1986 F-250 XLT 6.9 idi C6 switch to 300 4 speed

[nic55kel]

Nice job ......... only 11 more to do

Dave ----

Hi Dave,

I am going to hold off on doing the others until I see how this one works out.

When I do them I will pull the cylinder head and jig it up on a drill press.

Lovely weather today so I put it all back together.

Unintentionally I found out that if the the valve adjustment is too loose it is easy to throw a pushrod.

Anyway once I had the adjustment where I thought the midpoint of the lifter plunger travel was it ran really nicely again.

I think the best way to set the clearance would be with a bleed down tool and feeler gauge.

Going to try it on a few cold starts before I get too excited but definitely making progress.

The chevy stud is just long enough as you can see in the picture.

[Gary Lewis]

Hi Dave,

I am going to hold off on doing the others until I see how this one works out.

When I do them I will pull the cylinder head and jig it up on a drill press.

Lovely weather today so I put it all back together.

Unintentionally I found out that if the the valve adjustment is too loose it is easy to throw a pushrod.

Anyway once I had the adjustment where I thought the midpoint of the lifter plunger travel was it ran really nicely again.

I think the best way to set the clearance would be with a bleed down tool and feeler gauge.

Going to try it on a few cold starts before I get too excited but definitely making progress.

The chevy stud is just long enough as you can see in the picture.

Well done!

[FuzzFace2]

Well done!

So with that fix it makes the valve train adjustable right?

If so why not adjust them when running?

Back the nut off till you get a little noise, tighten the nut till it just stops making noise and then go 1/4 to no more than 1/2 a turn tighter.

Dave ----

[ArdWrknTrk]

Hi Dave,

I am going to hold off on doing the others until I see how this one works out.

When I do them I will pull the cylinder head and jig it up on a drill press.

Lovely weather today so I put it all back together.

Unintentionally I found out that if the the valve adjustment is too loose it is easy to throw a pushrod.

Anyway once I had the adjustment where I thought the midpoint of the lifter plunger travel was it ran really nicely again.

I think the best way to set the clearance would be with a bleed down tool and feeler gauge.

Going to try it on a few cold starts before I get too excited but definitely making progress.

The chevy stud is just long enough as you can see in the picture.

Tremendous that you were able to fix the pulled stud in situ Bob!

It would be reassuring if there were a few threads above the nut, but bowtie parts don't belong in a Ford anyway.

 

[nic55kel]

So with that fix it makes the valve train adjustable right?

If so why not adjust them when running?

Back the nut off till you get a little noise, tighten the nut till it just stops making noise and then go 1/4 to no more than 1/2 a turn tighter.

Dave ----

Hi Dave,

For me I don't really see any advantage to adjusting the clearance with it running and it is messy.

I just make sure the lifter is on base circle tighten to zero lash (by twisting the pushrod) and go 3/4 turn past zero lash.

Because this engine had thrown pushrods before I was tempted to go 1 full turn past zero lash but I would not want to do that without bleeding down the lifter and measuring the clearance. Going 1 full turn should not be a problem as the lifter has about 140 thou of bleed down and I just figure if I set the lifters on the tighter side there should be less chance of throwing a pushrod. When I do the rest of the studs I will measure and see how tight I can adjust them.

Gary thanks for the encouragement, I cold started it today and so far so good.

Jim, Yes it would be nice if the stud were a little longer but the locknut is fully on the threads so I don't think it is going anywhere. It was pretty straightforward after making the jig, to true the tap, that threaded the hole.

[Gary Lewis]

Hi Dave,

For me I don't really see any advantage to adjusting the clearance with it running and it is messy.

I just make sure the lifter is on base circle tighten to zero lash (by twisting the pushrod) and go 3/4 turn past zero lash.

Because this engine had thrown pushrods before I was tempted to go 1 full turn past zero lash but I would not want to do that without bleeding down the lifter and measuring the clearance. Going 1 full turn should not be a problem as the lifter has about 140 thou of bleed down and I just figure if I set the lifters on the tighter side there should be less chance of throwing a pushrod. When I do the rest of the studs I will measure and see how tight I can adjust them.

Gary thanks for the encouragement, I cold started it today and so far so good.

Jim, Yes it would be nice if the stud were a little longer but the locknut is fully on the threads so I don't think it is going anywhere. It was pretty straightforward after making the jig, to true the tap, that threaded the hole.

Well done!

[nic55kel]

Well done!

