8n restoration off to a hilarious start!

Didjit · Sep 6, 2014

Hey tractorbynet!

So last week I winched my wife's grandfathers' 8n out of the clay since she would like it rebuilt. I'm excited about the project, so I gladly obliged.

I got it home and put it on blocks in the barn and the extent of the work I did in the evenings after work this past week was degreasing and pulling off the old dry rotted tires.

Today, I started tearing the thing down and taking pictures of everything. I was counting on a full rebuild to begin with. I pulled the radiator, and its full of oil! Like not "oil in the water"... Like its full of clean 15-40. I scratched my head and dumped it into a bucket... Like a gallon of it. Kinda bewildered I pulled the water pump ... The water jackets are full of (guess what)... Clean oil.

With the radiator out of the way, I was able to turn the crank. Turns smooth when I turn it by a wrench. I scratch my head again and decide why not compression test it. I get 40 lbs on each cylinder, and according to what I've read, that's at the high end of the spectrum for these guys.

I pulled the head and the gasket looks fine... The pistons are shiny, no carbon lip around the tops of the sleeves, and all the valves open and close and seat nicely. I wiped it off with brake cleaner. Smeared a little oil on it and hand tightened the head bolts on the old gasket - just ordered a new one.

So... I'm wondering if I should do a full rebuild on this. I didn't ever fire it because the carb needs rebuilt and the gas tank is full of rust - it's full of BBs and turning around on my lathe as I type this.

I've cleaned radiators/water jackets in construction equipment with muriatic acid. Was thinking about doing that with the old pump and then replacing it. Dunno if that's half measure or if I should do a tear down of this motor.

I think father-in-law dumped oil in the radiator to be honest.

I know someone here has to have an opinion on this one

Didjit · Sep 6, 2014

Oh! Important factoid I omitted. No water in the engine oil. I didn't do an exacting fluid analysis, but nothing milky at all in there... And no metal. Hmmm... Pretty sure daddy dearest tried to add oil and selected the wrong hole.

Soundguy · Sep 6, 2014

what you've read is apparently very wrong. I'd quit using that source.

90 psi is book minimum compression spec on that 120ci flathead.

deffinately replace the head gasket.

redo the comp test dry then wet.. see what you get.

Didjit · Sep 6, 2014

Sounds like a plan. Thanks!

I'm thinking that while it might be better then I had imagined, I should probably just bite the bullet and do a compete engine rebuild. I don't want to make a habit of tearing this thing down.

Soundguy · Sep 6, 2014

find out where you are at with compression and oil pressure first. maybee pull a main and rod shell see what bearings are at .

once you know where you are at on crank journals and oil pump pressure , cyl pressure.. you can go from there.

or just forgo that and dive in and renew all.

if you go that route. get cam inserts fro the block to renew them clearances then she can be like new.

flusher · Sep 7, 2014

Didjit said:
Sounds like a plan. Thanks!

I'm thinking that while it might be better then I had imagined, I should probably just bite the bullet and do a compete engine rebuild. I don't want to make a habit of tearing this thing down.

I'd do the rebuild. Best way to get familiar with your 8N and you'll know that the engine is truly fixed and ready to go for another 60 years.

I'm finishing a rebuild on the C60 engine in my 1948 Farmall Cub. Could barely get 50 psi pressure in the cylinders. Spec is 110 psi. Next step--run the engine on the test stand.

Good luck