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Compression and whats up with #3

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ratface

03-31-2003 08:51:34




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hello all, finally got around to doing a compression test because of moderate smoking. Smoke color is white. The tractor is a 1949 8N with a 2N engine. Had all the plugs out but forgot to open throttle. The tracotor starts and runs well and is able to brushhog all afternoon. It does require adding oil about 1 quart every three weeks. Test was done after tune-up. Here are the numbers from 1-4: I did it twice so I'm including both numbers for each test.

Dry, 90-88, 92-92, 88-85, 90-89

Wet, 101-105, 95-100, 83-83, 95-95

What is the significance of no change with the number three cylinder. Overall prognosis?

Appreciate the wisdom of this board, rick

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Rich, NJ

03-31-2003 14:22:01




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 Re: compression and whats up with #3 in reply to ratface, 03-31-2003 08:51:34  
Last time I did a comp test I had a similiar situation. I figured that I wasn't getting the oil back into the cylinder. It was sitting all over the valves. It's probably a good idea to use some tubing to get back under the head and into the cylinder. Regards, Rich



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JD-Tractor

03-31-2003 10:29:44




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 Re: compression and whats up with #3 in reply to ratface, 03-31-2003 08:51:34  
Just a JD person! but grew up with a lot of ford experience !You guys did not address smoke problem of white Smoke which is usually indicative of water getting into the cylinders, How much water does this tractor use, (coolant )
Why is a JD person on this board you may ask!!! I monitor all of the boards as this is such a great website and a person can always learn something. Besides I may be spying on you guys for George Bush.....LOL

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Hobo,NC

03-31-2003 10:03:15




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 Re: compression and whats up with #3 in reply to ratface, 03-31-2003 08:51:34  
You may have a valve not seating good on three. At the least I would check valve adjustment. Its not aburnt valve or the Numbers would be lower, below 50psi. If its running good leave it along.



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Evil Steve

03-31-2003 09:32:43




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 Re: compression and whats up with #3 in reply to ratface, 03-31-2003 08:51:34  
rf-

I have to question your compression check. #3 should have shown at least the same compression wet as it did dry. Instead, it went down. Can't happen unless the test was improper. Might wanna check again. Remember, it takes 5 revolutions per cylinder to get an accurate result.

Agree with Dell re: #3 is low due to valve, but it could be a sticking valve too, not just burned.

If I were you, given the large comp diff with #3 vs other cylinders, I'd check the valves on #3 (remove valve cover and manually rotate engine to see if valves are fully retracting. If they are, then you might look at doing a valve job.

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Dell (WA)

03-31-2003 09:07:00




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 Re: compression and whats up with #3 in reply to ratface, 03-31-2003 08:51:34  
Rick..... ..If a wet compression test does NOT raise compression, the problem is usually burned exhaust valve. Your approx +10 psi "wet" increase is consistant with a "good" used engine and NOT a canidate for a rebuild. Ford N-Compression specs: 90 psi min. The engine starts eazy and has the power you need. Hard telling about your oil usage, probably seals and general ring wear, but as long as your sparkies don't foul, you're on top of things keeping your oil topped-up. Recommend use Autolite AL-437 or Champion H-12, or NGK BP4L sparkies, gapped 0.025. Your engine does NOT need rebuild unless you just really got that "need"..... ...Dell

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ratface

03-31-2003 09:36:54




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 Re: Re: compression and whats up with #3 in reply to Dell (WA), 03-31-2003 09:07:00  
This forum is almost live. Dell responded within minuetes of my posting. Thanks Dell. I had printed out some of your previous responses to compression tests and suspected a burned valve on three. This is a deduction from the vast knowledge of this forum but i have never actually seen a burned valve. How serious is it to operate the tracor in this condition? Big Dawg states he has gone from 120 psi to 95 psi in six years. Thats roughly a 5% drop in compression per year. Is this consistent and can I expect to be in the sixties in five years?

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BigDawg

03-31-2003 13:06:51




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 Re: Re: Re: compression and whats up with #3 in reply to ratface, 03-31-2003 09:36:54  
Just to be clear, I didn't say it went from 120 to 95 in six years. I have no ideas what it was 6 years ago, or if the previous owner even did a rebuild. I just know what it is now. Since it's within spec and runs fine, I just leave it.

Doug
Wisconsin



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Dell (WA)

03-31-2003 10:07:15




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 Re: Re: Re: compression and whats up with #3 in reply to ratface, 03-31-2003 09:36:54  
Rick..... ....compression loss is semi-dependent upon usage. I've known of N-Engines worn out in 1-yrs time doing field cultivation in sandy soil. That why the engine is "sleeved", you never have to bore the cylinders or replace the engine block, just renew the sleeves along with new rings and your compression is back to standards. Thats why bearings are replaceable "shells" instead of poured babbitt.

Theres many an N-engine being used with burned valves. Most ignore'em until they can't start the engine anymore then they convert to 12 volts to start'em eazier. Finally, the 12 volt bandaid looses its ability to start an engine with low compression and then they bite the bullet and complain about the cost of rebuilding. Ya can't win.

I have no idea why BigDog's N-Engine compression has gone from 120 psi to 95 psi in 6 years time except "wear from usage"..... .....Dell

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BigDawg

03-31-2003 09:25:00




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 Re: Re: compression and whats up with #3 in reply to Dell (WA), 03-31-2003 09:07:00  
Dell,

When I did my compression check, all cylinders were around 92-95 with no change with the wet test. (engine was warmed up but forgot to open throttle)

Some have commented that this is low. The previous owner said it was rebuilt 6 years ago. Is this consistant? Seems to run fine.

I hear people talking about compression around 120-130. What gives?

Doug
Wisconsin

PS Nice to see your name again.

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Dell (WA)

03-31-2003 09:46:41




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 Re: Re: Re: compression and whats up with #3 in reply to BigDawg, 03-31-2003 09:25:00  
Doug..... ..if compression increases "wet", that means the "wet" has sealed the worn rings. No increase means thats as good as it is going to get as long as it meets Ford specs: 90 psi MIN your good to go as long as it has the power you need to do your tractor jobs. 130 psi compression on 8N engine is brand new (1/2 hr break-in) and its all down hill from there.

While it is good practice to open the carb throttle during a compression test, if you've pulled all the sparkies first (as you should for eazier starter turning) any manifold vacuum caused by closed throttle is negated by open sparkies from other cylinders.

Just for perspective, my 165 hp dyno'd 1969 BMW 2002 with 387K miles compression is 165 psi, engine rebuild at 246K..... ...Dell

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