sofakingdom

iTrader: (1)

The 79xx series has .080" wall thickness. The 84xx is .105".

79xx is plenty adequate.

The exact part # push rod you need will depend on the length required, which can only be determined properly by measuring.

Zylinder

Can i also use the Magnum series "CCA-7608-16"
They are also one-piece and of Chromoly and way better than the high engergy.

Zylinder

Today i used a rocker and pushrod from my old set and did a test.
I put color at the valve tip installed the rocker and pushrod and screwed the roller tip a few times (cam on base cicle).


It fits not so bad.
These Pushrods are 7.205 in long.


The magnum and hitech series has only a rod with 7.200 or 7.250 in
The contact point moves a litte to the intake side (with 7.200)
Is that a problem, or should i use the next longer rod ?

Zylinder

Here a litte bit better

sofakingdom

iTrader: (1)

The Hi-Tech series is available in 5/16" diameter with .080" wall in .050" increments from 6.200" to 9.500", and in .025" increments from 7.300" to 7.500" and 8.000" to 8.450". It has you covered.

6.200" 7751
6.250" 7917
6.300" 7752
6.350" 7753
6.400" 7754
6.450" 7766
6.500" 7767
6.550" 7768
6.600" 7769
6.650" 7770
6.700” 7771
6.750" 7772
6.800" 7929
6.850" 7930
6.900" 7933
6.950" 7935
7.000" 7936
7.050" 7937
7.100" 7938
7.150" 7939
7.200" 7940
7.250" 7944
7.300" 7949
7.325" 7794
7.350" 7950
7.375" 7795
7.400" 7955
7.425" 7796
7.450" 7956
7.475" 7797
7.500" 7957
7.550" 7958
7.600" 7959
7.650" 7960
7.700" 7963
7.750" 7970
7.800" 7972
7.850" 7974
7.900" 7993
7.950" 7994
8.000" 7995
8.025" 7746
8.050" 7996
8.075" 7747
8.100" 7997
8.125" 7748
8.150" 7965
8.175" 7749
8.200" 7966
8.225" 7750
8.250" 7967
8.275" 7773
8.300" 7971
8.325" 7774
8.350" 7973
8.375" 7730
8.400" 7945
8.425" 7731
8.450" 7975
8.500" 7976
8.550" 7948
8.600" 7977
8.650" 7775
8.700" 7776
8.750" 7778
8.800" 7779
8.850" 7780
8.900" 7781
8.950" 7782
9.000" 7783
9.050" 7784
9.100" 7785
9.150" 7786
9.200" 7787
9.250" 7788
9.300" 7789
9.350" 7790
9.400" 7791
9.450" 7792
9.500" 7793


To properly do a push rod length test you need to use valve springs that are weak enough that the one in the lifter is stronger, or make a pair of the particular lifters you are using into solids, or make an educated guess at how far the lifter plunger depresses and add that length to whatever you find to be the optimum.

It doesn't matter where on the valve stem the contact point lands, within reason. That's one of the old myths that we had all hoped would get dispelled when Algore invented the Interwebz and information could flow freely. Unfortunately it didn't work that way... instead, all the old myths now just get repeated on the Internet just like they did in McDonalds parking lots on Friday night back in the day.

Correct adjustment is achieved when the witness mark on the valve stem is as narrow as possible. NOT when it's centered. Narrow indicates that the rocker tip's motion is most closely aligned to the valve stem's motion.

I would recommend not using the Magnum, get the Hi-tech. It's just a better product all the way around, for very little more money.

Order the rockers you want to use, along with an adjustable push rod. Repeat the process you just performed after installing a pair of your new rockers onto one cylinder on each side of the engine. Check each one by installing the adjustable push rod and adjusting it for the narrowest possible sweep on the valve stem (narrow witness mark). See what length it is, add .050" to it to make up for the lifter plunger being depressed, and order that length in the Hi-Tech series.

Zylinder

Thanks Sofa for your comments. You are right, the internet is full of unqualified statements even at superchevy.


Idea.:
I can measure how far the pushrod comes out of the aligning holes on base cycle and at full lift (without rocker). At half of this distance (half lift) the point of contact should be at the middle of the valve tip (correct ?). Now i make a sign on the pushrod at this half lift to koow when it takes place. Then i install the rocker (with preload) and turn the engine to that half point (mark at the pushrod). When the lifter bleeds off the sign also comes down and i can turn the engine a little more.
In this case the mark on the valve tip should end at the middle on the tip.


Is that correct ?

sofakingdom

iTrader: (1)

It doesn't matter where on the valve tip the contact point is.

