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Thread: Pontiac-Bent pushrods
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10-23-2006 #1
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Pontiac-Bent pushrods
One broke a couple of days ago and when I pulled th intake and val pan off I had 8 more that were bent. I had a day long event with NASA at Infineon a couple of weeks ago and haven't driven the car much since. I'm wondering if an oil starvation issue could cause damage like this? I never saw the pressure drop but I couldn't watch the gauge every second.
It's a Pontiac 400 with about .522 lift with 1.65 rockers and hyd lifters. About 400hp. Do I need stronger pushrods?
Robert
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10-23-2006 #2
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Originally Posted by firebob
I would say you have a mechanical interference issue. Coil springs binding, retainer hitting the valve guide area, valve hitting piston, etc.
Jody
10-23-2006 #3
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Ditto- have you scoped the bores to see if there is any damage? My guess is coil bind. Are you using 16 heads?
10-24-2006 #4
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Which bores? Lifter bores are fine. Yes, the heads are 16s. What difference?
Robert
10-25-2006 #5
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Were the push rod holes in the cylinder heads elongated for the 1.65 rockers you are running? If they were not, I believe that is your problem and there are only two solutions. Either pull the heads and have the holes elongated or lower the rocker ratio.
71 Formula, 455 SD/KRE D-Ports, Crower solid cam, TKO 600, 3:73 Eaton posi. 17" ARE 200s, , 1LE brakes, Koni, Rancho adjustable bars, Hotchkis springs
10-25-2006 #6
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Paul Spotts makes an excellent push rod hole elongation tool. That does indeed sound like your problem.
www.spottsperformance.comMatt
1965 Pontiac GTO – Spotts 421 Tripower | TKO600 | 3.90s | Vintage AC | Baers | Hotchkis/SPC/BMR Suspension | Intro Vistas | BFG KDW Redlines | 06 GTO Seats
10-25-2006 #7
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Found the actual link: http://www.spottsperformance.com/headtool
Matt
1965 Pontiac GTO – Spotts 421 Tripower | TKO600 | 3.90s | Vintage AC | Baers | Hotchkis/SPC/BMR Suspension | Intro Vistas | BFG KDW Redlines | 06 GTO Seats
10-25-2006 #8
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Holes are elongated for the rockers. No timing chain(gears) so that's not it. These pushrods are longer than most at stock being 9.17" long. Makes it easier for them to bend I would think.
Robert
10-25-2006 #9
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Big blocks are longer still, they don't bend without reason. I'd keep looking for an interference issue, somethings binding/hitting to force the pushrod to bend. Originally Posted by firebob
Jody
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