1978 351M stuck?
Thread Starter
|
5th Wheeling
Joined: Jan 2016
Posts: 34
Likes: 0
How do you bend a push rod while installing it ?
unless you got water in it it could sit for decades and turn over fine. whoever said it could dry out is on crack.
your push rods most likely bent because you have stuck valves or your cam is out of time with the crank or not turning , either of which would make it very hard to turn.
unless you got water in it it could sit for decades and turn over fine. whoever said it could dry out is on crack.
your push rods most likely bent because you have stuck valves or your cam is out of time with the crank or not turning , either of which would make it very hard to turn.
Thread Starter
|
5th Wheeling
Joined: Jan 2016
Posts: 34
Likes: 0
Depending on which pushrod bent that is what locked the engine. I did it once to mine. One pushrod got stuck going through one of the small holes in the intake. ( number one I think ) A real bear to get out. You must make certain that the rockers are in the correct seating. Did you remove the springs when you cleaned ? The Ex/ Int springs are different height. Exhaust springs on SOME 351M/400 have a taller spring seat cast in the head. Then torque the rockers to 25Ft LBs while the valve is closed. There is a sequence for that in a builders guide. HP Books How to rebuild ford v8 engines 351M
Lead Driver
Joined: Oct 2018
Posts: 7,903
Likes: 2,372
If you're sure you bent the push rods ands they didn't bend from engine rotation it may mean nothing.
Best thing is to crank the engine with the valve cover off and watch . but if the starter truly won't turn the engine obviously that won't work.
You should be able to turn the engine backwards if it's coming up against a valve. if it won't budge either way I'd pull the distributor that would eliminate the possibility if a seized distributor or oil pump. if it still won't budge you may as well pull the engine .
Best thing is to crank the engine with the valve cover off and watch . but if the starter truly won't turn the engine obviously that won't work.
You should be able to turn the engine backwards if it's coming up against a valve. if it won't budge either way I'd pull the distributor that would eliminate the possibility if a seized distributor or oil pump. if it still won't budge you may as well pull the engine .
Senior User
Joined: Apr 2019
Posts: 106
Likes: 1
If you bent a pushrod while torquing it down = rocker not seated correctly / Valve spring being depressed while opening up the valve. BIG no-no. Rotate engine till valve is closed with relationship to camshaft. What causes pushrod to bend is in the geometry. rocker to spring/valve to cam. You saw how every other one bent, that is the gamble you take trying to short cut on the correct procedure. I did that once also.
Lead Driver
Joined: Oct 2018
Posts: 7,903
Likes: 2,372
This is being overemphasized I believe. I have never had an issue with this on the dozen brands of engines I've rebuilt. when you factor the lift of the cam with a collapsed lifter the geometry change shouldn't hurt anything at all provided the pushrod is able to move freely. on a rocker shaft you have no choice but to tighten down all 8 valves at once .
If this is truly an issue on a 351-400 which I purposely avoid ,then that's just one more design flaw. obviously if the pushrod is out of place that's another matter.
If this is truly an issue on a 351-400 which I purposely avoid ,then that's just one more design flaw. obviously if the pushrod is out of place that's another matter.
Thread Starter
|
5th Wheeling
Joined: Jan 2016
Posts: 34
Likes: 0
If you're sure you bent the push rods ands they didn't bend from engine rotation it may mean nothing.
Best thing is to crank the engine with the valve cover off and watch . but if the starter truly won't turn the engine obviously that won't work.
You should be able to turn the engine backwards if it's coming up against a valve. if it won't budge either way I'd pull the distributor that would eliminate the possibility if a seized distributor or oil pump. if it still won't budge you may as well pull the engine .
Best thing is to crank the engine with the valve cover off and watch . but if the starter truly won't turn the engine obviously that won't work.
You should be able to turn the engine backwards if it's coming up against a valve. if it won't budge either way I'd pull the distributor that would eliminate the possibility if a seized distributor or oil pump. if it still won't budge you may as well pull the engine .
Lead Driver
Joined: Oct 2018
Posts: 7,903
Likes: 2,372
when you say it won't turn do you mean it won't turn either way very much or do you mean it's like it's welded ?
Locking up is always serious, but if it's seized tight both directions that's almost always a seized piston or bearings. neither of which can be fixed correctly without pulling the engine. but, if you want to dig into it you might be able to cobble it up good enough to run it a while.
