1978 Bent push rods replacement

[Business Woofer]

Hi, I have a 78' Thunderbird that was having issue running smoothly on idle. At first I thought it was the spark plugs since they were old and crusty and flooded. Turns out the some cylinders have no compression due to bent push rods I assume. I have a few questions as I want to make sure I don't do anything wrong fixing the motor.

First I need to know what oil does the 78' use? It's the 400M engine. The manual only gives me a ford number which comes up as 10W40. A friend told be to put in straight 50, but that stuff is thicker than honey so that cant be right? Some valves are stuck and its dry and crusty under the valve cover so I need lubrication as soon as the engine turns. The previous owner probably never changed the oil.

Which brings me to my second question, what is the best way to unstick a valve again so that it moves and functions again. Can I use a hammer with force and hammer the springs under the rocker arms? I fear if I replace the push rods some might bent again due to the valves still being stuck.

The oil pump works but no oil is coming up, I believe it may have been due to a collapsed and clogged oil filter that I replaced. But I haven't tested anything more yet as I want to avoid turning the motor any more until I fix the rods.

And my 3rd question is, since I removed the valve cover I have no place to fill the oil back up. I see a couple of holes on top of the cylinder head where I might be able to pour the oil in. Can it go in any hole? I accidentally poured some oil into the push rod insertion hole because I thought that was an oil channel. Is that bad?

Thanks in advance

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[Mikey97D]

Nice looking car!

Either a valve or lifter is stuck where the push rod(s) are bent. Or did the timing chain skip a few teeth?

I would start with putting the crank at TDC and checking that the rotor in the distributor is pointing at the correct cylinder (1-3-7-2-6-5-4-8 so it should be pointed at #1 cylinder)

If that is correct then you need to determine if it is a valve or lifter. What cylinder is not having compression and does it coincide with the bent push rod?

 

[Business Woofer]

I think the chain is fine, timing was correct too. I suspect stuck valves. Yes the cylinders that don't have compression are also the ones that have bent rods. I also need to know the type of oil it uses

 

[74 Harley]

You can use a wide variety of oil. Any 10-30, 10-40, 15-40, 20-50 will all be satisfactory. I use a 15-40 in my older engines, regardless of manufacturer. Any hole you see will allow oil down to the pan. Try spraying a penetrating oil like Kroil on the stems of your stuck valves. You can try tapping them down, but use a block of wood so you don't damage the valves.
If they go down but don't come back up all the way they may be bent. This could be why you have bent push rods.

 

[Business Woofer]

You can use a wide variety of oil. Any 10-30, 10-40, 15-40, 20-50 will all be satisfactory. I use a 15-40 in my older engines, regardless of manufacturer. Any hole you see will allow oil down to the pan. Try spraying a penetrating oil like Kroil on the stems of your stuck valves. You can try tapping them down, but use a block of wood so you don't damage the valves.
If they go down but don't come back up all the way they may be bent. This could be why you have bent push rods.

Doesn't that one hole where the push rod goes into go directly to the camshaft? Wouldn't I be flooding the camshaft or how does that work?
If I tap the valves with a block of wood do I place it on top of the spring?

 

[Mikey97D]

All those spots eventually drain to the oil pan.

74 Harley is saying to put the wood on top of the valve, spring, keeper, etc so while striking with a hammer you don't damage any items. You will need to remove the rocker arm to do this and would anyhow to replace a push rod.

Do you have a repair manual for torque specs?

 

[Business Woofer]

All those spots eventually drain to the oil pan.

74 Harley is saying to put the wood on top of the valve, spring, keeper, etc so while striking with a hammer you don't damage any items. You will need to remove the rocker arm to do this and would anyhow to replace a push rod.

Do you have a repair manual for torque specs?

I find the specs on the internet so yeah. And as mentioned before I should use penetrating oil? What about regular oil? And should I just try and get it into the spring under the rocker arm? Also do I need to be careful of how much as I could flood the cylinder maybe?

 

[Mikey97D]

Find a Haynes or Chilton manual for the car. There's instructions in the manual to help you learn about your car.

IMO, at this point it doesn't matter if you use oil on the valve or not. If the valve is stuck the heads need to come off to be rebuilt. Take the rocker off and use a piece of wood before hitting anything.
I'd also start looking for an aluminum intake manifold so I don't get a hernia putting the original back on, but I am not a purist.
Since the push rod is bent, whether the valve is stuck or not, I would want to inspect the lifter and cam if any damage was done when it bent.

It's fine to diagnose it all, but to fix pull the heads, cam, lifters, and push rods. Have the heads rebuilt and replace the rest. How many miles are on this motor? Fix it once and be done with it. I am certain a bunch here will disagree and that is fine.

 

[Brax]

Hi, I have a 78' Thunderbird that was having issue running smoothly on idle. At first I thought it was the spark plugs since they were old and crusty and flooded. Turns out the some cylinders have no compression due to bent push rods I assume. I have a few questions as I want to make sure I don't do anything wrong fixing the motor.

First I need to know what oil does the 78' use? It's the 400M engine. The manual only gives me a ford number which comes up as 10W40. A friend told be to put in straight 50, but that stuff is thicker than honey so that cant be right? Some valves are stuck and its dry and crusty under the valve cover so I need lubrication as soon as the engine turns. The previous owner probably never changed the oil.

