bent pushrods...why?
Thread Starter
|
Posting Guru
Joined: Nov 2003
Posts: 1,888
Likes: 1
From: Iowa
bent pushrods...why?
well today i found out why my 390 was only running on 6 cylinders, i found the #7 and 8 cylinder intake pushrods were bent into a moon shape, i replaced the pushrods left the valve cover off and turned it over to find out the lifters are collapsed no pressure to even move the pushrod while its turning over, any ideas what may have caused this.
Hotshot
Joined: May 2003
Posts: 11,141
Likes: 25
From: south louisiana
You likely have a couple of wiped exhaust lobes on the cam. Pull the lifters there and if so, you'll find new "oiling holes" in the lifter bottoms. Here's what happened-- lifter stops spinning in it's bore, wipes the cam lobe because it's not spinning, wearing down the lifter bottom to the point where it's completely thru the metal in the lifter bottom ( hence the oil hole) When this happens on the exhaust lifter, the intake opens a couple times, letting in an intake charge that's ignited , but prevented from escaping into the exhaust. Sometimes it'll "back fire" thru the intake, but sometimes not, and the resulting pressure bends the intake pushrod in trying to overcome the pressure as the cam trys to lift the rod
Hotshot
Joined: May 2003
Posts: 11,141
Likes: 25
From: south louisiana
I had the same thing happen when breaking in both a 400M ( Comp Cams 280H )and the 390 ( Crane 272 degree Energizer) in my 68 Merc. Near as I and Comp Cams tech guy could figure on the 400, was for one, I used too much "moly lube" on the lifters and lobes when assembling the motor. This coupled with using 20W-50 oil, prevented the cam lobes from "gripping" the lifter bottoms to set them spinning in their bores. Now I use straight 30 weight non-detergent oil to braek in a cam , this was recommended by the Comp tech guy, he says it's a little less slick than other oils. The cam in my 68 Merc was a Crane Energizer, it also wiped a lobe on break in. I think the problem there was it was 30 degrees outside when I fired it up, too cold for the oil and that allowed the wiped lifter to not spin. Now, I only use a light film of moly on the lifter bottoms , none on their sides and 30weight non-detergent oil for break in. Haven't had a problem doing it this way. I also make sure the lifters will spin freely in their bores when dropping them in.
Thread Starter
|
Posting Guru
Joined: Nov 2003
Posts: 1,888
Likes: 1
From: Iowa
when i assembled mine i used the grease that came with the cam and lifters, i didnt over do it and also ran straight 30 non detergent in it for break in, the motor ran great for the first 2 weeks of life, till the intake gasket went, then after i replaced that, this happened on start up in my shop the other day, it bent a pushrod, i replaced it, and it bent the same one and also another one this morning on start up, and i dont mean it was just a bend that you could barely see these pushrods were moon shaped maybe worse, so i replaced them, and i turned it over while the valve cover was off to notice the rockers on them wernt even moveing and you could push down the lifter with one finger.
Hotshot
Joined: May 2003
Posts: 11,141
Likes: 25
From: south louisiana
One other thing that I would suggest checking is the cam retainer plate. It is there , isn't it ? If it's not or it came loose ( those phillips head bolts suck , big time) it would allow the cam to "walk" forward and damage the lifters. Also remove the rocker shafts and check to make sure the rockers move freely. Examine the valve springs too, a broken one will also bend pushrods ( had a few in my 427 do that)
Mountain Pass
Joined: Jan 2004
Posts: 128
Likes: 0
From: Arlington, Texas
If the cam lobe is wearing down, you might be getting so much slack in the valvetrain that the pushrod gets loose and lodges on the body of the lifter instead of the cup. Might be causing coil bind and or the valve hitting the piston, bending the pushrod.
Just another theory.
Just another theory.
Trending Topics
Thread Starter
|
Posting Guru
Joined: Nov 2003
Posts: 1,888
Likes: 1
From: Iowa
the rockers are fine, no bad valve springs, no stuck valves, i dont tihnk a valve hit the piston cuz it actually ran fairly smooth on 6 cylinders with no knocking noises, im going to pull the intake today to check out any furth damage, i hope the cams alright it wasnt cheap.
FTE Stories
Ford Trucks for Ford Truck Enthusiasts
3 Best / 3 Worst Parts of Modern Ford Ownership
Brett Foote
10 Amazing Upgrades That Solve Common Ford Truck Owner Headaches
Pouria Savadkouei
Every 2026 Ford Engine Explained
Brett Foote
10 Ugly Ford Trucks That We Still Kinda Love
Joe Kucinski
10 Things Every Truck Owner NEEDS (2026 Edition)
Michael S. Palmer
Rezvani's Latest Post-Apocalyptic Monster Is a Ford F-150 Raptor Underneath
Verdad Gallardo
Top 10 Most Expensive Ford Trucks Ever Sold on Bring a Trailer
Joe Kucinski
2027 Ford Super Duty Buyer's Guide (Every Model, Engine, & Package)
Brett Foote
Top 10 Ford Truck Tragedies
Joe Kucinski
Logistics Pro
Joined: Feb 2000
Posts: 3,565
Likes: 9
From: Sun River St. George
The lifter should be dipped in oil and installed in the top of the lifter bore, it should slide down and meet the camshaft of its own weight. If you lay a finger on it to push it down it is to tight and will not rotate. Trust me on this. it wont "loosen up" on its own. It is easy to overdo the lube. I put the chamshaft in all smeared with lube, lifters just get oil. Spin the pump, prime the system, fire the motor.
Thread
Thread Starter
Forum
Replies
Last Post
CantAffordAToyota
1987 - 1996 F150 & Larger F-Series Trucks
30
Jan 23, 2021 04:20 PM
SwOkcOffRoader
Small Block V8 (221, 260, 289, 5.0/302, 5.8/351W)
11
Apr 2, 2016 10:07 AM
TheBlueMule
6.0L Power Stroke Diesel
2
May 18, 2015 06:59 AM
jccastl
Ford Inline Six, 200, 250, 4.9L / 300
4
Aug 21, 2006 11:32 AM
Troy77+79
335 Series- 5.8/351M, 6.6/400, 351 Cleveland
3
Mar 16, 2006 07:54 PM