Questions on disassembling and reassembling 8N engine

[Ken Windom]

I have my '51 8N taken apart sufficiently that I have decided to replace the piston rings (at least) before putting everything back together. I know it burns some oil but have no idea how long since the engine was overhauled. The flywheel does not want to come off. Any special techniques or tools required for this? I removed the 4 bolts holding it to the crankshaft and assume the dowels are just for alignment, but don't want to force anything and damage it.

How critical is it that the crankshaft be removed? I plan to check the surfaces where the connecting rod bearings ride, but was planning to leave the crankshaft in place unless they are worn enough to need grinding. I debated leaving the flywheel in place, but if the crankshaft does have to be removed, that is a lot of extra weight.

Do the lower rope seals have to be replaced if the oil pan is removed?

Thanks for your help on this. Hate to ask too many dumb questions, but this is the first time I have delved this far into an engine and I have not been able to find these specific answers online or in any of the books I have read.

 

[trucker40]

To remove a flywheel or anything thats got dowel pins you have to come off with it straight as you can until you get it off of the pins.If you get it crooked just a little it will hang up.Its probably a good idea to have somebody help you get it off.One of you needs to hold onto the flywheel so it doesnt fall and break and the other needs to hit it with a rubber hammer to knock it loose.If you know somebody that has micrometers you can check the rod journals with the crank in the engine.I dont quite get your question about the lower rope seals.If you remove the crank you need to replace the crank seals.If there is some kind of rope seal around the pan then if you removed the pan you should replace the seal.Somehow I thought it was just a gasket around the pan?Its been a long time since I had the pan off of one of those so hopefully somebody else will know what you mean.

 

[Anonymous-0]

The block MUST be taken to a machine shop to have the valves and seats ground as well as having the valve guides and springs inspected and probably renewed. While there, they can hot tank your block and measure the crankshaft. This is a great time to replace the oil pump as the block needs to be align bored when doing this.

They can also press in your sleeves if needed. It is far easier and cheaper to do it right the first time. An overhaul without a valve job is ridiculous.

 

[souNdguy]

A valve job without needing one might be said to be ridiculess too.

a wet / dry comp check can tell you about rings and valves.

a wet test that comes up very high.. like 120psi.. etc.. I wouldn't even touch the valves..

soundguy

 

[Dell (WA)]

uh? Tom.......generally you REBUILD the oilpump (replace the gears) and NOT replace the oilpump.
Yes, iff'n you replace the oilpump you MUST linebore the new pump as it is the front main bearing carrier. And yes this is a common engine machine shop procedure. ......Dell

 

[TheOldHokie]

(quoted from post at 10:30:57 06/24/09) A valve job without needing one might be said to be ridiculess too.

a wet / dry comp check can tell you about rings and valves.

a wet test that comes up very high.. like 120psi.. etc.. I wouldn't even touch the valves..

soundguy

From the sounds of it the head and pan are already off so compression tests are sort of moot....

If it burns enough oil to make you want to replace the rings put in a complete sleeve/piston/rings kit - roughly $110 more than a set of rings. My experience over the years with re-ring only jobs on oil burners is that it buys you only a small amount of additional time.

I'd also throw a set of new rod bearings ($30) at it while I had it apart. I simply don't reuse insert bearings once I have them in hand.

Obviously all gaskets and seals removed need to be replaced with new ones. Beyond that beware of mission creep.

TOH

 

[r geiger(oR)]

the valves may or may not need to be ground or refaced, but I would diffently check for stem and guide wear on the intake valves. Mine were worn so much that they were sucking in oil, fouling the plugs. Idle mixture even adjusted like it should after replaceing the worn guides.

 

[Britcheflee]

This is all very useful information for me:

I am going to replace sleeves and rings this fall as my poor old gal is smoking and I have to keep replacing/cleaning the spark plugs after heavy use such as brush hogging. I intend to replace all sleeves and rings - I do need to check compression however, would it not be prudent to do the valves? I saw a video somewhere where all you need to do is put some grinding paste on both surfaces and manually twist them back and forth until you get a good clean surface - is there any reason not to do this?

Thank you,

Lee

 

[Anonymous-0]

Do you believe everything you see on videos?

