8N Engine rebuild questions

Is there a special tool required to remove the valves(springs). There must be. Given that the valve springs are very strong, how do you pull it down far enough to remove the clip. I could use a better understanding of how that valve clip works too. If I understood it better, maybe I would have an easier time getting them out.

Were all 8Ns originally 6 volt systems. Mine is 12v now, but I'm not sure if it was converted? From everything I've read, I beleive that it was orginally 6v and was converted to 12v. I have been trying to find a 12v diagram for the 8N but have had no luck.

Many more questions to come!

Thanks,

Bill
wcp@priday.net
41 9N88110

I am having a little problem understanding the folling statement in the info on ordering a engine overhaul kit:

Specify With or Without rotating valves, width of oil pump gears(9/16"or3/4"),and Sleeve wall thickness and bearing size - .010, .020, .030, or .040.

A few things I don't understand about this statment:

What does it mean "with or without rotating valves"?

Is the question about bearing size in comparison to the original? If so, how do I know what the original was. I can measure the current size, but I don't know the original size.

I read somewhere that a diamond on the end of your serial number indicates that you have .090 sleeves. Is that correct?

Dave

Rotating valve.....some exhaust valves have "automatic" rotators to prevent burned exhaust valves, this is a good option to install if your early engine doesn't have them already installed, later engines had them.

Width of oilpump gear, measure it. so you can specifiy...or...bite the bullet, and buy a late N-oilpump. 3/4 is better.

Sleeve wall thickness.....important if you are replacing the cylinder sleeves because castiron sleeves won't fit innna block bored for steel sleeves. And steel sleeves won't "lock" innna block bored out for castiron sleeves. My opinion, castiron sleeves are better seals to piston rings, higher compression for more power and longer wear. Worth the extra cost to have the early block bored out for later castiron sleeves.

Bearing sizes are base upon the difference from the original standard crankshaft mainbearing journal size 2.248-2.249 and the current mainbearing journal size. The original standard rodbearing crankshaft journal size 2.0935-2.0945. These are 4-point measurements taken with 1/10000 capable micrometers. Plasti-gage is use to determine the currrent bearing clearance but doesn't really tell you what the journal size is. Usually there is etched on backside of bearing shell its mfgr size.

Engines after s/n 8N433578 had diamond to indicate that the block came from factory with castiron cylinder sleeves. Many blocks have been bored out to fit the better castiron sleeve so the diamond is not a "sure thing". Look at the blocktop under strong light and maybe magnifier glass, castiron sleeve will look almost 1/8 thick, steel sleeve will look less than 1/16 thick.

Both castiron and steel sleeve engines used the same piston diameter. Modern metalurgy 3-ring pistons are better than 4-ring pistons.

All this information is readily available in the highly recommended I&T FO-4 manual. $29 cheap, gettcha 1 and readitt..... ...respectfully, Dell

They developed an "adjustable" camshaft tappet to solve that problem (real problem with the popular V-8 engine). AND changed the design of the valvestem end to a "non-tulip" end.

There is a valvestem "cap" on exhaust valves, held on by a clip that rests on the adjustable tappet. That is the "valve rotator". Intake valves do not have the rotator cap, understand?

As I said, this information is all explained in the I&T FO-4 manual..... ....respectfully, Dell

Does the 8N have a thermostat. I saw some reference to one, but I don't see one when I remove the water pump. Is there supposed to be one there?

I started this entire project because of a severe knocking noise in the engine. I was noticible at low RPM's but has the RPMs increase it became very loud. I was afraid to run it for more than a few seconds. I started tearing it down, expecting to find something very obviously broken, but after tearing it down to the point of removing all the pistons, crankshaft and bearings I have found absolutley noting wrong. The only thing still attached to the block are the valves, the cam shaft and the front housing that includes the distributor. I have found no signs of wear in any bearings, no 'looseness' in rods or anything. It's been a bit frustrating because the noise was so obvious. I know this is a very vague question, but does anyone have any suggestions.

One thing that really concerns me is a loose part in the clutch area. When I removed the block from the transmission housing, there was a large 'c' ring type washer laying there. It is about 2 inches in diameter. It has rather uneven ends, so I can't tell if it is broken or just made that way. There is nothing in the cluth area that is broken and I was having no clutch problems. Any idea what it might be? I have a master parts catalog on the way that I am sure will help me to identify it. I have a web page that is in the very very early stages of development, but here is a picture of the part.

http://www.pfjconsulting.com/Pics/c-ring.jpg

One thing you could have checked for easily (prior to dissassembly), and should prior to buttoning it up again, is piston/valve to head clearance.

Set the head on the engine without a gasket. Use a couple of bolts screwed in just a few turns as locating pins. Slowly turn the engine over by hand through two complete revolutions. The head must not lift up off the block at any point, or you'll have inadquate clearance once bolted together with a gasket.

I suspect that you are correct on the source of the loose c-ring. I had my starter, including the bendix, rebuilt a couple years ago. I bet that is when it broke. It looks very similar to the current version, although not exactly like it.

12 volts is a common conversion but how to wire it depends upon what components you use - ie generator or alternator?, 6 volt or 12 volt coil?

If you use an alternator you must use negative ground. (There are exceptions, but rarely)

A check of the archives should get you a link to a wiring diagram if you plan to use the common GM alternator.

There is a special tool for valve removal but you can make one. Sounds like you need to get an FO-4 manual - I like the Master Parts Catalog 1939 - 1953 also as it has blow up diagrams of almost every part.

N - joy.

Mountainman...CA

Varnish and carbon are the main problem in this area. A bent screwdriver, handle of a brake spring tool, or other croooked-finger like fabricated prybar can be used to lever down on the top of the guide by reaching through the port.
Penetrating oil helps too.

Alternatively, there is a custom lever tool available from the Flathead V8 crowd that engages the slot on the bottom of the guide.

The clip engages a slot on the valve guide. When in position, the outside diameter of the clip is surrounded and locked in place by a 1/4 inch deep round relief in the block. To remove the clip, you must push the guide down against spring tension and varnish/carbon until it has moved down 1/4 inch and the clip is clear of the block. Then you can remove the clip with your fingers. Ignore the terribly misleading picture in the I&T manual -- you'll never be able to just yank the clip out with the pictured hook tool.

If you can't get the guide to move down, one option is to simply destroy the clip. Replacement clips are available and cheap.

All 8ns were 6 volts originally. All 12 volt 8ns were converted. Conversions come in all manner of designs and styles -- there is no one wiring diagram that covers them all.