The rocker tip swings in an arc. But the valve moves in a straight line. However, the valve is not parallel to the stud, so when the valve is closed, the tip is closer to the stud, but when it's open, it's quite a bit farther away. As the rocker moves, the tip starts out closer to the stud, swings out farther away, reaches a maximum when the rocker is partway open, then begins moving back toward the stud. Meanwhile, as the valve is being forced open at the same time, the tip of the stem moves farther from the stud. As you can see, the arc of the rocker and the "tilt" of the valve cause the contact point to move relatively less during the 1st half of the rocker arc since both the rocker tip and the valve stem are moving away from the rocker stud, but then relatively more during the 2nd half, as the valve continues to move away from the stud but the rocker swings back toward it.

Every head is different. Maybe not ALOT different, but they're DEFINITELY NOT the same. The angle that the valves make with the studs is different, the height of the valves in the head is different, the angle the stud is installed at is different, ... EVERYTHING is different. No 2 heads are quite "the same".

Rockers are different too: if you think of the rocker as having 3 "critical" points - the center that it pivots on, the push rod seat, and the tip that contacts the valve stem - no 2 rocker designs are identical. Those 3 points make a triangle, any one of the vertices of which can be different from the same vertex in any other rocker design, in either dimension (height or distance from the stud).

The object of the exercise of selecting push rod length, is to position the particular rocker you are using, in the point in its arc where there is as little as possible relative motion between its tip and the valve, perpendicular to the valve stem. At this point the motion of the valve is also maximized... that is, incorrect geometry results in both REDUCED valve lift and INCREASED guide wear. The side-to-side "scrubbing" motion of the rocker tip across the stem is what produces guide wear; to minimize wear, which is to say, maximize parts life, the "scrubbing" or "sweep" should be minimized. Furthermore, since there's more force available to cause guide wear when there's more spring load, then any error or compromise that is made, should favor minimizing the sweep at FULL OPEN (highest force) over full closed.

What you are describing won't work, because it doesn't take the valve's motion into account. The ONLY way to really get it RIGHT, is the way I've described repeatedly.

Use the adjustable push rod to find the length that results in the NARROWEST POSSIBLE sweep. Don't pay ANY attention to where on the stem the rocker lands because IT DOESN'T MATTER.

Buy the valve spring parts (shims keepers etc.), adjustable push rod, and rockers of your choice, as described. Set up the spring installed height correctly at its 1.750" spec by selecting a shim pack on each individual spring, within .015" at the worst and closer if you can get it. Install at least one pair of rockers on each head, one exh and one int. Find the push rod length that produces the NARROWEST POSSIBLE SWEEP on the valve stems, IGNORING where on the stems that sweep happens to be. They will NOT all be the same, but should be close: choose the shortest of all the ones you test. Place a 2nd order, for the Hi-Tech push rods in that length, from the part # table I posted for you. No more arguing or trying to get out of doing it RIGHT if you want it to come out right.

Zylinder

you are right.


At which point should i start with the tests ?
With the original pushrod length minus 0.2in ?
And than i repeat the test with 0.05in increments.


What i also need is a weak dummy spring.
in about 2 weeks i have the first parts and can start.


Tanks a lot for your time (all of you).

sofakingdom

iTrader: (1)

I usually start with the stock length, or whatever doesn't make it immediately look stupid.

Then just watch what the pattern does as you adjust. It will either narrow or get wider; keep going the same way or change direction accordingly. It will be easy to see.

cardo0

I'm hoping you understand here that w/o SA rockers you need to clearance each of the 16 p-rod slots for a smooth motion and almost no drag on the p-rod. If you leave bad alignment in the slots you will be right back with rocker damage again.

cardo0

Zylinder, I think you will find the adjustable p-rod is best used with the engine out of the car. All you really need for modest lift cams (under 0.500" lift) is that checker tool. . With p-rods on the shelf in 0.020" increaments at best do you expect to gain anything in accuracy with the much, much more difficult adjustable p-rod??? Let the NASCAR teams do the fancy methods. Even David Vizard recommends the checker tool and if you haven't read his "how to" book(s) on the small block Chevy you should.

Zylinder

The new parts arrived yesterday. I removed one exhaust spring and put a dummy in. The original pushrod length looks fine (7,200 in).
Markings are centered at the valve tip


How much ist the shift of the contact point with preload ? With the dummy in i cant set any preload.


Now i try to remove all of the debris and metal shaving out of the engine. I purchased a magnetic oil drain plug and serveral magnets (pan, filter, ...)


I hope the engine is back to life in a few days.

cardo0

As far as catching ferrous metal It's not too late to epoxy some strong magnets near the oil drain back holes in the lifter valley. FYI the ultrasonic toothbrush replacement brushes have a hell of a strong but tiny magnet. You can also paint the lifter valley to seal it. Electric motor winding coating used to be popular but I imagine something like POR 15 is just as good and just as tough.

Let us know how it runs.