Compression Test Completed (Fouled Plugs / Skipping Engine)

[CatGuy]

At lunch I had time to do a compression test on my '26. No idea how long ago this engine was rebuilt before I got it. There is still paint on the engine. I'm thinking.....40ish years ago....? I performed this with the throttle wide open, the choke wide open, all plugs out, the engine cold and for about 5 seconds each. If I was to suspicion.....I would say.....#1 has weak rings and #2 has a stuck valve or two......thoughts? What is thought to be the compression of a stock '26 T?

Dry: Wet:
#1 35 #1 45
#2 40 #2 40
#3 40 #3 45
#4 40 #4 45

[Scott_Conger]

looks fine to me
Once it's running and rings limber up, it will get even better
as far as missing, skipping, snarfing, at the level that you're experiencing, it has little if anything to do with rings or valves

at sea level, there is 14.7 PSI (atmosphere) and with 4:1 compression it's simply a math problem to see what theoretical "perfect" is. You're well within the range of relatively easy starting with a starter and decent/docile running. It won't climb Mt. Washington with ease, but will take you on many tours if that is your desire.

now the choice is to spend weeks/months diagnosing and serially replacing/rebuilding things, or get it running and have fun in about 2 weeks.

[CatGuy]

looks fine to me
Once it's running and rings limber up, it will get even better
as far as missing, skipping, snarfing, at the level that you're experiencing, it has little if anything to do with rings or valves

at sea level, there is 14.7 PSI (atmosphere) and with 4:1 compression it's simply a math problem to see what theoretical "perfect" is. You're well within the range of relatively easy starting with a starter and decent/docile running. It won't climb Mt. Washington with ease, but will take you on many tours if that is your desire.

now the choice is to spend weeks/months diagnosing and serially replacing/rebuilding things, or get it running and have fun in about 2 weeks.

I would prefer the two week journey since I've had this since the last of March and been trying to figure it out, but it looks like I'll be diagnosing a few things. Maybe give a good going over of everything engine/transmission related till they're all back to Henry's specs and then it should run and drive like.....a 96 year old car! Oh, the car does start very well and fairly quickly!

[Scott_Conger]

Well, I described the 2 week route on one of your other threads and got my head handed to me by folks who simply knew better and prefer tinkering over driving. I assumed then, and you've confirmed it, that it's time to get this thing on the road. Good for you, and I hope you have fun doing it. Months-long guessing games are fun for only so long. Any "T" that has spent a protracted time sitting, after a number of less than interested owners almost always need the same thing(s) done to make them reliable. Yes, you can pick away at these items serially and experimentally, each getting the car better and better, but I can almost guarantee you it will lead to walking home a few times before you're done, and that gets old fast. The advice I gave you earlier will save shoe leather and lead to more fun, sooner. If you're married, spouses sour on these things fast after being stranded just once. Don't be that guy.

[CatGuy]

Well, I described the 2 week route on one of your other threads and got my head handed to me by folks who simply knew better and prefer tinkering over driving. I assumed then, and you've confirmed it, that it's time to get this thing on the road. Good for you, and I hope you have fun doing it. Months-long guessing games are fun for only so long. Any "T" that has spent a protracted time sitting, after a number of less than interested owners almost always need the same thing(s) done to make them reliable. Yes, you can pick away at these items serially and experimentally, each getting the car better and better, but I can almost guarantee you it will lead to walking home a few times before you're done, and that gets old fast. The advice I gave you earlier will save shoe leather and lead to more fun, sooner. If you're married, spouses sour on these things fast after being stranded just once. Don't be that guy.

Actually my wife passed away a little over a year ago. Last year I bought a Model A and this year I thought I should get a Model T. My girl friend loves old cars, loves working on them and is quite good at it! She was right under the Model A with me taking the oil pan off! A guy ought to set the tools down long enough to marry a gal like that! I'll have to go back and re-read what you had posted now.

[Scott_Conger]

well, then, maybe a few more weeks of poking around won't be such a hardship after all!

rough way to get into the hobby, but nice that you have a pal to share it with. Good for you.

[speedytinc]

Not to be argumentative, but those compression #'s are not good. Playing with the math, a spec motor would have 58#
You have an effective compression ratio of 3-1. Thats a 25% reduction. 15 horse power? I would be inclined to run it & hope things improve after the other issues are addressed.
Not sure what you have done so far.
Let us know how she runs AFTER you have had your coils professionally blessed(preferably on an ECCT, but I would take a HCCT tune for now) & your timer looked @ by a competent T guy. No mention of timer condition. I bet it looks like a washboard road. If I had this T in the shop, she would be running well in an hour or we would know what the serious issues are.
You should put her in the hands of a competent, experienced T guy.

