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This is a much simpler procedure than I had thought. The #1 plug was a pain to get to beside the AC compressor, but a 3/8 U-joint and a couple extenders made it happen.
The plugs were carbon fouled, indicating a rich mix. That is what we expected.
We tested the engine COLD, so the WARM values would be a bit higher than what we recorded, probably in the 120psi neighborhood, I would speculate.
So, according to most, it looks like cylinder #1 and #4 are having issues with piston rings or some other piston/ring/cylinder issue. Procedure we used said a variance of 15% indicated an issue. #1 is off by 24% and #4 is off by 14%. The 105psi for the other cylinders seems a bit low, but maybe not so low for a COLD test.
PLAN OF ACTION
1. Tune engine
No sense burning fuel needlessly. I have a vacuum gauge and tachometer. Will use those to get it running a bit leaner. In the future I will install an air/fuel gauge, too, and figure out how to time with a timing light (vs a vacuum gauge). Will start with just the external adjustment screws and only move to fiddling with internal carb bit if necessary.
2. Soak #1 & #4 in Seafoam for 36 hours or so.
A fellow on youtube fixed his problem this way. Seems carbon fouling in/about the piston rings had resulted in them not sealing properly and a soak in Seafoam did the trick for him. If successful, call it good and get on with other work.
3. If Seafoam trick does not work, will have to deal with the rings in some fashion.
Will price out various options. My neighbor indicates that I can drop the oil pan, unbolt the rods, remove pistons, re-ring the pistons, replace rod bearings, and git 'er dunn. That has the upside of forcing me to replace the oil pan gasket and maybe some other bits. We might be able to manage this but we have never done such internal engine work before. The other options are not within our current capabilities due to inexperience and/or lack of work environment. If I had hte space, I would definitely tackle it. I do my homework and take my time to figure things out.
Options:
..a. Replace piston rings from bottom of engine. (Possible DIY. Parts cost seems minimal.)
..b. Rebuild (Cost of rebuild kit + labor.)
..c. Replace with rebuilt engine. (Rebuilt Ford L-6 300cid running $1700 or so. Then add labor.)
..d. Replace with used engine. (Cost of engine + labor.)
..e. Live with it. I have read folks on forums with a similar issue who just live with it for years.
If any of y'all have pointers, tips, disagreements (with my conclusions) or think I am missing something, do please chime in.
FWIW, oil pressure cold is 50psi at idle and warm is 25psi at idle.
A warm engine will spin over faster. Faster spinning will make the cylinder pressures higher overall
A warm engine will have parts expanded up to operating clearances; piston skirts and rings will seal better.
There is a good likelihood that the valves are not sealing perfectly and all that is needed is a valve job.
A warm engine will spin over faster. Faster spinning will make the cylinder pressures higher overall
A warm engine will have parts expanded up to operating clearances; piston skirts and rings will seal better.
There is a good likelihood that the valves are not sealing perfectly and all that is needed is a valve job.
Agree with the conclusion (living with it), but do you think that squirting oil directly into the spark plug hole and getting a higher reading (equal to the other cylinders) is in the valves?
I've always thought that an increase in compression after adding oil was typically ring seal/bore wear-related.
I've always thought that an increase in compression after adding oil was typically ring seal/bore wear-related.
What I've always thought is adding oil to a cylinder to check compression was largely a waste of time. Especially for an engine where the cylinders were vertical.
Especially for an engine with a dished piston.
If you squirt oil in and it does not find its way to the rings does it just raise the compression from the ccs it displaces? What if it all ends up in the piston dish?
Maybe the ring friction was substantially reduced such that the motor turned over faster the compression would be higher just because it was spinning faster?
A leakdown test is the preferred method. With that you not only have an objective measurement of the cylinder's condition (% leakage) but you also have a subjective feeling for where it is leaking by listening to the exhaust pipe, the throttle body inlet, or the PCV crankcase connections to determine if the leakage is from the exhaust valves, the intake valves, or the rings.
Or all of them.
What I've always thought is adding oil to a cylinder to check compression was largely a waste of time. Especially for an engine where the cylinders were vertical.
Especially for an engine with a dished piston.
If you squirt oil in and it does not find its way to the rings does it just raise the compression from the ccs it displaces? What if it all ends up in the piston dish?
Maybe the ring friction was substantially reduced such that the motor turned over faster the compression would be higher just because it was spinning faster?
A leakdown test is the preferred method. With that you not only have an objective measurement of the cylinder's condition (% leakage) but you also have a subjective feeling for where it is leaking by listening to the exhaust pipe, the throttle body inlet, or the PCV crankcase connections to determine if the leakage is from the exhaust valves, the intake valves, or the rings.
Or all of them.
I do not have the experience to settle the wet test rings vs valves question. But come Saturday, I will soak those cylinders down with Seafoam and let them sit 24 hours and then do another compression test, this time WARM. If if brings the compression up, great. If not, I will live with it and tackle other issues.
