valve tip wear - Team Camaro Tech
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post #1 of 5 (permalink) Old Sep 19th, 03, 04:36 PM Thread Starter
Senior Tech
 
Join Date: Jun 2003
Location: columbus oh.
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Question

after 5000 miles on the rebuilt motor,i pulled the valve covers to check hydraulic lifter adjustment.i found the #3 rocker wasn't sitting straight on the valve tip,and the valve tip was
"mushroomed" and pretty chewed up.after pulling the rest of the rockers on the passenger side i found similar mushrooming on the #3 intake and both valves on the #4 cylinder!the motor has only seen 5000 rpm a few times.the timing was found to be too advanced when a new balancer was installed.
could detonation cause this?the engine rotated freely when the cam was installed.
i will pull the rockers on the other head,and check the pushrods for straightness tonight,and try to get some good pics to post when it's light out.
thanks in advance for any advice or suggestions anyone might have!
Eric

86 camaro,383,topline vortecs,scat crank,wiseco forged 9.5:1,6"scat rods,comp xs282s,performer rpm,750 proform vac sec,msd in cap, hooker coated 1 5/8"headers,3"flowmaster,700r4,2800 stall,3.42 10 bolt posi,hotchkiss lca's,aje tube k member & a-arms
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post #2 of 5 (permalink) Old Sep 20th, 03, 02:46 AM
a67
 
Join Date: May 2003
Posts: 416
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Sounds like the pushrods are not getting 'guided' properly. If you have newer heads (> 87) most likely will need either self aligning rockers or guide plates.

If you have the original heads ('84 I believe the sig has), then the openings in the heads guide the push rods. Check that they were not drilled out which would then require self aligning rockers or guide plates.

Another to check for is that the rocker arm hasn't cracked. Had it happen on a ball pivot style which caused the rocker to slip to the side as it flexed.

Is the lash correct? If too loose can allow the rocker to flop sideways a tad.

Bob.
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post #3 of 5 (permalink) Old Sep 20th, 03, 10:24 PM Thread Starter
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well bob, i got the other side dissasembled and the #4 exhaust valve is showing the beginning signs of wear that the #3 and #5(typo in original post)valves were showing!these are 1980-84 #1402260 heads and they have not been drilled.lash was fine when i checked it just before the teardown(1/4-1/2turn in from clatter on a warmed up engine}.
the rockers show no signs of cracking but the slots on the worst two show signs of side loading.
also every offending vale tip has some light heat discoloration on its corresponding pushrod at the head/guide.could this be the effect of a wiped cam?
the pistons are dished and the most advance i think the motor saw was around 16*static with light springs from mr gasket and 12*vaccum.most of the time was at 14*,still if i heard detonation i always backed the timing off.i always run 92-94 octane too.
sorry for the long reply but i wanted to give as much info as possible.this one has me
thanks again
Eric

86 camaro,383,topline vortecs,scat crank,wiseco forged 9.5:1,6"scat rods,comp xs282s,performer rpm,750 proform vac sec,msd in cap, hooker coated 1 5/8"headers,3"flowmaster,700r4,2800 stall,3.42 10 bolt posi,hotchkiss lca's,aje tube k member & a-arms
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post #4 of 5 (permalink) Old Sep 21st, 03, 04:58 AM
a67
 
Join Date: May 2003
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There is another possibility, either the spring is binding or the retainer is hitting the top of the guide. Check the pushrods (roll across piece of glass) to see if any are bent. If so this is a sure sign that something is binding.

A wiped cam usually turns up as noisey loose lash. As the lobes wear down the lash opens up.

By any chance is the engine running self aligning rockers now? This can cause the push rods to bind on the guides (heat marks).

Bob.
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post #5 of 5 (permalink) Old Sep 21st, 03, 11:50 PM Thread Starter
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they're just stamped rockers (for now!)but i think the coil bind idea might have it.think it's time to bulletproof the valvetrain!i have the correct springs for the cam and am searching for matching retainers,locks,and stainless " hardened tip" valves.does anyone know what a good seat enlargement/valve job runs these days?


1

86 camaro,383,topline vortecs,scat crank,wiseco forged 9.5:1,6"scat rods,comp xs282s,performer rpm,750 proform vac sec,msd in cap, hooker coated 1 5/8"headers,3"flowmaster,700r4,2800 stall,3.42 10 bolt posi,hotchkiss lca's,aje tube k member & a-arms
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