How to test compression?

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Model T Ford Forum: Forum 2017: How to test compression?
Top of pagePrevious messageNext messageBottom of page Link to this message  By John Annaian on Saturday, November 25, 2017 - 10:15 pm:

Hi all,

Wondering how to test compression in a 27 T. I tried looking around in the forum but only found stuff about what gauge to use and adapters and stuff like that.

Right now the carb and exhaust manifold are both removed. I am assuming they need to go back on?

Do all spark plugs come out and you test one at a time? Leave plugs in and test one? How many cranks? Etc. I also read that the choke needs to be out and put the throttle all the way up or something?

Thank you for any help!


Top of pagePrevious messageNext messageBottom of page Link to this message  By Scott Conger - Wyoming on Saturday, November 25, 2017 - 10:19 pm:

I think now is an ideal time to test the car just as it is. Pull your plugs to ease cranking and test each cylinder in turn.


Top of pagePrevious messageNext messageBottom of page Link to this message  By Mark Gregush Portland Oregon on Saturday, November 25, 2017 - 10:22 pm:

Let the engine crank thru about 6 cycles for each hole.


Top of pagePrevious messageNext messageBottom of page Link to this message  By Charlie B actually in Toms River N.J. on Sunday, November 26, 2017 - 07:25 am:

With the carb off you eliminate 2 things you'd need to do which are make sure the choke and throttle are wide open. Plugs out. 6 to 7 cranks for each cyl. Test all 4 cyls in order and write each number down. Next shoot a few shots of oil in #1 and retake the test. Note if the pressure goes up (usually worn rings). If the pressure is low and doesn't go up it indicates possible valve leakage. Repeat with the other 3 cyls. 45/55 Lb range is great and oil test isn't necessary. Warm engines tend to raise compression as things swell a bit which is why I much prefer to comp test low pressure engines like the T when cold because that's what it'll be from a dead cold start & low/cold comp = hard starting.


Top of pagePrevious messageNext messageBottom of page Link to this message  By John Annaian on Sunday, November 26, 2017 - 09:35 am:

Thanks Charlie.

Just installed the carb and manifold and had the throttle and choke were open, and had the following:

#1 3 PSI
#2 23 PSI
#3 25 PSI
#4 22 PSI

These readings are approximate, my tester is a cheap analog dial type.

These readings I'd say are pretty low... especially #1.

I'll do a test with everything off later and see.


Top of pagePrevious messageNext messageBottom of page Link to this message  By G.R.Cheshire (La Florida!) on Sunday, November 26, 2017 - 10:28 am:

John the "Cheap" analog type compression gauges are fine. When using an adapter you need to ensure the adapter is sealed in the spark plug hole, I usually use pipe dope because the engine will not be running and pipe dope cleans up easily when you are done. ALL of those readings are low! I usually use this test for general testing, Grab 4 wine corks (have friends over to help dispose of the contents of the bottles) place corks firmly in Spark plug holes turn crank handle 2 complete turns if all 4 corks pop out you are good if not then break out the gauge.


Top of pagePrevious messageNext messageBottom of page Link to this message  By Mark Gregush Portland Oregon on Sunday, November 26, 2017 - 10:59 am:

GR love that testing idea! :-) After 4 bottles of wine would not care anyway.
John having the manifolds on or off would not make a difference. The readings are way too low and taking them off would not change that. 35 is regarded by some about as low as you want for an engine to run with any power, weak as it may be. At minimum I would say you need a valve job and rings but not knowing how worn the cylinders are can't comment any further.


Top of pagePrevious messageNext messageBottom of page Link to this message  By John Annaian on Sunday, November 26, 2017 - 11:06 am:

Yeah, figured that. Strangely enough the seller said he drove it around a few years ago... whatever

ill see if I have 4 corks and try that out! Lol

What could be the cause of #1 being almost 0? Head gasket cracked or leaking? It looks pretty rough around the edge. And at this point, I would think taking off the head would be a good idea to see how everything looks.

