vortec heads: rods keep bending
02-23-2021, 11:23 AM
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vortec heads: rods keep bending
I have just put a 350 in my 83 with some junkyard vortec heads. I started it for the first time yesterday and it ran for about 30 seconds and then cut out. I pulled the valve covers and found that 12 of my push rods were bent and one had snapped completely. I thought perhaps my adjustment was too tight so I got 16 new push rods and installed them with exactly zero lash. The engine would not restart I decided to give each valve a 1/4 turn of preload and bam all of my push rods bent just from the starter. I have stock vortec rocker arms, I am running a summit 1102 cam and speedway springs with a .55 max lift part number 180671515. I am so confused and now quite frustrated i don't see anyone else this is happening to.
02-23-2021, 01:57 PM
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Re: vortec heads: rods keep bending
Which ones bent? All intake or all exhaust?
You should probably start by checking the valve lift before the spring retainer contacts the valve stem seal. If that's at least .100 more than your gross valve lift, then check for valve-piston interference through a complete valve cycle.
Stock vortec heads, based on internet lore, have a max lift of only about .420 before you run into interference, though some have measured it closer to .500.
You should probably start by checking the valve lift before the spring retainer contacts the valve stem seal. If that's at least .100 more than your gross valve lift, then check for valve-piston interference through a complete valve cycle.
Stock vortec heads, based on internet lore, have a max lift of only about .420 before you run into interference, though some have measured it closer to .500.
02-24-2021, 10:57 AM
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Re: vortec heads: rods keep bending
it bent a mixture of both the intake and exhaust push rods my cam has a lift of .421/.444. I am not sure how to measure the max lift of on my heads
02-25-2021, 12:32 PM
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Re: vortec heads: rods keep bending
Sorry, it's too dark under your valve covers for me to see that right now.
When YOU looked at it, did YOU see witness marks on anything anywhere? Virtually always with metal parts, when something hits something, it leaves a mark.
I would immediately suspect the end of the rocker slots hitting the studs, or the retainers hitting the top of the valve guides.
AFAIK a single spring with a damper ("Z28" springs, Comp 918, Howards cheeeepies, etc.) will not fit over stock Vortec guides in the first place so I doubt it's that.
When YOU looked at it, did YOU see witness marks on anything anywhere? Virtually always with metal parts, when something hits something, it leaves a mark.
I would immediately suspect the end of the rocker slots hitting the studs, or the retainers hitting the top of the valve guides.
AFAIK a single spring with a damper ("Z28" springs, Comp 918, Howards cheeeepies, etc.) will not fit over stock Vortec guides in the first place so I doubt it's that.
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