FTE Stories
Ford Trucks for Ford Truck Enthusiasts
Top 6 Best Deals Available on New Fords & Lincolns Right Now
Brett Foote
This Hennessey Takes the Expedition Tremor's Off-Roading Capability to the Next Level
Verdad Gallardo
Top 10 Fords at 2026 Carlisle Ford Nationals
Joe Kucinski
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
Senior User
Joined: Apr 2019
Posts: 106
Likes: 1
The dist oil pump shaft would snap before the pump or dist could "lock up" the engine by design. The dist has a break away pin holding the gear to the shaft. So that's out. I went back and read all your posts. I can not see where anything you did would have caused the lock up. Even if the timing gear broke up you could turn it over. The factory cam gear is nylon. There is a lot of clearance between the valve and piston so that's not the issue. It may very well be a bearing failed. After sitting 16yrs it may have been a dry start that took out a bearing and it finally grabbed. It doesn't take much to wipe one out. Once they start to pinch sometimes they can rotate a very short while before seizure happens.
Lead Driver
Joined: Oct 2018
Posts: 7,903
Likes: 2,372
A locked oil pump could stop it if you were turning it by hand. a starter no. I've seem plenty of bent valves from kissing a piston. but maybe these things with dishes cut big enough to feed a dog in won't.
Given the limited information I'd say it has to be a bearing or seized piston.
Given the limited information I'd say it has to be a bearing or seized piston.
Thread Starter
|
5th Wheeling
Joined: Jan 2016
Posts: 34
Likes: 0
The dist oil pump shaft would snap before the pump or dist could "lock up" the engine by design. The dist has a break away pin holding the gear to the shaft. So that's out. I went back and read all your posts. I can not see where anything you did would have caused the lock up. Even if the timing gear broke up you could turn it over. The factory cam gear is nylon. There is a lot of clearance between the valve and piston so that's not the issue. It may very well be a bearing failed. After sitting 16yrs it may have been a dry start that took out a bearing and it finally grabbed. It doesn't take much to wipe one out. Once they start to pinch sometimes they can rotate a very short while before seizure happens.
Senior User
Joined: Apr 2019
Posts: 106
Likes: 1
Something to tickle your mind. The clearance between the NEW bearing and crankshaft is .0003. A hair follicle is .0001, It drops on the crankshaft during assembly trapped in the break-in lube. As the engine oil is pumped through the journal, the oil goes around the dirt. this leads to dry spot that makes a groove or scratch. The smallest dirt particles are hard on bearings. Even though you ran the engine many times does not mean that it did not spin a bearing and lock up. It has to run to lockup ! I had a rod bearing spin 1/8" just enough to cut off the oil to the number 5 main bearing. The engine ran long enough to get hot and warp the crank. The noise I heard sounded like a injector tip broke off in the cylinder. Once they go they inbed into the piston and scuff up the head and valves. So I didn't rush to shut it off. That set me back 24K for my 525HP N-14 Cummins. Oh and it locked up at the off ramp. Again I sure didn't think it was a bearing making that thump.
Freshman User
Joined: Jun 2020
Posts: 42
Likes: 1
Man, that sucks. I feel for you. I'm new to this too and the 77.5 I just got sat for 12 years. Luckily the owner did the hardest part and got the engine running before I bought it from him. I think the only thing he did was to rebuild the carb. The brakes were seized like yours and I had to get it towed home and have been working on that. But I do worry about the engine holding up once I really start driving it.
I hope you figure it out and it doesn't involve pulling the engine.
I hope you figure it out and it doesn't involve pulling the engine.
Lead Driver
Joined: Oct 2018
Posts: 7,903
Likes: 2,372
None of the scenarios seem likely but the fact is you have a seized engine from what you say. so one of them is correct.
if it's a piston you might be able break it lose and get a few more miles out of it. but they won't be good miles. if it's a bearing the engine is coming out.
if getting it going cheap is your main concern see if you can find another engine in a rust bucket or something. if you don't want to spend any time on it look for another vehicle.
if it's a piston you might be able break it lose and get a few more miles out of it. but they won't be good miles. if it's a bearing the engine is coming out.
if getting it going cheap is your main concern see if you can find another engine in a rust bucket or something. if you don't want to spend any time on it look for another vehicle.