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#1
07-08-2019, 02:23 PM
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PUSHROD SNAPPED IN HALF
Anyone ever have a pushrod snap in half? What would cause this to happen?
Last edited by BLACK 67 GOAT; 07-08-2019 at 02:36 PM. Reason: Add a picture |
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#2
07-08-2019, 03:31 PM
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bad geometry and push rod flex. what head and rocker ratio? guide plates correct? Is this a new combo or making changes?
__________________
1969 carousel red firebird 455, richmond 5 speed 1964 540 gto 1971 lemans sport convertible 1972 Maverick under slow construction |
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#3
07-08-2019, 03:42 PM
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What Brand?
Wall Thickness? Spring Pressure? more info needed......
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66 GTO Nostalgia Super Stock/Street Legal Car 421 CID, stock block, Wenzler Intake, 2- Carter 750 AFB's, 3.90 Gears, Full Factory Interior, Full Exhaust, Stock Suspension 3750LBS 9.77@136.99 Multiple NSCA/NMCA World Champion 66 GTO 389 3x2, 4 speed, 4.33 gear, Montero Red 33K original Miles 67 GTO 2dr Post, 428, Tri Power, 3.55 Gears 80 Trans Am Black SE Y84 W72 WS6 |
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#4
07-08-2019, 09:46 PM
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#5
07-09-2019, 07:11 PM
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Did you stack the spring? Should be straight forward as you assumed. Unless the push rd is hitting the head and forcing it out of normal geometry. Then the leverage would snap it.
__________________
1969 carousel red firebird 455, richmond 5 speed 1964 540 gto 1971 lemans sport convertible 1972 Maverick under slow construction |
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#6
07-09-2019, 08:30 PM
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PAC 1243 I think 240 on the seat and around 650 open |
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#7
07-09-2019, 08:31 PM
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#8
07-10-2019, 02:12 AM
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That's a lot of spring for 5/16" pushrods. Just sayin'.
__________________
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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#9
07-10-2019, 07:16 AM
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Well it does not look bent at all, atleast from your photo so you might just chalk it up to a defective tube section with a internal stress point, but still 650 psi open with 5/16" Rods is not something good to do I would say!
__________________
Wernher Von Braun warned before his retirement from NASA back in 1972, that the next world war would be against the ETs! And he was not talking about 1/8 or 1/4 mile ETs! 1) 1940s 100% silver 4 cup tea server set. Two dry rotted 14 x 10 Micky Thompson slicks. 1) un-mailed in gift coupon from a 1972 box of corn flakes. Two pairs of brown leather flip flops, never seen more then 2 mph. Education is what your left with once you forget things! |
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#10
07-10-2019, 07:40 AM
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Suspect a Tight Valve Guide
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#11
07-10-2019, 10:03 AM
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RA IV heads came with 11/32 pushrods as I remember.I know your 5/16 are heavy wall but as stated too much spring for them.Tom
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#12
07-10-2019, 12:02 PM
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wow!
I would expect to see at least some bending - but that looks like a clean snap!? I have bent one when a valve stuck on me, and have a second bent one I pulled from a grenaded engine - but have never seen a clean break like that before! I wonder if Steve nailed it? EDIT: I just noticed Tom's reply...
__________________
1970 Formula 400 Carousel Red paint on Black standard interior A no-engine, no-transmission, no-wheel option car. Quite likely one of few '70 Muncie three speed Formula 400's left. 1991 Grand Am: 14.4 @ 93.7mph (DA corrected) (retired DD, stock appearing) 2009 Cobalt SS: 13.9 @ 103mph (current DD; makes something north of 300hp & 350ft/lbs) |
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#13
07-10-2019, 12:28 PM
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Thanks for all the replies. I agree, I need some larger pushrods. I may try to get some tapered 3/8" in there or 11/32" at the very least. I may be wrong but I think 11/32 would be around 20% to 25% stronger than the 5/16".
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#14
07-10-2019, 01:28 PM
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11/32 are had to find,I think I got mine from Manton?Tom
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#15
07-10-2019, 02:39 PM
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If you were to build a 5/16 pushrod and a 3/8 pushrod at the same length and same wall thickness diameter the difference in column strength is 96.7 percent different.
This according to Manton. .
__________________
'70 TA / 505 cid / same engine but revised ( previous best 10.63 at 127.05 ) Old information here: http://www.hotrod.com/articles/0712p...tiac-trans-am/ Sponsor of the world's fastest Pontiac powered Ford Fairmont (engine) 5.14 at 140 mph (1/8 mile) , true 10.5 tire, stock type suspension https://www.youtube.com/watch?v=qDoJnIP3HgE |
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#16
07-11-2019, 07:32 AM
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Do you run a stud girdle?
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1967 Firechicken, 499", Edl heads, 262/266@0.050" duration and 0.627"/0.643 lift SR cam, 3.90 gear, 28" tire, 3550#. 10.01@134.3 mph with a 1.45 60'. Still WAY under the rollbar rule. |
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#17
07-11-2019, 08:25 AM
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Buckling Anslyses separates the Mech Eng men from the boys.
When i lost an EXH pushrod it "Z"'d into 3 straight pieces. i think the CYL head prevented the high end from bowing. Suppose you could end up with a clean 2- piece snap. As it bowed and broke at the place of maximal bow. But no constraint by the Head |
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#18
07-11-2019, 09:30 PM
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#19
07-11-2019, 09:34 PM
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