Turn Up 237

[niceguypmp3]

I have a 198-something 237 and I was wondering if anyone could help me to know how to turn it up a bit. the truck is pretty doggy and we would like to have some extra power. From what i've read/heard but without exact details, is that under a small cover on the pump is 3 screws, one for low idle, one for high idle, and the other is the mixture/power screw. Could anyone help me with this? I would Really appreciate it.

[fjh]

I have a 198-something 237 and I was wondering if anyone could help me to know how to turn it up a bit. the truck is pretty doggy and we would like to have some extra power. From what i've read/heard but without exact details, is that under a small cover on the pump is 3 screws, one for low idle, one for high idle, and the other is the mixture/power screw. Could anyone help me with this? I would Really appreciate it.

Could you varify which fuel system you have rob bosch or american bosch?

[niceguypmp3]

I'm assuming that the pump will say which system it is... correct me if i'm wrong. I'll try to check today or this weekend. If there is another way to know by how it looks or something, just let me know if you could. Thanks!

[NoClueJoe66]

This is how Otherdog turned up the fuel on the F model Mack he drove. Seemed to work well, note the second picture is what the end result where.......And before you ask the second picture is what the dash boards looked like in all F models. I swear it is....

[b61mack]

I have a 198-something 237 and I was wondering if anyone could help me to know how to turn it up a bit. the truck is pretty doggy and we would like to have some extra power. From what i've read/heard but without exact details, is that under a small cover on the pump is 3 screws, one for low idle, one for high idle, and the other is the mixture/power screw. Could anyone help me with this? I would Really appreciate it.

First thing you need to do is make sure the puff limiter is unhooked.

[other dog]

First thing you need to do is make sure the puff limiter is unhooked.

It was in this F-model-that's a carton of non-filter Pall Malls on the dash. "Hippy" was driving this truck when I turned it up for him. He got it when I got a new one and said it wouldn't run, but I knew better.

[niceguypmp3]

ok, First off... when we got the truck then it was OMG gutless. I found out about the puff limiter and i unhooked it, well, now it will smoke and has probably 30% more power. But it's still really gutless. I just went out and looked at the motor/pump and it is an '81 237 with a robert bosch pump on it. Does that help?

[MACKS]

You guys kill me,you can't get blood from a stone,leave it alone if you want more power buy a bigger motor.The 237 is a sweet running motor and maybe the best motor mack ever built,thats just my opinion and I ran a 237 for a number of years and was very happy with it's performance.

[Rob]

Now you have the fuel for the low end power you desire and you need the air to burn that fuel. Go with a larger turbocharger and install a pyrometer in the dash and the key: USE IT!! You also need to be aware you may shorten the life expectancy of the engine by asking more from it.

As Macks said; The 237 is a sweet running motor and maybe the best motor mack ever built.

[MACKS]

Niceguy,please don't be offended by my previous post ,I was just stating a fact .

[NoClueJoe66]

All joking aside the 237 is a great motor, just like the 300.

[niceguypmp3]

MACKS, when I first read your post, i was kinda shocked, but figured you are allowed to have your own opinion. I realize that turning up any motor for more power can possibly reduce its life expectancy. I'll explain to you how it is: It is in an '81 Mack econodyne (is what it says on the side of the hood). The truck is set up to carry the roll off boxes like waste management uses. Empty weight of the truck is almost 31k. Empty on the highway the truck can't even hold its speed up hardly any hills. What sucks is that the way it is geared, the truck is in high gear and maxed out on rpm's and can hardly hit 55-58 mph according to my GPS at which the trucks speedo is reading 63 which is definately wrong. Now if i get about 20k in the box and then i'm around 51k or so, it really slows it down, that 237 has what, 220-225 hp or something like that. Just on the interstate here on I-35 in southern iowa and at that weight there are hills that I hit the bottom maxed out at around 55 and when I get to the top then i will be anywhere from 30-42 mph and if it gets below 30 then I gotta downshift a gear because its really luggin the engine. It won't go above 30 mph in 4th gear on the high side. This thing must be geared for low speed around town driving/hauling. But I have roughly figured that it gets around 6-6.25 mpg which doesnt sound that bad. I figured if i can get even 20 or 30 more horsepower easily, that might help a bit on the highway. I don't want another 100 horsepower which would not be easy or cheap. Thanks for any help guys. I love this site.

