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  #1  
Old 03-03-16, 03:49
Malcolm Towrie Malcolm Towrie is offline
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Default Low compression

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
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Old 03-03-16, 05:57
Lynn Eades Lynn Eades is offline
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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.
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  #3  
Old 03-03-16, 06:10
rob love rob love is offline
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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.
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Old 03-03-16, 06:52
Malcolm Towrie Malcolm Towrie is offline
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Quote:
Originally Posted by Lynn Eades View Post
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.)

Quote:
Originally Posted by Lynn Eades View Post
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.

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Originally Posted by Lynn Eades View Post
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.

Quote:
Originally Posted by Lynn Eades View Post
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.

Quote:
Originally Posted by Lynn Eades View Post
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
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  #5  
Old 03-03-16, 07:17
Malcolm Towrie Malcolm Towrie is offline
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Quote:
Originally Posted by rob love View Post
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
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  #6  
Old 03-03-16, 10:08
Lynn Eades Lynn Eades is offline
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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?
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Last edited by Lynn Eades; 03-03-16 at 10:25.
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  #7  
Old 03-03-16, 14:59
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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.
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  #8  
Old 03-03-16, 15:06
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Quote:
Originally Posted by Malcolm Towrie View Post
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....?
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  #9  
Old 03-03-16, 15:35
Malcolm Towrie Malcolm Towrie is offline
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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
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  #10  
Old 03-03-16, 17:58
rob love rob love is offline
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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.
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  #11  
Old 03-03-16, 22:41
Malcolm Towrie Malcolm Towrie is offline
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It looks like the valve under the plug hole is the exhaust valve so it makes sense that that valve is more likely to stick.

Have you had it apart since? If so, did you find the valve springs weak or varnish build-up on the stems?

And after taking another look, Lynn's right. Those heads are not coming off without removing that angle iron rail, so my thought of simply pulling heads and intake off to do a quick fix isn't going to fly. And from what I have heard and read, doing valve work on this engine isn't that simple anyway.

Malcolm

Last edited by Malcolm Towrie; 03-03-16 at 22:49.
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  #12  
Old 03-03-16, 23:34
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The valve stems bend so easily on these engines... You will find that they run ok, but the valves won't seat tight into the block.
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  #13  
Old 04-03-16, 02:34
Malcolm Towrie Malcolm Towrie is offline
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Update: tapping on the valves with a brass punch on the worst cylinders (with the pistons at TDC firing) had no effect. I measured the height from the head of each valve to the spark plug seat with dial calipers before and after and there was no change. And no change in compression pressure. Oh well, it was worth a try.

It's unusual to bend valves on a engine especially as the usual causes like over-revving or cam timing slipping aren't applicable on a flatty. Why are these engines prone to it?

Malcolm
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  #14  
Old 04-03-16, 02:43
rob love rob love is offline
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A valve job in the original form is a big deal. You grind the valve and the seats,, then you grind the stem of the valve to get the right clearance. You can install adjustable valve lifters (I think they originally come from one of the old 8N Ford tractors but don't quote me on that). That will make it a lot easier to do the adjustment, but it requires removal of the cam I think, which is not something you are going to do in-frame.

Can't say I have ever had a problem with bent valve stems on a Ford.
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Old 04-03-16, 03:22
Malcolm Towrie Malcolm Towrie is offline
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Quote:
Originally Posted by rob love View Post
A valve job in the original form is a big deal. You grind the valve and the seats,, then you grind the stem of the valve to get the right clearance. You can install adjustable valve lifters (I think they originally come from one of the old 8N Ford tractors but don't quote me on that). That will make it a lot easier to do the adjustment, but it requires removal of the cam I think, which is not something you are going to do in-frame.

Can't say I have ever had a problem with bent valve stems on a Ford.
I can see some hassles with doing a valve job then!

So how do shops grind the valves with their mushroom tips? The seat grinders I have seen chuck the valve stem.

And grinding seats in the block must require a tool that locates in the guide bore? Sounds specialized. And nasty if you spread grinding debris around the valley.

