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Discussion Starter · #1 ·
Hello there tractor folk

I'm new to the forum and am seeking some help. 2 issues are on top of my list

I purchased a '48 8N from a shirttail relative in Wyoming and I'm starting through it.

1)
After 10 years in a field, I've just started thru my 8N. new wiring , clean carb new rad, new oil pres. gage. When started, gage quickly goes to 60 or so --may be pegged and stays there.

2)
It barely runs (when pulled to start) on one lung with only 35 psi in #2 and 0 to 5 psi compression in the other 3. Wet testing with all plugs out takes #2 to 70psi and barely affects the others. Amazingly, it let me drive it around for a couple of miles and up a pretty steep hill back to the barn.

What is the cause of the high oil pressure that I have?

Are there places on the forum I should be looking for "low compression overhaul tips"? I'm brand new to the forum and have read many many interesting posts.

Springsrick
 

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Welcome Springsrick! I don't know much about n's but there are many others here that do. I'm sure they'll show up soon to help anyway they can.
 

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1.
As far as the oil pressure issue, I would say you have a oil pressure relief valve that is sticking and needs to be replaced.

<center><img src=http://www.tractorforum.com/oilvalve.jpg></center>

(shown on engine block in front --- just behind coil)

2.
Addressing the compression issue. You can tell a lot about what that problem is by observing HOW the compression builds up on the compression gauge. If it builds up slowly over a number of puffs to the maximum it registers on that cylinder then the problem is usually worn rings and that can be confirmed by putting an ounce or so of engine oil or MMO in the cylinder and doing the "wet" test. HOWEVER, If compression gauge reading goes up to it's maximum reading attainable in the first couple of puffs and further puffs don't raise the reading anymore then you have a stuck valve. With a stuck valve a "wet" test will not produce much if any increase in max reading and will not affect the way the reading developes. You could pull your valve chamber cover on the side of the engine to confirm or disprove a stuck valve.

I feel like you might have a combination of problems. Another method solution for this is if you do a compression test, see if adding oil will bring the pressure up. You can place MMO in the oil and maybe some in the gas and let it run until it warms up. Leave the MMO in there for about a week and drive it a little each day to work it in there. Then change oil and filter.

Ultimately, I would say to do it right, you probably need to pull the hood, the head, the valve cover, and check for extensive valve wear, relapping the valves or probable replacement are going to be in order. Cleaning the oil galleries out and also replacing the head gasket while you are in there would be a good idea.

Let me know what direction you are looking towards and if any of this sounds like something you might want to tackle. If so, I can provide more in-depth assistance etc. Good luck Rick! :D
 

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Andy has some good points, but I would like to add, that with a long hard life, and sitting for so long, she could just be tired. Maybe a motor rebuild is in your future.

I have been shopping, and pricing rebuild parts for my N for a little bit, and the stuff's pretty cheap. Should be able to rebuild it for less then a grand.

So I would go through the easy stuff he said, but don't be suprised if you need to go farther. There tough little tractors, but nothing last forever.

Oh and by the way, go get your self the shop manual. There not pricy, and have all the info you would need to rebuild this tractor, and just keep it running.
 

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Good points, Paul. I know in a decent area of the country with available engine shops, you should be able to have your engine completely rebuilt for under $1000, actually closer to out of the door for about $750-800 total. There are several kits out there including extremely deluxe kits to basic overhaul kits. Prices are usually in the $350-400 range for the "super" kits and around $200 for the basic kits. If I was doing an overhaul to last another 50 years, I would splurge and spend the extra for the "deluxe" job. (deluxe usually includes: oil pump rebuild kit, water pump and lots of other external parts you may not need but probably wouldn't be bad --- belts, points, cap, hoses, filters etc)

The engine work for that price usually includes all cleaning, boring, honing, magnafluxing, new rods, pistons, valves, sleeves, gaskets, cam, bearings, camshaft gear, bushings etc. Basically everything to get it back to original spec -- which believe it or not is above 120psi in each cylinder. Anything under 90-100psi was considered good. 75psi and lower was tired but ok and lower than that per cylinder was tired engine needing replacement. As in any engine, the psi ratings and the difference between the cylinders is more important than the readings. Looks like you have a massive valve failure sitcking problem/head gasket problem causing the nearly 0 psi compression. You are getting absolutely no seal.

Remember when testing compression, only remove -1- plug at a time. Move the throttle to FULL position.
Starting at cylinder 0, do a dry test. Watch the needle on the compression tester. Does it stick at one point with repeated dry tests or does it move up? Wet test, place a little oil in the cylinder and then test the compression. Much better or no effect? If increased probably worn rings that are getting sealed temporarily is the case there. If not, you got a gasket or more likely inactive severely stuck valves.

