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Old 03-12-2004, 07:09 AM
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Broken Rocker In 350 Chevy

HI ALL

Yesterday whilst cruizin, i had a big rattling coming from my engine, took off valve cover to find number 8 rocker ripped apart at its base, and am not too sure why it happened.

Engine has stock 1.5:1 rockers, 7/16" screw in studs, guide plates, stock pushrods

My cam specs are as follows :
lift: .465 int., .488 exh.
lobe sep.: 112
Deg. Dur. & .050 Cam Lift: 224 Int., 234 Exh.
Deg. Adv. Dur.: 290 Int., 300 Exh.

Could it be that stock rocker will break at high revs with a cam with this much lift? Have reved it to 6000rpm. Have done 1800 miles since 600 mile breakin.

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Old 03-12-2004, 07:30 AM
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This is not a real uncommon problem. The rocker seat can become brittle over the years and then fracture. I have seen some that crack all the way around the top of the ball line and others crack like an egg shell. Many people do not replace the rockers on engine rebuilds and some never even get inspected. Since you had the one fail, you may want to invest in a complete new set while you have the motor down. Also, try to acount for all the pieces. One little fragment in the wrong place can really cost you.

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Old 03-12-2004, 07:36 AM
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Be sure and check the new one for enough oil, that my be what happened.

Troy
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Old 03-12-2004, 07:42 AM
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I've checked the oil supply to the rocker, and seems to be in check. I was told by my engine builder not to give it heaps till I could afford needle roller rockers, as standard types couldn't last with higher cam lift.
Are standard rockers really limited to a certain lift before they fail?
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Old 03-12-2004, 07:50 AM
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Yes, but your not there yet.

Troy
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69 ss rs full custom camaro 98 ISCA grandchampion
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Old 03-12-2004, 07:58 AM
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What sort of lift would cause binding or rocker damage Troy? Im only pretty new to the rodding game, sorry to be a pain
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Old 03-12-2004, 08:14 AM
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Anything over .450"-.460" lift requires the use of long-slot or roller type rockers. The slot on the bottom of the rocker binds on the stud, causing eventual breakage of the rocker and/or stud.
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Old 03-12-2004, 08:20 AM
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Thankyou for your help guys. Will replace all rockers with long slotters in the morning.

Thanks Again
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Old 03-12-2004, 08:56 AM
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Take your engine builders advise and save up for the roller rockers. It's a good investment IMO.
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Old 03-12-2004, 09:28 AM
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gt2betubbed, with roller rockers, does the motor seem to rev easier than with just stamped steel items?
Also, ive heard that aluminium roller rockers aren't as durable as steel itmes, and i was concerned about this as i can get the aluminium items for a much better price.

gt2betubbed, with roller rockers, does the motor seem to rev easier than with just stamped steel items?
Also, ive heard that aluminium roller rockers aren't as durable as steel itmes, and i was concerned about this as i can get the aluminium items for a much better price.

gt2betubbed, with roller rockers, does the motor seem to rev easier than with just stamped steel items?
Also, ive heard that aluminium roller rockers aren't as durable as steel itmes, and i was concerned about this as i can get the aluminium items for a much better price.

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Old 03-12-2004, 11:02 AM
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Well, rollers have less friction that stamped, but the increase is not really noticable. IMO, any roller rocker is better than a stamped. I've had the same problem with stamped as you with my old BBC, and went through two sets of stamped rockers. I bought the cheapest roller rockers I could find, and they are still on the motor today with no problems what so ever (sold the car to a friend). As for the integrity of the different rockers, I really don't know.
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Old 03-12-2004, 12:46 PM
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Any time I install an after market cam I install long slot rockers just for insurance. The roller rockers will be less friction, which = horsepower, and every little bit helps.

Troy
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69 ss rs full custom camaro 98 ISCA grandchampion
69 ss rs bb camaro wifes driver
66 Elcamino 350/all dz parts,ac,windows,loaded,my driver
69 ss chevelle bb conv.fresh frame off
26 T sedan street rod
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