Exhaust Brake on an M35A2

[Chris Deuce]

Hi,

I've been using this site for awhile to get my Deuce fixed up. Currently in the process of installing a Pac Brake C20373 on the deuce. So far I have removed the stock pipe immediately after the turbo and have the flex pipe extended out and attached to the brake (took a good beating with a BFH and some swearing, but it's the right length/shape now. I have the wiring for the micro switches on the clutch and throttle setup and will be using a 24V Mac air solenoid for activation. I ordered an adapter for the turbo V flange to the Brake V flange and the clamps and should be getting them soon.

i still need to find a good air supply to use and plan on tapping a T into the horn supply as I believe this is always pressurized with a solenoid on the horn itself. I have not seen a successful exhaust brake install on an M35 during any of my research, but hoping some of you can help out a little. I have a Mechanical Engineering degree and have rebuilt and tuned a few other engines so have a good working knowledge of them, but am hesitant on solely relying on engineering without any proven results. With the stock valve springs you can only run around 30 psi before you float a valve, so I've been researching and think I found a good solution. To my knowledge, they don't make any aftermarket heavy valve springs for the LDT 465, so I found the dimensions on them and found comparable springs to upgrade with. The best solution I can find is heavy duty springs for the Cummins 8.3L part number 3916588. These are the 65 lb. springs used when they install exhaust brakes on those engines (compared to the 35 lb. stock springs on them). Based on the free length and K value of these the preload should run right around 60 psi before valve float if installed on the LDT. These are an inner and outer combo so I'd be replacing both for the exhaust side springs if I go this route.

Potential problems:
- The inner diameter of the outer spring for the LDT is around 1 1/8" and the 8.3L springs are 1.065", so I'd have to open up the first coil on the to 1 1/8" to fit on the valve spring cups.
- Are the rockers, push rods, tappets, cam, etc. strong enough to deal with the extra force from these springs?

Does anyone with engineering or practical experience see any issues with this or have any better ideas for heavier valve springs for this install?

Thank you you all for your help, I'm hoping with the combined knowledge here that we can get a working exhaust brake for a decent price, as I have less than $300 total into this so far. Pictures below for brake setup without adapter installed yet, specs for LDT 465 stock valve springs and 35 lb. 8.3L Cummins springs (the ones I would be using are the 65 lb. ones).

 

[73m819]

Contract "CRANE TRUCK" he installed a exhaust brake on his truck, there is a write up somewhere on the install.

 

[Chris Deuce]

Finished up installing the exhaust brake today with an adapter from the turbo to the exhaust brake. Had to dis-assemble and re-assemble the MAC Air Solenoid 55 series to make it an internal pilot and plugged the external pilot hole after rotating the pilot housing 180 degrees. The wiring for these solenoids is:
Pin 1: +24VDC
Pin 2: Grounded when switching circuit is activated
GND: Continuous ground

I ended up going with the heavier valve springs for the Cummins 8.3L exhaust brakes, part number 3916588, they should arrive tomorrow. Then we'll see how much needs to be done to make them fit the valve spring cups. These are rated at 65 psi for the 8.3L and should hold up to 60 psi on the LDT 465 by my calculations.

 

[gimpyrobb]

Not sure how I missed this thread when you first started it.

Does the pacbrake have any temp restrictions? I would think having it attached to the turbo like that would melt the seals out of the air cyl at least.

 

[gimpyrobb]

http://www.steelsoldiers.com/showthread.php?3255-Deuce-exhaust-brake-details&highlight=

 

[Chris Deuce]

Every installation manual I can find from Pacbrake states that the direct mount to the turbocharger is the preferred method since it minimizes the chance for exhaust leaks. The air cylinder is pointed in the other direction with the fitting for the airline approximately 8-10" away from the turbo with good clearance all around it. I will definitely let you know if it is a problem though.

 

[WillWagner]

Gimp, It will be fine mounted there, OP, The rockers, IIRC, are just stamped steel and the cam is old school cast iron. I would run it like it is now. The truck is 14k, it isn't heavy. I feel the 60 lb Cummins springs will be too much for the valvetrain on the LDT

 

[rustystud]

Gimp, It will be fine mounted there, OP, The rockers, IIRC, are just stamped steel and the cam is old school cast iron. I would run it like it is now. The truck is 14k, it isn't heavy. I feel the 60 lb Cummins springs will be too much for the valvetrain on the LDT

I agree about the valve springs. These Cummins engines have roller cams not flat tappet cams like ours. With that heavy of springs it will eat the cam lobes extremely fast.

 

[rustystud]

Not sure how I missed this thread when you first started it.

Does the pacbrake have any temp restrictions? I would think having it attached to the turbo like that would melt the seals out of the air cyl at least.

If he uses the special lube that "pac-brake" specifies then he will be OK. You need to add this lube every month.

 

[WillWagner]

I agree about the valve springs. These Cummins engines have roller cams not flat tappet cams like ours. With that heavy of springs it will eat the cam lobes extremely fast.

Negatory, the tappets are flat sliders. They went to rollers 2004 ish on the C and 1998 for the L. Still, even with some type of "conditioner" in the oil, I would be concerned about valve train components holding up to added pressure of a taller, heavier wound spring that wasn't made for this engine.