I hope some of this rambling helps.
Andy
 

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I'd suggest that after sitting, you likely have some stuck valves AND some rings stuck to the piston. You will likely have some rust on those valves as well. From what you desrcibe, it wouldn't seem like bearings are a problem, so a valve job and rings, hone the cylinders, and you'll probly be good to go. But like Andy said, once you have the engine apart, you may as well go the full route, and be trouble free for years.

BTW, I was taught to do a compression test with all the plugs out.;)
 

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Originally posted by parts man

BTW, I was taught to do a compression test with all the plugs out.;)
Im with Parts man on this. I was always taught to take all plugs out. That way you get a common cranking speed for each cyl.
 

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Discussion Starter · #9 ·
Thanks to all of you!

I ran the test with all the plugs out and with the throttle open.

I still had the hood on so it was a bit of a pain to "fish" in the compression tester but I did.

I have since pulled the hood and am prepared to pop the head.

I'm thinking of running the dry and wet compression tests one more time.

I HAVE DISCONNECTED THE LEADS AT THE GENERATOR AND COIL, DO I NEED TO TO WIRE THEM BACK UP BEFORE SPINNING THE ENGINE FOR COMPESSION TESTING --TO AVOID GENERATOR DAMAGE? OR IS IT OK TO CRANK THE ENGINE WITH THOSE LEADS DISCONNECTED?

It's Saturday here in sunny Colorado Springs and I can't wait to get into fixing my compression probs.

Andy, I'll pull the oil pressure relief valve and see If I spot anything.

Springsrick
 

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Discussion Starter · #12 ·
Progress Update!

Well, I have news

I did a diagnostic test for the cause or source of low compression recommended by my neighbor who rebuilds small engines.


THE DIAGNOSTIC TEST FOR POOR COMPRESSION:
I attached an air chuck to a threaded fitting that goes in the spark plug hole. Same basic drill as compression testing but this time you bring the test cylinder to TDC (at least close enough that the valves are closed) and then you give the cylinder some air . If the air come out the exhaust pipe, and not the carb, it's the exhaust valve that has the problem (most common). if the air comes out the carb, it's the intake valve that is not seating. If it comes out the cooling system fitting on the head, it's a head gasket or cracked head. I guess you might pick up other failure to the water jacket as well. If the valves are tight, I guess you would get ai out the oil breather.

MY RESULTS:
Each of my cylinders showed major leakage at the exhaust valve.
Cylinder 2 had noticeably less than 1 ,3, and 4 but still a lot.

Action Taken:
I pulled the head.
All 4 of the exhaust valves were burned.
I wrestled with the keepers and Valve guides on cylinder 3 (it was the worst) and finally got them out. The exhaust valve wobbled quite visibly when I got the lower keeper off which seems to me like a sign that I need new guides. The intake just barely wobbled.

Request For assistance:
1) what must I replace?
2) what would I hate myself for not replacing?
3) what do people think about adjustable tappets(or cam followers)? If they are good is there a better brand?
4)Any tips on sources of quality parts? (When working on my model "T" Fords, I found that some of the parts that came out of Taiwan were truly JUNK!)
5)Are there cross references to preferred parts from modern vehicles for Valves or valve springs etc.
6)How much wiggle or wobble is to much in valve guides?

Thanks again to everyone for the helpful comments.

PS. What do you thing of starting a reference library thread for things like "Engine diagnostics tips" that would be nothing but the "How to"

Then people could say something like "Try test #4 and tell me what you get". it would mean you would n't have to dig the jewels out of the other threads.

SpringsRick
 

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Good ideas and insight there Rick! :D I have never heard of the blowout test into the cylinders. Interesting test! Did you have any problems getting the head off the engine? Did you have the FO-4 manual and follow and specific order (some of these heads are extremely tight etc) --- just curious --- different strokes for different folks! :D


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1. Replace all of the valves, intake seals, valve guides, springs, retainers, gaskets etc. (remember in any rebuild kit you might get 8 valve seals/gasket --- Please ONLY install 4 on intake side)

