So I broke a rocker stud today..

[WHATA SQUIRT]

what would cause this? hyd. flat tappet cam..found lifter in valley and push rod against camshaft..this all went wrong at about 3500 rpm just cruisin'..

[Fiat48]

Leak test that cylinder and see if you have a bent valve. It is possible the stud just broke, regardless of brand.
See if the pushrod is bent also. Try to rule out piston/valve contact before replacing parts.

[RICHARD TILL]

i`ve had this happen three times on two different motors in the last ten years. i wish i knew the answer too. there was no other damage. just replaced the stud and went ahead. these motors even had stud girdles on them. both roller cams. maybe its just the weakest link in the chain theory in my case.

[victorfb]

more info needed. what kind of rockers are being used? how much lift on the cam? too much lift with stock style rockers can cause a bind. fulcrums may be sticking with excessive wear and no oil supply. how much seat preasure and how much spring preasure at full lift? did you check for coil bind? excessive wear in valve guides causing sticking? intake or exhaust? what style valve seals? unbrella type seals on the exhaust valves allows a bit more lubrication to the guides. were the heads run hot first then brought back down to 3500 rpm? are you running pushrod guides? was the pushrod bent? were the rocker studs recently removed and reinstalled/replaced? torqued properly? obviously many variables here, but even if everything was correct, you can still just have a bad stud that was bound to break. we all know ARP makes a great fastener, but ive had a bad batch that stretched a few head bolts and that wasnt even on the final step. couldnt even get to 50#. just one of those things. that said, make sure to go through the entire valve train real good and check for all these things. proper pushrod length and valve train geometry is very important.

[victorfb]

also i believe some people have had problems with the gen5 blocks that have had missaligned lifter bores. just something to look into if your running a gen5 block.

[WHATA SQUIRT]

ok, so rockers are comp pro magnum,cam is comp 240-4 .564 lift,heads are factory cast 188 style heads, valve springs matched to cam,seat press.have to look at build sheet,push rod guides were installed,push rod doesnt appear bent, motor never saw more than 150*,or turns more than 4600 rpm ..this thing is brand new only 2-3 hrs on it,and built by very reputiable builder..not that mistakes aren't made..the odd thing here is the stud broke half way in side poly lock,possible torque issue,I dunno but its broken now.

[WHATA SQUIRT]

also I noticed that the lifters are only about 80% on trhe camshaft .not centered fo sure..this is a gen IV block,cam appears to be pushed back some is this normal? One would think cam and lifter should be centered...?

[058]

also I noticed that the lifters are only about 80% on trhe camshaft .not centered fo sure..this is a gen IV block,cam appears to be pushed back some is this normal? One would think cam and lifter should be centered...?Flat tappet lifters are never centered on the lobe. They are offset to promote rotation.

[Beer-30]

Could be as simple as a faulty stud. It happens. Were they new or re-used?
As Fiat said, check all remaindant components for pre-failure bendage.

[WHATA SQUIRT]

unfortunately the only part that we re-used were valves and rocker studs...damn..well I guess its time for more camshaft anyway,just not the way I wanted to go about it..

[Havasu47]

If the rocker nuts were removed the first time without unlocking the set screw it will put tremendous stress on the stud where you describe the stub breaking, or if the nut is used to finish tightening after the set screw is already tight.

[Wicked Performance Boats]

Just buy a new set of quality rocker studs and move on. Budlight