We will look forward to your findings. My high school job was in a small engine shop. My boss told me as long as a gas engine has 85psi of compression it will run. Never forgot that.
What I've always thought is adding oil to a cylinder to check compression was largely a waste of time. Especially for an engine where the cylinders were vertical.
Especially for an engine with a dished piston.
If you squirt oil in and it does not find its way to the rings does it just raise the compression from the ccs it displaces? What if it all ends up in the piston dish?
Maybe the ring friction was substantially reduced such that the motor turned over faster the compression would be higher just because it was spinning faster?
A leakdown test is the preferred method. With that you not only have an objective measurement of the cylinder's condition (% leakage) but you also have a subjective feeling for where it is leaking by listening to the exhaust pipe, the throttle body inlet, or the PCV crankcase connections to determine if the leakage is from the exhaust valves, the intake valves, or the rings.
Or all of them.
All good points I had never thought about. Leakdown is usually what I do. I think I have done one compression test since high school and that was because I didn't have a leakdown tester. Now that I've lost "my" shop, I have a feeling that I'll be doing more.
Hey Jfruser,
You ask for opinions so.... I think I have an opinion but have a couple of questions first.
you state the OP is 50 and 25 cold, What is it hot at running temp?
How long are you planning on owning this truck?
What weight oil are you using?
What do you use the truck for? Hauling,loads where you need the power? or just DD and not too many miles?
Have you pulled the valve cover off to see how it looks? Sometimes you can learn a lot about the engine when looking under the valve cover.
Hey Jfruser,
You ask for opinions so.... I think I have an opinion but have a couple of questions first.
you state the OP is 50 and 25 cold, What is it hot at running temp?
How long are you planning on owning this truck?
What weight oil are you using?
What do you use the truck for? Hauling,loads where you need the power? or just DD and not too many miles?
Have you pulled the valve cover off to see how it looks? Sometimes you can learn a lot about the engine when looking under the valve cover.
Yep, I asked. Thanks for chiming in.
Oil Pressure
50psi cold at startup. 25psi after the engine is warmed up good. Stays around 25psi even when I ran it 60+ miles. I did the compression test cold. Will do the Seafoam trick and then do the compresion test warm this coming weekend.
How long are you planning on owning this truck?
Indefinitely. We have no intention of selling it. The idea is for it to be my son's local daily driver while we keep it running and improve it as we have time. When my son turned 12YO, he was born again mechanical. With new(er) Japanese cars & trucks, we could do a few things. With a truck of this age and simplicity, we have been working on all sorts of systems. Son (and I) are learning all sorts of nifty things keeping it running. And it is favorite vehicle by far.
What weight oil are you using?
Just changed it from the oil the previous owner had in September 2021. It has been driven 3000 miles since then. Not sure what HE had in it, but I am running Pennzoil conventional 10W-30 with ZDDP additive included.
What do you use the truck for? Hauling,loads where you need the power? or just DD and not too many miles?
Local daily driver for my son. Tow his bitty little sailboat (Boat and trailer are maybe a few hundred pounds, tops. I can tool the trailer+boat around the yard one-handed.). Thus far about 600-700 miles/month. Don't trust it yet for a long trip out of town. We use it to haul bulky loads, but not a lot of weight, as it has a full-size box that is not 5' in the air like new trucks. Easy access. It is a half ton with the frame that has the cut-outs, so it is not a heavy duty vehicle. I think of it as a "grandpa's" or retired old man's truck, given its configuration (see signature). Easy to get into as an old Crown Victoria, but still a truck because Grandpa always drove a truck and Grandpa always will drive a truck.
Have you pulled the valve cover off to see how it looks?
Not yet, though that is on the list to get sorted, as there is an oil leak at the valve cover gasket. Maybe I ought to move that up, priority-wise.
With the info you listed, if it was mine I would be looking for the long game
OK, my opinion or .02 worth I vote for Option E then B .....
First I would pull valve cover to see condition of oil deposits and crud.
Find a bore scope to borrow and check how much ridge is at top of cylinder wall.
If pretty clean and not much ridge, I would do the leak down test as Frenchtown mentioned
If it was clean and leak down test proved to be valves, pull head and have valve job done.
If it was all nasty I would save my money and go with your option B. My experience is engines never heal themselves, the longer you wait the worse they get and cost more to rebuild.
So, I would go with E,,, save my money for a while then go to B.
OK lets go thru your options as I see it. Explained below
Options:
..a. Replace piston rings from bottom of engine. (Possible DIY. Parts cost seems minimal.)
..b. Rebuild (Cost of rebuild kit + labor.)
..c. Replace with rebuilt engine. (Rebuilt Ford L-6 300cid running $1700 or so. Then add labor.)
..d. Replace with used engine. (Cost of engine + labor.)
..e. Live with it. I have read folks on forums with a similar issue who just live with it for years.
