bberry

Member
Hi I have a 770 I've posted on here about before. It has stock internals, but hotter coil, tuned timing, and a tuned carb. I recently took about 7 rings out of the governor spring. I don't have a working tach right now but I'm pretty sure I'm conservatively free revving somewhere between 2500 and 3000revs, maybe even a bit higher. I was wondering if someone would know a ballpark of how much horse power iI might be running... Before anyone starts in with Tue nay saying I have fabbed both a scatter shield for the clutch and fan for safety.it is a trusted tractor and well maintained I wouldn't have braved the modification if I wasn't sure no one would die... Thanks for any help
 
rpms do not add hp,only tire speed which will pull more,but a tuned carb with no mods to cam or engine will just produce near stock hp.A fabed shield????????????
 
Yes a steel scatter shield. I don't mean to sound half cocked here... But a faster turning motor produces more rotating inertia which in turn provides more power. Physics 101 I do realize that addind cubes and compression adds power as well. However if what you're saying were to be completely correct, no one would be disabbling governors in order to to limit restrictions of air and fuel during heavy loads. I'm not looking for an answer of 120 hp just wanting to know how much someone who may have done this gained. I'm not new to this concept, I added 12hp to my 1850 by adding 400 more revs. Dyno certified... Now since my timing is also matched along with proper carb adjustment hp can follow without other modifications... And the reason for the shield is bc I'm spinning a 55 year old flywheel design at an extra 1000 rpms which adds about 4 times the centrifugal forces to the entire part along with a single plate stock clutch engaging at another 1000 maybe rpms than it was designed for...
 
I think a little math lesson is in order.

HP can not be measured directly, it is calculated from torque and rpm which can be measured directly. The equation is HP=(tq*rpm)/5252.

On most if not all engines, peak torque and peak HP happen at different RPMs, peak torque happening first followed by peak HP as RPMs increase. After the torque peaks it begins to fall off, on a normal governed engine peak HP is just below high idle rpm.

On your 770 depending on how you are tuned, timing, how much air the carb can flow, increasing the RPMs may or may not get you "extra" HP, only the dyno will tell you. If you want more power at the same RPMs you need to at the minimum increase your compression ratio, after that you start getting into different cams, more displacement, head work, etc..... Your extra rpm will get you moving faster, which generally helps, the faster you're going when the pan drops the farther you'll go, but only if your engine hangs in there.

Your thoughts on a 55 year old flywheel design isn't the issue, clutch/flywheel designs haven't changed much. The material it's made out of and its condition would be my biggest concern. That's why a lot of pulls want to see SFI clutches in tractors, that's why a lot of pulls are strict about RPMs.

Is your 1850 diesel or gas? A 12 hp increase with a 400 rpm increase isn't that impressive. If you picked 12 hp at the same rpm you'd have my attention because you would have increased your torque by a noticeable amount.

To answer you question more directly I tuned my friends 770 with some mild work, nothing crazy. At stock rpm we started out at 60hp and by making some adjustments we picked up 10 hp and made it hang in better at the end of the track.
 
an other post says what I do,engine needs to be able to hang in there with larger load, tuned stock will not do that.your engine will go to high torque rpm or under with load applied,a dyno only simulated that load,in a pull it keeps increasing,keeps coming on fast!!!!!!! I agree,people turn rpms up for several reasons,but in my 35 yrs of watching,participating,stock is stock and every dyno is different,must be tuned correctly to achieve normal hp numbers,a number makes no difference,how it pulls is all that matters,balance,tires,pressure,where you drive,hitch height,track soil type,your ability to read the track,timing,(very important),gearing ect.ps,you need the shield AND a steel fly wheel !!!!! I was last puller in a stock class,first puller in the next "OPEN" class,backed up.hooked again went 60 feet more with no changes except for 30% increase in rpms,but my engine stayed up there the whole pull,Good luck.In my opinion,concentrating on hp numbers distracts from how the tractor pulls,make it do what you want it do.
 
You need to put it on a dynamometer to measure your torque and then calculate your horsepower at the RPM you run at.

As stock your tractor was tuned and rated for maximum horsepower and maximum fuel efficiency at 1750 RPM. The peak torque was below that, maybe around 1200 to 1300 RPM. At high RPM your torque and fuel efficiency may drop off quite a bit. Adding 50 to 60 years of wear on the cam and valve train won't help.

Talk to a cam shop about re-grinding your cam and adjusting your ignition timing to match the RPMs you want to run at. Oliver 1600, 1550, and 1555 specs and parts might also help.
 
Thank you for your help. I was thinking about a cam. Maybe later this year ever looking into a new crank if a stroker crank is available do you know of anywhere? I took some values or ground speed with my tire size and figured via GPS I must be turning about 2700 revs
 

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