Malcolm
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  #16  
Old 04-03-16, 04:42
rob love rob love is offline
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Grinding seats is not that messy. Lots of rags in areas you want to protect. Some of the older manuals will show a cutter to reface the seats, but for the last 70 years or so they are done with specially designed grinding stones. Seems like we rarely to never need them for the modern engines, since the computer keeps everything so clean and the fuel mixture just right. I bought a complete valve grind set-up because I have more old engines than new ones.
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Old 04-03-16, 05:37
Malcolm Towrie Malcolm Towrie is offline
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I found this for grinding seats in the block. Neat how the pilot locates in the guide bore and the lifter bore. I guess this is what you have?

https://www.youtube.com/watch?v=QDEJ3coQa14

I'm still curious about refacing the valves. The refacing tools I have seen look like this, with a collet chuck holding the stem. How is the flattie valve held with the mushroomed tip?

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Old 04-03-16, 05:48
rob love rob love is offline
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Open the collet further, slip the valve in, and tighten the collet on the straight part of the valve stem.

The valve grinder puts the stem against the side edge of the stone.

Yes, the valve grind kit I have is essentially the same (mine is snap-on) as that shown in the you-tube video. Their guide tool is a bit more specialized than the ones I have, but certainly a good idea to get the valve seat bore aligned to the lifter. I take exception to them describing the tools as obsolete or antique. Those are what I learned on.
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Old 04-03-16, 06:11
Malcolm Towrie Malcolm Towrie is offline
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Quote:
Originally Posted by rob love View Post
I take exception to them describing the tools as obsolete or antique. Those are what I learned on.
Ouch. Touched a nerve, did it?
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Old 04-03-16, 18:05
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Quote:
Originally Posted by Malcolm Towrie View Post
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.


Quote:
Originally Posted by Malcolm Towrie View Post
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!
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Last edited by Tony Wheeler; 04-03-16 at 18:12.
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  #21  
Old 04-03-16, 19:50
Malcolm Towrie Malcolm Towrie is offline
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Originally Posted by Tony Wheeler View Post
Yes I was suggesting there's no immediate problem Malcolm. You seem hell bent on removing the heads prematurely.

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!
Your post and its annoyed tone puzzle me, Tony. You say the motor is running well, yet it has 2 cylinders with 30 psi compression. Yes, it starts and drives, but it is not a well-running motor IMO.

I didn't think for a minute that valves stuck open because of long storage was the issue here, for the reasons you explain in such detail, but I suspected the springs on these engines were fairly light, so maybe varnish build-up on the stems or carbon on the seats preventing some valves coming down tight? A long shot, but the tapping the valves idea was suggested and it was easy to do, so why not?

So as a newbie to these engines, with the heads so temptingly accessible, it seemed a simple job to pull both the heads and intake manifold and check for ALL the various top-end related issues that could be causing this, AND fix them in the time we had available. All in one fell swoop.

Of course, now I know it isn't that simple to pull the heads, nor is it that simple to do a valve job on these engines, so we'll just run the old girl as-is until there's a space in her schedule to do the work.

Malcolm
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Old 05-03-16, 16:02
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Originally Posted by Malcolm Towrie View Post
Your post and its annoyed tone puzzle me, Tony.
I think you've misread me Malcolm. It happens sometimes in this kind of forum. It's probably my lame attempts at humour. I assure you I'm not annoyed!


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Originally Posted by Malcolm Towrie View Post
You say the motor is running well, yet it has 2 cylinders with 30 psi compression.
Yes, that's what you reported Malcolm: "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."

It's not uncommon to find minimal compression in several pots on these old flatheads. They'll still run happily for many years to come, and if restricted to parades they'll probably outlive the owner. Even in hard use they remain indestructible - my F15A road truck shows 40-70 psi in all pots and rattles alarmingly when cold, but after warm up I never hesitate to wring every last screaming rpm out of it through the gears. I'm sure Jacques if he's reading this will attest to its performance up steep mountain tracks - albeit at 4000 rpm! In practice, apart from a thirst for oil, it's a perfectly serviceable motor, and I enjoy not having to nurse it like a $5000 rebuild.

Of course, being accustomed to modern motors, it can be quite disconcerting to see readings of 30 psi, and the natural response is an overwhelming urge to pull the heads off and investigate. Perhaps that's why most owners avoid performing compression tests! However, we need to remind ourselves that compression tests are purely diagnostic, and pots showing 30-50 psi at cranking speed will still produce plenty of power.