Now that I think about it, the seller did say one piston was very clean looking through the spark plug holes. Must have been 1.


Top of pagePrevious messageNext messageBottom of page Link to this message  By Rich Bingham, Blackfoot, Idaho on Sunday, November 26, 2017 - 11:09 am:

The range of pressures indicates there's most likely a bad valve in #1. The rest could be marginal. You can assess the condition of the cylinders when you pull the head for a valve job - if they look OK and measure up, there's a possibility of stuck rings. What's the back story on this motor ? How found, length of storage, use, what did the oil look like ? Etc. etc.


Top of pagePrevious messageNext messageBottom of page Link to this message  By John Annaian on Sunday, November 26, 2017 - 11:55 am:

The seller had it stored in a garage for a few years, and judging by its condition, is say it's been in a barn before him. Length of storage since last used is 3 years.
Use for that time ran was driving it around sellers yard, unsure how long.
Oil looks like its black still... I haven't drained any to check but I was able to look through the transmission access door cover.


Top of pagePrevious messageNext messageBottom of page Link to this message  By Markus Huether - Germany on Sunday, November 26, 2017 - 12:13 pm:

We can be happy that Henry Ford did not locate a 8 cylinder motor in the T. :-)


Top of pagePrevious messageNext messageBottom of page Link to this message  By Scott Conger - Wyoming on Sunday, November 26, 2017 - 01:02 pm:

You can and should, shine a flashlight into #1 to see if you have a valve stuck open. If so, it is possible to soak with penetrating oil and tap it shut with a hardwood dowel rod. Will take a few turns of the motor to fully unstick completely. I am not a big fan of pulling a head "just because". Invariably, you get into more than planned from the outset.

There is no point in doing a valve job on an engine that has a bad bottom end. I would change the oil, clean the innards through the bottom access pan, oil the mains with an oil can, rotate the engine through, change intake/exhaust manifold gaskets, put on new carb and coils, and start the car. It is quite possible everything you are experiencing will resolve themselves within 100 miles. And if it doesn't, you can now delve deeper.


Top of pagePrevious messageNext messageBottom of page Link to this message  By Charlie B actually in Toms River N.J. on Sunday, November 26, 2017 - 01:40 pm:

John you simply MUST do the wet/oil test. Everyone is totally guessing as to you engines condition. #1 has a real problem. Very possibly a stuck valve. As to 2 thru 4: the comp is quite low BUT you don't know if you just need a good valve job or if the piston rings are shot. The oil test will answer this. Though I'd do #1 too I believe it's a valve. If 2 thru 4 go up with a squirt of oil added it's rings. If they don't go up it's valves. Knowing this information can make a HUGE difference in what you need to do to your engine. As in pull the head & manifolds for a valve job or pull the engine for ring/cyl. boring. Do it. It pays dividends.


Top of pagePrevious messageNext messageBottom of page Link to this message  By John Annaian on Sunday, November 26, 2017 - 01:42 pm:

Don't worry, I will! :-)

Really super busy right now, hopefully I can do it later today. I will post my results and try to read the gauge more carefully too. I'm thinking the valve is stuck too, I'll open the valve cover.


Top of pagePrevious messageNext messageBottom of page Link to this message  By Fred Dimock, Newfields NH, USA on Sunday, November 26, 2017 - 01:55 pm:

This is what I did to my 1919 T that was in storage for over 45 years.
Pulled the plugs and poured about 1/8 cup of MMO in each of the cylinders..
Drained the oil, over filled it with kerosene, and let it soak for about a week - maybe two.

Then drained the kerosene, over filled it with oil and let it soak for a week.

Then drained the oil and filled it with the correct amount of oil.

During the soaking times I rebuilt the carb, made sure that the coils were OK, and cleaned the gas tank.

When the Happy day arrived I move the car outside, added some gas, attached a 12 volt battery (non-starter car so I had to crank it), choked it a bit with the throttle half way open, put the spark lever all the way up, turned the switch to battery, and pulled on the crank. When it went put put I pulled the spark lever down and adjusted the throttle.

