Mandrewoid Posted December 11, 2023 Share Posted December 11, 2023 Following on a thought I had in a previous thread. I know a few people with Cummins pickups( same fuel pump as my E6-275L. ) Who have replaced their governor springs with higher RPM springs, and they say it really awakened the truck quite a bit. I know these trucks were made with the L destination for low rpm in order to be more fuel efficient. Fortunately for me in my off-road application the fuel economy is pretty much irrelevant, what matters to me is having the widest possible power band. There are times where I can definitely tell that the pump is de-fueling due to high RPM, but I'm not talking 2000rpm, I'm talking about anything above 1550rpm the engine starts to work less hard. It is my understanding that higher RPM governor springs will help to solve this problem. Obviously I'm not going to go 4000rpm like the truck guys do. But I am thinking perhaps a stock spring from a Cummins would work in the Mack application. Or possibly the spring out of an E6-350, or maybe even just a 285 non-L Does anyone have experience with this? In the Cummins, the fuel pump is mounted with the governor springs on the outside so it is a 10 minute job. On the Mack, it seems to be on the inside, so the fuel pump may have to come off... Looks like the stock Cummins is set to 2800rpm. That should do nicely, as long as I don't actually allow the engine to over-rev Quote Link to comment Share on other sites More sharing options...
JoeH Posted December 11, 2023 Share Posted December 11, 2023 2100 is your maximum governor target. The precursor endt676 motor which is pretty much an E6 with a 2 valve/cylinder head, allowed 2300 when shifting, but was governed around 2100. 1 Quote Link to comment Share on other sites More sharing options...
JoeH Posted December 11, 2023 Share Posted December 11, 2023 Are you sure you can't back off a travel stopper bolt? Much like the idle adjustment screw. 1 Quote Link to comment Share on other sites More sharing options...
JoeH Posted December 11, 2023 Share Posted December 11, 2023 I would not put a 2800rpm give spring anywhere near this motor, all it takes is one screw up and you're floating valves and smashing them against pistons and now you're into needing that spare motor. 1 Quote Link to comment Share on other sites More sharing options...
Mandrewoid Posted December 11, 2023 Author Share Posted December 11, 2023 You can still adjust the high idle stop. I don't want my engine to actually turn 2800, I just want full fuel all the way to 2200. The notice on the sun visor says it's good for 2300rpm. I'm sure people have pushed that a bit and gotten away with it too. I have found that on an incline of any sort, I can't get above 1700rpm, then when I try to shift I'm down to 900 by the time it gets in gear. Then I'm turning the sky black for 3 minutes before we get some boost and some RPM going. If I could shift at 2000 or 2100 it would be much better for everyone especially the guys behind me. And if I can maintain 2000rpm in field in second gear that would be nice too. The governor springs from my spare motor would be guaranteed not to hurt it, but not sure how much of an improvement it would actually be. Quote Link to comment Share on other sites More sharing options...
67RModel Posted December 11, 2023 Share Posted December 11, 2023 I thought about this at one point too. These engines are governed at 1750 for fuel consumption / noise driver fatigue reasons. If you could wind them up to 2100 you could catch the next gear at a higher rpm....say like 1200 rpm. The difference in horsepower between 900 rpm and 1200 rpm is about 65hp, which is not an insignificant amount. Another option would be to install a Jake Brake and shift using the Jake. I think this a better option since a Jake Brake is a much more desirable thing to have than a 2100 rpm governor but obviously its much more costly. I guess you could have both as well. The attached picture is for a Maxidyne E7-275. I assume the numbers are similar for an E6.... Quote Link to comment Share on other sites More sharing options...
MACKS Posted December 11, 2023 Share Posted December 11, 2023 I have a low rpm engine in my 96 cl,only supposed to hit 1800 but it revs way over that,not sure how high but easily runs past 21-2200,I’m certain the pump was never worked on just the high idle screw looks to be turned in pretty far,with a twelve speed it shifts perfectly at 1800 and has a ton of power after the shift at around 1500-1600.. Quote Link to comment Share on other sites More sharing options...
MACKS Posted December 11, 2023 Share Posted December 11, 2023 What transmission do u have,sounds like u have the wrong gearing for that engine? Quote Link to comment Share on other sites More sharing options...
