Cylinder Compression Test

[Logan]

I pulled the spark plugs and tested compression to see why my engine was running so rough, and found out what it was.  The compression was: cylinder 1-zero; 2-128 psi; 3-85; 4-135; 5-133; 6-140.  So I guess I have a stuck valve on number 1 and probably bad rings on 3 and maybe some carbon build up on 6.  Here's my question: I know I need to get the valve going on 1 and will try unsticking it with some Marvel Mystery Oil.  If I do that, how well will it run with low compression on one cylinder and high on another one?  I really don't want to dig into the engine to fix the other problems.  I guess I'll try to unstick the valve first and see how it goes from there.

[54 Kaiser]

Try and unstick the valve if that's what it turns out to be Logan. But I'd suggest - rather than digging too far into the engine - that you buy a new head gasket (Lots of folks here have NOS ones and they are not expensive) pull the head off and check the valves. It's more likely you have burnt valves than bad rings. Even the zero compression cylinder could be a severely burnt valve. One nice thing about a flathead is that the head is easy to pull. Just drain the cooling system below the level of the head, disconnect the rad hose, and pull the distributor. Then start pulling head bolts. (Be sure to re-torque them in the correct order to 35 lb/ft.)

Valves are available. You'll need a valve grinding/lapping kit to get them just right. And then set up the clearances. Chances are your compression will be within a few pounds of each other when you're done.

[jmxkf1]

I have a head gasket you can have for $20 obo.   Jim

[Logan]

When I poured a little oil into number 3 it jumped from 85 to 115 psi, so I do think that there are piston or ring problems there that will eventually need to be fixed, i.e. it will need a rebuild at some point, but it very could need a valve job too.  First thing I will try to do is unstick the valves in number one if that is really what's run, and see how much imporvement I get.  I'll let you know how that goes.  We'll see where we have to go from there.

[54 Kaiser]

Forgot about adding the oil. That pretty much clinches it on number 3. Rings. And if you're going to tear the mill down to do the one cylinder, you might as well do the whole thing.

Or... buy an already rebuilt one.

Me? I'm cheap. I'd do the rebuild myself. And then I'd KNOW it's done right. As with transmissions, a lot of commercial engine rebuilders only replace what actually has to be replaced. They don't put the entire "kit" in the engine. Transmission shops are terrible for this practice. One mechanic I know tells me some of the "big name" transmission places will put less than 1/4 of the kit in an automatic if everything else looks good.

[Logan]

Wow, that's terrible about the transmission shops.  I dont' have the time or really the money to rebuild the whole thing now, so I will see what I can do with what I have.  We'll see.  I would be inclined to rebuild it myself when the time comes, although I've really never done that.  I did rebuild a small, two-stroke motorcycle engine, but that was pretty simple.

[54 Kaiser]

Not that bad doing a car engine really. Except it's heavier and there are more cylinders. AFAIK, the kits include everything you need to do the rebuild. Kanter's Master kit is a little over $1,000 and includes everything. Including new pistons, valves, camshaft, oil pump, etc.

[Logan]

Hmm, that's not TOO bad.  I do have an engine stand I've never used (Christmas present).  I'll have to think about it.

[Logan]

I've been pouring Marvel Mystery Oil down the carb like it's going out of style, but nothing, so I guess I will end up pulling the head.  Jim, I sent you an e-mail--I'm interested in buying the head gasket.

As I understand all you need to do is take off the distributor, the throttle linkage and then unbolt it, no?  When I get it off, should I just take a mallet and pop the stuck valve down (assuming it is, in fact, a stuck valve)?  Anything else I should know about this operation?

