Low compression

[Malcolm Towrie]

I just did a compression check on a Canadian universal carrier with a Ford flathead V8. The results were not good. They indicate it might be valves, at least on the two worst cylinders. Removing the heads with the engine in place looks tricky due to the angle iron support for the side panels running fore-and-aft. The heads are held down with studs and nuts so they have to be lifted enough to clear the studs and that brings them up pretty close to the angle iron supports.

Can it be done?

Thanks,

Malcolm

[Lynn Eades]

Malcolm, I have not yet done this, but I make the following suggestion,
remove all of the engine cover assembly. (this depends on your answers to the following questions)

You are going in, presumably because you have a valve problem (stuck or burned?) You suggested this.
Have you thought about a blown head gasket? (between two adjacent cylinders?)
A compression test indicated a low or no compression?
You then repeated the test with a little oil in the cylinders to seal the rings?
If nothing changed, then you have a valve problem?
If the compressions went up you have a ring problem.
If you have a ring problem, then it's an engine out job anyhow.

Before you do any more can you give us a bit of a back ground?
If the rings are stuck (or a valve) because the engine has sat a long time, then they might free up with use.
If you know the history and the engine has become tired you might end up with a big job on your hands.
Going back to the start of my circle, If you remove the whole cover, it will give you reasonable access to do the job , along with that it gives you the opportunity to tidy up other areas that might need dealing to. Valves that have not been out for a while can be hard to remove, so you will need all the room to do a good job. At the very least you need some room to just clean up the block face, for a new gasket. This is hard enough working around the studs, without all the other stuff being in the way.
Have I convinced you yet?
Tell us a bit more.

[Malcolm Towrie]

Originally Posted by Lynn Eades

Have you thought about a blown head gasket? (between two adjacent cylinders?)

Lynn, no leakage heard with mechanics stethoscope at the plug holes of adjacent cylinders during leak-down test, so no, I don't think it's the head gasket. (Even if it is, I still need to remove heads.)

Originally Posted by Lynn Eades

A compression test indicated a low or no compression?

Worst two cylinders, #6, and #7, were 30 psi. Then #2 and 3 at 50 psi. #1, 4, 5, and 8 were 90-95 psi. Oil rings are good. No smoke, and no carbon on plugs or valve/head visible through plug hole.

Originally Posted by Lynn Eades

You then repeated the test with a little oil in the cylinders to seal the rings?

I added oil to #7 and no change, still 30psi. So not rings, at least for that cylinder. I'm thinking, pull the intake manifold and heads and check bores, valves, guides, seats, head gaskets. Maybe I can get a decent amount of compression back without pulling the engine. IF I can get the heads off with the engine in place. Then it's a winter project to pull engine.

Originally Posted by Lynn Eades

Before you do any more can you give us a bit of a back ground?
If the rings are stuck (or a valve) because the engine has sat a long time, then they might free up with use.
If you know the history and the engine has become tired you might end up with a big job on your hands.

The carrier was running OK last summer and fall in parades and displays. It started and ran OK just before I did the compression test two days ago, even with horrible compression on 4 of 8 cylinders. I put that down to the high inertia of the massive rotating assembly on these old engines carrying the crank through the weak firing cylinders without noticeably slowing down.
This carrier is in very nice, restored condition and the engine was supposed to have been rebuilt. Looks like it wasn't.

Originally Posted by Lynn Eades

Going back to the start of my circle, If you remove the whole cover, it will give you reasonable access to do the job , along with that it gives you the opportunity to tidy up other areas that might need dealing to. Valves that have not been out for a while can be hard to remove, so you will need all the room to do a good job. At the very least you need some room to just clean up the block face, for a new gasket. This is hard enough working around the studs, without all the other stuff being in the way.
Have I convinced you yet?
Tell us a bit more.

There's plenty of room to get access to the block decks and valves IF I can get the heads off with the angle iron supports in place. That's the big question I have.

Malcolm

[Tony Wheeler]

Originally Posted by Malcolm Towrie

Oil rings are good. No smoke, and no carbon on plugs or valve/head visible through plug hole. The carrier was running OK last summer and fall in parades and displays. It started and ran OK just before I did the compression test two days ago

Hmmm....motor doesn't blow smoke, doesn't foul plugs, performed OK in parades last year, started and ran OK two days ago. And the problem is....what exactly....?

[Malcolm Towrie]

Tony, the owner likes his equipment to be in good condition, but as I think you are suggesting, he's resigned to running the carrier as-is over the summer.

I'll certainly pull the plugs again and give the accessible valves a "nudge". I was surprised I couldn't hear clearly where the leakage was coming from during the leak-down test, so valves stuck open enough that they don't hiss could be the explanation.

Thanks for the suggestions.

Malcolm

[rob love]

On mine, every valve that was stuck was directly under the spark plug hole.

Again, I think that for any amount of work an a carrier engine, removing the dog house will actually save time. You could build a stool with four legs that sorround the transmission and actually sit down to work as opposed to crouching, twisting like a controtionist, and sticking your head in the dark space. If nothing else, I suspect the quality of work will be better.

[Tony Wheeler]

Originally Posted by Malcolm Towrie

Tony, the owner likes his equipment to be in good condition, but as I think you are suggesting, he's resigned to running the carrier as-is over the summer.

