Resurrecting and diagnosing…

[Matfirstattempt]

When I first bought this truck before Covid, I thought it would be a great project, and it was. The truck ran and then somehow it seemed I lost compression. Anyway, here I am in 2025 picking the project back up and I need some advice.

 

I'm hoping that this is valve issue instead of a ring issue. I got the manifold off and to get good access to the valve windows. When I spin the fan, I can see all tappets moving. But I’m curious if that movement is truly going to tell me anything about the valves seating or if I need to pull the head? I really don’t want to if I don’t have to, but in this far in and id like to drive this truck a bit in the summer firing on all 6 cylinders. 

Any thoughts on how I can continue diagnosing without the head having to come off?

 

side note: I never learned to wrench on engines - I’ve learned as I go. I’m impressed at how these engines worked, particularly the tappets and their rotation! Anyway. 

[Plymouthy Adams]

lost compression but did you read each cylinder......did you do a dry and then a wet test.....as for the valves, could be they moving up and down but still not closing....the removal of the head would be most beneficial in reading the worthiness of the engine.  

[Dodgeb4ya]

# 3 and 4 cylinder exhaust ports are rusty...

As mentioned compression test required ...all cylinder readings need to be close in psi  and preferably top out 90-100 lbs or even better if higher.

These engines can even run smooth if all cylinders are at 70lbs! Won't have full horse power as new though.

Possibly some valves not seating 100% because of rust and or burnt valve and seats.

On old tired engines it's common to see top compression rings broken too.

[Los_Control]

I want to say this is a tough call on which direction to go next.

I wish you would have come here and asked ..... before you pulled the manifold off. .... Thats OK though .... just do not remove anything else before testing    

 

You think it lost compression while sitting ... totally possible and if it did, not enough to really make a difference.

Still need to see compression readings on each cylinder. .... A compression gauge is inexpensive and needed .... you can still check compression with the manifold removed.

 

These engines do not have a lot of compression to begin with .... very likely you lost spark, the engine turned so freely you thought it was lack of compression.

Need to test these things first.

You need to be above 60psi compression for it to even think about running .... If you have 70 + in 3 or more cylinders,  you are pretty safe .... 

 

You might want to pickup a complete engine gasket set ... for a rebuilt engine ..... cheaper then buying gaskets individual, you still may pull the head .... not a big deal.

 

First check your spark .... fix that if no spark. ... then put it back together.

Then check compression ..... I think it is important to check compression even if it runs .... just to write down the information and keep a log as you go.

[Matfirstattempt]

Sorry all, when put away a compression. Test was done. See photo

 

 

[Matfirstattempt]

33 minutes ago, Los_Control said:

I want to say this is a tough call on which direction to go next.

I wish you would have come here and asked ..... before you pulled the manifold off. .... Thats OK though .... just do not remove anything else before testing    

 

You think it lost compression while sitting ... totally possible and if it did, not enough to really make a difference.

Still need to see compression readings on each cylinder. .... A compression gauge is inexpensive and needed .... you can still check compression with the manifold removed.

 

These engines do not have a lot of compression to begin with .... very likely you lost spark, the engine turned so freely you thought it was lack of compression.

Need to test these things first.

You need to be above 60psi compression for it to even think about running .... If you have 70 + in 3 or more cylinders,  you are pretty safe .... 

 

You might want to pickup a complete engine gasket set ... for a rebuilt engine ..... cheaper then buying gaskets individual, you still may pull the head .... not a big deal.

 

First check your spark .... fix that if no spark. ... then put it back together.

Then check compression ..... I think it is important to check compression even if it runs .... just to write down the information and keep a log as you go.

Yes, but I really wanted to see the tappet area. Pulling the manifold was my best sight to it. I do have a full gasket set.

Edited February 23 by Matfirstattempt

[Los_Control]

With those numbers, compression is not your no start issue.

It is common for the rings to stick to the pistons and not seal against the cylinders ..... possibly that is what is wrong with number 3.

I had one that was down around 25 and after running it and a few heat cycles .... I soaked the cylinders with MM oil and got it up to 95-100.

Then I let it sit for a year and is down around 70 .... it is rings and I may end up putting new rings in it yet .... not a big deal to pull the head and drop the pan and then replace each cylinder one at a time ..... they use to do this operation in a day at the local gas station.

 

I'm thinking you have a spark or fuel issue as to why it will not start.