[joefrazer]

Yes, pull the head and check for a stuck valve. Before you take a mallet and tap it back down, I'd pull the side inspection cover and take a look at what things are like in the valve chamber. This can be done without removing the intake/exhaust manifolds. The valve stuck for a reason and gum and varnish are just one cause. On my 50K, the guide actually became out of round and it caused the valve to seat at an angle. I wouldn't have noticed axcept for the tappet being scored...something only removing the inspection cover will reveal.
If all looks OK there, then...with the valve still stuck up, take some PB Blaster and spray liberally down in around where the valve meets the guide. Also, do the same from below. Put some rags or shop towels in the valve chamber to catch the runoff or it'll dilute your oil. Too much sprayed in the affected area is never enough as you do not want to have to do this again...take it from someone who's been there and done that!
Then, once you're satisfied that you've cleaned up the problem, tap the valve down. Then, turn the engine over to ensure that the valve is opening and closing as it should.
Some things to note:
1. Make sure you drain the cooling system to below the top of the block or when you pull the head, you'll get a nasty surprise.
2. Buy a valve cover gasket and fuel pump gasket, you'll need both at reassembly. Autozone has both available.
3. When you remove the distributor, make a note of the extension's position in the block. This is the long rod that goes down into the block. It's has a slot cut into it at the top and bottom. The bottom half goes into the oil pump and the top fits into the distributor base. When you pull the head, put the rod back into the block in the same position BEFORE you crank the engine in the test mentioned bavove. This will ensure that you have the distributor where it needs to be when you reassemble everything. Make note of it's position before you remove it to put the head back on and reassemble it in the same spot. If you don't, there's a 50/50 chance of getting it wrong and the car will be difficult to start because the timing will be 180 degrees off.
Let us know what happens!

[54 Kaiser]

He may want a side cover gasket too Joe. (Or a tube of RTV gasket maker.)

[Logan]

So, do I have to take the fuel pump off to acces the valves through the side cover?   Is there a difference between the valve cover gasket Joefrazer talked about and side cover gasket that you mentioned, 54Kaiser?  I was thinking they were one in the same.  I do know I need a new head gasket if I remove the head.

Thanks for the tips; any more are welcome.  For instance, when I look through the side cover at the tappets, what exactly am I looking for?  Joefrazer, you mentioned scoring of the tappet.  Did you need to get a new guide for that?  My goal here is to get a maximum benefit (i.e. good running engine) for a minimum of work.  That might be an oxymoron, but I don't want to put a ton of time and money into this right now--a full engine rebuild will be a project for a future date: several years down the road.

[Fabian 51K]

When you pull the valve cover you will see from the bottom of the tapet chamber to the top (1) the tapet with adjuster, (2) the bottom of the valve stem (3) valve spring keeprs 2 ea. valve spring, (4) valve guide. The scoring will probably look very shiny, or like an indentation that does not look like the rest of the tappets (Normal wear is a round spot in the center of the tapet from where it pushes tha valve, this is ok) This can be seen at the top of the tappet and the buttom of the valve stem. you will want to look for broken valve springs and keepers. On a 54 Kaiser you may not need to remove the fuel pump sense it sits under the valve cover and there is no vacume pump, but you may need to disconnect the fuel lines. The gaskets are the same, they can be purchased at many places.

[Logan]

It worked!  The exhaust valve in the #1 cylinder was stuck--it could move, but couldn't move all the way down.  I ended up pulling it out (with vise grips and a lot of elbow grease).  Then I kept spraying it with PB Blaster and working it into the guide a little farther each time until it could go all the way to the bottom and finally move up and down without interference.  What a difference when I started it back up--no more rough spots!  I also adjusted the tappets while I was in there and cleared up the clacking noise.  So thanks everyone for all the advice, it really worked well.


One question I have though: I wanted to adjust the timing.  I assumed that lossening the screw and bolt about 1/3 of the way up the distributor would allow me to advance / retard it, but when I moved that plate the top half of the distributor did NOT move and the timing did not change.  So what am I missing?  How do you adjust the timing?  Also, although it runs smoothly at idle when I start to accelerate it seems a little less smooth, not bad, just not perfect.  Additionally the transmission shifts into second gear early, at about 5 mph.  I see a rod running from the accelerator linkage to the trans that I assume adjusts that.

Again, it's great to have this forum and get good advice from people and be able to do it yourself!

[superk226]

How did the compression test turn out after the valves were freed up and adjusted?  Larry