What are symptoms of bad valves

Still having issues with my Case 870 gas. Thought it was fule related so went through the the fuel sytem, new filters, fuel pump, rebuilt carb, and cleaned tank. Stil had issues, cap. rotor, points all looked burnt and poor, so they were replaced today,,, and it still does it. Seems to have a miss, when running full throttle under load, it will start losing power, then start wanting to quit, will backfire , rated rpm is 1900, it will drop down to 1500 or less and start acting like this. It diesels pretty bad when you shut it down after this. Wondering if maybe I have a bad valve or some thing internal messed up.

YOUR going to laugh at me but change the gas your using and move up in octane . she is getting to hot on top of the pistons also check your timing at full throttle and check the advance in the dist. To get close to the quality of gas that was called REGULAR back when that tractor was built now you need 93 octane as that was the octane of low grade regular. Just try one tank after you check the rest.

Vet, I did buy a couple bottles of octane booster, one bottle treats 21 gallons, my tank hold 50, and is about 3/4 full, maybe bit less, but more. The bottle does not say what it raises the octain to, is there any danger if I end up adding a bit too much? As far as the advance in the dist, are you saying to make sure it is free and working, it seemed OK when I rebuilt the points and such. I do not have a timing light, and the tractor is 6 miles away at one of my feilds. Any options for me to check the timing without a light? Also, another odd thing-my operating temp "gauge" which has always worked since I've had the tractor, and will ussually run operating temp at 190-205 degrees, only will show 140 now for high, radiator is full, she pukes out any excess, but doesnt boil over so I am assuming that the gauge is bad? Just wondering if any of my issues with running would affect cooling system, or possibly not cooling the head, cylinders.

One of the things that causes dieseling and running hot is late timing. Jim

Your waisten your money on SNAKE OIL as here we have been down that road with CenPeco stuff and we had that lab tested at a lab in Columbus Ohio and it did nothing as to what it claimed. What the hello are ya out as you have been fighting this for awhile . I fought it for a couple years on gas tractors around here as we still WORK them not play with them . solved our plug problems loss of power problems by just changing the gas. we can get 93 octane here and that is what we have brought out to the farm three hundred at a time . Try it . Drain what is in there and just try one tank. If you think it is a valve then do a compression test . I am not the local guru on Cases as that is a nother guy around here . But everything you are telling me leads me to 87 octane gas and pre detonation . 87 burns fast and hot it is ok for car and light truck engines NOT for and engine working under load . 93 burns cooler and longer .

as to setting the timing yaq need a good lite , yea a good lite will set ya back a C note . But each time you change points timing should be checked and reset if needed. You can dump all the snake oil you want and get nothing out of it.

His tractor should have a shut down solenoid on the carb , but someone may have been to cheap to replace when it went bad.

From what was said below you still NEED to set your timing. I'd be adjusting the valves too and also do a compression check.

this Questio is for tractor vet ,, for serveral summers , i burn e-85 in my gasser tractors ,,adjuted the carb , they run a little cold natured at 1st , dont do heavy tillage work . mostly haying .. left the timing alone , BUT ,, yoiu raise some good thought provoking ideas about timing , thev tractors are case vac , sc , dc, 730 .. Would you care to pass along advice ? thanx, Jim

Octane in a bottle is usually just acetone, toluene or xylene. It isn't TEL. Pour in 25% 100LL and the rest premium pump gas.
I agree valve lash and ignition timing. Timing marks on the tractor may not be accurate either.
The advance mechanism maybe hungup too.

