Re: 706 dies under load question

Posted by The tractor vet on April 08, 2012 at 10:04:02 from (75.19.127.43):

In Reply to: Re: 706 dies under load question posted by RMF1066 on April 08, 2012 at 08:55:13:

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 .

Replies:

• Thanks tractor Vet agpilot 15:11:53 04/08/12 (0)

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