Well the starting has become worse and worse as the weather has become cooler. Only running on maybe 4 cylinders and shaking like a Polaroid. Once the engine is warmed up it starts to run quite smoothly although after the last cold start it has a tick again.

I have been mechanicing for a long time and this is a new one for me. Always something new to learn.

After lots of researching on bent pushrods and to paraphrase Holmes "When everything you have tried didn't fix it, whatever is left no matter how improbable must be the truth", I have come to realize the problem must be sticking valves.

Seems obvious now but hindsight and all.

So with that decided I pulled the cylinder head. The good news is that there is still cross hatching visible on the cylinder walls and so I am glad I did not decide to do bearings or whatever when I had the engine out.

I put the head on my bench and played whac-a-mole on the valves with a deadblow and bingo. The exhaust valves have a definite spring to them and reflect the hammer. The inlet valves are like hitting semi wet cement and if watching closely I can actually see them creeping back to the closed position. As you can see in the last picture it looks like tar in the inlet port.

I think what has happened is the modern fuel with its much more aggressive solvents has picked up all the varnish and other deposits in the intake manifold and allowed them to get sucked into the combustion chambers. I guess as the tar warmed up it became more fluid and the engine would start to run close to normally. Anyway I feel like the mystery is solved and when I fix it this time it will really be fixed. Lots of cleaning ahead.

Maybe something to think about for those looking to resurrect old engines.

[Gary Lewis]

Well the starting has become worse and worse as the weather has become cooler. Only running on maybe 4 cylinders and shaking like a Polaroid. Once the engine is warmed up it starts to run quite smoothly although after the last cold start it has a tick again.

I have been mechanicing for a long time and this is a new one for me. Always something new to learn.

After lots of researching on bent pushrods and to paraphrase Holmes "When everything you have tried didn't fix it, whatever is left no matter how improbable must be the truth", I have come to realize the problem must be sticking valves.

Seems obvious now but hindsight and all.

So with that decided I pulled the cylinder head. The good news is that there is still cross hatching visible on the cylinder walls and so I am glad I did not decide to do bearings or whatever when I had the engine out.

I put the head on my bench and played whac-a-mole on the valves with a deadblow and bingo. The exhaust valves have a definite spring to them and reflect the hammer. The inlet valves are like hitting semi wet cement and if watching closely I can actually see them creeping back to the closed position. As you can see in the last picture it looks like tar in the inlet port.

I think what has happened is the modern fuel with its much more aggressive solvents has picked up all the varnish and other deposits in the intake manifold and allowed them to get sucked into the combustion chambers. I guess as the tar warmed up it became more fluid and the engine would start to run close to normally. Anyway I feel like the mystery is solved and when I fix it this time it will really be fixed. Lots of cleaning ahead.

Maybe something to think about for those looking to resurrect old engines.

Yuk! That "tar" is UGLY! And it runs and drips.

Yes, I think you found a smoking gun. Or a sticking valve. Are you going to lap them, check the guides, and replace the seals while you are working on them?

[nic55kel]

Yuk! That "tar" is UGLY! And it runs and drips.

Yes, I think you found a smoking gun. Or a sticking valve. Are you going to lap them, check the guides, and replace the seals while you are working on them?

Hi Gary,

Yes I will strip the head, give it a good once over and do the seals and lap the valves if indicated.

I did a compression test on the engine when it was still running good before all this mess and the readings were really good. All between 140 and 155 so can't see doing more than a quick touch up on the valves.

I think I will try oven cleaner on this tar and I also have to figure out how to clean out the intake. Brake clean doesn't seem to touch it so I think I will have to emulsify it, hence oven cleaner.

Will keep you posted.

[Gary Lewis]

Hi Gary,

Yes I will strip the head, give it a good once over and do the seals and lap the valves if indicated.

I did a compression test on the engine when it was still running good before all this mess and the readings were really good. All between 140 and 155 so can't see doing more than a quick touch up on the valves.

I think I will try oven cleaner on this tar and I also have to figure out how to clean out the intake. Brake clean doesn't seem to touch it so I think I will have to emulsify it, hence oven cleaner.

Will keep you posted.

There is brake cleaner and BRAKE CLEANER. Brandon/Bruno2 brought some big name brake cleaner over and it wouldn't touch what I expected it to melt. I pulled out my favorite, O'Reilly's house brand, and it melted the stuff.

Anyway, good luck!