1969 426 Hemi. Have a Comp Cam Hydraulic Thumpr roller cam and lifters, using stock rockers, have 40lbs of oil pressure at idle.


Problem is I am getting some lifter tapping across engine. Talked to Comp Cams, need .020 to .040 preload. Turned engine to correct position to adjust each rocker, first they said go to zero lash and half turn.

That helped a bit but still have tapping, then they recommend adjustment zero lash and go one full turn, I tried that and still have some tapping, it was a small improvement.

Now they are saying with this particular cam and lifters I have go to zero lash and then go at least one and a quarter turn.

I'm getting a bit nervous going that much. I myself in the past with other motors (other then Hemi) never had to adjust preload on a hydraulic that far, usually half a turn max.

Are the factory adjusters on a Hemi a finer thread and require that much turning?

Thanks,
Wolf

What procedure are you using for setting the lash?

Exhaust start to open/ adjust intake.
Intake opens and starts to close/ adjust exhaust

Are the adjuster screws 3/8 fine thread? If so that would equate to .0416 per turn. So 1 1/4 turns come out to .0520 preload. They claim most lifters have up to .200 of adjustment for preload. If the Cam and lifter company is suggesting this I guess it is worth a try.

Thank You for that info. I will pop the covers off and find out what the adjuster thread is.
I noticed I didn't do the sequence correctly, I should be doing exhaust closes and intake starts to open on cyl 1 and then adjust both rockers on cyl 6, then do the same on 8 & adj 5, then 4 & adj 7 etc...etc.

I'm going to do this over again with the correct sequence and see what 1 1/4 gives me.

Thank You!

I would adjust them one cylinder at a time just like comp cam suggests. Mopar had a lash setting chart. I used to do it by the chart however they claim cam profiles have changed and you need to be sure you are setting the lash on the base circle of the cam. This should be your lifters and instructions.Adjustment

Ok, I will stay with the Comp instructions and do one cylinder at a time like I have been. Finding the thread pitch on the adjusters is first thing tomorrow.

Good stuff...thx!

Could be a bad lifter right out of the box.

I was just going to suggest that. He needs to re-lash all of them and run it. If it keeps making noise again re-lash and write down which ones changed. If this keeps happening on the same one or more there could be a cam and lifter failure.

Its crossed my mind. The motor was built and ran on a dyno, the shop says they didn't hear any lifter tapping. The motor then sat for a year in the shop, I turned it over by hand a couple of times a month.

I got to identify adjuster threads so I at least know how much preload is one turn. In the end if it takes me to 1 1/4 turn and I still have problems, I will go for a new set of lifters.

Thx..

You need to stay on the same cylinder and adjust the valves on that cylinder and move on to the next. Do not observe the valve closings/openings on one cylinder and adjust a different cylinder.

I had similar issues with mine , turned out four adjusters were tapping the baffles in my stock covers. Not sure what covers you have but if there stockers look for witness marks on the baffles.Good luck!

Loose baffles (broker spot welds) are another noise maker.

The method I was taught many years ago to has never failed me.

EO/IC rule (Exhaust Opening and Intake Closing). using a remote starter button/ switch to bump the motor around

Set the intake valve when the exhaust valve is beginning to open. This will put the intake lifter at the base circle which is where you want it to be.

Then set the exhaust valve when the intake valve is almost closed.

I have trouble remembering the above, so I wrote it on a piece of cardboard and prop it up for referencing as I adjust each valve

If adjusting hydraulics, loosen the adjuster until there is noticeable play between the rocker and pushrod / valve

While rolling the pushrod between two finger tips, begin slowly tightening the adjuster.

Just as you hit Zero lash you will feel a slight but distinct resistance. You can loosen a 1/4 turn or so and retighten to confirm several times until you get the "hang" of it.

The above resistance will be felt even with empty lifters. You will also note the " free play" is gone.

From that point, depending on adjusters threads per inch determines how far to tighten. Most are 3/8 x 24. So if one divides 1inch by 24 =.0416" per turn. All camshaft Manufacturers' I am aware of recommend. 0.020" to .040" preload.

With the above, I have always used 1/2 turn beyond zero lash.

I also agree with starting at the front of the motor, and do each valve working towards the back. Then repeat the process on the other side

Hemi covers don’t have baffles
I ran mine (440 & 383) at zero lash + 1/4 turn, no tap,

if this is a cam with fast ramps you are prob going to have some noise !

Uhhhh....yeah they do....

That little thing? I don’t even consider that a baffle

Nobody mentioned a sticking lifter. Sometimes they get a little buildup on the plunger causing them to get sticky. Use to put in a can of Rislone oil treatment to clean them up. 99% of the time the ticking went away.

and have re-tacked more than one spot weld on them.

Another thought couple of thoughts?
Are you sure it's a lifter tick and not an exhaust leak ? a small one can sometimes mimic lifter noise
I am not sure how pronounced the noise is but some hemis are known to make a bit more valvetrain noise
keep us posted