Mandrewoid Posted December 12, 2023 Author Share Posted December 12, 2023 2 hours ago, MACKS said: What transmission do u have,sounds like u have the wrong gearing for that engine? Maxitorque 8 speed. Everything on the truck is factory. It used to be a cement mixer. Just made for local city driving. Now I'm taking it all sorts of off-road up very steep slopes trying to keep my speed and engine rpm up in order to unload my load. Overall GVW is pretty similar to the mixer configuration, because the tank has a very heavy subframe and I've got 5990 USG of manure 1 Quote Link to comment Share on other sites More sharing options...
JoeH Posted December 12, 2023 Share Posted December 12, 2023 (edited) Have you tried backing off the high idle screw? That's how we upped one of our endt676 motors from about 1800 to 2100... Edited December 12, 2023 by JoeH Quote Link to comment Share on other sites More sharing options...
MACKS Posted December 12, 2023 Share Posted December 12, 2023 7 hours ago, JoeH said: Have you tried backing off the high idle screw? That's how we upped one of our endt676 motors from about 1800 to 2100... That’s what I would first and check your linkage make sure your getting full throttle,check shut off cable also… 1 Quote Link to comment Share on other sites More sharing options...
mrsmackpaul Posted December 12, 2023 Share Posted December 12, 2023 Okay, simple answer is pull some shims out of here The round doo hickie with 4 bolts thru it This will put more tension on your governor spring so the motor revs harder before the rack starts to close the pump off Pure WAG (wild ass guess) from a dumb ass but I reckon you'll see a result Paul Quote Link to comment Share on other sites More sharing options...
JoeH Posted December 12, 2023 Share Posted December 12, 2023 17 hours ago, Mandrewoid said: You can still adjust the high idle stop. I don't want my engine to actually turn 2800, I just want full fuel all the way to 2200. The notice on the sun visor says it's good for 2300rpm. I'm sure people have pushed that a bit and gotten away with it too. I have found that on an incline of any sort, I can't get above 1700rpm, then when I try to shift I'm down to 900 by the time it gets in gear. Then I'm turning the sky black for 3 minutes before we get some boost and some RPM going. If I could shift at 2000 or 2100 it would be much better for everyone especially the guys behind me. And if I can maintain 2000rpm in field in second gear that would be nice too. The governor springs from my spare motor would be guaranteed not to hurt it, but not sure how much of an improvement it would actually be. Remember this is an old truck. Things are beyond broken in, and fatigue does set in with use. Our 1979 has a weak valve spring that kept letting a spacer disk for the Jake brake that rests on the valve stem pop out. Only way that can happen is through valve float. If the springs aren't stiff enough anymore then they won't keep tension on the rockers and pushrods. Mack engineered these engines for maximum performance and longevity. These engines typically don't hold up to being pushed passed where Mack set them to. I wouldn't take the chance on putting anything in there that could let it go passed 2100. Quote Link to comment Share on other sites More sharing options...
mechohaulic Posted December 12, 2023 Share Posted December 12, 2023 4 hours ago, MACKS said: That’s what I would first and check your linkage make sure your getting full throttle,check shut off cable also… my thoughts exactly. slight adjustment to max RPM screw can be done. with fuel peddle check max RPM. remove pin from fuel pump disconnecting linkage manually run up RPMs . check any difference. cab mount set up while driving may be cutting full fuel . I wouldn't be changing internal springs. check all fuel linkage pins . have seen a Mack engine run away (title usually held buy DD). scared the heck out me. fuel shut off cable has been know to keep an engine from full fuel as stated. Quote Link to comment Share on other sites More sharing options...
Mandrewoid Posted December 12, 2023 Author Share Posted December 12, 2023 4 hours ago, mechohaulic said: my thoughts exactly. slight adjustment to max RPM screw can be done. with fuel peddle check max RPM. remove pin from fuel pump disconnecting linkage manually run up RPMs . check any difference. cab mount set up while driving may be cutting full fuel . I wouldn't be changing internal springs. check all fuel linkage pins . have seen a Mack engine run away (title usually held buy DD). scared the heck out me. fuel shut off cable has been know to keep an engine from full fuel as stated. In neutral I've got 1990RPM. Under significant load I've got 1800. My understanding is that the e6-285 has different governor springs than the e6-275L but otherwise should contain identical internals. The low rpm version was designed for fuel savings, which is no longer an important issue for this vehicle. Time savings and performance is worth it for us. The people that do extreme truck pulls with these, are there any of those guys here? On 12/11/2023 at 2:10 PM, JoeH said: Quote Link to comment Share on other sites More sharing options...
