So I know the lifters need to be adjusted from time to time... how often is this typically necessary and how would I know if they are out of adjustment?

 

Once done, it`s normally not very often. Good for several thousand miles. However it could be incorporated in your tune ups to check if the lash is correct as a precaution.

 

Stock GM cam on street driver I would do it every other oil change (before changing oil) or about every 6000 miles. If you race the Vette or drive really hard maybe every 3000 miles. Stock rocker nuts/studs need to be changed out to poly-locks with flat top studs for severe useage but would be OK for street driver.

 

Are there easy to follow instructions anywhere or is this something best left to the pros?

 

It's easy. Get the engine hot. I have the procedure at home, and will update. But, when #1 is at TDC you can adjust half the valves, then when I think #6 is at TDC you adjust the rest.

 

Do it when the engine is fully warmed up. Take off the valve cover and note the adjustment screw & lock nut on each rocker arm. I have done it with the engine running which takes a bit of skill and tends to splash oil out. With the engine stopped and using a feeler gage with the proper thickness as specified in the owner's manual, set the individual rocker arm making sure all the tension is off the push rod/rocker and turn the engine over a bit at a time with the distributor main wire out so the motor does not start. Mark each rocker with chalk as it is adjusted and work your way around the valve train. I prefer this method and it has worked for me.
Good Luck,

Fred

 

The above procedure is not the way to go if you have the GM LT-1 cam profile. The clearance ramps are too long on that design to do it that way. You need a different procedure for the LT-1 (30-30 cam requires it too).

PM me if you want me to email you the procedure.

-Mark.

 

Learn something new every day, especially on this forum. I currently have a Crane LT-1 cam. PM sent. Thanks.

 

All you need to remember is "exhaust opening, intake closing". That is, at each cylinder's pair of valves, bump the motor over until the exhaust valve starts to open, and adjust that cylinder's intake valve lash. Then, bump the motor over until the intake valve begins to close, and adjust the exhaust lash. This way you can walk down one bank of cylinders at a time, and not go back and forth from one side of the car to the other. Setting lash on mechanical lifter cams should be done using feeler gauges and with the engine hot.

 

There's a paper documenting how to adjust the lifters by John Hinckley & Duke Williams on how to set the lash when the engine is cold. I just adjusted my lifters using this method. It was also my first time adjusting solid lifters. I have yet to fire up my engine, maybe this week...I hope!

 

This is the easiest and best way hot or cold. One bank at a time. That 90 and 90 and 90 BS with the balancer takes too long. Just pull the coil wire so the engine will not start until your done.

 

Definitely believe in doing things the easy way. But is this procedure accurate? It seems like just opening and just closing would be hard to get exactly the same for each rocker.

 

You would have to study the take up and closing ramps of the camshaft to see how this works. This procedure places the valve your adjusting on the heel of the lobe right where you want to be. Accurate, fast and dead nuts every time.

 

If I did it and found it to be not accurate, I certainly wouldn't be advising it on a forum. I learned it from a Car Craft or Popular Hot Rodding Cam and Valvetrain special issue.

 

Sounds good. Thanks.

 

I used it on every one of the Walts Puffers and the rest of my hot rods, including the one in the picture link below. You can also see the fuel tank has my customary signature gold leaf "Iron Cross" on it.

 

That is the method I am refering to.

You can also do it with the open/close method and be just as accurate. You just want to avoid trying to set them at TDC like you can on many other cam profiles. Once you are familiar with one method it will become second nature.

I like Dukes method as it follows the 1-8-4-3-6-5-7-2 firing order logicaly. For example If the engine is set to the #8 TDC firing position, the #1 intake valve is no way going to be on a ramp as it just got finished firing so that valve can be adjusted. At the same time, the #4 exhaust valve is not going to be on a ramp as #4 is about to fire next so you can adjust that valve. Rotate the crank 90 degrees to #4 TDC firing position and do the next pair of valves (#8 Intake and #3 Exhaust) and so on down the firing order. If you do it a few times you can memorize it.

-Mark.