This is just a shade tree timing method but it might help until you can get a light on it. Mark where the distributor is, loosen it and turn it just a little, maybe 1/16" to 1/8" at most in the opposite direction the rotor turns. This will advance the timing. If the engine speeds up noticeably and idles smoother, it might have been timed late. I haven't worked on many of the more modern gassers, but most of the old ones should labor just slightly at idle when they are timed right. This won't tell you if the advance is working right or not, but it's just another quick diagnostic tool. You still need to beg, borrow or steal a timing light so you can check the high idle timing. Jim

You should be able to run more advance with E85

I am not into the alkihol thing , played with it way back and what we learned was if it ain't just wright ya make LOTS OF SPARE PARTS . Temp humidity play a big roll in it Played with it in a blowen 487 Donavin (sp) and a 1650 oliver with a turbo . When we would hit the combination just wright they made lots of power and if we did not lift the head then we threw the crank out on the ground . On the 487 if it was to lean it was piston time or putting the blower back on after it came back from orbit or welding up the block from a couple rods that did not like the inside . We do not have much E85 here what we do have is 87-89-93 no just how much alkihol is in it depends where you get gas. My wife drives a 03 Durango with a 5.9 to some but to me it is still and old iron block 360 and engine that has been around since 72 or was it 72 can't remember just when it came out . Now it will tell you how god the gas is by how many miles ya get before ya have to rob the bank for the next fill up. If you get gas at Shell here in town it will do in winter just shy of 16 mpg if we get gas at the Smith station it will do over 16 If she gets gas at Wal Marts it gets 13 when they change the gas for summer blend and sofar we are still getting winter blend on summer blend it will do 17-17.5 Wife works for the Girl Scouts and is running the wheels off it and she wrights down every mile and every gallon that goes thru it . From what i have heard you get less on E85 then reg. gas and that stands to reason as with what little i have played with alkihol it takes twice alkihol as gas to make pony power. and have had to drain off alkihol from the oil pan on the 487 between runs when we had her FAT .

Bet you have too high heat range spark plugs in. Put in about 2 heat ranges lower plugs and I bet your problem goes away.

Plug wires, maybe?

You need to identify the missing cylinder, then go from there.

You will find that the heat range has been moved up with unleaded gas.

Dave, I suggest you should believe your temperature gage, at 140 degrees you should not be coughing up coolant. If the coolant is not circulating properly for some reason - the heads can become hot resulting in spark knock, loss of power as you discribe. Since the hot coolant is not flowing past the temperature gage it reads cold.

whatr is 100LL? I can get Track Tek 111 Racing Fuel. Contains 4.0 Grams Lead Per Gallon. 114 Octane (research). 106 Octane (motor) Would this be over doing it?

100LL is avation fuel. Blue in color. Drag racers used to buy it for their race cars. It was the replacement for leaded airplane fuel. It is 100 Octane Low Lead Avaition Fuel. I don't know what it goes for now, but it used to be about $1.50 per gallon higher than car gas. It was (is) available at the local airport. It is very different than auto gasoline. It evaporates very fast and leaves a sticky feeling on your hands. Smells very different , too. Quick price check shows $4.42 - $4.55 per Gallon.

The first thing I do is listen for an uneven cranking. This will easily show you if one or two cylinders is quite a bit different. The best way is to do a compression test. I would doubt that you have bad valves if it passes a compression test. Valve clearance can create issues at low/high RPM,s.

100 Low Lead aviation gasoline. Similar to 96 octane pump gas with just enough lead for valve protection but not enough to cause fouling and deposits.

Coil might be breaking down. If you use it for light duty might have carbon under valves. Had a 4000 ford that sounded like yours and was carbon under valves from just putting around.

(quoted from post at 22:04:35 05/19/11) Also, another odd thing-my operating temp "gauge" which has always worked since I've had the tractor, and will ussually run operating temp at 190-205 degrees, only will show 140 now for high, radiator is full, she pukes out any excess, but doesnt boil over so I am assuming that the gauge is bad? Just wondering if any of my issues with running would affect cooling system, or possibly not cooling the head, cylinders.

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I missed this point. If it's running cold and all sooted up with carbon. Then yes all these trouble can be traced back to low coolant temps and carbon.
Change the stat, check the gauge, put it on a pto dyno and work it hard while spraying a water mist into the carb inlet.