 

[rustystud]

Negatory, the tappets are flat sliders. They went to rollers 2004 ish on the C and 1998 for the L. Still, even with some type of "conditioner" in the oil, I would be concerned about valve train components holding up to added pressure of a taller, heavier wound spring that wasn't made for this engine.

OK first off you must be very specific when talking about Cummins engines . The ISC 8.3L engine came with roller cams. There is also the ISL 8.3L and the ISM 8.3L engine. All are different. On the same engines there where the "electronic" versions and "mechanical" versions. All had different specifications. Since 1998 Cummins has come out with about 5 different versions of engines every year ! OK maybe not that many but a lot ! So Like I said you must be very specific when talking Cummins engines.

 

[Chris Deuce]

Thank you guys for the great advice. I'm going to leave the valve springs alone for now. I should receive my pressure gauge in a few days and will be able to tune the brake once I get that it. Just finished installing a pyro and plan on doing a brake adjustment today then taking it for a drive to start increasing fuel while keeping it under 1100. Looking around I know people do go higher than that, but I'd like to have a decent life out of this engine and keep it from melting down.

On on a side note, since I won't be installing the heavier springs I'd like to maintain 30 psi backpressure over a larger RPM range. I'm thinking of installing an exhaust wastegate from the manifold to after the exhaust brake with 30 psi opening pressure. I could plug up the orifices in the exhaust brake butterfly and maintain 30 psi backpressure. Another option is to make a spring loaded pressure release valve on the butterfly itself and tune the pre-load on the spring to create 30 psi backpressure. Any ideas on which would be easier?

 

[gimpyrobb]

If the springs are rated to 30psi, why would you want to go that high? I'd keep it at 25psi.

 

[WillWagner]

OK first off you must be very specific when talking about Cummins engines . The ISC 8.3L engine came with roller cams. There is also the ISL 8.3L and the ISM 8.3L engine. All are different. On the same engines there where the "electronic" versions and "mechanical" versions. All had different specifications. Since 1998 Cummins has come out with about 5 different versions of engines every year ! OK maybe not that many but a lot ! So Like I said you must be very specific when talking Cummins engines.

ISC 8.3L, roller followers in 2003-4. before that, flat slider tappets, ISL 8.9L introduced in 1998, looked the same as the CAPS ISC but stroked 10mm and had roller followers, ISM is 11L and has always been a roller follower engine and is not in the same class as the C and L. C has always been a midrange engine, L has bounced back and forth between midrange and heavy duty and the ISM has always been a HD engine, it started out in 1985 as the L10, 10L engine.

Yes, every emissions year model change there are a bunch of different engines released, This last emissions update saw a B3.3, B4.5, B6.7, C8.3, L9, ISX12, ISX15, ISF3.8, ISV5.0, ISD, ISG and a hand full of others. The D, G and F are Chinese. Thjat is just automotive, Industrial has more because engines as large as 95L are in use.

 

[rustystud]

ISC 8.3L, roller followers in 2003-4. before that, flat slider tappets, ISL 8.9L introduced in 1998, looked the same as the CAPS ISC but stroked 10mm and had roller followers, ISM is 11L and has always been a roller follower engine and is not in the same class as the C and L. C has always been a midrange engine, L has bounced back and forth between midrange and heavy duty and the ISM has always been a HD engine, it started out in 1985 as the L10, 10L engine.

Yes, every emissions year model change there are a bunch of different engines released, This last emissions update saw a B3.3, B4.5, B6.7, C8.3, L9, ISX12, ISX15, ISF3.8, ISV5.0, ISD, ISG and a hand full of others. The D, G and F are Chinese. Thjat is just automotive, Industrial has more because engines as large as 95L are in use.

That is exactly why I said you need to be very specific about Cummins engines. Having worked on the ISC, ISL, and ISM, and M11 engines in the past 25 years I've had to be very exact ordering parts. It's not like the days of the small block Chevy anymore.
But getting back to the original question of using heavier springs. If the valves and cam where never designed to use that kind of pressure your only asking for trouble. Does anyone know if the LDT or LDS engines valves are "hardened" to handle high pressure springs ? Is the cam "hardened" enough to handle the pressure ? I don't know, but I bet you they are not.

 

[Wildchild467]

Pacbrake had one that looked like it would have fit our application because it had a 45 degree bend in the brake mechanism. I think it fit a 5.9 cummins.

 

[winfred]

musing around about a modern or at least less primitive turbo with the prime suspect being my hx-35 that got evicted from my 12v cummins by a turbonetics ball bearing unit, but this talk of e-brakes got me thinking of failed project i own, scored a perfectly good he351vgt from a common rail cummins a while back for a song, they have a sliding ring style housing that goes from 5 or 7cm (can't remember exactly) to somewhere in the mid 20cm range, its water cooled and the vg rack is potentially adaptable to manual control, haven't played with it in a couple years but it may be worth a look, i might drag it out of the building this weekend and look it over for possible fitment issues and snap a few pics for the group

 

[gimpyrobb]

That would be great! Please start a thread for it though as it will get lost in this one(I'd never find it in a search later on).

 

[rustystud]

That would be great! Please start a thread for it though as it will get lost in this one(I'd never find it in a search later on).

Agreed ! I would follow that thread !

 

[74M35A2]

I have a PacBrake butterfly exhaust throttling brake that came factory stock on an RV Cummins ISL-400hp engine that I am probably not going to use. It clamps directly to the turbo with a band clamp. Air actuated cylinder. PM me if interested.