 

I adjusted my valves cold using the standard SB valve adjustment with #1, then #6 at TDC from the Motors manual. The cam is a new Crane LT-1 and used their recommended cold spec tolerance. Should I go back and use the "bump" procedure to readjust the valves. I am concerned about doing damage during the critical first twenty minutes when the engine is started. Wasn't planning on adjusting the valves hot until after about 100 miles.

 

This procedure and specifications are for stock stamped rockers. If you have non-stock rocker ratio you will need to adjust the setting to account for the different ratio. The procedure is still the same but the spec will be different.

For the LT-1 The factory specification is .024"/.030", but you should set them at .021"/026" cold with the engine not running to compensate for the fact that the rocker ratio at the top of the ramp is closer to 1.37 rather than 1.5.

Also, you should use the procedure developed for the 30/30 cam because the exhaust cam is on the ramp at TDC and the inlet is barely off.

The following text is the procedure:

"30-30" SOLID LIFTER CAM VALVE ADJUSTMENT

By John Hinckley and Duke Williams

The traditional method of adjusting valves one or more cylinders at a time with each cylinder at TDC is fine for hydraulics and for most solid-lifter cams, but NOT for the factory "30-30" solid-lifter cam used in '64-'66 L-76 327/365 Corvette engines (and in '67-'69 Camaro 302/290 Z/28 engines); this cam has VERY long clearance ramps that are .020" high, and at TDC for any cylinder, both the intake and exhaust valve for that cylinder are still on their ramps, NOT on the cam's base circle, which is why the Service Manual for all cars so equipped says specifically to set them "hot and running".

There is, however, a better way to adjust the valves with a "30-30" - you can set them "cold and not running" by setting the intakes at 90 degrees ATDC and the exhausts at 90 degrees BTDC - so the lifters are on the base circle, not on the ramps. This has been confirmed with cam lift/crank-angle diagrams, and I've done mine this way - results in a nice mechanical "singing" sound, no "clacking", it runs better, sounds better, idle is more stable, and throttle response is improved. Several other Z/28 owners have followed this procedure as well since we developed it, and all of them have seen the same positive results.

Set them cold at .026"/.026". The actual measured (stamped rocker arm) ratio at the lash points is actually about 1.37:1 (not the design 1.5:1, which is a max lift measurement), so the clearance ramp, which is exactly .020" high on the lobe, is all taken up at .0274" clearance; .030" clearance with the valve closed is too loose - the ramp ends/begins before the .030"clearance is taken up, resulting in the valve being lifted off and returned to the seat at greater than ramp velocity. This will contribute to valve seat recession, and can cause valve bounce at the seats at high revs - it will also be noisy.

You can adjust two valves at each 90-degree rotation point, starting at #1 TDC, turning the crank 90 degrees at a time seven times (measure and mark your balancer first at 90-degree intervals from TDC). Removing the plugs simplifies rotating the crank, but you were going to change them anyway, right? Proceed as follows:

TDC #1 - 8E, 2I
90 deg. - 4E, 1I
180 deg. - 3E, 8I
270 deg. - 6E, 4I
0 - 5E, 3I
90 deg. - 7E, 6I
180 deg. - 2E, 5I
270 deg. - 1E, 7I

Start at TDC #1, then rotate 90 degrees at a time, setting at .026" cold. If you like, you can then go back after you're done to each cylinder's TDC position and check clearance on that cylinder's two valves, and you'll find that they've closed up to .024", indicating that both valves are still on the ramps at TDC, as I pointed out in the beginning.

 

I assume you are talking about the LT-1 from the 1970-71 days. I had one and a mechanic showed me how to do the "hot and running" lash set with a feeler gauge that GM specified. This procedure included oil clips on the rocker arms to keep the oil from spraying all over and a modified rocker arm cover (my idea, the guys at the Chevy dealership used a piece of cardboard) to keep the oil from pouring all over the exhaust manifold. I set the lash this way several times on my 1970 LT-1 with smoke in the eyes and denting up several feeler guages until another member of the Corvette club pulled a card from his wallet with the hot but not running TDC method. You got to love these guys who keep car specs in their wallet rather than pictures of the kids. I used that ever since. I eventually sold that car to that same guy. It seems reasonable that once the lash is set hot, the engine could be allowed to cool and a measurement taken for the "cold lash." I am now a hydraulic anti-pump up kind of guy.