

 

I'm sorry Dan, I thought I'd sent you a file on how to adjust the lifter preload.

There are a lot of different ways to adjust lifter preload. It's just that some work better than others.

The method that is shown in the Service Manual works well on stock cams, but cams that have faster ramps (read that aftermarket performance cams) can give false readings when the GM method is used. I've experienced this myself and recently read the same thing in one of the mag Tech articles.

Of course, if you ask "How Do I Adjust My Lifter Preload" on a forum, you'll get different ways of doing it because guys generally settle on a method that they like best. All of them will work, but, remember, it's just that some are easier and more fool-proof than others.

Over the years I've tried about all of them and have settled on the method that works best for me. It is also the same method that most of the big cam companies recommend and it's the same method that you will read about in several of the magazines that address this issue.

Basically, what you want to do is work one cylinder at a time. You watch the intake rocker to adjust the exhaust; then you'd watch the exhaust rocker to set the intake.

Sounds crazy, right? But that's how it's done. Watching the intake rocker lets you know when the EXHAUST is on the base circle of the camshaft lobe - which is exactly what you are after.

That's the most critical part of properly adjusting lifter preload - TO MAKE ABSOLUTELY SURE THAT THE LIFTER IS RIDING ON THE BASE CIRCLE OF THE LOBE.

So, when the valve tip of the rocker on the intake lobe moves completely down (valve open) and continues until it's almost all the way back UP (valve closing) the EXHAUST will be on it's base circle. You stop bumping and then set the EXHAUST preload.

Now you watch the Exhaust rocker and AS SOON as the rocker begins to move downward (Opening the exhaust valve) you stop bumping. At that point the intake lifter is on the base circle of the camshaft lobe, so you set the preload for the INTAKE.

You want to first find zero clearance and once that's found you then set the preload.

To find zero clearance, you spin or move the pushrod of the lifter you're working on up and down. Some spin the pushrod until A SLIGHT DRAG is felt; that indicates zero. I prefer to move the pushrod up and down and when I can no longer move it up or down I know all the clearance has been taken up and I've got true zero.

At that point you'd continue to make additional turns of the adjusting nut/polylock to establish the preload.

The amount of preload varies from person to person. Some like 1/4 turn, others like 1/2, still others like 3/4 or 1 full turn. I always use what the cam maker recommends since they designed the thing and know which preload works best.

The less the preload, the more rpm the engine can see before lifter pump up. With aggressive cam ramps, though, this can cause the valve train to be bit noisey with tapping sounds.

Choose your poison.

I'm sending the file now. Let me know if I can help further.

Jake

BTW, yes, once the preload is properly set you still can wiggle the rocker tip side to side.

------------------
1986 Corvette Coupe, 415 CID, Edelbrock 6073s, ZZ9

 

Okay, here's my problem. After I set the lash on the cylinders and rotate the engine, and rockers on the valves I just lashed are totally loose, whats that about??

------------------
1987 Chevy Camaro IROC-Z
L98 TPI 350 (5.7L)
TH 700R-4 Transmission
Borg Warner 7.75" 9 Bolt Rear End

Current Mods: LT4 Hot Cam, Comp Cams 1.52:1 Roller Rocker Arms, Edelbrock TES 1 5/8" Headers, Hooker 3" Aerochamber Cat-Back System, Performance Resource Chip, Accel Ignition Coil, Cap, Rotor, 8.8mm Wires, K&N Filters, JET TPI Air Foil, All Free Mods, Falken ZIEX Z-Rated Tires.

Best ET (w/o LT4 cam): 14.32 @ 97.7mph
(corrected for elevation)

7.5" 10 Bolt with 3.42s soon to come!

 

Lifters bleeding down?

 

it means you were NOT on the base circle when you set the lash the first time.

sorry to tell you, but you did it wrong. It is worth learning though.


good luck with it.

 

What does that mean, the base circle??

 

The round part of the lobe that provides no lift.
If you look directly at the top or highest part of a camlobe, the base circle would be on the other side.

if you turn the engine clockwise (facing front of engine), and watch the rockers/lifters of the #1 cylinder,
when the exhaust just starts to move to open the valve, the intake is on its base circle. You may then adjust the intake valve.

When you see the intake valve closing back up, then the exhaust is on its base circle and can be adjusted.

help?