Which brings me to my second question, what is the best way to unstick a valve again so that it moves and functions again. Can I use a hammer with force and hammer the springs under the rocker arms? I fear if I replace the push rods some might bent again due to the valves still being stuck.

The oil pump works but no oil is coming up, I believe it may have been due to a collapsed and clogged oil filter that I replaced. But I haven't tested anything more yet as I want to avoid turning the motor any more until I fix the rods.

And my 3rd question is, since I removed the valve cover I have no place to fill the oil back up. I see a couple of holes on top of the cylinder head where I might be able to pour the oil in. Can it go in any hole? I accidentally poured some oil into the push rod insertion hole because I thought that was an oil channel. Is that bad?

Thanks in advance

1) I take it you actually verified the push rods are bent.
2) I would remove the spark plugs then remove all the rockers and push rods making sure they are put in a separated container so they go back to the original position removed from
3) on one of the cylinders you think is stuck move the piston of that cylinder to TDC.
4) remove the spring retainer clips retainer and springs. You will need a fulcrum type tool. Remove the valve oil seal. Your valve should move up and down easily. If not spray the valve stem with penetrating oil PB blaster type and let sit 30 minutes spray again let sit use a plastic mallet or hammer and tap the valve till you free it up then work it up and down spraying with penetrating oil also rotate the valve.
5) put new oil seal on the valve replace the spring, keeper and retainer clips.
Do this to every cylinder but ensure that the piston is at TDC for the cylinder you are working on
6) when all valves are done and working put the engine at number 1 TDC and replace the push rods with new ones of the correct length for the number one cylinder. Place the rockers on and slowly tighten them to proper torque
7) manually turn the engine to the next firing order cylinder to TDC and repeat step 6 turn motor to next firing order cylinder and repeat step until all 8 cylinders are done
8) replace the valve covers drain the oil and replace with 10/30 detergent type
Crank the motor with the coil wire pulled out until oil pressure is achieved
Replace coil wire plugs and wires start engine and hopefully everything is good again.

 

[Business Woofer]

So progress update: I replaced all push rods and torqued the rocker arms back on. I tried a small crank and one of the new rods immediately bent. So now I'm soaking the stems with PB blaster as mentioned for a day and then repeat that a couple of times. Then try again. After replacing the oil filter and oil I can also confirm the oil is finally coming back up so that's a huge relieve for now.

A couple of valves are stuck in a way where the spring is being pushed down but only comes up very slowly. Which brings up a new question: If the spring is all the way down, and the push rod is also all the way down, almost leaving the rocker arm seat, is it normal for the rocker arm to be loose even when torqued? Because the rocker arm tightens again once the valve spring comes back up slowly

 

[Brax]

So progress update: I replaced all push rods and torqued the rocker arms back on. I tried a small crank and one of the new rods immediately bent. So now I'm soaking the stems with PB blaster as mentioned for a day and then repeat that a couple of times. Then try again. After replacing the oil filter and oil I can also confirm the oil is finally coming back up so that's a huge relieve for now.

A couple of valves are stuck in a way where the spring is being pushed down but only comes up very slowly. Which brings up a new question: If the spring is all the way down, and the push rod is also all the way down, almost leaving the rocker arm seat, is it normal for the rocker arm to be loose even when torqued? Because the rocker arm tightens again once the valve spring comes back up slowly

Just so you know there is value seals on the valve stem hence the reason for the above procedure the valves need to move freely. Hopefully the hydraulic lifter will pump up one everything is free and properly assembled.

 

[scubafreak]

I had 4 valves stuck, despite that I was able to drive the car out of the garage. remove the valve seals, soak the valve stems, I had to heat up the valve stem to be able to release it.
But my engine is a 69 Thunderbird which I'm completely rebuilding.

 

[Business Woofer]

I got all valves free now and everything is working, however the engine isn't running entirely smooth. But smooth enough where it doesn't violently shake or shut off. It can idle and be driven now.
Some guy said put water in the carburetor to loosen some of the dirt since the oil was extremely contaminated and it was just solid pieces everywhere. But again that sounds wrong to me lol

 

[74 Harley]

Don't do that. I've heard of that being some but it is a great way to bend connecting rods and crack rings.
If you want to flush the crankcase dump 2 quarts of atf in it and let it run about 20 minutes. Then change oil and filter.
So if it is running rough start by checking all of your vacuum lines.
Next check you carburetor mixture adjustment.
You could also be due for a timing chain...

 

[Brax]

I got all valves free now and everything is working, however the engine isn't running entirely smooth. But smooth enough where it doesn't violently shake or shut off. It can idle and be driven now.
Some guy said put water in the carburetor to loosen some of the dirt since the oil was extremely contaminated and it was just solid pieces everywhere. But again that sounds wrong to me lol

Did you do a compression test on all the cylinders if any are low you may need a valve job

 

[Business Woofer]

Did you do a compression test on all the cylinders if any are low you may need a valve job

yeah some of them are still low, higher than they used to be but low

 

[Brax]

yeah some of them are still low, higher than they used to be but low

They should be within a few lbs of each other, it’s possible the valves are burned which would mean removing and doing a valve job. If it’s carbon or deposits not allowing the valves to close fully you can try spraying water from a spay bottle as you keep the engine running a spray bottle like a window cleaner bottle. The idea is the water hits the hot carbon and dislodges it folks been doing it for a long long time. You can also try a valve soak with a he heads on there are videos on line good luck