TD roller rocker pre-load

[Toby_Goodmk]

I am green here so I apologize for an easy question. I am chasing some false knock at low boost pressure that I feel may be part of the valve train. I removed the DS valve cover tonight and could spin many of the pushrods. I run Dave Husek's roller lifters and he stated .050 preload. Now having some knock around sense....wouldnt having .050 preload always have tension on the lifter....making it impossible to spin the pushrod by hand?

I am running 1:55 TD

 

[wantattype2]

No , because when the motor is shut off the oil pressure in the lifters bleed off enough to let the pushrods spin.

 

[Toby_Goodmk]

so....million dollar question. You cannot adjust the rocker with it running. How would you set and check if correct?

 

[TurboBob]

lots of tutorials for setting the valves.

basically you adjust valves when they are closed.. loosen the adjuster nut and let the internal spring in the lifter raise the plunger to the top.

slowly tighten the adjuster to take up all the play, then tighten it another "amount". Everyone has their opinion on how far to go.

this puts the lifter in "preload", if the intake is off you can see a gap between the plunger and the snap ring.

Make sense?

Bob

 

[wantattype2]

so....million dollar question. You cannot adjust the rocker with it running. How would you set and check if correct?

On my car I have Adjustable push rods and by measuring the length I found that by lengthening them one turn made the push rod .030 longer. So in my case when I install them and adjust them to zero lash adding one turn preloads the lifter .030
Since you have adj rocker arms you need to find out how much one turn of the adjusting screw moves the cup in the arm.

 

[Toby_Goodmk]

lots of tutorials for setting the valves.

basically you adjust valves when they are closed.. loosen the adjuster nut and let the internal spring in the lifter raise the plunger to the top.

slowly tighten the adjuster to take up all the play, then tighten it another "amount". Everyone has their opinion on how far to go.

this puts the lifter in "preload", if the intake is off you can see a gap between the plunger and the snap ring.

Make sense?

Bob

Engine hot or cold?

Performing this on a hot air car will take a little planning since it will take a bit to remove DP, and valve cover on pass side if engine needs to be warm.

 

[fastblackracing]

You can do this cold, you need to find the threads per inch of the adjusting screw, a lot of them are 3/8-24 TPI. 24 TPI is .042 thou per tread or 1 turn of the adjuster, do you know what TPI yours are?

 

[Toby_Goodmk]

You can do this cold, you need to find the threads per inch of the adjusting screw, a lot of them are 3/8-24 TPI. 24 TPI is .042 thou per tread or 1 turn of the adjuster, do you know what TPI yours are?

Thanks....he recommended .050

 

[Toby_Goodmk]

ill check tpi

 

[fastblackracing]

Thanks....he recommended .050

Does the false knock happen right when you floor the gas pedal or is it later on?

 

[Toby_Goodmk]

tpi is a 3/8-20

 

[Toby_Goodmk]

Does the false knock happen right when you floor the gas pedal or is it later on?

When building the boost up about 5 psi. It can be a gradual RPM build at highway speed or an aggressive roll into the throttle from a stop. I dont have the nads to nail it yet till the KR issue is solved.

 

[Toby_Goodmk]

1-1/4 turn is .050, just checked with dial indicator in a vice

 

[fastblackracing]

1-1/4 turn is .050, just checked with dial indicator in a vice

awesome sounds like you got it handled.

 

[Pronto]

tpi is a 3/8-20

20 pitch should be one turn=.050

 

[fastblackracing]

3/8 -20 is not a common thread. You sure its its not 24tpi, as your bench vise test results support it being 24tpi.

 

[RmvBfrFlght]

When checking for the zero preload position, gently jiggle the push rod up & down. Doing it this way it is easy to feel for when the lash goes to zero.

I don't know who came up with the pushrod spinning idea, as it doesn't work. Even worse on an engine that has been run as the mating parts get highly polished. This makes it real easy for the pushrod to be spun even with preload on it.

RemoveBeforeFlight

 

[Pronto]

3/8 24 pitch is the norm for fine thread. One turn would be .0416

 

[Toby_Goodmk]

3/8 -20 is not a common thread. You sure its its not 24tpi, as your bench vise test results support it being 24tpi.

I have one of those TPI check tools from craftsman, and the 20tpi fits right into those grooves. Here is another interesting factoid. The supplied bolts for the rocker arms one snapped at 25lb, I have to be doing something wrong lol. I was able to extract the thread left into the head, but I felt the other bolts and they feel stretched in the middle. And, this is a 6 mark USA bolt. Is there a sequence placing the arm back on the head with the valves intact? I thought even amounts of torque back and forth would allow an easy push of the valves and lifters.

 

[RmvBfrFlght]

The T&D's use a 7/16"-20 adjuster, which makes 1 turn equal to .050" change. There is also something about where the adjuster sits vertically within the rocker. There is an oil feed hole that needs to remain open. Too far down (and maybe up) and the oil hole gets closed off. I don't recall the exact cont, but you can check this via the number of threads the adjuster is above the nut.

For the retaining bolts, I'd buy new ones, no sense in using ones that have possibly been over-torqued.

When I tighten the shafts down, I thread in the bolts finger tight. Then check that all pushrods are properly seated in the rocker cups and the lifter cups. Then tighten each retaining bolt about 1/4 turn at a time. Doing the center one first, then the two outer. Then torque them to spec (25 ft/lbs).

RemoveBeforeFlight