 

Okay, I think I know what you mean, so I may have to rotate the engine some to get the valves in the right places?

Should the rockers be tight throught their range of motion, or can they be loose at any places?

------------------
1987 Chevy Camaro IROC-Z
L98 TPI 350 (5.7L)
TH 700R-4 Transmission
Borg Warner 7.75" 9 Bolt Rear End

Current Mods: LT4 Hot Cam, Comp Cams 1.52:1 Roller Rocker Arms, Edelbrock TES 1 5/8" Headers, Hooker 3" Aerochamber Cat-Back System, Performance Resource Chip, Accel Ignition Coil, Cap, Rotor, 8.8mm Wires, K&N Filters, JET TPI Air Foil, All Free Mods, Falken ZIEX Z-Rated Tires.

Best ET (w/o LT4 cam): 14.32 @ 97.7mph
(corrected for elevation)

7.5" 10 Bolt with 3.42s soon to come!

 

yes you will have to move the engine around several times to get them all.
they should never develop any more clearance once they are set correctly.

 

I think you are a little confused on what to do. You bump the engine to get one of the rockers (let's say #1 exhaust) in the correct position. Then you set that rocker. Now you bump the engine again to get the next rocker (the #1 intake) into correct position, set that rocker. Now you bump the engine - Get the picture?

After setting a rocker you bump again to set the next and keep on 'til you've done all 16.

The easiest way for one person is to go to your local auto parts store and buy a hand held bump starter.

It has two alligator clips, one goes to the 12V terminal on the starter solenoid and the other goes to the "S" terminal on the solenoid.

Now pull the ECM/injector fuses and the BAT wire at the distributor. You don't want the injectors firing fuel into the engine as you set the lifter preload.

When you pull the trigger (it's like a handgun) on the bump starter, the starter will turn the engine.

Use the bump starter to turn the engine as you watch the rockers.

You can turn the engine by hand, but you'd have to remove all the spark plugs so you won't be fighting the cylinder compression. If you do it by hand, use the center bolt on the harmonic damper and ONLY turn in a clock-wise direction, otherwise you'll loosen the bolt and get nowhere.

You may have to jack up the front of the car (PUT IT ON JACKSTANDS IF YOU DO) and climb under to make the jump starter connections.

You can do it with the help of a buddy by letting him/her bump the engine using the ignition key.

Go to the refrigerator, take out an egg and look at it. The camshaft lobe is similarly shaped. The "pointy" end of the egg is the same point on the camshaft lobe that will have the valve at it's maximum lift off the seat. The opposite end, the rounded end, is the base circle; that's the end the lifter must be riding on in order to set the lifter preload properly. The area in between those two points are the ramps.

I realize this may seem difficult for you, but after you get the hang of it it'll be a piece of cake.

Hope this helps.

Jake

------------------
1986 Corvette Coupe, 415 CID, Edelbrock 6073s, ZZ9


[This message has been edited by JakeJr (edited March 01, 2001).]

 

Thanks guys, I guess I will go try it now.

------------------
1987 Chevy Camaro IROC-Z
L98 TPI 350 (5.7L)
TH 700R-4 Transmission
Borg Warner 7.75" 9 Bolt Rear End

Current Mods: LT4 Hot Cam, Comp Cams 1.52:1 Roller Rocker Arms, Edelbrock TES 1 5/8" Headers, Hooker 3" Aerochamber Cat-Back System, Performance Resource Chip, Accel Ignition Coil, Cap, Rotor, 8.8mm Wires, K&N Filters, JET TPI Air Foil, All Free Mods, Falken ZIEX Z-Rated Tires.

Best ET (w/o LT4 cam): 14.32 @ 97.7mph
(corrected for elevation)

7.5" 10 Bolt with 3.42s soon to come!

 

tell us how it turns out man, i'm anxious to know what's goin on with that bad boy.

------------------
89 IROC-Z 350 TPI

-Flowmaster Catback
-Performance Resource Chip
-700R4 (Rebuilt) Too much done to actually list
-K&N Airfilters
-Ported Plenum
-2.77 Gears (not much to brag about but eh, its there)
-MSD 8.5 mm plug wires
-Problems every other day with the car (probably not a mod, but to me it sure makes a difference)