This action resulted in my killing every mosquito in Town, but it ran.


Top of pagePrevious messageNext messageBottom of page Link to this message  By Scott Conger - Wyoming on Sunday, November 26, 2017 - 02:01 pm:

Charlie

If everyone is totally guessing as to the engine's condition, is your guess of a stuck valve more valid than someone elses?

John

Charlie's advice is sound. And his guess is pretty good, too.


Top of pagePrevious messageNext messageBottom of page Link to this message  By Charlie B actually in Toms River N.J. on Sunday, November 26, 2017 - 03:45 pm:

I said everyone is guessing and I did mean everyone. Yours truly included.


Top of pagePrevious messageNext messageBottom of page Link to this message  By Charlie B actually in Toms River N.J. on Sunday, November 26, 2017 - 03:47 pm:

Tongue in cheek. LOL


Top of pagePrevious messageNext messageBottom of page Link to this message  By Gene Carrothers Huntington Beach on Sunday, November 26, 2017 - 04:06 pm:

John, Are you hand cranking? If you are this can add a variable compared to a elect starter results. Just thinking about 2 - 4.


Top of pagePrevious messageNext messageBottom of page Link to this message  By John Annaian on Sunday, November 26, 2017 - 04:58 pm:

Yes, hand cranking!

Okay everyone here are the results. Got a friend to help.

Pulled out the manifold and carb again... then pulled all of the plugs, screwed in my plug adapter, then the tester screwed into there. Got a friend to spin the handle around 1 crank a second, probably about 10 times to make sure. Removed the valve cover so I could see which were opening and closing. All valves move freely.

DRY - NO OIL

1 - 25
2 - 30
3 - 40
4 - 25 (Forgot to write this down stupidly... I remember it was about this)

WET - SPRAYED SOME OIL

1 - 20
2 - 25
3 - 30
4 - 27

Yes, these readings are where they should be. The dry IS for the dry readings and wet IS for the wet. I am kind of shocked that compression went down... but... I don't know. Wet seems a bit more accurate or reasonable to me.

Looking at this info, i would think get some new valves fitted?

I have not done this stuff before so I don't know how much new valves will even raise compression... I don't think I would need it completely rebuilt, however I think around 40 PSI would be plenty.

Anyways guys, what do you think? New valves? Rings? Pistons? ??

By the way, I looked the the exhaust holes and noticed what appears to be one piece valves? https://imgur.com/gallery/erC97


Top of pagePrevious messageNext messageBottom of page Link to this message  By John Annaian on Sunday, November 26, 2017 - 05:00 pm:

Should add this is in a barn with no insulation at all letting all the cold air in... so this engine is probably 30 degrees F right now.


Top of pagePrevious messageNext messageBottom of page Link to this message  By Spencer Vibert - Granby ,CT on Sunday, November 26, 2017 - 06:02 pm:

Sounds like it needs a valve job your readings should be around 45-50 for a good running motor


Top of pagePrevious messageNext messageBottom of page Link to this message  By John Annaian on Sunday, November 26, 2017 - 06:40 pm:

Thanks Spencer. I'll see what others have to say too but I agree, needs some new ones fitted. One or two have a different shape slightly so I assume they are not seating correctly, not sure though.


Top of pagePrevious messageNext messageBottom of page Link to this message  By Scott Conger - Wyoming on Sunday, November 26, 2017 - 06:59 pm:

"sprayed oil"
should be a liquid, not something from a can

"valves...different shape"
how do you know?

now, I'll say this again: try to start it. Your compression may come up into a reasonable range once the rings are exercised. I would not be surprised if it DOES need a valve job (which is way more than just replacing the valves), however you do not know if this thing is going to knock like no tomorrow with a shot bottom end, and a half-way valve job right now will be for naught.


