Rev Limiter in 8070 Question

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   My appologies now if this is dumb question, but I have been trying to research the answer on the Internet with no luck. We have a Allis 8070, 7060, and a 7045 on the farm. 
The 8070 seems to have a RPM limit in place, so no matter where the throttle is at, the RPM's on the tractor won't exceed 2500-2600 RPMS. 

If all the tractors have the same 426 engine, and the only difference is the type of fuel pump between the 8000 series and the 7000 series what is causing the RPMS to limit to 2500 on the 8070 and not the 7000 series tractor? 

Thanks for helping to answer this question that I have been wondering about. 

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tthams Members Profile Send Private Message Find Members Posts Add to Buddy List Bronze Level Joined: 18 Oct 2020 Location: Denison, Iowa Points: 140	Post Options Post Reply Quote tthams Report Post Thanks(0) Quote Reply Topic: Rev Limiter in 8070 Question Posted: 07 Jul 2021 at 8:16pm
	My appologies now if this is dumb question, but I have been trying to research the answer on the Internet with no luck. We have a Allis 8070, 7060, and a 7045 on the farm. The 8070 seems to have a RPM limit in place, so no matter where the throttle is at, the RPM's on the tractor won't exceed 2500-2600 RPMS. If all the tractors have the same 426 engine, and the only difference is the type of fuel pump between the 8000 series and the 7000 series what is causing the RPMS to limit to 2500 on the 8070 and not the 7000 series tractor? Thanks for helping to answer this question that I have been wondering about.

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DrAllis Members Profile Send Private Message Find Members Posts Add to Buddy List Orange Level Access Joined: 12 Sep 2009 Points: 21723	Post Options Post Reply Quote DrAllis Report Post Thanks(0) Quote Reply Posted: 07 Jul 2021 at 8:25pm
	First off, all tachometers aren't created equal. Your 8070 should see an actual 2650-2700 RPM at full throttle which is controlled by the governor which is built into the injection pump. Your 7060 should be 2500-2550 RPM top again controlled by the governor. Just because the hand throttle moves a little extra doesn't mean it will ever over-ride the maximum governor setting.

tthams Members Profile Send Private Message Find Members Posts Add to Buddy List Bronze Level Joined: 18 Oct 2020 Location: Denison, Iowa Points: 140	Post Options Post Reply Quote tthams Report Post Thanks(0) Quote Reply Posted: 07 Jul 2021 at 8:50pm
	Thanks thanks for the reply Dr. Allis. I never thought the tachs could be off by 300-500 RPMS. I know the tachs are feed by the alternator. Interesting enough the alternator just quit this week on the 7060. It will be interesting to see if a new alternator changes anything on the tach.

DrAllis Members Profile Send Private Message Find Members Posts Add to Buddy List Orange Level Access Joined: 12 Sep 2009 Points: 21723	Post Options Post Reply Quote DrAllis Report Post Thanks(0) Quote Reply Posted: 07 Jul 2021 at 8:55pm
	Tachometer powered by the alternator on the 7060. 8000 series is not. There is a chance someone has messed with your injection pump high idle settings and they may not be where they should be. There's also a chance your hand throttle cable or linkage isn't adjusted properly too. Edited by DrAllis - 07 Jul 2021 at 8:57pm

MACK Members Profile Send Private Message Find Members Posts Add to Buddy List Orange Level Joined: 17 Nov 2009 Points: 7664	Post Options Post Reply Quote MACK Report Post Thanks(0) Quote Reply Posted: 07 Jul 2021 at 9:40pm
	Both pumps have external screws to limit the RPMs. MACK

tthams Members Profile Send Private Message Find Members Posts Add to Buddy List Bronze Level Joined: 18 Oct 2020 Location: Denison, Iowa Points: 140	Post Options Post Reply Quote tthams Report Post Thanks(0) Quote Reply Posted: 08 Jul 2021 at 6:04am
	Thanks. This seems like an easy enough fix to try after I replace the alternator.

DrAllis Members Profile Send Private Message Find Members Posts Add to Buddy List Orange Level Access Joined: 12 Sep 2009 Points: 21723	Post Options Post Reply Quote DrAllis Report Post Thanks(0) Quote Reply Posted: 08 Jul 2021 at 6:09am
	Those adjustment screws don't change themselves. Throttle linkage issues can keep you from reaching full speed. If someone has changed the pump speed setting I imagine they wanted it faster. Make sure you're not diving into an area you have no business being in.

tthams Members Profile Send Private Message Find Members Posts Add to Buddy List Bronze Level Joined: 18 Oct 2020 Location: Denison, Iowa Points: 140	Post Options Post Reply Quote tthams Report Post Thanks(0) Quote Reply Posted: 08 Jul 2021 at 7:02am
	Great words of wisdom! My plan is to push the throttle open when the engine is off and see which screw it is hitting. I then plan on adjusting that screw only to prevent the throttle from going that high. This sounds like a simple fix in my head. If not I might take it to a shop and have them mess with it. I am sure this will make sense, but I have a teenage son that loves to help at the farm, and he is good help, but his motto is faster is better. He loves to open that throttle up and peg the tach no matter what I say. I like taking care of the equipment, but a teenager believes he always know more.

injpumpEd Members Profile Send Private Message Find Members Posts Add to Buddy List Orange Level Access Joined: 13 Sep 2009 Location: Walnut IL Points: 5087	Post Options Post Reply Quote injpumpEd Report Post Thanks(0) Quote Reply Posted: 08 Jul 2021 at 7:56am
	Sometimes the linkage gets adjusted so excessive pressure is put on the hi idle screw, and the boss on the throttle arm can break off, thus having no hi idle stop. If that were the case, re-adjust the linkage to pull it to the needed amount, and go from there. A low cost photo tach can be bought online and is very handy for verifying rpms.
	210 "too hot to farm" puller, part of the "insane pumpkin posse". Owner of Guenther Heritage Diesel, specializing in fuel injection systems on heritage era tractors. stock rebuilds to all out pullers!

tthams Members Profile Send Private Message Find Members Posts Add to Buddy List Bronze Level Joined: 18 Oct 2020 Location: Denison, Iowa Points: 140	Post Options Post Reply Quote tthams Report Post Thanks(0) Quote Reply Posted: 08 Jul 2021 at 8:23am
	I just bought a photo tachometer. I never knew they existed. I plan on trying it out. I am came across this thread with some good advice. https://www.allischalmers.com/forum/7060-throttle-cable-replace_topic180079.html I have a transmission oil temperature tach I plan on installing in the 7060 and 7045, and need a power source in the dash to use. I will look at the throttle linkage then and see if I can adjust it that way first.

LYNNMN Members Profile Send Private Message Find Members Posts Add to Buddy List Bronze Level Joined: 13 Sep 2009 Location: Garfield, MN Points: 118	Post Options Post Reply Quote LYNNMN Report Post Thanks(0) Quote Reply Posted: 08 Jul 2021 at 11:09am
	The 8070 i had i was told by someone to have RPM slowed down because that motor was prone to blow. Also turned HP down