JoeH

Not sure how big your pump is but I'll take a wager that 1,000-2,000 psi pressure relief will probably get the job done on shifting. If you go this route I'd start on the low side pressure relief setting and build up to the sweet spot.

Hydraulic oil doesn't compress, so the response time could be better than you're thinking. Don't think you'd build all that much heat if you just used it as a shift assist, you're talking about 1-2 seconds of braking time per shift. It will mean more wear and perhaps shock load on your hydraulic system, mostly I'm thinking about the pump drive shaft.

You don't need 150hp of braking power to slow the engine down.  You may be stalling that thing out doing that.  Typical Jake's have an electric switch on the clutch pedal, another on the throttle lever on the pump. Then there's a manual system hi/lo/off switch on the dash.  Hi/lo is two heads/one head. If you were going to run your pump as a brake I'd build it into your pedals so it's instantly on or off.

If you put a butterfly valve on, you'd need to use it constantly for shifting and probably clean it every so often. Lack of use the soot will jam up the butterfly valve and it can jam when it engages and not release. As far as using it as a brake for the truck, I'm not sure the exhaust valves can handle the back pressure. Fine when shifting, but on actual braking it may generate too much pressure any closed valve springs.

One more spitball idea, throw a butterfly engine brake in the exhaust pipe for upshifting. It'll make the truck a whole different animal. It'll cut your engine speed down much faster so you'll be getting into gear closer to 1100 or 1200 rpms. We had a jake brake on one of our Maxidynes for decades, and it made the truck faaast.

I would expect block and internals to be the same, only differences I would think are injectors, turbo, and fuel pump. I'd expect valve springs to be the same, only reason to put heavier springs in would be to avoid valve float while running higher rpms.

Several "active" fault codes, mostly related to it missing it's whole back half...

Got the engine running today on a bucket of diesel and a couple spare batteries. Neutral safety switch on the trans had gotten unplugged some time in the past 10 years, other than that it fire right up!

And it's official, it has 14,090.741 miles on it. 3,887.550 engine hours, 3,105.5 of which are idle hours.   A lot less than my 2003 that has 28,000 hours on the tachometer.

Took me a minute to figure out what that things in! That's a cabover, not sure what model truck.  Your exhaust is a different layout than mine.  There should be a tag between the two halves of the turbo. May need to crawl deep in there and clean it off.

I'm not sure there is an em6-350, I think the Maxidynes tapped out at 300.  If it's a 350 then I'd expect it to be an e6-350. I drive an E7-350 triaxle with an 8LL most days, 8 gears will get it to 70+ mph.

If the 350 runs, you might be happier dropping that and the 9 speed transmission into the truck.  That will give you much better gearing for what you're trying to do.

5 hours ago, RS Disposal said:

I wou8ld really appreciate that

Garrett rebuilt turbo.

Mind you my #1 answer was a superliner with an E9! That's what I would buy! But parts are hens teeth for those motors I hear. Other than that, a true Mack motor (non Volvo mp series) only gets you 12 liters, which probably doesn't meet his needs.

I'm unwilling to go near an MP engine any time soon.

On 12/11/2023 at 1:02 PM, Mandrewoid said:

Or possibly the spring out of an E6-350, or maybe even just a 285 non-L

You did mention you have a spare motor. What is it exactly? And is your current motor an E6-275L or an EM6-275L? Knowing if they have the M in there is important.

I'm thinking your best spring change would be like you said, swap either just springs from your spare motor or swap the whole fuel pump.  For a pump swap it'll need to be an EM6 pump not an E6 pump because it sounds like you have very tall gearing. The EM6 motors make 90%+ of peak torque from 900-1100 rpms all the way to the governor, whereas a standard E6 has a much smaller power band.

1 hour ago, Mandrewoid said:

No this is incorrect. You can set the high idle screw to 2300 rpm all you want, but if you have 1800rpm governor springs, you will only make idle power at 2300rpm. 

What you can do is put 3000rpm governor springs in and then turn the high idle screw down so you don't exceed 2200 rpm. At that point it will likely behave a little bit like a farm tractor. As soon as the engine rpm drops to 2100, all the horsepower will be available. You won't have to wait to drop down to 1700rpm. 

Let us know what you do and how it turns out, I'd just hate to see the motor take a hit if it gets over revved. My experience with fuel pumps is very limited.

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.

12,000/day x 365 days = 4,380,000 per year.

Can you post a picture of the exhaust side of your engine? I have 2 endt675 motors, one from a U model the other is in an R model. I think the exhaust manifolds are the same, but seeing yours will help me compare to the U model I have.

Sorry to confuse you with yet another turbo model added to the possibilities. Just rechecked, you're running an ENDTB 675 which will be the 237hp variant! Sorry this turbo is for the 283hp variant! 

I do have a 237 endt-675 sitting outside my garage, I'll see if it has a tag on it tomorrow!

The X in the part number on my turbo just means rebuilt.

FridayParts Turbo S3B085 Turbocharger 631GC5134 174840 199453 Compatible for Mack Truck E6 Replacement https://a.co/d/g7huQZv

The things Amazon has for sale never ceases to surprise me.... Not bad at $600...

Here's a couple more pictures to drool over...

I put this turbo on my 1979 endt676 about a year ago. Got it through my local Mack dealer, Bergeys. May have been about the last one they had in stock.

Can smarter heads than mine tell if this is the high idle adjustment screw?

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.

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.