Bent push rods 390
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Bent push rods 390
pulled head on a 390 with 3 bent pusrods ( all intake, from each bank ) All valves fine, re did all guides , tested springs, , no binding, reassembled ran great for less than 100 miles, a bad miss, 2 different push rods bent (intake each bank ) spinning up oil pump (2000rpm) with lifters in, head on, intake off, rocker assembly off, oil pressure sits at 45psi, no spike to point to a bad oil pump valve, rocker shafts not scored, lifter / cam surface no were , flat lifter face, oil used GTX 10w30, never synthetic but changed regularly @5000miles
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From: Big Sky Country
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The "dirty little secret" is a procedure that was fallowed for 1st head replacment and gives no explanation or theory as to the reason for a untouched 390 bending 3 push rods after 50,000 well maintained miles.or a reason for the shorter life of replacements.
Note* All old push rods (3 straighten ) are the same length
Note* All old push rods (3 straighten ) are the same length
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My one experience with bent pushrods was on a marine engine. Long story short it was not laid up correctly for winter. On spring startup it bent a couple of pushrods as a result of corrosion between the valve guide and head. Valves were effectivly frozen. I imagine inadequate valve to guide clearance could cause the same problem... the valve basically locks up when warm.
It required head re-build and new/used pushrods to get it going again.
It required head re-build and new/used pushrods to get it going again.
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YES ! Both (2) heads , one from each side of the motor ( engine ) had been , removed, taken off as described in " Ford's dirty little secret " in an attempt to diagnose the reason for the bent push rods on the well maintained , 50,000 mile motor, no burrs on stems, or any other damage as in valve / piston kissing, valve spring not binding, rocker arm shaft rolls straight, no ridges or burrs, replaced valve guides as long as the valves were out. Replaced bent push rods drove for less than 100 miles lightly and different push rods bent.
don't feel bad if this stumps you, Two prominent race engine builders , 1 car, 1 airplane, Napafix and a Ford Dealership have no ideas
don't feel bad if this stumps you, Two prominent race engine builders , 1 car, 1 airplane, Napafix and a Ford Dealership have no ideas
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The pistons aren't showing "witness" marks from valve to piston contact?
You sure the cam is correctly installed?
Are you tightening down the rocker shaft correctly?
Trying to spin the engine past 5000 rpm with an RV cam?
Josh
You sure the cam is correctly installed?
Are you tightening down the rocker shaft correctly?
Trying to spin the engine past 5000 rpm with an RV cam?
Josh
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As mentioned , NO CONTACT OF VALVE TO PISTON
As mentioned, Installation proceduer was fallowed as Noted in " Ford dirty little secret"
As mentiond, the push rods bent after 50,000 well maintained miles,NO CAMSHAFT WAS CHANGED
As mentioned, LIGHTLY USED
As mentioned, Installation proceduer was fallowed as Noted in " Ford dirty little secret"
As mentiond, the push rods bent after 50,000 well maintained miles,NO CAMSHAFT WAS CHANGED
As mentioned, LIGHTLY USED
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Then worn exhaust cam lobes from using the wrong low zinc modern energy conserving engine oil, which causes excessive combustion pressures... which equals bent intake pushrods.
Use diesel oil from now on.
Josh
Use diesel oil from now on.
Josh
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From: Halifx Pa
My one experience with bent pushrods was on a marine engine. Long story short it was not laid up correctly for winter. On spring startup it bent a couple of pushrods as a result of corrosion between the valve guide and head. Valves were effectivly frozen. I imagine inadequate valve to guide clearance could cause the same problem... the valve basically locks up when warm.
It required head re-build and new/used pushrods to get it going again.
It required head re-build and new/used pushrods to get it going again.
I remember a friend had this problem years ago, but he was putting large cams in his small block and running at high rpm's when it happened.
Please keep us posted on your findings, best of luck and maybe we can all learn something here.
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Have you ever actually checked each valve to see just how much preload is on each lifter ? Checking the way that article says does nothing as far as I'm concerened to set preload which at tdc on each valve should be IMO .020-.040. I've built more than a few FE motors over the years in my shop and always set preload the same as any other motor, a little different procedure with FE's but I'm only concerened with actual lifter preload = how much the push rod pushes the lifters plunger down at that cylinders TDC.
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The lack of zinc = cam lobe wear is a good one, I think measuring cam lift at this time may be the next step, as I am looking for a existing problem , not a problem that occurred after assembly ie. pre loading lifters
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From: Central Florida
I caused 3 or 4 pushrods to get bent in a 360 by fiddling with the distributor advance trying to correct what was actually an ECU issue. While driving, I experienced a significant "miss" just as you did. It ran much worse after that so I pulled the valve covers and discovered the bent pushrods.
Does any of that story align with your situation?
Does any of that story align with your situation?
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