Thread: Broke Comp Cam promagmun rocker

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I broke a rocker this weekend. Pat, do you still recommend Crower roller rockers. I have 1.7 stud mounted rockers. Used in 496ci 9.5:1 engine with solid roller cam with .650 lift, about 298 duration. Should I use aluminum or stainless. Crower also has centerline rockers in each type. Luckily I caught this before it dropped any junk into the engine. I was going to use Crowers originally but I've had this new set of Comp Cam rocker laying around the shop for a few years. Figured I might as well use them. Dumb. Thanks, Keith

cam not to big so spring seat and open is not very hi most aluminum rockers will do the job stud rockers i used. Crane golds . Harland Sharp. Scorpion.PBM andHowards .all will hold up good . the Crower.s are very nice. any rocker in this list will work if you get the mild lift right . you say you busted steel body a ultra pro magnum Comp rocker? check your valve train for coil bind . check push rods. i would send that rocker back to comp i would think they would want to look at it . i use this rocker in two builds looks good no come backs

Here is a basic guideline for spring pressures:

Recommended Valve Spring Pressures: Engine Builder

Originally Posted by 1gary

Here is a basic guideline for spring pressures:

Recommended Valve Spring Pressures: Engine Builder

thats nice gary .he was not ask about that .i said for that size cam all rocker arms will hold up as that cam many not need a big spring i base spring rate off how much rpm needed to hold the lifter on the lobe. he has springs. he wanted to know what rocker would hold up

Your right Pat.Just thought if he was experiencing coil bind it would break things.

Originally Posted by 1gary

Your right Pat.Just thought if he was experiencing coil bind it would break things.

who knows ? as he busted one rocker arm i would say that if he did run i to coil bind or ran out of room retaner to valve guid ? that spring was setup wrong . if he went in to valve float with a roller cam that bad to bust a rocker he better start looking it the pins in the lifters cam lobes pushrods as well has bent valves

Thanks for the quick reply. The rocker I broke was the older design promagnum. Before I had these on the engine I had a set of Unknown brand aluminun rockers on the engine for 2 years. They were ok but seemed to be getting a little loose. I checked for coil bind back when I put the engine together. Can't remember seat pressure right off. It is what Comp cams recommended when they ground the cam. Cam is a custom grind billit. Shift point is 7000 Valves are +.100 manley sever dutys. The heads are heavily ported and flow benched 781s

yep if steel core cam i like abit more seat and open then they may call for with ss valves 3/8 stem valve heavy valve train parts if it,s going upstairs . yes do not run no name rockers .if you stick to that line up i listed you will be ok . from what i seen your not the first to bust the older ones .i will say i do like there new rocker take the time to setup and check the mild lift after you get the new rocker arms

Although Pat has said "mild" lift twice now, I'm thinking he means "mid" lift.

Have had lot of Comp rockers break on marine engine builds. Which cyl by the way?

Originally Posted by techinspector1

Although Pat has said "mild" lift twice now, I'm thinking he means "mid" lift.

why yes i do . i would never use the comp old rocker on a boat in. but seen T&D fail in time in off shore use .in fact i never used much of Comp rockers or roller lifters i think both there roller lifters and rockers are better built in the last couple of years

Originally Posted by turbo2256b

Have had lot of Comp rockers break on marine engine builds. Which cyl by the way?

The one that broke was #8 Exhaust.

If I use Crowers should I soak them in cat pee for awhile. Yes, I remember :-)

Originally Posted by BigBlockBird

The one that broke was #8 Exhaust.

seeing how them rockers were used before less you marked were they lived before put them back in order ?i can not see how you could read any thing in to this . but i can see the Ex side failing first in time . but i am all ears if he can shed any light why one rocker would fail on just one hole before any others if its valve train harmonics. i loved to see any proof he has on this as i been building bbc for many years now my luck with top end of bbc been very good.i have many out there running very hi rpm

Originally Posted by BigBlockBird

If I use Crowers should I soak them in cat pee for awhile. Yes, I remember :-)

sure if your cat has alot of zinc in his peee