If any of y'all have pointers, tips, disagreements (with my conclusions) or think I am missing something, do please chime in.
A. In my opinion, impossible task. First since you have a 2 WD I believe you have to loosen the motor mounts and raise engine to just remove pan. NASTY job under the engine with oil dripping. Also, I don't believe you can change the rear seal without pulling the trans, clutch, flywheel. I don't see how the pistons can be removed around the crank. Either pull head but Easier to pull engine.
B. Find a good machine shop in your area and get prices. You may be surprised as your engine might only need honing and polish crank
cam bearings, cam and lifters and rings. this is one of the things we never know until tare down and checking. Everything could be bad.and worn out.
C. Compare pricing with Machine shop. I preferred rebuilding and using my existing engine.
D. You already have a USED engine. Why buy another one that may end up like yours.
E. It is always hard to answer questions Not knowing your circumstances like,,,mechanical abilities,, machine shop costs in area,, budget,,, time and space this may be the best option.
Well ,,,you ask for opinions and that is my .02 worth of opinions. LOL
Maybe some more knowledgeable engine and truck guys will also have opinions and chime in.
I just finished my 79 250 4x4 300 6. LOTS of work and time.
As I said I would, I dumped some Seafoam in cylinders #1 and #4 Saturday morning and did a WARM compression test this Sunday afternoon. I tested all cylinders but did only DRY. We also replaced all the spark plugs. The old ones had some carbon which is supposedly a sign of a rich fuel mixture.
OBSERVATIONS
1. I am not sure the Seafoam did much of anything. Sure, cylinder #4 bumped up 20psi, but so did cylinders #5 & #6.
2. Run WARM, cylinder #4 is only 12% off the cylinders with the best compression, so no worries according to most of what I've read (15% or 20% less is cause for worry).
3. Cylinder #1 only improved 7psi from cold to warm. Tested it twice to confirm. And is 30% off the cylinders with the top compression, worse than the 24% when run cold. So I think there is something amiss with cylinder #1.
Here is a photo from inside cylinder #4. Using a snake camera for the first time time. We were already into things when I remembered we had the snakey camera. No idea how to interpret this. I believe lower right carbony-looking bit is the top of the piston.
I think this engine is a bit tired. If we keep it long enough, we will eventually rebuild it. But that is a ways into the future. I think it is serviceable as-is, though it may not run as smooth as it ought to. Until then, we have lots of other issues to manage on the truck. I could be wrong and it is ready to go all asplodey at any moment.
Facts, opinions, and the undiluted Wisdom of the Ages are all appreciated.
I think a good long drive up hills and down with fresh gas and Seafoam, Lucas, or something heavy dosed to clean the carbon up, will do wonders for that engine. It won't hurt to have some blow by or use some oil as long as it isn't pushing it out as fast as you put it in.
Years ago it wasn't that unusual to put a quart or more a week in engines. I had a 283 Chevy I had to run a lot of 90 weight in to keep the oil useage to an unreasonable level. Kept on running though.
There is a vertical score mark in the cylinder which contributes to lower compression.
Additionally. cylinder #1 is characteristically the cylinder that has the most wear since the inrush of (relatively) cold coolant from the radiator, and the increased bore distortion from the open end of the block both work to accellerate more wear and less compression.
I stand by my original recommendation: RUN IT.
But you do see now how engine temperature - and also cranking speed - contribute to the compression numbers.
There is a vertical score mark in the cylinder which contributes to lower compression.
Additionally. cylinder #1 is characteristically the cylinder that has the most wear since the inrush of (relatively) cold coolant from the radiator, and the increased bore distortion from the open end of the block both work to accellerate more wear and less compression.
I stand by my original recommendation: RUN IT.
But you do see now how engine temperature - and also cranking speed - contribute to the compression numbers.
I am going to live with it. It runs and there are higher priority tasks that need doing. A rebuild some time in the future, maybe, when I have the facilities to make that happen.
I expected a bit higher compression numbers, but was not sure what the difference would be.
Also, it is funny to read or watch folks do compression tests on youtube. Some will get a 106psi and say, "That's great compression" while others look at 120psi as poor performance.
Originally Posted by yardbird
I think a good long drive up hills and down with fresh gas and Seafoam, Lucas, or something heavy dosed to clean the carbon up, will do wonders for that engine. It won't hurt to have some blow by or use some oil as long as it isn't pushing it out as fast as you put it in.
Years ago it wasn't that unusual to put a quart or more a week in engines. I had a 283 Chevy I had to run a lot of 90 weight in to keep the oil useage to an unreasonable level. Kept on running though.
The guy on Project Farm says good things about Seafoam, so this evening I dumped a can in the gas tank, 4oz in the motor oil, and a can of Seafoam spray down the carb. I then went on a 30 mile trip. I will let the Seafoam hang out in the crank case until next oil change and then do another compression test.
Not sure I expect anything, but I figure there are worse ways to waste $50.
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