9N/2N Backfires

[Burt]

OK, this is my first tractor, so go easy on me.
I changed fluids, plugs, points, condenser and replaced fuel line but not the filter under the gas tank, just the one at the carb.  It runs better now but still, backfires when slowing down.  At full throttle, it runs OK.  I played with the flutter valve to no avail.

I did however, set the points at .018 vs. .015. I got this spec from a DVD by J & N productions on tune-up for Ford tractors.

It did backfire before also.

Carb next?  Re-set points to .015?

Any help or suggestions?

Thanks

WillyB

[Pete P.]

Burt --

Leave the points at 0.018" -- that's an excellent recommendation; it compensates for wear in the distributor.  Basically, you want the points as wide as you can get them and still have spark.  The narrower the gap, the weaker the spark. 

Backfiring under load is almost always a symptom of weak spark.  You say you backfire when closing the throttle, though.  I've never seen an N do that although it is very common in large truck engines, etc. due to unburned fuel igniting in the muffler -- these little 120 cid flat heads just don't push that much fuel into the muffler and the muffler isn't that hot (at least not that I've seen.) 

I wonder if you don't have weak spark still and it's just showing funny.  Have you tried to run a heavy load for a prolonged period (brush hog works, but anything to heat everything up and really work her?)  Is the spark at a test plug nice and blue? 

If it were me, I'd tune the carb, then pull the carb. drain plug to be sure that gasoline flowed freely, then take the dist. back off and go over everything closely to be sure it's all 100 % and nothing was missed, dirty, etc.

There is a possiblity the valve timing is off, but I doubt it -- it should backfire all the time then.   

Hope this helps,

Pete P.
Harborcreek, penna.

[Burt]

Pete:

Thank you for your reply.  I will try all of your suggestions.  I appreciate the time you took to answer my plea!  Right now, I noticed that it runs really good when colder.  It seems to "flump," or falter rather than backfire now only when warmer.  It also runs OK under load.  I put a blade on it and scraped a road OK with it.

I haven't messed with the filters under the gas tank.  I only changed/cleaned the one at the carburetor.  That is next...kind of waiting to get a bit more gas out of the tank before I have to drain it.

Snowed lightly here tonight (Goldendale, WA), elevation is about 1800 above sea level so I might just have to keep this puppy running all Winter before I disable it to fix more stuff on it.

One other bulletin board suggested that I add Marvel Mystery oil to the gas and engine to free up any stuck valve/lifter issue.

I will re-build the carburetor also, (weather permitting) so once again, thank you.

It's an adventure.

Burt

[Pete P.]

Burt --

I'm a bit envious, still in the 50s here, no snow 'till end of week maybe.  Last year this time we had 30" or so (Penna. lakeshore.)  I'm sure that's nothing by your standards, but I love winter.  Anyhow, I digress...

I'm starting to wonder about fuel in your case.  For sure a good carb tuning and fuel flow inspection is in order. 

RE -- Marvel oil or the like -- stuck valves are a common occurrance on the flat head Fords, but usually only if one hasn't been run for a while (a year or so.)  Sometimes the trick works, sometimes not.  It will, however, foul the living daylights out of your plugs -- so be prepared to change them.  Oh, yea -- it smokes terrible too.   Personally, I'd do a compression test both hot and cold.  If you have a sticky or otherwise poor seating valve the compression test will tell you without the bad plugs, etc.  If you have one cylinder that's weak then you could try the Marvel oil -- if not then you know valve seating (or anything compression related) is not the issue.

One thing that I do recommend is Lucas Upper Cylinder Lubricant in the fuel.  (Other similar products work too.)  Flatheads don't have much of a water jacket in the head.  New fuels, especially higher octane blends, burn very rapidly.  Some have said that all the combustion is done in the first inch of piston travel.  I can't verify that, but the point is that these engines were designed to operate on distilled, leaded gasoline which burned much slower than the modern 89 octane.  Modern fuels will deposit all the heat in the upper portion of the cylinder where there isn't much cooling ability.  In extreme cases the head can warp from heat; even in normal use the engine is not operating smoothly.  The upper cylinder lube retards combustion rate and allows the fuel to burn over more of the stroke resulting in smoother operation and less heat in the head.  Also -- and to your point -- it tends to lend an oil coating to the valves which may inhibit sticking.   I run the stuff in all my flatheads and haven't done a valve job or head gasket in about six years now.  I have, however, gone one heat range up in spark plugs to prevent fouling.

Good luck,

Pete P.
Harborcreek, Penna.
   

[ontarioparts]

I would suggest that that little filter under the gas tank be changed so as to eliminate that as a problem, and then continuing onto the other problems.

I had an experience twice where the engine would buck, almost cut off, and then stutter back on. In both instances the fuel filter was severely clogged. On changing the filter both engines roared back to life, and the machines were back to normal. Those little filters can drop an engine

regards
Marlon
Ford Tractor Parts

[Burt]

Reply to Marlon and Pete:

Thanks for your responses.  Here's what l did so far.  An old timer recommended that I take all the plugs out...similar to Marlon's idea, put 1/4 cup of 30W oil in, crank it for about 5 to 10 seconds, then put in my old plugs and start it up.  I did.  About stunk up the county over here.  Ran out all the smoke and then put in new plugs.  Its got more power now.  I have to borrow a compression tester because I don't have one.

The "chuffing," was probably caused by water in the fuel, I'm told.  I put in some HEET and it doesn't "chuff," any more.  My next is to follow some more advice and I have the new sediment bowl and fuel line ready to put in.  The carb has been overhauled also, so it's running much better after that.

I'l report after changing the fuel line to it's original morphology.  The previous owner took out the sediment bowl and put an in-line filter in.  I'm all for getting after that little filter in the gas tank I hear so much about.  That came with the sediment bowl. 

The weather has been a bit cold and since I have to drain fuel, I don't want to do this indoors.  The sun's supposed to be out today Dec. 22nd and tomorrow, so I'll get at it and provide reports to you all afterwards.

Again, thank you for all your responses.  These old beasts are amazing, tough, addictive and fun.

Burt (Goldendale, WA)

[Pete P.]

Burt --

Sorry I didn't realize you were without a settling bulb; I think you'll like having it -- they're great at trapping coarse dirt and water, and you can see the amount of contamination and dump it out as needed.  You'd be suprised how much snow finds its way into a fuel tank while plowing or being stored outside. 

Good luck & stay warm,

Pete P.
Harborcreek, Penna.