706 dies under load question

I have been fighting my 706 263 gas for a few days now. It will stay running just putting around the barn lot and down the road but when I take it to the field and put a real load to it it runs great for a couple of rounds then coughs a couple of times and dies, some times I can clutch it and fiddle with the choke and keep it running. It seems to heat up 10 to 15 deg right before it dies. When it dies it will fire right up. I have put a new coil on it and rebuilt the carb it seems to have good gas flow to the carb and the fuel bowl is clean i looked in the tank and it looks good and clean. Any ideas on what might be the problem would be greatly appricated.

be sure the fuel vent in the cap is clear. The heating could be lean operation (not good)
Fuel flow must be good and like a soda straw for 5 minutes. If the tractor is truing to sieze, it could be from excessive timing, or low octane fuel. Best guess is that 89 R=M fuel is minimal. Try mixing 5 gallons of premium in the tank if the timing is correct, vent is open and the screen at the carb is clean, and flow as above is good. Jim

The Tractor Vet has said numerous times you need 93 octane fuel in these tractors. I would check your float setting and if that carburetor
has a shutoff solenoid it may not be opening fully starving the engine. Hal

Just check your fuel cap,sedimint bouwl screen and make sre you are geting a good flow to the carb. Pull the plug at bottom of carb and let run for a couple of minutes to make sure. You do not have to run premium fuel. Whoever thimks you do is off their rocker.

Bob

Ran 656 and 706 gassers a lot when I was a kid. What's the oil pressure when it stalls? I would check out the fuel things first but it sounds an engine on the verge of "letting go". Are the valves properly adjusted? Is it burning oil? What does the blow by and valve cover vent smoke look like and is it excessive?

Also a cruddy radiator can cause these symptoms

Classic too high heat range spark plug symptoms. Install a set of champion D15Y"s or the equivalent brand of your choice and your problem will be solved. Also The Tractor Vet is 100% correct about running 93+ octane gas if you work these old gassers. BTDT!

Yep , Change the splugs to either 386 motorcrafts- C86 A/C's , next put a timing lite on it and being that it is a C263 and hoping that at some point someone before you did not upgrade her to the C291 conversion set the ing timing at 23 degrees BEFORE TDC. at full throttle . And ya need 93 octane gas , not 89 not 90 , 93 only . NOW HERE IS THE KICK we can no longer get straight 93 gas as now over here it is now laced with alkihol and it Does NOT work . Why not ya say well ALKIHOL is and oxygenating agent and it leans the burn and when ya lean the burn to keep the whacked out nut cases happy it makes this old mechanic vary unhappy . Why you ask well i have our 706 down at the moment with a torched out #1 piston from the last load of gas we got as our fuel supplier brought us a 250 gallon load of this NEW mandated 10% methanol blend 93 and never told us . We filled the 706 and hooked to the grinder and started grinding corn like we always do and she came under full load and before i could get to the PTO lever she started to loose power and you could hear the preignition , i got the PTo shut off and you could tell that she was hurt then all of a sudden she was hammeren hard due to the top ring getting up on top of the piston . So now i am not sure just what we are going to do . We can't get forged pistons that ya can afford to buy , ya can not get the gas that will work as i spent half a day on the phone with people tryen to get straight 93 gas and the best that we can get would be 90 octane as that is the best coming from the refinery thru the pipe line . 90 will run old 460-560's just fine IF they have not been up graded to the higher compression pistons . I know that back years ago the a lot of the guys around here that had 560 gassers had then upgraded with the 706 C263 pistons . BUT back then on farm gas was between 93- and 95 octane . The look on our fuel supplier's face when i dropped the piston on his desk was price less . As this is not the first piston that he has seen from us . Our 706 is the tractor of choice for feed grinding mowing hay raking hauling round bales planting or ya just need a tractor . It starts every time no matter the weather , no plug it in vary little warm up time . And besides we all just like it . But now i am not sure what we can do as i am running out of idea's . One fuel supplier said that he could get us what he called SPORTMANS gas and it is 94 octane BUT it only comes in 55 gallon drums and at the small price of 6.25 a gallon. Yea wright. Ba enough that the junk 93 is 4.19 a gallon and we use about 650-700 gallon a year on gas and 12-1400 in diesel . Myself i believe that we are fighting a battle that we can not win because nobody will stand together for two min and agree on just one thing and nobody will fight to try and get what they need . I do believe now that the days of the old trusted work horse are coming to a close as i am plum out of ideas and it is not from lack of trying . The EPA has beat us on this one .

