Push Rod Length?

[SubLime440]

I'm shaving my heads .050 and have the Harland Sharpe Adjustable rockers (MP .509 cam).... Do I need to get new pushrods because of geometry or can I adjust the rockers to compensate?
Should I get an measuring push rod?
Anybody?

[DAVE JONES]

I cant tell you from real life experience since I bought and set my roller rockers up after the heads were cut.
It would also depend on how well you had them set up before they were cut. The adjustable portion of the rockers is to easily set preload or backlash to your liking . Shimming the rocker shaft would probably work but again. It would depend on how you had it setup previously. See what the others have to say. If it were me, I'd look into the shims first to see if that would work. My guess is that they will.

[SubLime440]

Have not been set up before... Bought them on Moparts board... I need new pushrods (ball-cup) anyways, I just don't want to get the wrong size....
Anybody run into this situation????????

[Hammer 74]

I have had heads cut and made up the difference with adjustable Crane rockers. Not .050 but I think you can just use the rockers to make up the difference. You have to remember that the only change to the geometry by removing material from the head or block is the pushrod length. the adjuster on the rocker can be backed off .050 and be in the same relationship as before the heads were cut. Rocker shims scare me. I think they compromise stability of the shafts. Maybe I would use them on a 2bbl 318 with stock valvetrain but not anything more powerfull. The most important factor is the relationship of the rocker angle to the valve which will not change with your head milling so I think take up the slack with the rocker. Thats what they are for and to equally preload the lifters/ set lash. My 2 pence.

[SubLime440]

That is what I was hoping for.... Good I'll just get some standard length push rods..... Thanks Again..!!!!

[Glen440]

Wait!
I ran into problems with mechanical valvtrain. I was running factory mechanical setup on my 400. I was using
stock Mopar pushrods and they worked great. I then went to put it on my 440. I bought Mopar pushrods for the 440 and they were 1/4 inch too short. I measured them and they were the right ones. I ended up getting cut to length pushrods. You don't want to fool around with the geometry or you'll bend pushrods. The rule of thumb is to have 1 to 2 threads showing on the bottom of the rocker when properly adjusted. I made one to length and then tried it on a few rockers to make sure.
The shims I think hurt rocker oiling. .050 is alot and you may get away with adjusting it but maybe not. The more you adjust the adjuster down the more it tries to bend the pushrod. The hardest thing is cutting them.
Luckily my brother is a machinist so he cut mine.
Just looked at the last post- you can't back them off .050 cause if your cam is pretty big it'll spit pusrods when its at full lift. Geometry only changes when you screw the adjuster in and out. My friend had lots of problems on his stock car with milled heads and stock length pushrods.

[Hammer 74]

The 509 cam you are using is a hydraulic cam and you need to preload the lifters some. Glen440 is correct that the geometry changes when you move the adjusters. Not sure what his length problem was but if you knew what the factory tollerances were on lifter preload you would probably feel save using the adjusters to take up the slack. If you were to use rocker shaft shims you could get away with a .03 shim.
Hydraulic lifters have around .15" of adjustability and all you need is .05. It would be like you loaded the lifters an extra .05. My 4 cents worth.

[Glen440]

You should run very little preload on hydraulic lifters or you'll get early valvefloat. The max preload I think is .060
you should run on lifters. I was told to set mine at zero then turn the adjuster 1/4 turn. With .150 preload your valves likely won't close.

[Hammer 74]

If you were to run 1/4 turn preload on your lifters you will get a tapping from them when you start up the motor until the lifters punp up. 1/4 turn is only .0104 preload. I did not say to load the lifter .15, I said that is how much a stock lifter can handle and is what the factory used with for a new motor. I have seen stock pushrods that were .045" different in length from one stock motor to another.
I use Crane rockers and they say to go 3/4 to 1 1/2 turns preload. That equates to .0312 to .0625 preload. I am not sure how much Harland Sharp wants but the crane numbers are for a 3/8-24 screw.
Think of it this way; before you milled the head you would have say .041 preload (1 turn). You take .05 off the heads and then without readjusting the rockers installed them. You would now have .091 preload. The .05 you took off the head would translate into about 1 1/4 extra turns of preload. The factory would have left it alone.
Do what Harland Shark recomends as far as preload and you will be fine with stock length pushrods.

[SubLime440]

Now I'm worried.... I should probably buy a measuring push rod first before purchasing new push rods for this setup.....

[Diplomat360]

You really should get the checking pushrod and go over your setup...make sure the dimensions are right...if you don't, and problems arise later on you'll never know whether the pushrod length is causing you the problem or maybe something else.

I'm going with a Crane 1.6:1 mechanical rocker arm, plan on having only 1-2 threads showing, and doing a check on the length first. Ask your local machine shop if they can lend you a pushrod length checker...

[bwlizard]

Is lifter preload and valve lash the same ?

[waynebo]

you gota be careful,if you backup to much on the adjuster nut you will have the pushrod cup hitting the rockerarm @full lift.@ max lift look @ the bottom of the adjuster stud and pushrod cup and see what it looks like,plenty of clearance no problem. Mopey