 

[Britcheflee]

Well, this was just showing the process (admittedly on a small lawnmower)- so, are you telling me that do not need to do this? It would be a bit frustrating to take it all apart, do the sleeves and put it all back together only to be told that I should have done the valves!

Thanks,

Lee

 

[Anonymous-0]

Someone below suggested replacing the valve guides without grinding the valves. That would be the recipe for TOTAL DISASTER as the holes in the new guides would not be concentric with the old valve seats. Install the guides BEFORE you grind the seats

As far as an "overhaul" without a valve job, I stand my ground that it would not only be ridiculous but TOTALLY RIDICULOUS! You already have the block at the machine shop for heavens sake. It is not like a valve in head motor where you can casually have your wife carry the head in any old day. If there is much wear most of these engines need sleeves and pistons. If you don't have time to fix it right the first time, how would you find time the second time?

 

[souNdguy]

should you?

well.. it's like this.

a quickie job to get back onthe road for not much money might be like: new rings and new bearing shells.

doing the lines is great.. doing the valves is great.. bu the time you keep adding things.. it's a full rebuild.

hand lapping the valves is fine for units needing only minor attention.. just got to clean it real good.

on the other hand.. I wouldn't lap the valves on a machine that had valves that held 120psi.. it's leab em' be.

that's what the wet/dry comp test tells you.

measure the liners too.. see how far worn they are.. or oval even.. if the liners are in spec, ream the ridge and go in with new rings and bearing shells.. etc

again.. might look at the oil pump.. depending on oil pressure... it's endless..

all up to you.

soundguy

 

[souNdguy]

I didn't see where the OP said he had the block at the machine shop.

you know.. some people actually do this kind of stuff in their back yard shop... I hear TOH has a nice set of sleav R&R tools...

soundguy

 

[souNdguy]

IMHO.. i wouldn't even have pulled it down without a comp test.. unless it was a teardown due to damge that precluded the comp test.. etc.

at least that way you could get a good feeling of before / after..

sounduy

 

[Anonymous-0]

I guess I am just as stubborn as you are. You state that "people actually do this stuff in their backyard shop." Yet, since the original poster doesn't know how to remove the flywheel, wouldn't it be illogical to assume he has a micrometer set, a taper gauge for cylinder wear, Flathead valve tools, valve seat grinder, let alone a crankshaft grinder?

If he had this equipment he wouldn' be posting on here in the first place. No hard feelings!

 

[Ken Windom]

Thanks very much for all the comments. I think the "SS Mission Creep" has already left port The question now is whether she will find smooth sailing or rough seas before getting back to safe harbor.

The rest of this post is rather long, but it gives some of the details of where I am and how I got there regarding my tractor ('51 8N with side-mount distributor).

The old tractor is ugly and in desperate need of repainting and other cosmetic changes. I did not want to do that until some of the internal problems had been corrected (don't want to mess up a good paint job taking things apart) but have been using it heavily for the past 6 years and not had time to do more than routine maintenance. Now that I can get to it, I have been wavering between a complete rebuild versus just replacing what needs replacing. Each time I do something, though, it leads me to something else.

I did a dry comp test before tearing it apart: 105 psi on 3 cylinders, 110 on the other one. The head is now off, along with starter, generator (at the shop having the brushes checked), oil filter, water pump, governor and the part of the timing cover where the governor attaches. I took off the clutch and found that it was worn down so far that one of the springs was coming in contact with the flywheel. There is oil in the part of the bell housing where the Sherman transmission is located (reported in an earlier post) and oil/grease on one the right brake shoes and drum. The gasket on one valve cover had a visible oil leak (cover was installed with gasket twisted). Oil was also coming out around governor housing (bottom was not flat). There is a lot of oil that appears to be coming from somewhere around the front timing gear cover but I cannot pinpoint where it is coming from. The exhaust indicates it is burning some oil.

The oil pan is still attached, but I have concluded that it probably will have to come off. I removed part of the timing gear cover, so I think the only way to refresh the gasket where it mates with the oil pan is to replace the entire oil pan gasket set (hence the question as to whether the rope seals would have to be replaced).