[Matfirstattempt]

So in the saga of diagnosing the down cylinder, I pulled the head  (man I love breaking this thing down and learning). So big question: is there anything I would see in the cylinder wall to indicate ring issues? I plan to check valve sealing with some solvent around the valve at the top of the compression stroke. Any thoughts on what else I ought to do here or next steps?

Head removed 2.HEIC

[Los_Control]

Seeing nothing strange or large gauges in the cylinder wall is a good thing.

 

 

From what we can see in the photo looks ok .... the thing with stuck rings is they are stuck.

 

Rings need to rotate freely while installed on a piston.  They rotate around to help seal, also they expand and contract to the shape of the cylinder.

Cylinders will wear into a egg shape because of the forces of the rods thrusting the pistons. .... the rings need to be able to move to accommodate these things.

 

The rings are made from cast iron ... the pistons are some sort of aluminum alloy .... the two dissimilar metals will corrode and stick to each other.

If the rings are stuck to the side of the piston, they can not move freely like needed and they will not seal .... A common issue with old cast iron rings.

Modern engines have better metals for the rings and not a issue.

 

At this point, you kinda want to drop the pan and remove the rod cap and bearings on that piston and pull it out.

Then see if you can gently free the rings and get them to rotate in the ring landings and then put it back in.

Just depends how far you want to go .... you might remove each piston one at a time and free the rings, clean them and re-install .... or just replace the rings with new.

 

With your last compression test, I think your rings still have some life to them ... just sticky right now .... this is where soaking in marvel mystery oil or such will help without taking the engine apart. .... Since you are already this far, you might as well drop the pan and take a physical look at your rings and pistons and make a choice of what to do next.

 

I'm kinda where you are. I  bought my truck in 2018 and it had one low cylinder like yours .... while working on my truck I have got the cylinder to 95-100.

Then I let the truck sit for a year because life gets in the way, I lose compression in that cylinder ... then I get it back up and the engine stops smoking .... then it sits for long periods again and starts smoking again and loses compression. .... Currently it is smoking again so I know that cylinder is not sealing.

 

My plan is to ignore it. In the process of new tires and today working on new wire harness .... March or April I will license it and drive it.

I will take it on a long country drive for a few hours and keep a eye on it.

After driving it all day, I hope the rings will be happy and seal up again and stay that way .... If not, I will pull the head and drop the pan and pull the pistons and replace the rings most likely.

While in there I will lap the valves and inspect them.

 

When you have cylinders above 100, your rings are in good shape maybe ... possible if you pull the piston out, you may have a broken ring. Same with me.

 

[Matfirstattempt]

@Los_Controlim very certain the valves need attention. The way I look at it, with the head off, I might as well replace the valves and springs. You’re right, pulling the pan isn’t an awful idea either. Can I easily pull a piston and replace rings while keeping the crank in the engine? I’m farther than I’ve ever been in wrenching on an engine so I’m in complete noobie land.

[Los_Control]

I'm a old carpenter, not a mechanic. ....

If you valves are as good as they look in the photo .... possibly they need to be lapped. Go ahead and apply some liquid to them and see if they seal ... gas would be ok, water not ideal.

First of all, when you have compression up to 110 .... that is ideal for a old flathead 6 ... some rebuilt engines do not get to 110 ... This tells me there is a good chance your engine has been rebuilt at some time in the past and it is in good condition. I suspect the valves are in good condition also.

When a engine sits for a long time, at least one cylinder the valves will be partially open and rust can attach to the seats .... lapping the valves is just getting the valves to seal with the seats again ... look it up.

 

Replacing the rings and doing a valve job on these engines was usually done with the engine in the vehicle at your local gas station.

There was a mechanic on duty .... they could typically replace all the rings in a day .... if the engine needed valve work also ... then it was 2 days.

Sometimes the engines were torn down to just work on the valves and not the rings ....

They also had large boring machines available that they could mount to your engine and bore the cylinders to the next larger size without removing the crank or engine from the car .... unheard of today, we simply pull the engine and send it to a machine shop .... Back in the day, it was done exactly as you are doing it.

 

Back then, cast iron rings were the best we had ... they wore out in 70K-80K miles depending on oil changes .... today they last 300K+ miles and the engines wear out before the rings ...

 

Did you happen to notice your oil pressure when you had it running last? .... Good oil pressure means you have good bearings ... if the bearings are worn, you will have low oil pressure.

It is possible to replace the bearings also while in there ... If needed .... I doubt you need it ... but maybe. Is easy to replace the rod bearings with the crank installed, a little more tricky to replace the main bearings with crank in place ... but doable.