[NoClueJoe66]

If you think that things underpowered you would die driving a 3126 Cat cause they absolutely suck. The truck I drive is a '94 chevrolet 6500 w/a 8LL, and i so underpowered that it gets down right ridiculous. It has a Moffett Mounty lift on the back of it so thats a extra 4000 pounds which dont really help at all. The first pic is just to show you the truck, the second pic is a load i took to a marina we deliver to frequently. On one hill I skipped 2 gears the first downshift and dropped 2 more gears puttin me into second gear before i reached the top. That's at a 45 mph run at the hill. I'd love to have a R-model with a 237 or 300 just toget away from that damn 3126. A least the mack has the torgue behind it.

[HK Trucking]

It is in an '81 Mack econodyne (is what it says on the side of the hood).

I thought you said it was a 237 Maxidyne?

Is it, or isn't it?

[Maxville Truck]

niceguypmp3, the puff limiter does just that, it limits the fuel until you start to build boost, in reality what it is, is an old school way of limiting full fuel (versus a computer waiting for boost), until you have more air to burn it, it works in conjuction with intake pressure through a "reverse relay".

The reversing relay provides an output pressure signal to the air cylinder that decreases in direct proportion to the increase in engine manifold pressure. Therefore, the maximum fuel which can be delivered to the engine is controlled by the Puff Limiter air cylinder and not by the injection pump governor during low manifold pressure conditions. Reversing relay is mounted directly to the engine inlet manifold

THat is out of the mack manual.

Enough of that...

What you need to do is face the pump. near the rear of the pump, on the top is a tin cover held on by 4 screws..

Remove the cover, locate the "rack limiter" usually 2 screws clamp it to the body of the pump. make note of the location, loosen the screws and slide the "rack limiter" towards the front of the engine maybe a 1/16 to an 1/8 of an inch. tighten the clamping bolts and replace the cover. give it a try if you give it too much you will see a trail of smoke even with boost..

personally I would hook the puff limiter back up, you will see the same power (if the system isn't malfunctioning) just with a bit more delay waiting for the turbo to boost. and of course less smoke.

[David]

Add an aftercooler. It will give you about 50 hp.

[Mark from OZ]

IF it is an econodyne it should have a radiator intercooler. if it is a 237 you could ad an intercooler but you need re calibrate the pump

different injectors re do the timing and match a turbo ect . it goes on and on to do it properly mark

[other dog]

IF it is an econodyne it should have a radiator intercooler. if it is a 237 you could ad an intercooler but you need re calibrate the pump

different injectors re do the timing and match a turbo ect . it goes on and on to do it properly mark

I don't remember a lot about this, but we'd-no, I mean i've seen others-take that little cap off the top of the pump and loosen the nut towards the rear and back it off just a little. Half a turn made a big difference, and wasn't enough to hurt anything. Remember-a little dab'll do ya! Backing the rear nut off one full turn was about as far as you'd want to go, then tighten the front nut while holding the rear one. Trying to turn it up too much is what got most people in trouble-the old "if a little is good, more's got to be better" theory. I had some offset wrenches, it's a tight spot in there. This was late 70's maxidyne engines.

There was one guy in particular around these parts who was famous for turning up a Mack. He'd blow a 300's doors off with a 237. He drove a company truck and wasn't concerned about hurting the engine of course. When he got a new R-model with an econodyne he wouldn't mess with it because they told him at the Mack place he would end up screwing everything up if he tampered with the fuel because everything had to be set together. Far as I know he never did because he was afraid to mess with it, because it was something new to him.

[fjh]

I don't remember a lot about this, but we'd-no, I mean i've seen others-take that little cap off the top of the pump and loosen the nut towards the rear and back it off just a little. Half a turn made a big difference, and wasn't enough to hurt anything. Remember-a little dab'll do ya! Backing the rear nut off one full turn was about as far as you'd want to go, then tighten the front nut while holding the rear one. Trying to turn it up too much is what got most people in trouble-the old "if a little is good, more's got to be better" theory. I had some offset wrenches, it's a tight spot in there. This was late 70's maxidyne engines.

There was one guy in particular around these parts who was famous for turning up a Mack. He'd blow a 300's doors off with a 237. He drove a company truck and wasn't concerned about hurting the engine of course. When he got a new R-model with an econodyne he wouldn't mess with it because they told him at the Mack place he would end up screwing everything up if he tampered with the fuel because everything had to be set together. Far as I know he never did because he was afraid to mess with it, because it was something new to him.

What your discribing sounds correct for an american bosch pump. His pump is robert bosch.Maxville has the drill for that!

I.d be curious if the truck is a six speed or other econodyne does not sound right for 237.also if while pulling under load you still see smoke if so it may be leaking boost!The older engines had a stamped metal intake that could split and leak!