The valves were coated with carbon, but I was able to get most of that off by soaking them in Sea Foam and taking a wire bristle wheel to them. The stems are in spec, and the area where they seat looks good, so thought lapping them might be sufficient. From comments here, I am now wondering if I should just go ahead and do a complete engine overhaul with new pistons/rings/sleeves/valves/guides/etc. and all the gaskets/seals that involves. It may be overkill, but at least I would know the engine is OK. Oh, and yes, I definitely plan to take the block and head to a machine shop for a hot bath and resurfacing.

I could go on, but don't want to bore you or take up too much bandwidth on this forum. Any additional comments are welcome, plus you can contact me privately by email if you prefer. Thanks again for all the help.

 

[souNdguy]

I don't assume the OP doesn't have a caliper set.. I have 2-3 various sets laying around and I'm not a mechanic nor a mechanical engineer... besides.. some places ( auto parts stores ) loan tools. ( with refundable deposit). or rent them cheaply.

measuring sleave wear is a moot point if you are driving in new liners.

dropping the crank off at the machine shop is a far cry from taking the entire thing in, leaving it at the doorstep and telling them to call you when it's ready to bolt back to the tranny.

again.. for the valves.. they may or may not need it.. since he's into it and didn't do a comp test.. I'd default to deffinately looking at them.. whether that means hand lapping for ones that look good, or dropping it off for valve work if they don't look good.

dropping the block off for valves is cheaper than dropping it off for -everything-.

lots of people here over the years have rebuilt their first engine via cookbook and this forum. I don't see why this guy can't be the next one.

If no one ever tries to undertake something they havn't done.. then we become stagnant. The first time any of us attempt something 'for the first time' we are going at it as best we can with research, perhaps a manual, and perhaps limited experience from a related project.. it all builds on itself... ie.. learning..


soundguy

 

[Ken Windom]

SouNdguy,

Thanks for the vote of confidence. Actually, I own 3 micrometers. It's true I have not rebuilt an engine before, but I do have quite a bit of experience building high-pressure hydraulic systems and have worked on some pretty sophisticated equipment in my time. I was inspired by Roger Welsch's books and figured I have at least as much going for me as he did when he started. I just don't want to charge into something head-long and realize too late that I should not have done step 2 without having first done step 1. My mother was fond of saying: "It's better to remain silent and appear a fool than speak and remove all doubt." I disagree, and would rather seem foolish asking a question and making sure I am doing something right rather than discovering too late that my assumptions were wrong.

 

[souNdguy]

I agree.. hard to go into this with less than ole rog did.. and look how good his turne dout with a lil research and help from others.. I've conversed with him a few times.. seems like a nice guy.

soundguy

 

[Dan]

I had never seen the inside of ANY engine before rebuilding the one on my 1954 NAA Rustbucket. I got through it perfectly with basic hand tools, an I&T manual, lots of help and research here, and a good local machine shop for the crank and valve work. Been working hard for over 3 years now on my 42 acres mowing and general duties with 60 psi oil pressure and always starts right up.

Since then I have a 1948 8N and a 1939 9N engine rebuild under my belt.

These engines are internal combustion at its easiset. If I can do it - you can do it. Dig in, do some research, and yell for help when you have questions - it is very satisfying to rebuild your own engine.

Dan

 

[Jay, Tx]

I'm no expert. But I just went through somewhat the same situation myself. Mine was burning oil at a pretty good rate, and spewing oil all over my right foot. But still had somewhat decent oil pressure.

Here's what I did. I did not want to split it in half, but you're already there.

I replaced the sleeves, pistons and rings. $130.00 +/-.
Installed a new valve set, guides, retainers, springs, etc. #125.00+/-
Mic'd the rod journals, within spec.. Installed new rod bearings. $40.00?
Lapped the new valves in the old seats. Free since I already had the tool and paste.
Since I never took out the crank, I left the upper rope seals in, and left the lowers about an 1/8" long on each side too kinda mash the old uppers when the pan went back on (suggestion from this site).

Put everything back together.

I did have a few other issues getting her fired up, but none related to the rebuild itself. After a new starter drive assembly and new carb, everything came right to life.

She now runs better than she ever has. Runs about 30-35psi of oil pressure at working RPM (falls off to 15-20 at idle), burns no oil, and blows no oil.

I couldn't be happier. And never had to break her in half.

Not recommending this course of action. Just relating my experience.


Jay