yea back when you were a kid the gas was a whole bunch different and on farm gas was 93 to 95 octane . all ya got to do is read the owners manual on fuel requirements and it tells you that for a 656-856 93 is the minimum octane . and that was BEFORE alkihol being added .

I have an 806 gasser with duals on it, weighed down my 14 ft disc good, and twice over the years I have melted the pistons. The pistons get so hot the skirts collapse and the piston head melts. That hard knock the next morning is a sure sign yep done it again. By running it 3/4 throttle instead of full thottle seems to be working. The best gas I can get is 92 ethanol blend. It will pull hard for 15-20 minutes, then starts to shut down just like you are saying. I used to see this same problem on Ford gas semis when the were on the road. They are great winter or chore tractors, not so good on a heavy steady pull.

Thank you Vet. I believe you have forgot more about IH then I will ever know. I would like to think I know a little about old tractors but from I have gathered from your post is put a new set of plugs in it then make sure it is in time then sell it cause I'm going to blow it up cause I'm not going to be able to find the right fuel. I trust your knowledge but I find it hard to understand how all these ticking time bombs are still around with the poor grade gas that is being used today. But I'm going to check my plugs and the timing and give it a whirl. Thanks again for your insight. Ryan

I have fought this around here for years . We have a ton of old gassers in my area on dairy farms and most of them are one owner tractors other then the dozen or so 706's that people bought off me . My one good friend has his dad's 460 gasser that was bought new in 61 and they have fought fuel and oil problems with it from day one . First problem was valve burning and that went on for some time till they switched to I H low ash oil , that fixed the valve burning . Then came the loose of power and seizing while under load or hard pulls while plowing . Changing grade of gas solved that . Now you have to keep in mind here that each time the engine was rebuilt the head was milled down because of warping , each time this was done it raised the compression ratio . BUT back then the rebuild kits came thru with FORGED pistons . Now a new rebuild kit comes with a CAST Aluminum piston and a cast piston will not transfer heat from the top to the skirt as fast as a Forged piston will and it will swell more above the top ring due to heat . The difference between the skirt and where the rings set runs about .019 -.021 smaller then the skirt , and when these engines are working the heat from this new gas burns way hotter then the old gas did thus the cast piston can and will swell over .025 -.027 . and this will lead to a seized engine and this happens above the top ring . Most times you will NOT see a rise in the water temp . as it happens so fast that the excess heat that is building in the cylinder can not transfer to the water jacket and to make the temp gauge go up . Myself i started noticing gas related problems as far back a 1975 when unleaded gas first came out . I have always played with engines since 1962 always wanting just a little more out of them and lets go fast. as nothing from the factory was good enough. Bought a new 73 Ford F250 4x4 with a 360 and a Automatic , what a dog and what a gas hog even back then when gas was 32 cents a gallon . Ok it had a problem wright off as the timing was not set and the power valve had a leak . The night i bought the truck and drove it the 32 miles home it sucked up 16 gallon . Took it back as i am not working on a brand new truck even though i was a master ford tech with the papers to back it up . OK so they fixed it sorta you could get 10 mpg but it was a DOG . well both myself and a buddy had almost twin trucks his was a 4 gear and mine a slush box , i had powerful steering his did not both red both 4.10 gears both with traction loc. well one Saturday morning while he and i were getting a little of the fur from the dog that bit us friday night we got this hairbrain idea that we would FIX this gutless dog syndrome of these two truck . setting over in the corner was a new in the crate ready to run just add oil starter , alt and fan 428 SCJ and on the shelve were all the parts to build a 10.5 to 1 390 with a C8ax6250 D cam and lifters and a set of 1.76 rocker and a hard to find and get 428 police 4bbl intake Mine got the 428scj and Mikie got the build 390 and we were done by 10 that night . Now the dog was dead and we now had two trucks that would flat smoke the tires like all four . And oh wait no more 10 mpg . The 428 was getting a whisker over 16 and the 390 was getting a bit better BUT we now were running hightest -105 octane verses 95 reg. back then it was only 3 cents a gallon more . And oh we were running Amacco NO LEAD . Life was good Till 75 and gas started to change and octane started down BECAUSE they started dropping the octane rating and engines were for cars and light truck compression ratios were dropping . The compression ratios were dropping back in 72 and unleaded fuels were in full force by 75 . The end of gas powered tractors ended with the 66 series, BUT ya could still get gas that would run then well till the early 90's and that is when the problems really started. Now some will not agree but they are not the ones that work on tractors for a living . Most of the guys on here are here to get answers to there problems and there are only a couple that worked on the for a living . Now there are some models of I H tractors that i have never laid a hand on and i am by no means and expert on them but the ones i have worked on and can go to the tool box and get every tool to do the job i am working on with out going back for more tools and get the job done wright the first time with out a come back then i would say that i know that tractor , and i have seen about every problem with that tractor SOFAR . Also along with my early days of engine building for lets go fast and what the cause was when something went wrong and ya end up with lots and lots of shell we say spare parts. I know what the problem is when i see damage inside and engine. Am i to old to learn sure hope not as no one has throwen dirt in my face just yet .

