just re-adjusted the valves on my l36 after about 100 miles of driving, question

[Brandon T.]

Ok when the engine was out I followed the shop manual I have fo GM v8's

I went through the process og getting to zero lash..the manual then told me to go 1 full turn past zero lash, I've heard 1/4-1 full turn past zero lash.

So, what I did was went a HALF turn past zero lash...we installed the engine and have ran it about 100 miles.

today took the valve covers off to do a check, you could spin the push rods fairly easy with your fingers..

So, I decided to go another 1/4 turn to tighten them a little.

so after doing this 1/4 turn MORE I'm 3/4 turn past zero lash but you can still spin the pushrods with your fingers..

are you supposed to be able to or no? again this is on a 68 l36 390hp hydrolic lifter car.

what you think?

[Duke W.]

Re: just re-adjusted the valves on my l36 after about 100 miles of driving, question

The lifter preload spring force is not that great, and once the engine is "oiled up" from operation and properly adjusted it may still be easy to spin the pushrods even if lifter preload is within the acceptable range.

But you're following the wrong procedure. "Spin" is a poor indication of preload. What you should do is wiggle the pushrod up and down. If no clearance indicated the lifter has preload. If you can detect clearance, the is no preload.

Any preload between 1/8 to one turn from zero clearance is acceptable. A very small amount of preload will allow the engine to recover more quickly from a lifter pump-up episode.

The greater the lifter preload the more "wear allowance" the valve train will have.

If you plan on revving the engine to near the valve train limiting speed frequently, use minimum preload. If you want to set and forget the valve train for the life of the engine, use the shop manual recommend preload.

If you think that's too much use less. The only important issue is that the lifters have some preload, but not enough to "bottom" the plunger in the lifter housing, which effectively turns a hydraulic lifter into a mechanical lifter, so the acceptable amount of preload covers a wide range. On a SB one full turn preloads the lifter about .072". It might be slightly different on a BB due to the different rocker arm ratio assuming the thread pitch is the same.

If you have kept track of the number of turns from zero clearance and are confident it is 3/4 turn, then just leave it alone, and you should never have to adjust them again for the life of the engine.

If not, redo the procedure. From each crank position called out in the CSM, loosen each nut while wiggling the pushrod up and down until you detect clearance. Then tighten the nut until the clearance just disappears, then apply the amount of preload you choose within the range discussed.

With care and a little experience you should be able to easily detect the "zero clearance" point from which you apply the preload.

Duke

[Brandon T.]

Re: just re-adjusted the valves on my l36 after about 100 miles of driving, question

The lifter preload spring force is not that great, and once the engine is "oiled up" from operation and properly adjusted it may still be easy to spin the pushrods even if lifter preload is within the acceptable range.

But you're following the wrong procedure. "Spin" is a poor indication of preload. What you should do is wiggle the pushrod up and down. If no clearance indicated the lifter has preload. If you can detect clearance, the is no preload.

Any preload between 1/8 to one turn from zero clearance is acceptable. A very small amount of preload will allow the engine to recover more quickly from a lifter pump-up episode.

The greater the lifter preload the more "wear allowance" the valve train will have.

If you plan on revving the engine to near the valve train limiting speed frequently, use minimum preload. If you want to set and forget the valve train for the life of the engine, use the shop manual recommend preload.

If you think that's too much use less. The only important issue is that the lifters have some preload, but not enough to "bottom" the plunger in the lifter housing, which effectively turns a hydraulic lifter into a mechanical lifter, so the acceptable amount of preload covers a wide range. On a SB one full turn preloads the lifter about .072". It might be slightly different on a BB due to the different rocker arm ratio assuming the thread pitch is the same.

If you have kept track of the number of turns from zero clearance and are confident it is 3/4 turn, then just leave it alone, and you should never have to adjust them again for the life of the engine.

If not, redo the procedure. From each crank position called out in the CSM, loosen each nut while wiggling the pushrod up and down until you detect clearance. Then tighten the nut until the clearance just disappears, then turn the amount of preload you choose within the range discussed.

With care and a little experience you should be able to easily detect the "zero clearance" point from which you apply the preload.

Duke

thanks duke, actually I am about to head back to the basement to take off 1/4 turn so I'll be back at 1/2 turn past zero lash.

thanks

[Brandon T.]

Re: just re-adjusted the valves on my l36 after about 100 miles of driving, question

Well, I take that back..after I tightened them andother 1/4 turn to make it 3/4 pass zero lash.

I tweaked the timing and carb idle a tad.

decided to take it down the road before backing them off to 1/2 turn past lash and I thought it was smooht before, it's now smoother now whether me going another 1/4 turn did anything or not I'm gonna leave it alone.

I'm sure it was the timing and carb idle but she's set now. For the first time I've had the engine back in I punched it fairly hard not WOT but close several times, and she feels RIGHT.

[Brandon T.]

Re: just re-adjusted the valves on my l36 after about 100 miles of driving, question

btw wanted to add it chirps 215x70's when hitting 3rd without being in wot, haven't had the guts to go wot yet

[Chris W.]

Re: just re-adjusted the valves on my l36 after about 100 miles of driving, question

Well, I take that back..after I tightened them andother 1/4 turn to make it 3/4 pass zero lash.

I tweaked the timing and carb idle a tad.

decided to take it down the road before backing them off to 1/2 turn past lash and I thought it was smooht before, it's now smoother now whether me going another 1/4 turn did anything or not I'm gonna leave it alone.

I'm sure it was the timing and carb idle but she's set now. For the first time I've had the engine back in I punched it fairly hard not WOT but close several times, and she feels RIGHT.

Brandon,

I would get some more miles on it before you do a final adjustment on the valves. For the first 1000 miles or so, your engine should run better and better as it gets seated in. You may also find that you will have to slow down the idle after you get some miles on it.

After a 1000 miles or so, check the valve adjustment, re-set the idle and then drive and enjoy your car.

Chris