pmolitor Posted October 1, 2012 Share Posted October 1, 2012 I have a 1990 ch613 with an EM6-275L. What does it take to make this a 300 or a 350? Someone has already messed with the governor as it will rev to 2100 rpms but it still has no power after1750 rpms. I know that my 1979 rs with an endt676 300 runs well.... But I wouldn't think that it would walk all over the newer truck like I still have the brakes on. Quote Link to comment Share on other sites More sharing options...
slpwlker Posted October 1, 2012 Share Posted October 1, 2012 ever think it might be a low rpm motor? now does it run good up to 1750 and then die out? and how does it pull up till then? Quote Link to comment Share on other sites More sharing options...
smorse54 Posted October 1, 2012 Share Posted October 1, 2012 WE had 2 MH models with this engine,T2050 trans. and 5.55 ratio carriers.You ran the engine between 1000 and 1700 rpm.Anything over 1700 they had nothing,but if kept in the designed operating range they pulled well.The only drawback to this setup was the fast low gear,making it difficult to get 80K moving from a standstill.Steve Quote Link to comment Share on other sites More sharing options...
pmolitor Posted October 1, 2012 Author Share Posted October 1, 2012 Mine has 4.42 rears with eaton 9 speed. Not sure which 9 speed. The first 3 gears are realy low. I gross 63000lbs with tag trailer and excavator. With the rs I can run 70mph all day long. With the ch I drop to 45mh on the same hills. I wouldn't think 25hp would make such a difference. Quote Link to comment Share on other sites More sharing options...
oilburner Posted October 1, 2012 Share Posted October 1, 2012 I drove a 365 hp detriot once that was a low rpm engine, being used to a 2250 rpm i could not belive how weak the thing was. I was coplaining to a guy about how it had no power and he said i did not know how to drive it! well i was a little upset by his worlds so i said well hot shot driver how about a lesson, and he gave me one he said to never shift it over 1500 and and down shift it about 1250 or a little before it may seem like it ain't going to do it but it will. Now i thought about it and what he said so i tryed it and to my suprise that was the only way to get up to speed with it, i was always hitting the gov. before shifting and it was just a dog. The engine pulled better at 1500 then at 1800 why they would make a engine like thiss i don't know but after looking a a hp and touqe chart for the engine i could see that is were the touqe toped out, it made some more hp but the touqe would fall off after that. Now that was not a mack and may not help at all but it did make driving that old truck a little better hope this helps you out. Quote Link to comment Share on other sites More sharing options...
GearheadGrrrl Posted October 1, 2012 Share Posted October 1, 2012 Peak torque is at 1020 RPM, upshift at 1800 and downshift at 1000 and it'll work fine. Quote Link to comment Share on other sites More sharing options...
rsb502 Posted October 1, 2012 Share Posted October 1, 2012 25hp rating is a pretty big difference and its also two different engines with different emissions control stuff I bet the 90 has a puff limiter so it doesnt smoke like crazy and the 79 does not. As far as 2100 rpm goes, an E6 is played out at about 16-1700 dont run it higher youll just burn more fuel and kill the engine faster, those engines run best under 1600 I dont think I ever ran the old E6 300 I drove anything over 1650 to pull maybe a bit higher for road speed but thats it. Shift that thing around 15-16 it will run better, trying to shift it so far past its power band you are just coming back into the very top of it in the next gear so its not gonna do much either, remember old Mack engines are high torque rise low rpm engines, not 238 detroits. Quote "Any Society that would give up a little LIBERTY to gain a little SECURITY will Deserve Neither and LOSE BOTH" -Benjamin Franklin"If your gonna be STUPID, you gotta be TOUGH" "You cant always get what you want, but if you try sometimes you get what you need" Link to comment Share on other sites More sharing options...
theakerstwo Posted October 1, 2012 Share Posted October 1, 2012 25hp rating is a pretty big difference and its also two different engines with different emissions control stuff I bet the 90 has a puff limiter so it doesnt smoke like crazy and the 79 does not. As far as 2100 rpm goes, an E6 is played out at about 16-1700 dont run it higher youll just burn more fuel and kill the engine faster, those engines run best under 1600 I dont think I ever ran the old E6 300 I drove anything over 1650 to pull maybe a bit higher for road speed but thats it. Shift that thing around 15-16 it will run better, trying to shift it so far past its power band you are just coming back into the very top of it in the next gear so its not gonna do much either, remember old Mack engines are high torque rise low rpm engines, not 238 detroits. you got it right. Quote glenn akers Link to comment Share on other sites More sharing options...
