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1980 Bronco 5.0l valve adjustment

TTMotorsports

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Jan 7, 2021
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Lucerne Valley, CA
So got a stock 1980 Bronco 5.0 v8. I need to check push rods for straightness to determine why I'm having a misfire. When doing this do these motors have a set torque spec for rocket arm bolt of like 20 ft lbs or do you have to rotate motor until valve would be closed and tighten to remove slack, then half turn or so like some small block Chevys. I'm not a ford guy and have never worked on these motors before just Chevys or replacing the Ford motors.
 
The only reason to rotate the engine is if you're worried that the push-rods are fucktons (we're talking on the order of half an inch here, hydraulic lifters have tons of adjustment) too long or short in which case you'd want to tighten them on the base circle and confirm that there is not so much preload that the valve is open and not so little that the pushrod has slop.

ALL the Ford pushrod shit from the 80s and 90s uses those same pedestals and 5/16 bolts. I rattle them down with a 3/8 impact.
 
Check to make sure the valves are not all tight. I had a customer that bought a 5.0 truck that the previous owner had the head gaskets replaced and the shop shaved the heads excessively and that was causing the valves to slightly hang open. Truck ran but had multiple random misfire codes.
 
SLOWPOKE693 said:
Check to make sure the valves are not all tight. I had a customer that bought a 5.0 truck that the previous owner had the head gaskets replaced and the shop shaved the heads excessively and that was causing the valves to slightly hang open. Truck ran but had multiple random misfire codes.
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They must have removed a fuckton of material. How many intake manifold gaskets did they have to stack to make it seal up. :laughing:
 
I torque them down 18, rotate the engine twice, go to 20.
Probably overkill, but I've been doing it for 20 years.

If I was looking for a misfire, rockers would not be my first choice, it's always a duraspark issue.
 
Ok checked all push rods and all were perfect. Torqued to 17 ft lbs. Cranked over motor with the steal me junction. Than re torqued 23 ft lbs. Now the motor won't start. I'm getting spark at every spark plug and I check compression before all this and all cylinders were 118-125 so they're good.

Cylinders 4, 5, 7 we're not firing and unplugging spark plug wire it didn't change how it ran. I just need to get this thing running even with the misfire so I can sell it just needing some work to get running good.
 
welndmn said:
I torque them down 18, rotate the engine twice, go to 20.
Probably overkill, but I've been doing it for 20 years.

If I was looking for a misfire, rockers would not be my first choice, it's always a duraspark issue.
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For an 80, this or even vac leaks, lean carb, vac advance (or combo of them)
 
TTMotorsports said:
Ok checked all push rods and all were perfect. Torqued to 17 ft lbs. Cranked over motor with the steal me junction. Than re torqued 23 ft lbs. Now the motor won't start. I'm getting spark at every spark plug and I check compression before all this and all cylinders were 118-125 so they're good.

Cylinders 4, 5, 7 we're not firing and unplugging spark plug wire it didn't change how it ran. I just need to get this thing running even with the misfire so I can sell it just needing some work to get running good.
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What is the color (quality) of the spark when you checked it @ those cyl's? Try swapping plug wires around?
 
I installed brand new plugs in every cylinder and did the same thing. It has brand new cap rotor plugs and wires, new timing chain. New fuel pump filter and rebuilt carb.
 
I think the rocker arm adjustment is the last thing I would check for a random misfire.

Check the firing order, check the distributor bushing for tightness, plug wires, rotor, cap, and ignition module.
 
arse_sidewards said:
Especially on an engine with no adjustment. :homer:

But hey, props to him for pulling valve covers and figuring that out the hard way.:laughing:
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We just had a 85 Ranger in here that sat for a decade and now was way down on power. We found 4 pushrods on the right bank just floating loose. We checked them for straightness and reinstalled. Then changed the oil/filter and fuel tank/pickup.
 
DMG said:
We just had a 85 Ranger in here that sat for a decade and now was way down on power. We found 4 pushrods on the right bank just floating loose. We checked them for straightness and reinstalled. Then changed the oil/filter and fuel tank/pickup.
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That's a fun one.

I guess it had enough valve spring to not stick a valve but not enough valve spring to close the valve faster than the lifter dropped. :laughing:
 
arse_sidewards said:
That's a fun one.

I guess it had enough valve spring to not stick a valve but not enough valve spring to close the valve faster than the lifter dropped. :laughing:
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Something like that. Not sure.
 
Yeah I know there is a 5.0 HO firing order aka 351 firing order. I haven't had a chance to dig into the vacuum lines to find the one or more I failed to hook up causing my no start issue.
 
DMG said:
We just had a 85 Ranger in here that sat for a decade and now was way down on power. We found 4 pushrods on the right bank just floating loose. We checked them for straightness and reinstalled. Then changed the oil/filter and fuel tank/pickup.
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Id bet on shitty old gas varnishing the valve stems so they stuck partway open. Changing the tank was the right move.
 
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Ranchtruck said:
Id bet on shitty old gas varnishing the valve stems so they stuck partway open. Changing the tank was the right move.
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Plus it had the wrong tank that was too big and rubbed the rear driveshaft. But yeah.
 
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