Yes we quit field working the gassers in 1978 I wouldn't want to try it on today's weak no lead gas. Even back then we were overhauling about every three seasons just pulled the snot out of them.

This round has been 12 years with now the second piston since the major rebuild . when i did the rebuild the last time we did things that normally don't get done on a tractor engine . Like the balancing of all rotating member cam was sent out and rebuilt and blueprinted . Head was C C'ed and portmatched . Block was line bored and the deck was trued and contour bores recut , dist. was rebuilt and recurved to the C291 spec.'s as we installed the change over kits to go from C263 to C291 . The carb was rejetted to the C291 jet with a little light polishing . Rockers were reground . Some governor work for faster response . Made for a huge improvement and was vary impressive .

What about using octane boost or higher octane aviation gas? Would either of these work?

Thanks for the following comments: "BUT back then the rebuild kits came thru with FORGED pistons . Now a new rebuild kit comes with a CAST Aluminum piston and a cast piston will not transfer heat from the top to the skirt as fast as a Forged piston will and it will swell more above the top ring due to heat . The difference between the skirt and where the rings set runs about .019 -.021 smaller then the skirt , and when these engines are working the heat from this new gas burns way hotter then the old gas did thus the cast piston can and will swell over .025 -.027 . and this will lead to a seized engine and this happens above the top ring." end quote..
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I had one of the 1700 or so new 1965 Corvettes sold to the public with the highest performance 396 ever built. One big reason advertized was that it had Forged pistons when the lower rated 396 in Camero had cast as well as other lower cost parts. Mine was factory Redlined at 6,400 and most took it much higher and for long periods of time. Now I know more why my 396 was considered one of best built high HP/high RPM engines GM sold to the public back in '65 thanks to your comments of heat transfer in cast vs forged pistons. It would be interesting to hear more on other designs in that '65-'66-'67 series of Corvette highest HP engines. ag

I had a Cub Cadet that behaved like that. It had a burned valve and the compression would go away after a few minutes.

Thanks to all that have replied to my question. This afternoon after Easter dinner I put a new set of plugs in it and new points and condinser. Then back to the field with her I went. I put her in third at 3/4 fuel and droped the field cultivator 45 min later finished the field with out a problem. I brought her back to the barn and hooked up the planter and back I went. I planted 20 acres at just under pto rpm in 4th gear and she never missed a beat. I don't know what helped the most the new plugs or a little lower rpm but it done the trick! Thanks again to all with all your helpful information, Ryan

Very good. See the comments on page 1 regarding fuel. Jim