Yes I was suggesting there's no immediate problem Malcolm. You seem hell bent on removing the heads prematurely.

Originally Posted by Malcolm Towrie

I'll certainly pull the plugs again and give the accessible valves a "nudge".

Actually I'd hoped to save you the trouble by pointing out that the motor is ALREADY running well. That's impossible with stuck valves. Perhaps I should have elaborated as it can be difficult to visualize:

The so called "stuck valve" or "sticky valve" syndrome common to flatheads is caused by corrosion of exposed valve stem on open or partially open valves during long standing - the result being a snug fit in the guide which cannot be overcome by the puny valve spring. Hence while the valve will OPEN fully and freely, it will stop on the way down when the band of rust on the stem hits the guide. Symptoms are ZERO compression, and if it's an intake valve, some audible blowback through the carby when cranking over. Such a motor will definitely not run! The solution as Rob describes is to "tap it down, crank the engine, tap it down again, crank the engine...." Generally after several repetitions accompanied by ample lubrication of the valve stem it will require only a single light tap, whereupon the valve will snap shut under valve spring pressure with a satisfying "plop". Thereafter a few more repetitions will generally see the valve no longer sticking at all.

The point being that stuck valves, once unstuck, cannot become restuck! Once they're dislodged and start moving again the corrosion quickly rubs off and the valve will seat normally - particularly once the motor starts running. The idea that valves might stick partially open is a mechanical impossibility. For example, consider a motor running at 3000 rpm, with the valves hammering up and down 25 times per second. No collar of rust on the valve stem can persist under those conditions.

re: I added oil to #7 and no change, still 30psi. So not rings, at least for that cylinder. I'm thinking, pull the intake manifold and heads and check bores, valves, guides, seats, head gaskets.

You're certainly itching to pull those heads off Malcolm! Can I suggest you restrain yourself long enough to perform wet and dry comp test on ALL FOUR deficient pots. That way you'll be in a position to confirm your "not rings" diagnosis.


re: This carrier is in very nice, restored condition and the engine was supposed to have been rebuilt. Looks like it wasn't.

I'm probably clutching at straws here, but it's just possible the motor WAS rebuilt and the valve clearances were insufficient. It's not unheard of and it can lead to valves not sealing perfectly after running in, because the clearance is further reduced as the new valves and newly ground seats bed in. This would be consistent with compression readings: 90-95 psi indicating rebuilt motor; 30-50 psi indicating zero valve clearance on those pots. It would also explain: "Oil rings are good. No smoke, and no carbon on plugs or valve/head visible through plug hole." That does not sound like a tired old flathead with burnt valves.

In any case the heads should not be removed until this possibility can be excluded. That means removing the intake manifold and checking valve clearances. Yes it may be wishful thinking but you never know your luck sometimes!

[rob love]

Removing the doghouse and the two angles is a little bit of work (moreso on a mk1 than a mk2), but once the dog house is off, working on the engine becomes a whole lot easier. I cannot imagine trying to do a valve job with the doghouse in place.

Lynn was mentioning stuck valves. I had several stuck on my flathead after it sat for a couple years. All the stuck valves were the ones right under the spark plug holes, so a little tapping with a small brass drift was able to seat them without any removal. I would tap it down, crank the engine, tap it down again, crank the engine....after 3 or 4 of these all but one got better. The last one actually fixed itself while sitting overnight....those self healing Fords.

[Malcolm Towrie]

Originally Posted by rob love

Removing the doghouse and the two angles is a little bit of work (moreso on a mk1 than a mk2), but once the dog house is off, working on the engine becomes a whole lot easier. I cannot imagine trying to do a valve job with the doghouse in place.

Lynn was mentioning stuck valves. I had several stuck on my flathead after it sat for a couple years. All the stuck valves were the ones right under the spark plug holes, so a little tapping with a small brass drift was able to seat them without any removal. I would tap it down, crank the engine, tap it down again, crank the engine....after 3 or 4 of these all but one got better. The last one actually fixed itself while sitting overnight....those self healing Fords.

Rob, Lynn, sorry, I hope I'm not coming off as a bit of an ungrateful dick here (I probably am ). The doghouse is not the problem, IMO. It's the angle iron supports. Can I remove the heads with them in place? The carrier owner has some parade obligations in the spring that preclude major surgery at this time. But checking the valves, gaskets, etc if I can just pop the heads off may be feasible.

Malcolm

[Lynn Eades]

Malcolm, I don't think there is enough room to get the heads off with the lower rails still in place.
You will have to lift the head 1 5/8" to clear the outer studs, but higher to come off the center (2 3/8") and top (inner) studs (2 1/2")
Bearing in mind that you can probably roll the head "out" to get off the higher studs earlier (if you follow) but you would need to be lifting the head "square" from the deck, for say 2 1/4".
I don't have a carrier with an engine in it, but don't think that is possible.
It would be good if someone else chimes in (in case I am telling porkies)

In your current situation, maybe a re read of Robs advice is a good move?

[charlie fitton]

You can access and inspect the valve (springs and tappets) by removing the intake manifold. you can quickly assess whether something is stuck that way.