JoeH Posted December 12, 2023 Share Posted December 12, 2023 Extreme pullers aren't stock by any stretch. Tons of money dumped into special parts. Running a motor like that you get a few hard runs and you destroy things. 1 Quote Link to comment Share on other sites More sharing options...
JoeH Posted December 12, 2023 Share Posted December 12, 2023 Can smarter heads than mine tell if this is the high idle adjustment screw? Quote Link to comment Share on other sites More sharing options...
Joey Mack Posted December 12, 2023 Share Posted December 12, 2023 yes it is.. the slotted screw adjust engine speed and the outer nut is the jam nut, for lack of better words.. you loosen the jam nut, then set the idle speed with the slotted screw then,,, when your happy,,, hold the slotted screw with the screw driver, and lock it down with the outer nut.. I used to use a photo tach and reflective tape on the balancer to set RPM... sure wish I had that tool today... Jojo Quote Link to comment Share on other sites More sharing options...
JoeH Posted December 13, 2023 Share Posted December 13, 2023 So all Mandrewoid needs to do is turn that screw a turn or two one way or the other to get to 2100 rpm I figure. 1 Quote Link to comment Share on other sites More sharing options...
Joey Mack Posted December 13, 2023 Share Posted December 13, 2023 no thats the low idle screw.. i guess you are looking for a stopper.. Is the throttle linkage adjusted correctly? Quote Link to comment Share on other sites More sharing options...
67RModel Posted December 13, 2023 Share Posted December 13, 2023 (edited) 1 hour ago, Joey Mack said: I used to use a photo tach and reflective tape on the balancer to set RPM... sure wish I had that tool today... Jojo Harbor freight makes one that works very well for like $35. It’s nice to have around. It comes with the reflective tape. https://www.harborfreight.com/digital-photo-sensor-tachometer-66632.html Edited December 13, 2023 by 67RModel 1 Quote Link to comment Share on other sites More sharing options...
Joey Mack Posted December 13, 2023 Share Posted December 13, 2023 Holy Crap!!! I had no idea they sell one.. I am going to buy one ASAP.. Thanks bud.. Quote Link to comment Share on other sites More sharing options...
mechohaulic Posted December 13, 2023 Share Posted December 13, 2023 1 hour ago, Joey Mack said: yes it is.. the slotted screw adjust engine speed and the outer nut is the jam nut, for lack of better words.. you loosen the jam nut, then set the idle speed with the slotted screw then,,, when your happy,,, hold the slotted screw with the screw driver, and lock it down with the outer nut.. I used to use a photo tach and reflective tape on the balancer to set RPM... sure wish I had that tool today... Jojo you will have soon Jojo ; give me some time .worked on a screening plant today changing screens , owner came over said " weren't you here when this screener was new "? yes I was ;; "kids today don't know how to repair they just change parts; . 72 yrs old climbing on a screening plant to remove /change screens . ARE YOU FU--- serious, Quote Link to comment Share on other sites More sharing options...
mechohaulic Posted December 13, 2023 Share Posted December 13, 2023 3 minutes ago, Joey Mack said: Holy Crap!!! I had no idea they sell one.. I am going to buy one ASAP.. Thanks bud.. NO DON'T spend give me a day . have magnetic OTC. it's yours 1 Quote Link to comment Share on other sites More sharing options...
Joey Mack Posted December 13, 2023 Share Posted December 13, 2023 I cant thank you enough.. I wish I had one when I built the 3 John Deere 3179's.. I did it by ear, but I would have liked to set them to spec, and hear how they ran at the correct low idle.. I know that when I crank up the ENDT 673 in my shop, I will need it.. Quote Link to comment Share on other sites More sharing options...
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