Top of pagePrevious messageNext messageBottom of page Link to this message  By Charlie B actually in Toms River N.J. on Sunday, November 26, 2017 - 07:06 pm:

I cannot, for the life of me, think of a reason why the comp would go down with the addition of oil.. Was it engine oil you used or something much lighter like brake fluid or WD40? Shooting straight into the cyl hits the piston and basically by-passes the valves intirely so their out of the picture. Can't understand this. Still, it does look at this point that freshening the valves will up the comp. Just might get you into a good range.


Top of pagePrevious messageNext messageBottom of page Link to this message  By John Annaian on Sunday, November 26, 2017 - 07:24 pm:

I know, that's what I don't understand either.. gun oil is what I used but I will use liquid oil tomorrow. Once again, never done this before.

I will gladly try starting it I guess... so what needs to be done exactly? Reinstall carb and the exhaust manifold... it doesn't need a radiator for now since it's not going to be on for long. Do I need to fill it with water and block off the side outlet? Should the oil in it be okay for a quick start? I will check if it needs to be filled. How do I wire it up? I have the coil boxes and the actual box that mounts on the head, and spark plug wires. I don't know how they should be wired though. I am also worried some dirt or paint chips found their way into the spark plug holes...

Once again, this WAS driven. So the compression must be in the low end of the good range at the least.


Top of pagePrevious messageNext messageBottom of page Link to this message  By John Annaian on Sunday, November 26, 2017 - 07:28 pm:

Actually, ignore that. I know I'm going against the flow here... but I'm just going to do a valve job first and see at the very least. Then I will be more prepared about this and know more.

So, tomorrow will check with liquid oil and then a valve job!


Top of pagePrevious messageNext messageBottom of page Link to this message  By Scott Conger - Wyoming on Sunday, November 26, 2017 - 07:55 pm:

You have a car that ran 3 years ago.
You don't know how well it ran.
You're not going to start it to see what you have.
It seems to have low compression (though I would not be too sure about that, now) and you think it needs a valve job (even though there are other reasons for low compression).
You're going to fix something that you don't know needs fixing (a vacuum gauge attached to the car while it is running will tell you some things about the condition of the car).
I really do wish you luck, because I think you're going to need it.


Top of pagePrevious messageNext messageBottom of page Link to this message  By Charlie B actually in Toms River N.J. on Sunday, November 26, 2017 - 08:32 pm:

Please re check the wet test before going any deeper as you may have done something wrong. I have never seen results like the ones you got. Report back please!!


Top of pagePrevious messageNext messageBottom of page Link to this message  By John Annaian on Sunday, November 26, 2017 - 09:30 pm:

I will Charlie! tomorrow! I dont know where you are, but where I am it is dark at 3 (And its 9:30 now)

Scott, and anyone else, I have changed my mind again and will test it. Thinking about it now, Id like to see if the heat will burn up some carbon and will free everything up, as you are probably wondering. Just havent done anything like this before, but if the guy had it running all I have to do is add some gas and hook up the wires again!

So, I will ask these questions again. it would be of great help if I could please get them answered...

1. Do I fill the block with water and block off the outlet hole on the side? The radiator is dirty and I do not want to clog the block up.
2. How long should I run it for to get it all "warmed up"?
3. Will the oil in it be okay for this test? (I will check the level and fill if needed)
4. I am worried some paint flakes and dirt specks got into the spark plug holes while I was testing the comp. Should I be?? I really do not want anything getting scored...
5. What do you mean by a vacuum gauge attached while running? Shouldnt I just test after it ran so its warm and freed up?

Thank you again everyone for your patience.

Charlie, my friend was getting tried of cranking as he had cranked it 10 times each cylinder. Is it possible since he was tired and cranking slower for the wet results they could have lowered?


Top of pagePrevious messageNext messageBottom of page Link to this message  By Gene Carrothers Huntington Beach on Monday, November 27, 2017 - 02:59 am:

John, Put your manifolds back on, hook up the wires. clean the timer, add some gas and try starting the car before you do any more waste of time. No water needed, 5 minutes is plenty long enough. No worries about oil slight dirt in cylinders. It'll all get blown out if it starts. Don't worry about a vac gage.
Wow you need to get a book and do some studying and a bit more advice from guys here before totally messing it up any more.

