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#1
12-17-2018, 07:14 PM
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What causes valves to drop?
Is it broken springs, retainers, low quality valves, or other things?
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#2
12-17-2018, 07:28 PM
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Unless everything is just wore out, low spring pressure high rpm, valves not suited for the task and resulting valve bounce is a timebomb.
I have a couple sets of ra 4 heads got from a buddy that succumbed this way.
__________________
 1963 Cat SD Clone (old school) streeter 1964 GTO post coupe, tripower, 4speed (build) 1965 GTO 389 tripower, 4 speed, driver 1966 GTO dragcar 1966 GTO Ragtop 1969 Tempest ET clone street/strip 1969 GTO Judge RA lll, auto 1969 GTO limelight Conv. 4speed go and show (sold) 1970 GP SSJ 1970 GTO barn find..TLB…390 horse?….yeh, 390 1972 GTO 455 HO, 4 speed, (build) 1973 Grand Safari wagon, 700hp stoplight sleeper 525ci DCI & 609ci LM V head builds |
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#3
12-17-2018, 07:45 PM
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Several possibilities. ..I was assembling a set of E-heads recently. As I reassembled the springs, 1 of the valve locks cracked. Not new but they didnt have a lot of run time on them. Simlle thing that would have been really bad if it happened during a run.
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#4
12-17-2018, 08:15 PM
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I haven't had a issue but my son was asking about it. My new build will have a solid roller with 0.600" lift and I just don't want trouble. Lots of street miles and some strip passes.
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#5
12-17-2018, 10:09 PM
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New build? Care to share specs?
Kevin |
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#6
12-17-2018, 10:27 PM
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Could be a bunch of stuff. I buy real good retainers, you have to make sure the keepers fit the valve notch real well. High revs, low spring pressure piston smacks the valve. Then make sure Rocker arm geometry is good. and of course make sure there is no spring bind.
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#7
12-17-2018, 10:43 PM
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Extremely worn valve guide with a two piece valve.
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#8
12-17-2018, 11:13 PM
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Quote:
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#9
12-18-2018, 01:50 PM
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Or a 409 with coil bind or exhaust valve hitting block(chamber in the block) and breaking rocker arms that hit the retainer.
__________________
Skip Fix 1978 Trans Am original owner 10.99 @ 124 pump gas 455 E heads, NO Bird ever! 1981 Black SE Trans Am stockish 6X 400ci, turbo 301 on a stand 1965 GTO 4 barrel 3 speed project 2004 GTO Pulse Red stock motor computer tune 13.43@103.4 1964 Impala SS 409/470ci 600 HP stroker project 1979 Camaro IAII Edelbrock head 500" 695 HP 10.33@132 3595lbs |
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#10
12-18-2018, 08:50 PM
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What happens to the new LS motors, the seats?
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#11
12-18-2018, 08:55 PM
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Quote:
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#12
12-19-2018, 02:55 AM
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The last time I had a valve drop (my first attempt at a blown-alky Pontiac almost 30 years ago) was due to the head falling off the intake valve of #2 cylinder. The whole corner of the iron block exploded onto the track (I foolishly picked up the wrist pin and burned my fingers!). Photo is the exhaust valve from #2.
As many of you are aware, I pay a lot of attention to Mickey Thompson's dealings. But I have to admit that he was somewhat "behind the curve" in promoting his two-piece intake valves. My intake valve simply "came apart" at the weld.
__________________
Anybody else on this planet campaign a M/T hemi Pontiac for eleven seasons? ... or has built a record breaking DOHC hemi four cylinder Pontiac? ... or has driven a couple laps of Nuerburgring with Tri-Power Pontiac power?(back in 1967) |
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#13
12-19-2018, 09:38 AM
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Quote:
From heat? |
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