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Old 12-15-2011, 07:11 PM
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new lifters and pushrods, car runs rough now

Long story short, snapped 1 pushrod and had 3 more come out of the engine and it ate 4 roller hydraulic lifters. Tossed in a new set of roller hydraulic lifters and stock length push rods (7.200)

Got the car back together fine, all valves/springs were seated at the same height so doubt the valves are bent. When I started it up it ran good ( about 5 seconds) shut it down and double checked everything and put it back together. Started and ran good for about 10 seconds then got really rough. Double checked al the vacuum lines and everything is good.

Too frustrated so I walked away for the night and need some things to look for. I hVe no power brakes so that's why I'm thinking no vacuum/low vacuum. Engine is A LT1

The lifters were soaked in oil 24 hours, and the pushrods snapped cause my engine builder didn't put in what I paid for.

Thanks for the help anyone can offer

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Old 12-15-2011, 09:25 PM
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check compresion

Liffters are stupid sometimes they pump up keeping valves open . I've been there . I checked compression. It was low on a few cylinders . They will probly bleed off after a hours . I had sticking valves . The guides were gummed up .
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Old 12-15-2011, 09:54 PM
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Quote:
Originally Posted by Eric63M
Long story short, snapped 1 pushrod and had 3 more come out of the engine and it ate 4 roller hydraulic lifters. Tossed in a new set of roller hydraulic lifters and stock length push rods (7.200)

Got the car back together fine, all valves/springs were seated at the same height so doubt the valves are bent. When I started it up it ran good ( about 5 seconds) shut it down and double checked everything and put it back together. Started and ran good for about 10 seconds then got really rough. Double checked al the vacuum lines and everything is good.

Too frustrated so I walked away for the night and need some things to look for. I hVe no power brakes so that's why I'm thinking no vacuum/low vacuum. Engine is A LT1

The lifters were soaked in oil 24 hours, and the pushrods snapped cause my engine builder didn't put in what I paid for.

Thanks for the help anyone can offer
Was the cam degreed in? What about the geometry of the rocker to the valve tip?

Fair to good chance the lifter preload wasn't set correctly. At least this should be checked first.

More HERE.

HERE is a list of valve train points to check. Coil bind or insufficient clearances in the valve train like the valve spring retainer to the valve guide boss are two common causes of bent p-rods.

You might add some details of the build- stock or aftermarket heads, valve springs replaced w/what springs, different retainers, valve to piston clearance, cam specs, etc. to help pin it down.
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Old 12-15-2011, 10:12 PM
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Quote:
Originally Posted by big nasty
Liffters are stupid sometimes they pump up keeping valves open . I've been there . I checked compression. It was low on a few cylinders . They will probly bleed off after a hours . I had sticking valves . The guides were gummed up .
Thought this might be what it is. wasn't sure so I walked away before I took a hammer to the car.

Quote:
Originally Posted by cobalt327
Was the cam degreed in? What about the geometry of the rocker to the valve tip?

Fair to good chance the lifter preload wasn't set correctly. At least this should be checked first.

More HERE.

HERE is a list of valve train points to check. Coil bind or insufficient clearances in the valve train like the valve spring retainer to the valve guide boss are two common causes of bent p-rods.

You might add some details of the build- stock or aftermarket heads, valve springs replaced w/what springs, different retainers, valve to piston clearance, cam specs, etc. to help pin it down.
The Cam was never out of the car, just the pushrods and lifters. Geometry is all good, checked that. I think it is the preload, just seems to hit or miss on cylinders and you can tell when one runs right with the "idle" (more like 2200 RPM to keep it from dieing, but good news is i'm back to 75 lbs oil pressure @ 2200).

As far as the build; Comp 280XFI Cam (checked the lobes and they're all good. comp 26918 valve springs 125lbs seated 367lbs open. I paid for 3/8 hardened pushrods when the motor was built, but pulled out stock pushrods. Wasn't too happy to find that but it is what it is. Has AFR 195cc heads, 12.X:1 compression.
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