Clean oil and Gas

You didn't say what year. Any T guys or clubs close to you?


Top of pagePrevious messageNext messageBottom of page Link to this message  By Fred Dimock, Newfields NH, USA on Monday, November 27, 2017 - 06:17 am:

If the oil is as dirty as you said, I would make sure I flushed it out as much as possible before starting it


Top of pagePrevious messageNext messageBottom of page Link to this message  By John Annaian on Monday, November 27, 2017 - 06:48 am:

Gene, I have a book and I have studied it a bit. I know the basics of it all, I just really don't want to mess anything up here. I could have gotten it started probably without posting, but again, don't want to mess anything up.

Fred, Ill drain some and check it. It'll probably need more anyways.


Top of pagePrevious messageNext messageBottom of page Link to this message  By Charlie B actually in Toms River N.J. on Monday, November 27, 2017 - 07:45 am:

If you simply must do it follow Gene's instructions. You have enough comp to get it going.


Top of pagePrevious messageNext messageBottom of page Link to this message  By John Annaian on Monday, November 27, 2017 - 09:30 am:

Don't know when it will be, pretty busy for now, but hopefully this week.

Charlie I will still try and get you those oil results.


Top of pagePrevious messageNext messageBottom of page Link to this message  By John Annaian on Monday, November 27, 2017 - 05:09 pm:

Update.

Decided to check the oil today.

Opened the top petcock. A few drops.
Opened the bottom. Also, a few drops.

The oil is dark dark brown, and very thick and had some little dots or specks floating on the top. I'll fully flush it tomorrow to get it all out and refill, and then test! Wonder if the seller never changed it and if it's original... looks it for sure.

Charlie, before I drained the oil I did add some to cylinder 1 to see what happened. I couldn't get it past 0 again! Guess I'm cranking too slow! :-) Ill try again to see if it's a little easier with new oil.


Top of pagePrevious messageNext messageBottom of page Link to this message  By Charlie B actually in Toms River N.J. on Monday, November 27, 2017 - 06:04 pm:

John at this point I'm not sure what's going on but change the oil and gomfor your start/test.


Top of pagePrevious messageNext messageBottom of page Link to this message  By Val Soupios on Monday, November 27, 2017 - 07:33 pm:

John last year I picked up a T that last ran in 1960. It had no compression. I spent a day freeing up the valves that were stuck and threw some fogging oil down the cylinders. Threw in a battery, some gas and a little water in the radiator. I pulled the crank through 4 times with the choke out and the throttle open, turned the switch on and walked around to the front of the car to crank her over and she started as I reached for the crank. It smoked like a chimney for about 10 minutes, spit and sputtered a few times and then smoothed out. I checked the compression and it was between 25 and 30 pound per cylinder but the more I ran it the better it ran! Now it is the smoothest running Model T engine I have ever owned and compression is up to an even 40 pound per cylinder. I might add that it has the original cast iron piston and 2 piece valves which suggests that it has never been apart.
Bottom line, I would not start taking anything down until you have it running first. You may find that it needs nothing but exercise.


Top of pagePrevious messageNext messageBottom of page Link to this message  By Scott Conger - Wyoming on Monday, November 27, 2017 - 07:42 pm:

Val

I have had the same experience as you...and as for your last two sentences, I could not agree more. It will be interesting to see how this whole project goes...if indeed it ends up being reported.


Top of pagePrevious messageNext messageBottom of page Link to this message  By John Annaian on Monday, November 27, 2017 - 08:08 pm:

Don't worry Scott! I'm not like the people who get ya hooked and never report the outcome.

Val and Scott, I will be sure to update. I am hoping that will be the case with this one!

Now, another question. What fuel line diameter is needed for a Holley NH?


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