 

You will take the rod loose from the crank, you will set the bearings aside and carefully push the piston up out of the block.

 

Here is a very dirty piston from a flathead Ford V8 .... The rings are a spring, you can see the gap and they open and close while at the same time they rotate around the piston. The piston has been sitting in my attic for years and covered in dust.

This engine was rebuilt and the rings and bearings are like new ... I could spend $$ and replace them, or just disassemble and clean and re-install.

Some will say you must replace with new .... Me, these are fine ... they just need to be cleaned ... probably better quality then todays aftermarket parts we have to buy.

 

So that is what I'm saying with your engine, take the 2 rod bolts loose, push the piston out the top and inspect it.

What you find will tell you your next step

[Ivan_B]

His dry and wet compression tests are the same, so the rings are probably not the problem. I would inspect the #3 valves and seats, they are probably not sealing well. Once the issue is confirmed, I would check/clean/replace/lap all the valves and call it a day. There is probably no need to mess around with the pistons/crank assembly, if there are no signs of bad things inside the bores (rust, pitting, vertical marks, wear spots).

 

For a quick valve check (assuming that a simple visual inspection does not show the problem) shine some bright LED flashlight into the exhaust\intake port and see if the light is coming through the closed valve, in a dark garage.

Edited February 24 by Ivan_B

[Matfirstattempt]

@Ivan_Bthats what I did - the light - and easily noticed issues. Noticed some space in cylinder 3 (the problem cylinder). So I’ll lap all, as you said, to be sure. there is some minor wear that can see but nothing drastic.
 

Is there anything else I should adjust/replace while in there? 
 

on a side note - what’s the best way to clean this absolutely filthy grease sponge?! Foaming degreaser, a tarp for the floor and a hazmat suit? 

[Ivan_B]

What kind of wear do you see? Any pics? If the valve/seat are worn, you might need to do some repairs, no use in lapping them. The valve/seat should have an even, straight, correct angle, flat sealing surface; if that makes any sense 😄

Also, you should probably check that the valves are straight, when you have them out (put one in a drill chuck and see how much it wobbles at the sealing edge). As for the other things to check - I've never taken these flat-heads apart, yet, sorry. So let's wait for someone more knowledgeable to chime in.

 

For the grease sponge, are you referring to the block? The best way, of course, is to take it out and properly de-grease with a pressure washer. Otherwise, yes, some de-greaser and a hose will do. Carb cleaner is also an alternative; less messy, but more expensive.

 

Also, you might need some crazy chemicals if you want to clean those valves shiny as new. I had good results with heated CLR (placed the valves in a metal can and placed the can on the stove). Make sure that you do it outdoors or wear some good quality dust mask, because those CLR fumes are probably not very healthy 😇

[JBNeal]

If replacing the valves, might as well replace valve guides.  I could wiggle every exhaust valve in their guides when I went through the 230 on the 1-ton back in '04, so I replaced all valves with the motor still in the truck.

additional information - valve guide replacement

additional information - valve guide driver

[9 foot box]

   I bought this tool to get to the two piece valve keepers. Cover the bottom oil return holes, so you don’t lose any keepers into the oil pan. With the manifolds off, you could probably use the loaner tool from Advance Auto. You probably need a torque wrench when you get to putting the head back on. But I’m getting ahead of the process, you need to chase all the threads that go into the block and use thread sealant on the threads, to get a proper three step torque sequence. That includes the manifold bolts. They all go into the coolant chamber. A retired seller used to say we are all in this together. Being a newbie, it’s hard to tell what advice to listen to. If you don’t have a Service Manual for a B1 or B2, it would be helpful. I have bought original printed manuals for my cars and trucks, that might be a little worn, but have better visual pictures than reprints. There’s a story about the rooster, but it reminded me of your five year ago post of the pig on your door. 

[Dodgeb4ya]

I see a lot of loose carbon by the exhaust valve on #3...

Carbon could be stuck on the valve seat/face.

[Matfirstattempt]

@9 foot box just purchased a kd700 for the valves after reading JBneal’s post. I’ll pick up a set of thread chasers, for sure. I also need to remove a stud from the manifold that busted off.

 

@Dodgeb4ya I’m pretty sure I saw bits of stuff (carbon) when I shined a light up from the manifold side, yes. I’m hoping that lapping will be enough. Do you think I need to cut the seats again?