pmolitor Posted October 1, 2012 Author Share Posted October 1, 2012 The 79 has a puff limiter and it works. Im shifting between 1550 and 1650. It has no power when crusing down the highway. I'll drop from ninth gear to seventh on the same hills I don't have to shift with the 79 6 speed. I've had three mack dealers tell me the internals are the same as a 300 to 350 em6. But they all tell me I have to do diferent things to acomplish that. One tells me injectors, the next tells me injector pump and turbo, and the last tells me all three. The rpms are ok. 1650 to 1700 at 70mph. I just want to maintain that speed when loaded like the 79 can. Quote Link to comment Share on other sites More sharing options...
oilburner Posted October 2, 2012 Share Posted October 2, 2012 The 79 has a puff limiter and it works. Im shifting between 1550 and 1650. It has no power when crusing down the highway. I'll drop from ninth gear to seventh on the same hills I don't have to shift with the 79 6 speed. I've had three mack dealers tell me the internals are the same as a 300 to 350 em6. But they all tell me I have to do diferent things to acomplish that. One tells me injectors, the next tells me injector pump and turbo, and the last tells me all three. The rpms are ok. 1650 to 1700 at 70mph. I just want to maintain that speed when loaded like the 79 can.I am sure that the timing is one of the biggies, and the injectors, but the rest i'm not sure about, but i will say this the old 300 tiptrubine engine will do there thing about anywhere in the rpm range, from 1000 to 2100 they pull great, and i would rather drive one of the 300 or 350 than any of the late model stuff as long as they are hot and have a good working pryometer in it don't want to turn it in to toast, best old engine mack ever made in my opinion. Quote Link to comment Share on other sites More sharing options...
Lmackattack Posted October 2, 2012 Share Posted October 2, 2012 Fried of mine turned a 300 low rpm motor into a 2100 rpm motor. That thing drank fuel very fast but pulled better than before. All he did was have a pump shop re cal the pump and set it to a standard 300 timing spec. 1 Quote Link to comment Share on other sites More sharing options...
David Posted October 2, 2012 Share Posted October 2, 2012 You may also have a difference in final drive ratio. Quote Link to comment Share on other sites More sharing options...
pmolitor Posted October 2, 2012 Author Share Posted October 2, 2012 I was wondering if I could just get the pump recalibrated. From what I can tell all the internals are the same. it should be better on fuel than the 79 due to having an overdrive. Quote Link to comment Share on other sites More sharing options...
rsb502 Posted October 2, 2012 Share Posted October 2, 2012 You can have the pump set up for more power, if I remember right to go to the same everything (stock parts)as a 300 you have to change, the injectors, turbo, pump settings, and....... I think thats it actually. I am sure just bumping the pump up will get you more power, you can find a turbo from a 300 or 350 and swap it to get more air to keep your temps down with a hot pump it also makes more power by keeping the air/fuel ratio closer to where it should be. I will say this, dont get greedy with the pump if you have it redone, you can go way up on fuel and not make a lot more power you will just get everything hot on hills and smoke like crazy. Quote "Any Society that would give up a little LIBERTY to gain a little SECURITY will Deserve Neither and LOSE BOTH" -Benjamin Franklin"If your gonna be STUPID, you gotta be TOUGH" "You cant always get what you want, but if you try sometimes you get what you need" Link to comment Share on other sites More sharing options...
pmolitor Posted October 3, 2012 Author Share Posted October 3, 2012 300 to 350hp would be great. I bought this truck so I could help my brother in his business 2 hours away. But not being able to maintain 55 to 60 sucks. Guess I need to find a donor engine. Quote Link to comment Share on other sites More sharing options...
Lmackattack Posted October 3, 2012 Share Posted October 3, 2012 The big over drive can hurt your mpg. Most of the low rpm engines I saw had a T2060,2070. Behind them. Top gear was .60 over drive. And had. 5.02-5.73 rears. This was a common dump truck spec around here. If you bump up your pump to 2100 rpm and don't Chang the gearing, the engine will burn more fuel trying to keep up the fast drive line speeds. It sounds silly but that's how it works. There is a fine line with to much overdrive and not having the power to pull it.If I recall my friend never changed anything but the pump timing and had it calibrated for a 2100rpm maxidyne. I remember i could run it out of fuel in about 11 hrs. and his other truck of simmilar spec still had 1/4 tank left.!That's my .02 Quote Link to comment Share on other sites More sharing options...