FYI: I used WD-40 on the guides and seals when I installed mine.On the intake guides the seal is needed because you have negtive pressure (vacuum) and if they were not their you would suck the oil out of the crank case. On the exhaust side you have no vacuum so no seal is needed. (and they burn up and cause lots of problems if you install them!)
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BTW:
The intakes set at .010-.012 and the exhaust set at .014-.016.
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2. Funk V8 Conversion? (hahaha)
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3. I should caution you enless this is a rebuilt motor that someone has put 8n tappets in they aren't adjustible. Adjustable units are ok, but I would always stay with original spec and NOS items if possible.
<hr>
4. Without a doubt, only place: www.just8ns.com
Tell Don Barkley that Andy from Tractorforum.com sent you! :D
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5. N/A
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6. Nothing excessive - should be pretty tight. :D
<hr>

Part numbers for replacement 8N parts:
Valve Guide - Solid 8N 8BA6510B
Exhaust Valve - 8N 6505A
Intake Valve - 8BA6507A
Valve Key Lock - 7HA6518
Valve Springs - 8N 6513
Valve Seal - 8BA6571 (4 for intake plus guide)
Valve Wrenches 8WR1770 (tappet)

Rick, I hope some of this rambling helps. I think you might need some assistance with the removal and replacement of these parts as they are sometimes tricky. I have some little tips that tend to help out a little bit on occassion. Let me know if any of this is helpful and if there is anything I can help you with. Thanks so much for sharing this journey with all of us!

WE WANT PICTURES!!! :D

And Yes, if you produce pictures and step-by-step notes, I will gladly publish them up in a good section "DIY how to section!"
Good idea, Rick!

Andy
 

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Discussion Starter · #14 ·
Adjusting tappets Etc.

Andy,
Thanks for the comprehensive reply.

My Engine Block number is *8NI3530* (I believe that makes it a late 1947 casting probably sold in 48 . Right? If not , What?

Yes I do have the FO4 manual. I'm not sure what you meant by "did I follow the specific order". I guess the sequence of taking off the hood before trying to get to cylinder head nuts might be what you're referring to. If it's something else, what did I miss?


1) I had a hard time getting the #3 valve guides out---actully broke the exhaust by trying to pull up on the valve head and the result was the guide didn't move but the mushroom on the lower end of the valve cracked off the lower end of the guide by trying to spread the cast iron. Clearly I could use some of the special tips you offered. Please advise how to remove guides without Tool in Fig. F014 "Jack type lifter". All I have is a a squeeze type lifter with a ratchet lock and I just couldnt budge the guides from the block with it.


2) Now that I have WITH CONSIDERABLE DIFFICULTY pulled the valves out of #3 cylinder, I am puzzled by the chapters 22 thru 27 of the manual that refer to "Free Exhaust valves", Exhaust Rotators, and adjustable tappets. I'm familiar with all but "Free Exhaust Valves" from other engines. The question is what is the best thing to put back into my block now that I am tearing the valve train down? (chapter 26 says Adjustable tappets are available in a Kit 8N6546B and that the kit is recommended for 2N, 9N, and 8N rebuilds. Kit also gives "special exhaust vlaves and free type exhaust valve rotators.--- JUST 8N'S doesn't list this kit)

3) In an Earlier response you also spoke of Basic overhaul kits @ ~$200 and Deluxe @~$300-400. Didn't find them either. Please advise of sources.

Thanks to all,

Looking forward to comments from all who have "been there, done that"

Springsrick
 

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Well I have not been there "yet". Maybe this winter. But I was also a little confused by the parts of the manual discribing the valve train.
 

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Discussion Starter · #16 ·
Success!

I'm overdue in informing all the helpful advisors that I'm out of the Shop and back in the saddle -- and loving it.

A brief recap
--Re high oil pressure
Found a stretched spring and a small nut laced in the oil relief cap all part of the bogus prescription to fix oil pressure.
Now I have 30 to 45 psi with new spring and gasket.

--Re low compression no power:
I replaced whole valve train and went for adjstable tappets and an exhaust valve rotator kit.

I cleaned up my air cleaner which had nearly the whole oil bat area clooged with Wyoing topsoil, and I overhauled the Carb.

I installed a new radiator and a new oil filter.

RESULTS: It started within 5 minutes of my first try--I had to reseat the coil on the distributor.

It runs great and sounds great.

I bought a simple 6 ft blade and a box scraper from a neighbor who had sold his 8N years ago.

The tractor handles both well.

I'm very pleased with the performance even though it took me 2 months with the other item in the "job Jar"

Still smokes --- my guess is probably rings

Thanks again to Andy, Partsman, and Ingersol444. and the encouragement from many others.
 

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Thats great!! Seems like you have a nice running tractor, that will last for a wile. Smoking is probably just worn rings/cyl's, but at least not you can use it, and if you decide to do a full rebuild later, you have time to plan for it. Enjoy the tractor time!!!
 
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