[Norman Kling]

A few things to do:
1. Be sure the compression gauge is accurate. If you have access to another one, compare the readings.
2. If you can get it running, warm it up and run for a mile or so and check right after running. If the compression comes up and evens out, it might just because all the oil has drained off the rings.
3. Take off the valve covers on the side of the block and if you have adjustable valve guides, you can check the valve lash. If one is a bit tight, it might prevent the valve from closing completely. If they are adjustable, you can re-set the gap.
4. While you test the compression, add a little oil to each spark plug hole, Only about a tablespoon full. Just enough to get the cylinders wet with oil and the ring grooves wet. then turn over the engine a few times. If the compression evens out, your problem is in the rings. If it stays about the same, it is likely burnt valves. If a valve is sticking, the compression will drop off to almost zero on that cylinder. But if the valve is slightly burnt but still closing, your compression will slowly leak out and the reading on that cylinder will be low but not as low as a sticking valve. Both too small clearance in the lifters and burnt valve will give similar symptoms, but will take removing the head to fix. Head gaskets are in short supply, so before you remove the head be sure you have a new gasket on hand.
You might do these things in any order, but be sure you have fixed it before you install the head and properly torque the head, because gaskets are hard to find.
Norm

[CatGuy]

Not to be argumentative, but those compression #'s are not good. Playing with the math, a spec motor would have 58#
You have an effective compression ratio of 3-1. Thats a 25% reduction. 15 horse power? I would be inclined to run it & hope things improve after the other issues are addressed.
Not sure what you have done so far.
Let us know how she runs AFTER you have had your coils professionally blessed(preferably on an ECCT, but I would take a HCCT tune for now) & your timer looked @ by a competent T guy. No mention of timer condition. I bet it looks like a washboard road. If I had this T in the shop, she would be running well in an hour or we would know what the serious issues are.
You should put her in the hands of a competent, experienced T guy.

I plan to look into the timer this weekend. I would like to find a competent T guy in the area that wasn't too busy to help. Maybe someday. On my own, but I'll get it.

[Scott_Conger]

John, I think you and I are in perhaps 100% agreement and I think a reread of my post would confirm that...right down to the fact that this thing will very likely get better with running...the vast majority typically do, which is why those numbers don't phase me. The only difference is it would take me probably double that time (or a little more) to have it running well enough to finish diagnosis.

[CatGuy]

When you say better with running.....How does that work? Some MMO in the gas tank and drive, drive, drive....? I've so far only driven it on three drives of no more than 2 miles. Maybe I should take it on a long half hour, 10 mile drive to see if it straightens out? Maybe once it really warms up it'll work some of it out? Will that hurt anything? It's annoyingly rough and shifts really bad going into high.

[Scott_Conger]

the RINGS will likely get better

from your earlier description, I'd say there is a strong suspicion that your coils are in very poor shape and the timer and carb are probably not far behind

your description mentioned little change on 3 cylinders when shorting coils and when shorting one coil the engine stopped. That tells me that 3 of those coils are very likely very weak and giving very poor incomplete combustion which is one source of fouled plugs, and for all practical purposes it is mostly running on that one cylinder for which the shorted coil kills the engine. This is why you must race the engine in low and cannot go over 25MPH in high. An overly rich carb trying to compensate for a vacuum leak will also foul plugs severely. Until and unless you verify proper operation of all above, or fix what isn't right, simply running the car is not going to fix much of anything, and will really put a strain on a naturally weak crankshaft.

As far as compression, my all original '19 has similar compression. It has been on 3 National Tours, countless Regional tours and thousands of miles just having an easy drive. It is down on power and not a hill-climber, but is a very well-mannered car. As far as being an efficient engine, I used to check the plugs and they were always clean. I quit checking them years ago and the car is still an easy starting and well running car...and as stated before is not exactly a barn-burner on the highway but will smoothly pull 35MPH all day long on relatively flat roads.

I have 3 other T's, two of which have new(er) engines with good compression. None of them run any smoother than my tired car...they are simply more powerful, which is John's point.

[perry kete]

It shifts really bad going into high

Model T's do not shift like other cars when changing gear from low to high. When you start in low tromp the peddle down hard don't ease into it, when you shift from low to high (about 8-9 MPH) back off of the throttle let the peddle out and then advance your throttle again. Be sure to have the timing advanced when running full out so you don't overheat the manifold and make it glow red.
It takes getting used to shifting a Model T