farmall M motor build update!!

V8S10

Member
hey guys got the 110 race fuel in the M this morning to break her in on the dyno..runs so much better and doesnt diesel when you shut it off and it doesnt pop spit or bang when you open it up... i tried using the 35 venturie and it ran well but the choke had to be on 3/4 of the way to run good other wise when you would run it wide open it would rev up and down a little bit? i got 65 horse on the dyno with it the way it was but the choke was on and it would run perfect? :) but im going to try a smaller venturie like you guys said to so hopefully it will fix the problem?? what do you guys think?? i have a 27 and a venturie that doesnt have any numbers on it but its bigger then the 27 by a little bit? i have a 656 sitting in the yard and i think thats got a 29 maybe ? what would work ?? thanks guys! ill keep ya updated
 
Start small. dyno run. Tune. Adjust. Then go one size bigger and do the same. When you go too big it will start to run odd and be hard to tune.
 
give it more fuel so your not using the choke to reduce the air to a stoich that internal combustion engine will run on
 
29 will give you a couple more hp but the 27 will give you more grunt . you should get about 70 or 71 that's what mine got with near the same setup . set it at 25 degrees at 1600 rpm . grunt is what you need in tractor pulling .
I had to open the main jet a bit to get enough gas . are you sure your getting enough gas ?
 
Sounds like you just need more gas, not less air. The more air-gas you get in there the more hp! Vic
 
i tried a venturie tht didnt have a number on it but was a little bigger then the 27 and it solved the problem and im getting about the same horsepower as i did with the 35 venturie! it lugs really good and sounds great on the dyno!very happy with the results sofar! i would think the main jet in the carb would be big enough since the bowl was of a 6cylinder 301 combine engine? when you say 70 horse your meaning at 540? or what its got for horsepower when its lugged down just about before it dies? my dynos rpm gauge is all messed up as sometimes the guage doesnt come back and at peak rpms on a tractor it bounces all over sometimes and then sometimes it doesnt so idk if i trust what it reads or not? the other gauge seems to work fine!
 
(quoted from post at 09:20:54 05/19/13) i tried a venturie tht didnt have a number on it but was a little bigger then the 27 and it solved the problem and im getting about the same horsepower as i did with the 35 venturie! it lugs really good and sounds great on the dyno!very happy with the results sofar! i would think the main jet in the carb would be big enough since the bowl was of a 6cylinder 301 combine engine? when you say 70 horse your meaning at 540? or what its got for horsepower when its lugged down just about before it dies? my dynos rpm gauge is all messed up as sometimes the guage doesnt come back and at peak rpms on a tractor it bounces all over sometimes and then sometimes it doesnt so idk if i trust what it reads or not? the other gauge seems to work fine!
By mechanically closing the choke you made the 35 venturi the size of the same venturi that it would run on with choke open and yes the same power . If you run the big venturi with enough gas to not have to close the choke mechanically you will produce more horsepower as Vic and others have said.
 
alright well ill see what i can do then opening up the main jet would be what to do right ? when i had the 35 venturie in the carb i tried adjusting the main fuel load screw out bit it made no difference and would still need the choke on... what would be the size to open the jet to if i have to make it bigger? it has the big metering stem in it with the i belive 6 big holes in it .. i pulled out a spark plug today to do a compresion test again and i got 170 psi , the plugs we a blacker and had a little hint of almost a brown color ?
 
yes mine is 71 at 540. don't know why your cylinder pressure is so low , mine is 220 and probably is making the difference in hp . there could be a difference in dyno mine is right with a friends and that's all the comparison I have .
 
well ive got a friend with another dyno we might try later in the season... im gonna keep breaking it in the way it is... the cylinder presure was 130 after like 20 minutes of running and now after about 2 ta 3 hours of running its around 170? do you think it will keep going up ?
 
I don't think so , are you sure your ring gap was within specs when you built the engine ? should have been about 3 to 4 per inch but there's a spec on it . you should have put each ring in the cylinder and checked the gap on it .
 
good to talk to you Mitch , I'll give you a call and catch up tomorrow . your not working any crazy hours are you ?
 
not sure? it was the rings that came with the pistons in a kit? i believe i got them from ag parts!
 

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