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Originally Posted by Malcolm Towrie View Post
Yes, it starts and drives, but it is not a well-running motor IMO.
This seems at odds with your earlier report Malcolm: "The carrier was running OK last summer"....."but it is not a well-running motor IMO." I guess it comes down to one's definition of "motor running well". To my mind, if a motor is firing on all cylinders, and drives the vehicle satisfactorily, it's "running well". It may be down on power, but that's a different question. That's generally tolerable on MVs, thanks to plenty of gears and no need to keep up with traffic. Indeed, lack of power is arguably essential to the MV driving experience!

Of course, I fully understand your earlier point: "the owner likes his equipment to be in good condition". Particularly when: "This carrier is in very nice, restored condition and the engine was supposed to have been rebuilt." I too would be keen to address low compression issue in such a vehicle. I was merely urging forethought and proper diagnosis.


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Originally Posted by Malcolm Towrie View Post
the tapping the valves idea was suggested and it was easy to do, so why not?
I suspect there was some misunderstanding / miscommunication here Malcolm. It wasn't immediately clear from your initial post that YOUR motor was already running, and in Ron's discussion of stuck valves it wasn't immediately clear that HIS motor was not running! Again, it's inevitable with this kind of information exchange. As you say, no big deal in this case.


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Originally Posted by Malcolm Towrie View Post
So as a newbie to these engines, with the heads so temptingly accessible, it seemed a simple job to pull both the heads and intake manifold and check for ALL the various top-end related issues that could be causing this, AND fix them in the time we had available. All in one fell swoop.
Yes, it's always tempting to whip off those heads, but in practice it achieves very little. Unlike OHV heads you can't send them away for a valve job! Unfortunately the "quick fix" you were hoping for does not exist on flatheads, because the "top end" is actually in the block.


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Originally Posted by Malcolm Towrie View Post
Of course, now I know it isn't that simple to pull the heads, nor is it that simple to do a valve job on these engines, so we'll just run the old girl as-is until there's a space in her schedule to do the work.
I think that's basically what we were advocating Malcolm, as the time frame seemed unrealistic, and the diagnosis unconfirmed. As Lynn says: "if the engine has become tired you might end up with a big job on your hands." Another possibility yet to be ruled out is broken rings, which can also occur in a poorly rebuilt motor. If I were you I'd be keen to complete the wet and dry comp test, and if it all points to valves as we suspect, I'd be keen to remove the intake manifold and check clearances.

Anyway good luck with it Malcolm and keep us posted with any developments.

Cheers,
Tony
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  #23  
Old 05-03-16, 21:27
Lynn Eades Lynn Eades is offline
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I myself am wondering what else can affect the compression of the four centre pots?
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  #24  
Old 06-03-16, 06:04
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Tony Wheeler Tony Wheeler is offline
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Yes I noticed that too Lynn, seems rather a coincidence. The mathematical probability is: 4/8 x 3/7 x 2/6 x 1/5 = 1/70. In other words, in a motor with 4 deficient pots, the odds of them all being centre pots is 1 in 70. It's quite suspicious but I can't think what it might indicate, unless perhaps BOTH head gaskets are leaking between adjacent pots, which is quite some distance in this case.

Of course, the effect of this 1 in 70 chance is that all four weak pots fire consecutively, followed by all four strong pots, followed by all four weak pots, etc. In terms of crankshaft acceleration / deceleration it's the worst possible combination.
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Old 06-03-16, 06:41
Malcolm Towrie Malcolm Towrie is offline
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Of course, the effect of this 1 in 70 chance is that all four weak pots fire consecutively, followed by all four strong pots, followed by all four weak pots, etc. In terms of crankshaft acceleration / deceleration it's the worst possible combination.
Good point! Further evidence of the massive moment of inertia of the rotating assemblies in these older engines which allows acceptable running even with such large differences between cylinders. I came across a Ferret last year that had the ignition timing set 90 degrees BTDC. Yet it started and ran. The only way I figured that could happen is the rotating assembly was damn near unstoppable once it got moving so it just drove through the period when combustion was trying to reverse its direction.

I wondered if this engine had ran very rich in its past, choke stuck closed-type rich, with liquid fuel trickling along the floors of the dual plane intake manifold and preferentially dropping down into the first holes it came to, the cylinders nearest the carb. But I suspect the gas wash would still have affected the corner cylinders to some extent, and my wet/dry compression testing didn't support bore/ring wear, so that scenario seems unlikely.
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Old 06-03-16, 07:30
Lynn Eades Lynn Eades is offline
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Malcolm, I assume that the MkI* dizzy is the pre 42 divers helmet type.
If you had a crab dizzy it would be the leads that come off the cap from 11.00 o'clock around to 5.00 o'clock.
Another coincidence is that the compressions on the low cylinders are the same on each bank 30,30, and on the other bank 50 and 50. Very unusual.
Calculate that one Tony.

