bending pushrods
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Freshman User
Joined: Jan 2009
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From: Forsyth MO
bending pushrods
I have a 1970 f-250 with 390, have had heads completly worked oversized valves an all, new edelbrock performer390 intake manifold, carter carb, new oil pump, new lifters, new push rods, new crankshaft with matched timing chain and gears. I am bending pushrods on #3 an #4 , ran compression check getting 130+ psi on all cylinders except #4 which is less than zero.No needle movement at all BIG FAT QUESTION MARK WHY
Fleet Mechanic
Joined: Dec 2006
Posts: 1,338
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From: UPSTATE NY
you could have a bad cam or valve timing could be off, could also be a stuck lifter. wierd you are only getting 130 psi from all that work. thats what the readings always are on my tired 360. or if you have a valve that is sticking open and the valve spring cant return the valve freely the rocker arm stalls and the pushrod falls out of the little holster and gets caught on the edge, next cycle the valve gets pushed so far down the spring cant compress anymore and the pushrod has to give. maybe you need to run a quart of tranny fluid through your motor or question the quality of the work that was done on the heads.
Hotshot
Joined: May 2004
Posts: 12,170
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From: The hills of No. Calif.
Have you replaced the bent pushrods on #4 before doing the compression test? If the intake pushrod is bent and the intake valve won't open, then it won't pull any air into the cylinder to compress and you'll get a reading of zilch on a compression test.
I would assume with a new engine you're not running old nasty gas through it, as that can bend pushrods on an FE when the residue from the bad gas glues the valve stems to the guides, and those long pushrods become the weak link that gives in the valvetrain.
I would assume with a new engine you're not running old nasty gas through it, as that can bend pushrods on an FE when the residue from the bad gas glues the valve stems to the guides, and those long pushrods become the weak link that gives in the valvetrain.
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Freshman User
Joined: Jan 2009
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From: Forsyth MO
bent pushrods
sorry fellas guess i should have given a little more info.I actually repulled the heads off and had machine shop recheck their work,they are verry good and correct and the heads ran great when i had the original two barrel intake and carb on it. all mods have been done in the past three months. My family and i have moved from KC MO to close to Branson MO three weeks ago, i pulled an overloaded trailer from there to here and by the time i got here every lifter in the truck had collapsed due to oil pump putting out only half volume. The timing chain and gears almost snapped in two, which is why cam, chain, gears and oil pump, an lifters went in last week now bending rods. Is 130+ psi not enough I don't have any specs. Also what is valve timing? This truck is my daily driver i love my truck I've had her for four years very reliable. I have no need for a modern truck they don't even offer a big block any more and they are made of aluminum foil. Just want to get her dialed in so i can stat working on the cosmetics thanks
Senior User
Joined: Jun 2004
Posts: 249
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From: Sacramento, CA.
I noticed you did not mention new bearings and rings, were they not replaced?
You loose oil pressure through worn bearings and loose compression with rings.
You said you got over sized valves in your heads, what is the valve to piston clearance? Did you replace the pistons?
If the machine shop surfaced the heads you may need under sized pushrods.
You loose oil pressure through worn bearings and loose compression with rings.
You said you got over sized valves in your heads, what is the valve to piston clearance? Did you replace the pistons?
If the machine shop surfaced the heads you may need under sized pushrods.
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Freshman User
Joined: Jan 2009
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From: Forsyth MO
bent pushrods
The block has never been touched to my knowledge. The valves are not touching the pistons, an no oil is getting by the rings. the block has no noise at all no lower end knocks or anything
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Lead Driver
Joined: Oct 2004
Posts: 8,062
Likes: 35
From: Central Oregon
On the last rebuild on my 428FE I had problems on bending push rods, the brand new lifters were stuck at the full pumped up position and bent5 push rods on the passenger side bank. I replaced all the lifters and the problem went away.
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Freshman User
Joined: Jan 2009
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From: Forsyth MO
bending pushrods
I was wondering about that lifter issue they are new but i'm sure they had been sitting on the o'reilly shelf for a while. Will try to get the lifters warrentied hope this works THANK YOU
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