broken push rod

broke a intake push rod today after a beating. it seem find till i was cruising back then it let go. this is the second time in 3 years that it has happen. thought that i bent a valve to bc after fixing the push rod it didnt run every well on the ride home but found that i knock off a plug wire wild working on valve covers and didnt notice it. the intake push rod brakes the top off think that the push rod is rubbing on the rocker under side but need to check it out. thought it was a fluke 3 years ago but it has happen again

Same valve?

What size pushrods? What cam?

back in the day i had some 5/16 that had the ends pressed in and they would come "unpressed" from time to time

dfree383 wrote:Same valve?

What size pushrods? What cam?

3/8" 8.750" solid flat .024 lash haven got it apart yet doing the honey dooooo. daughter is getting married and everything has to be right she got the whip out sometimes that a fun thing but not this time

How big of cam? wall thickness on pushrods? ? How much spring? How old are they?

dfree383 wrote:How big of cam? wall thickness on pushrods? ? How much spring? How old are they?

258 @ .050, .615 lift, .080 wall, 140 seat 360 open, 3 years this happen at drag week in 09 then again yesterday same push rods but different location first time was intake on # 7 this time #2 & #3 intake

I'd put some new springs in it when you replace the pushrods and replace all the push rods, keep the old ones for spares.

Be sure to check all the lifter and rocker cups real close.

is the mid lift system the way to go for geometry on the valve train. when i build the engine 10 years ago i used the center of the valve stem method that comp and a few other use.

Are You referring to using miller rockers?

dfree383 wrote:Are You referring to using miller rockers?

no im using scorpoin rockers

quick 52 wrote:is the mid lift system the way to go for geometry on the valve train. when i build the engine 10 years ago i used the center of the valve stem method that comp and a few other use.

The way Comp Cams tells you to do it is a good method.

Can you post a picture of the broken pushrod?

466cj wrote:

quick 52 wrote:is the mid lift system the way to go for geometry on the valve train. when i build the engine 10 years ago i used the center of the valve stem method that comp and a few other use.

The way Comp Cams tells you to do it is a good method.

Can you post a picture of the broken pushrod?

i called scorpoin this morning and they said the center valve stem method is what they recommend also got some pic.[img:7b97]https://i1227.photobucket.com/albums/ee432/quick52/DSC05725.jpg[/img:7b97]

one pic didnt come out

Hard to make out much detail, but they do not look over heated. Looks like a stress crack or metal fatigue. Some pictures of the rocker ball area would be helpful. What do the ends on the other pushrods look like. Are they worn? I think if it was me I'd put a new set of pushrods in it, but not the same ones.

Steve

Any signs if valve float ? Star pattern on the valve tip, chafing on the locks?

Have you checked the pressure on the springs.

well found the problem the rocker was to tight on the under side PR to rocker it had a light wittness mark and only .009 clearance. the PR was being side loaded. when i set it up i focus so much on getting the best pattern on the valve stem dead center and narrow that i over look the big picture good clearances a lesson i wont forget. the new contact mark moved alittle around .030 off center but is wider was .050 wide now .075. installed all new PR and im getting a stud girdle got to get a spring pressure tester for on the engine friend has one if not ill pull them and check them when i get the girdle

Glad you were able to get to the root cause. So very much with this stuff is attention to detail, every change can cause an issue, sometimes issues you just would not expect. All I can say is I try to eyeball everything and watch what everything is doing over the full motion. Sounds like you found an ok comprimise. Looks like you were using a 180 degree ball end. You could go to a 210 degree ball end if you want to preserve the better geometry.

Steve

466cj wrote:Glad you were able to get to the root cause. So very much with this stuff is attention to detail, every change can cause an issue, sometimes issues you just would not expect. All I can say is I try to eyeball everything and watch what everything is doing over the full motion. Sounds like you found an ok comprimise. Looks like you were using a 180 degree ball end. You could go to a 210 degree ball end if you want to preserve the better geometry.

Steve

there was still room in the cup it was the rocker body that was the clearance problem. i was thinking of milling the PR slot deeper to gain clearance but needed new push rods anyways so i used a shorter PR

I see. Yes certainly could clearance it. Those Scorpion rockers are a bit chunky LOL

Keep in mind, just because your roller is in the center of the valve tip doesn't mean your geometry is good. The pushrod end of the rocker is equally as important.

well i hope to build another engine this winter maybe ill figure it out by then ive been play with this one sence 1999 thought it was good lots of passes and miles but there i go thinking again.