pmolitor Posted October 3, 2012 Author Share Posted October 3, 2012 I've got 4.17gearing right now. I have a spare set of 4.42s. At 70mph I'm turning 1600 to 1700 rpm. Droping gears maxes me out to 1800rpm and still won't maintain. don't know what trans I have. It is a eaton 9 speed and I can start in 3 gear loaded without slipping the clutch. Quote Link to comment Share on other sites More sharing options...
slpwlker Posted October 3, 2012 Share Posted October 3, 2012 May try changing the ratio's one weekend and see how it does. Why take off in that taller gear loaded. just putting more strain on your driveline. Quote Link to comment Share on other sites More sharing options...
pmolitor Posted October 3, 2012 Author Share Posted October 3, 2012 I would need to go to 3.87 gears to make the low holes better I think. I usually start in 2nd and skip gears when empty. When loaded I start in first. I don't need to break things. Just tried the 3rd gear thing a coulple times to see how it performed. Quote Link to comment Share on other sites More sharing options...
slpwlker Posted October 3, 2012 Share Posted October 3, 2012 I would need to go to 3.87 gears to make the low holes better I think. I usually start in 2nd and skip gears when empty. When loaded I start in first. I don't need to break things. Just tried the 3rd gear thing a coulple times to see how it performed.Your going in the wrong direction. The higher the number the lower the gearing. a 3.87 will give you better top end and worse low end. just my $.02 Quote Link to comment Share on other sites More sharing options...
Lmackattack Posted October 3, 2012 Share Posted October 3, 2012 sounds like its gearedI've got 4.17gearing right now. I have a spare set of 4.42s. At 70mph I'm turning 1600 to 1700 rpm. Droping gears maxes me out to 1800rpm and still won't maintain. don't know what trans I have. It is a eaton 9 speed and I can start in 3 gear loaded without slipping the clutch.if your only turning 1700RPM at 70MPH your truck has real tall gearing to keep the factory designed 285L in its sweet spot. When you re cal the pump to a 2100 RPM 300 You will have more top speed but not the needed HP to pull it to 2100rpm. Like I had said before the idea with the 285L and 300L were slow RPM / fast driveline speed. most of the 300L I drove were max 62 MPH trucks. My advice for you would be to first find what trans ratios you have then gear it to run 1800-1900RPM at your desired highway road speed. just be carefull because a 300 may be able to pull a load to 60MPH with little trouble but 70MPH may be flat footed. Quote Link to comment Share on other sites More sharing options...
pmolitor Posted October 3, 2012 Author Share Posted October 3, 2012 It has 4.17 gears with 11r 24 tires. I don't mind the low rpms cuz the truck sips fuel. Just don't like droping 20 mph on hills when my 79 will accelerate up them with the same load. Does the 300L have more torque.Is there a 350L? I'll look tknight and see what trans is in the truck. Thanks for all the info. Quote Link to comment Share on other sites More sharing options...
rsb502 Posted October 3, 2012 Share Posted October 3, 2012 I would put the 4.42 rears in it, almost every dump truck here has 4.42 with an eaton OD trans and 4.64 with a Mack OD. I know I ran an R model tri axle dump (actually several different ones) with 350 E7 and 8ll trans with 4.42 and that seemed to be the best set up you could get for what we did, we hauled 74000 on those trucks and they ran 70-74 mph with it, slowed down on hills and 74 was 2100 rpm wound out so we tried to run em around 16-1800 and they ran great for several hundred thousand miles. I can say if it was mine and I had 4.42 rears there, they would already be in it you will be amazed at the difference in power going from 4.17 to 4.42 it doesnt sound like much but the torque multiplys a lot. 1 Quote "Any Society that would give up a little LIBERTY to gain a little SECURITY will Deserve Neither and LOSE BOTH" -Benjamin Franklin"If your gonna be STUPID, you gotta be TOUGH" "You cant always get what you want, but if you try sometimes you get what you need" Link to comment Share on other sites More sharing options...
pmolitor Posted October 4, 2012 Author Share Posted October 4, 2012 Sounds like I got a winter project. I need to rebush the neway suspension anyways. i've only had this truck for a month....wish I could have drove it loaded before I bought it. Quote Link to comment Share on other sites More sharing options...
pmolitor Posted October 4, 2012 Author Share Posted October 4, 2012 Didn't realize that my avitar was a pic of my 79RS. I cant get pics of my CH to transfer from my dumb phone to the site. Quote Link to comment Share on other sites More sharing options...
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