Re: How to convert RM octane number to R+M/2

Posted by The tractor vet on October 08, 2012 at 08:17:59 from (75.24.0.62):

In Reply to: How to convert RM octane number to R+M/2 posted by AG48 on October 07, 2012 at 20:28:45:

We use the 93 in our 706 gassers or for that matter all of the gas tractors we have get the 93. This gas we get today is NOT the same as back then . And for you the machine shop got into your nickers on the valve seat as the valve seat were hardened from the factory .as for the lead in the gas Ammaco had lead free gas way back. The problem with running the 87 in the I H tractors is that the 87 burns way hotter at peak combustion , And it will plum melt pistons . Back in the day of these tractor were new gas was higher octane as reg. was 95 and hightest was 105+ . compression ratio's were in the 9.5 to 1 on a standard engine and on high performance engines or as we called them back them 4 bbl engines or dual quads or tri power the compression ratio's ranged from 10.5 and up . Pistons back then were forged not cast they would take heat better . Problems with gas tractors did not raise it's ugly head till in the late 80's . Back then there was only like 3-5 cents between reg . gas and hightest . Now we are talking 20 cents. Ok so it is 20 cents a gallon more and for us that is around 120-140 a year more for the 93 over the 87 . It takes three years of buying the 93 over the 87 to pay for one piston replacement not figuring in labor.The tractor will work all day long doing what it was designed to do running the 93 . The 93 burns cooler and longer then the flash burn on the 87 . Myself i have found that running the 93 in my S/MTA or Vernon's S/MTA we have less plug problems . Let me put it to you this way your not going to take a car or pick up with a factory STOCK engine of the day with a 9.5 to 1 compression ratio and run it today on 87 , you can squeak buy on the 93 IF you lose maybe 5 degrees of timing on the top end . I have played with engines now for over fifty years i know a little about them and what fuels they need. Back in the days of gas powered semi's like the 477-534 fords the 549 I H the big mack gas burners the white Mustangs they all ran the 105 hightest and they were low compression engines BUT working engines and they got HOT same as a tractor engine as it is not like a car engine that is just looping along . A tractor engine working is running at or darn close to full throttle or i should say the butterfly is over half open to wide open tiering to maintain the perset throttle setting . A gas engine gets hotter then a diesel . Go out on a cold morning and start your car then get out and open the hood and touch the exhaust manifold , Do that on a diesel . Put a pyrometer on a gasser and go make a round plowing and see how hot she gets then do the same with a diesel . all that heat has to some place . and it is suppose to go down thru the pistons and transfer into the cylinder walls , Today with what we get in the rebuild kits for pistons that heat is not carried away thru the cast piston fast enough like it did when the pistons were forged. Now we have to have gas that burns cleaner so now it burns hotter and faster. The old M's -450's were long stroke slow turn the new 4-6 cylinder engines are short stroke fast turn higher compression make more heat they can not transfer that heat fast enough to the cylinder walls . I have a collection of Clevite pistons out of a 706 due to 87 octane gas. Twice due to the fuel supplier bringing use the 87 gas when the 93 was ordered and once due to my friend's kid nit thinking and bought 87 at the gas station one time while we were at the away fields. I fought with one customer for a year over his 460 over gas and oil issues because he was so cheap that he would even spend two hours looking thru buckets of rust bolts and when i found one he would wire brush it and rethread it then wonder whay it took so long to make a repair to save 20 cents on a new bolt . He use the 460 gasser on a manure spreader twice a day it ran great started great Going down hill , but when he made the turn to come back up hill with half a load on she would start missing and start pulling down and start to seize up and quit . Then it would not turn over . let it set for fifteen twenty min and it would start up and it might make the end of the long field and maybe not . And about every month it would eat and exhaust valve . Because he would not buy the low ash oil . He was blaming everybody for his engine problems . Two I H dealers and two other guys , then he started on me . After the third time on the valve jobs two of which i ate and at that time i showed him the scored liners and burnt piston tops we put in 6 new pistons with new rings and were able to lightly hone off the aluim. piston deposits Did the valves over and i changed the oil to low ash and gave him a five gallon bucket to go . Put in a full tank of 93 and set him on his way . And i would go over each day and check the tractor and when it got low on fuel i made him go to the little gas station and fill it with the 93 and if it needed oil i made sure that he put in the low ash did this for three months and told him that if it went down after three months the next bill was on him. That was twelve years ago and it is still running each and every day . Oh and now he has a bolt bin with new bolts .

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