8N Sputtering update: vacuum gauge readings

RE: "Sputtering" vacuum gauge diagnosis info.

Bit the bullet & bought a vacuum gauge today.
Readings at idle are ~16-20 bouncing quite fast. Clears up at faster rpm to rock steady. At fast idle it clears a bit & drops when it "sputters".

The instructions sheet says:
"Needle vibrates rapidly at idle-steadies as rpm is increased."
"WORN VALVE GUIDES"

Looks like several hit it on the head.BTW,I do have WORN split guides.
Can't confirm,as I haven't fixed it yet, but the info with the gauge is pretty convincing.

Gonna start gettin ready for a rebuild, no use in just doin the valves!All the way.

• Sputtering thread from Tractor Talk page

Good point. I am considering getting my crank balanced after it's turned. I have a few areas (of rpm) that cause moderate vibrations.

I have polished my 641, and most likely will do that. More smoothing & removing cast imperfections, don't really want to get too deep cause would hate to get into trouble with my block.

And I can't think of a WORSE reason to overhaul an engine, just because the vacuum gauge pulses. Do the dreaded compression test. Ford specs: 90psi min (dry). What is your oil pressure at idle and running speeds? Does it BURN OIL? Is it hard to start? Does it have enuff power to gitt yer chores done? I can think of a number of reasons that an engine splutters, encluding bad sparkies wires, sticky valve stems, broken valve springs, heck worn camshaft lobe.

Its yer engine, do what you want to do; but DON'T make an overhaul decision based upon a spluttering idle pulsing vacuum gauge reading..... ...respectfully, Dell

I am LOOKING for a reason, any reason to do a Full rebuild in a restoration program. I need to do it before spring mowing season. I have my garage cleaned up (monumental event). I know my compression readings by heart 1=90, 2=75 3=90 4=90. Slight improvement wet. Split valve guides swap holes (almost).
I already knew it had sloppy guides & stems.
I did a mild valve lap & replaced 1 or 2 valves in 2001 while recuperating from back surgery.

This tractor runs awsome, great power & leaks more oil than it burns. Bearings make no excessive noise & will plow till the muffler gets red.

I don't NEED a rebuild. That said , I want to get it done now cause the time is right. I want to get rid of the "sputter". No way I am going to do a valve job without a complete rebuild, BTW I will replace the sleeves & pistons, turn the crank & maybe oil pump & line bore. I will check on the valve seats, & possibly have them replaced if ANY questions.

The vacuum gauge vibrates like it is posessed at idle, at high idle (~600-700) it shows 2-3 inches drop when the sputtering is going on.

I do not recomend anyone else do a rebuild if their tractor misses a tiny "sputtering" miss like mine. But I am at the point in a FULL restoration on a working tractor where this was enought evidence for ME to do it before March.

I have another tractor to use but I am addicted to this 8N, it is my ZEN tractor! This is my main hobby in the winter,tweaking,tuning,diagnosing,& deciding how far I want to go. Got an engine stand yesterday before I bought the vacuum gauge, see where I'm comming from??

I know what you mean about this unusual addiction to rebuilding these great tractors. That is what possessed (and that is an accurate description) me to buy a worn out rusted scrap yard bound NAA and bring it back to life. I am having the time of my life and can't wait to get my engine bcak from the machine shop to finish the engine side of the project. Then it is on to the front end, or maybe the rear brakes, or rear seals - hummm...

Good luck,
Dan