The design of the manifold would let the petrol do that if the engine sat level in the carrier.
What was the situation with the fuel pump (i know you had another thread about it, but wasn't really following it)
These engines don't bend valves, blokes trying to remove valves can bend them.
If your pump was over riding the needle valve I guess it might have washed oil from the valve stems,while it was trying to stay running. (before it was parked up)
As Tony said, It probably would have fixed its self while running.(this time around)
Does this engine run the original carb, or is it running a 94?
If the choke was on, it probably would have flooded, and stalled.

I think the answer is to run it up, get it hot, re do the compression test, dry, then wet. Open the throttle once, and lock it open for the duration of the test. write down what you get, and if it is still the same as before, lift that inlet manifold, and check the clearances.
Then you'll know what has to be done.
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Old 06-03-16, 14:47
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Another coincidence is that the compressions on the low cylinders are the same on each bank 30,30, and on the other bank 50 and 50. Very unusual.
Another very astute observation on your part Lynn, which escaped me completely! Strangely it seems to point even more strongly to head gaskets as mentioned: "perhaps BOTH head gaskets are leaking between adjacent pots..."

I don't know the likelihood of that, as it's quite some distance and would normally involve water jackets, but it would certainly explain equal compression in adjacent pots, because they're both leaking through the same passage (in the opposite direction).

Of course, even it were possible, there would need to be some explanation for it occurring on BOTH sides. I wonder if it could occur in a rebuilt motor if the heads weren't torqued (or re-torqued) properly. Might be worth warming it up and re-torquing heads before next compression test, taking special note of the central stud (which is first in the tightening sequence anyway).

Again, it's a longshot (extreme longshot...?) but very easy to do and always worthwhile anyway.
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Old 06-03-16, 20:31
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Just came across this Ford film featuring valves. Won't necessarily fix your problems but may at least be a distraction! https://www.youtube.com/watch?v=-x9HIZuTmsE
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Old 06-03-16, 22:26
Malcolm Towrie Malcolm Towrie is offline
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Originally Posted by Lynn Eades View Post
Malcolm, I assume that the MkI* dizzy is the pre 42 divers helmet type.

What was the situation with the fuel pump (i know you had another thread about it, but wasn't really following it)
If your pump was over riding the needle valve I guess it might have washed oil from the valve stems,while it was trying to stay running. (before it was parked up)
Does this engine run the original carb, or is it running a 94?
If the choke was on, it probably would have flooded, and stalled.
I volunteer at a military museum in Oshawa, Ontario and there are always lots of things needing fixed so my focus has swung away from this carrier for a while. However, I will check the torque on the head nuts cos that's easy to do.

To answer your questions, yes, it has the divers helmet dizzy.

The fuel pump wasn't pulling up fuel from the tank when I tried to start it to do the testing. I had to rig up a temporary supply.

Re carb, I can't remember. The owner buys restored vehicles from the UK, so it might be a British carrier, so a Solex? I'll check.

I meant choke stuck partly closed rather than fully closed. It was quite common with the automatic chokes on cars over here. I've seen it cause severe wear right at the top of the bores, where the compression ring needs all the help it can get.

Malcolm
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Old 07-03-16, 02:44
Malcolm Towrie Malcolm Towrie is offline
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I checked the head torques tonight. With the wrench set to 55 ft-lb, I was able to get some movement on maybe 1/3rd of the nuts. But hot compression test results were exactly the same.

I also did a wet test on the bad cylinders and saw very little difference, a few psi higher. In fact I was surprised by how small the difference was. I squirted 4 good shots of oil towards the back of the cylinder, so I think that should have got to the rings?

After the tests, just out of curiosity, I started the engine again to check timing with a timing light since I had marked TDC on the crank pulley earlier. The light showed only occasional spark on #1, occasional no-spark periods on #2, and steady spark on 3, 4, 5, and 6. The engine ran out of gas before I got to 7 and 8. I got some more gas, and it wouldn't start hot. (This is the first time I have tried to start it hot.)

I'm beginning to think this engine doesn't run as well as reported.

Malcolm

PS: the carrier has a Zenith carb with a governor.

Last edited by Malcolm Towrie; 07-03-16 at 03:01.
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