[peterj]

just a little history....when these trucks were built , most of the speed limits for trucks were 55... many wre 45 for trucks... it was rare to find 60 any were on the east coast..... the trucks were built and geared for 58-60 tops.. 200hp (net) will only pull 55-57 on a level road ..no wind... if you had a truck that could get up a hill at 40 you had a big horse....4ways on every up hill.. we ran 6-71 gmc mostly then..if you made it up a hill in the high side of a 10sp rr you were doing good... up the hills on pa pike- 10 to 15 mph...

back to topic... i have 237 (endt675) in my h67... i have plenty of hp...i only bob tail... i need more RPM...robert bosch pump... iv'e been told the screw to do the rpm is in the back of the pump, turbo end....

ware and which way do you turn it???? pics??

thanks..

[Maxville Truck]

just a little history....when these trucks were built , most of the speed limits for trucks were 55... many wre 45 for trucks... it was rare to find 60 any were on the east coast..... the trucks were built and geared for 58-60 tops.. 200hp (net) will only pull 55-57 on a level road ..no wind... if you had a truck that could get up a hill at 40 you had a big horse....4ways on every up hill.. we ran 6-71 gmc mostly then..if you made it up a hill in the high side of a 10sp rr you were doing good... up the hills on pa pike- 10 to 15 mph...

back to topic... i have 237 (endt675) in my h67... i have plenty of hp...i only bob tail... i need more RPM...robert bosch pump... iv'e been told the screw to do the rpm is in the back of the pump, turbo end....

ware and which way do you turn it???? pics??

thanks..

I have the robert bosch on all my #$it trucks. But they all have the Smoke control built into the top of the pump..... If you remove that "cover" in the rear top of the pump, then remove the "rack limiter" now get a flashlight and look into the pump straight down. you may have to turn the engine over to see what is nessecary to turn up RPM's it is a funny shaped spring holder about the size of a dime with 2 dimples in it... you push the spring down and turn in the "spring holder" clockwise, may be a 1/2 turn or more. The spring pushes against this nut thingy and holds it in place. remember how many clicks because you have to turn the motor over and do it again on the other side of the Governor flyweights (inside the pump).

I'm attaching an awesome picture of the inside of the governor housing as viewed from the engine side of the pump (physically impossible to do).. the "nut thingy" I'm refering to is item 1 in the picture.

MAXVILLE's DISCLAIMER-------That is not the right way to turn rpm's up, the proper way is to take the cover of on the engine side of the pump and remove the springs and put the right springs in for the required RPM, also it should really be done on a test stand by a trusted Pump Shop. In my area both Lacrosse Diesel and Eau Claire Diesel are good at it.. When you turn rpm's up you also increase your HP a little too, doing my method will make your throttle more sensitive and if you do not get it precisely the same on both sides your governor may act "weird"

[niceguypmp3]

Thanks for all of the replies everyone. I was afraid that I would get ignored. I went and looked at the truck again, and yes, the hood says econodyne on it and the engine plate says it is a 235 horsepower 237 And it also has an intercooler. I think the guy we got the truck from said that it at one time had the engine replaced. So I dont know if the turbo/intercooler setup was from the old engine or what the deal was. I would of taken that cover off and slid that plate like maxville had mentioned, but I didn't have a stubby screwdriver with me to reach the screws. Also, It looks like the passenger rear screw is a small allen in the middle or something, so that might be fun, but the other three require a stubby straight blade screwdriver. I will let you all know how it turns out. Thanks again!

Almost forgot, it also has the 5 speed 2 stick trans.

Edited March 16, 2009 by niceguypmp3

[peterj]

thanks maxville...that pic was GREAT.. now i understand.. i was brushed off by an old mack machanic , mumbling about taking it off, put it on a stand and recalibrating the whole thing... he didnt want the job... didn,t think it would be that complicated, i,ve done many gm,s any my cat..not that hard.

thanks again..

[Rob]

I've had a couple of early 70's 237 engines that I've "turned up". One I used an E6-350 turbocharger and intake, the other a 300 Maxidyne turbocharger and manifold. Both trucks had the mufflers removed and ran straight pipes. I've never done pump work myself, cause I have a friend that does that for a living. I do know the timing was retarded a bit and advance recalibrated. Can't answer if injectors were modified other than being rebuilt on either of these engines but they both ran much different, and stronger after modification. I like a pyrometer and use it as a tool to let the engine live. Too expensive to break something being naive.

Rob

[niceguypmp3]

I went to turn the truck up today and I noticed that relating to the 4 screws that hold that top rear cover on, 3 are regular screws that came out easy, the 4th looks like a factory rivet thingy. Does that sound right? I imagine that i would need to pry the cover off at the same time that it hopefully prys that rivet out of the hole? I knew I should of taken a picture of it.