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Old 10-13-2014, 12:59 AM   #1
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Adding "real" Jake brake to an ISC

Does anyone have any experience adding a Jake Brake (engine compression brake, NOT exhaust brake) to an ISC engine? I see the parts required can be bought (used) at a reasonable price at a number of salvage operations. The changeover looks fairly straightforward, with the Jake Brake components essentially replacing the existing rocker arm supports. And it appears the signal that activates the PacBrake can be used to operate the compression brake and cause the Allison to downshift

I'm surprised how little info I've turned up searching the Internet about this swap. A diesel mechanic friend (who has never made this swap) says he does not see any problems with it. There is quite a bit of info about adding Jake Brakes to the 5.9 engines used in Dodge trucks, but nothing I can find about the ISC.
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Old 10-13-2014, 07:56 AM   #2
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??? I Googled "jake brake on isc" and found lots of discussion...
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Old 10-13-2014, 05:01 PM   #3
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I've searched for a few hours, nothing about a compression brake for the ISC 8.3. Have you considered a VVT-Varible Vane Turbocharger? Apparently that is what Cummins uses on the ISC.
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Old 10-13-2014, 05:12 PM   #4
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FYI, The "Pac Brake" (Paccar Part) will have better Braking than the "Jacobs" brand, my 1989 Pete Cat 3406B model came with a Jacob and I had switched it to the Pac Brake when it came out within a year after the purchase, at that time new in box was $1,200.00
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Old 10-13-2014, 05:18 PM   #5
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You might find that upgrading to a PRXB exhaust brake from Pacbrake would be cheaper and far easier.
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Old 10-13-2014, 05:22 PM   #6
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Quote:
Originally Posted by DMTTRANSPORT View Post
FYI, The "Pac Brake" (Paccar Part) will have better Braking than the "Jacobs" brand, my 1989 Pete Cat 3406B model came with a Jacob and I had switched it to the Pac Brake when it came out within a year after the purchase, at that time new in box was $1,200.00
I believe that the CAT 3406B was a great engine before the introduction of modern electronic engine control. It's my understanding that the operation of engine brakes was quite a bit different on engines of that era. As a result, I suspect your experiences with the Paccar and Jacobs brakes is not relevant to today's engines. My Jacobs engine brake works quite well with my C-12.
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Old 10-13-2014, 05:43 PM   #7
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Quote:
Originally Posted by Vanwill View Post
Does anyone have any experience adding a Jake Brake (engine compression brake, NOT exhaust brake) to an ISC engine?
Quote:
Originally Posted by DMTTRANSPORT View Post
FYI, The "Pac Brake" (Paccar Part) will have better Braking than the "Jacobs" brand, my 1989 Pete Cat 3406B model came with a Jacob and I had switched it to the Pac Brake when it came out within a year after the purchase, at that time new in box was $1,200.00
DMTTRANSPORT
The OP asked about adding an "engine compression brake" to an ISC engine... NOT a Jacobs brand exhust brake or any other brand of "exhaust brake".
IMO you are comparing apples to oranges..... and to some other fruit, and confusing the issue....(aka: simply "muddying" the waters).
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Old 10-13-2014, 06:21 PM   #8
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DMTTRANSPORT
The OP asked about adding an "engine compression brake" to an ISC engine... NOT a Jacobs brand exhust brake or any other brand of "exhaust brake".
IMO you are comparing apples to oranges..... and to some other fruit, and confusing the issue....(aka: simply "muddying" the waters).
Oh, so its called a Compression Brake, I was referring to a over head engine brake not an exhaust brake, what is it you are looking for sorry I muddied your water LOL! FYI, I happen to know the difference, it's not a COMPRESSION Brake it actually holds the exhaust valves open...............Releasing the COMPRESSION!
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Old 10-13-2014, 06:26 PM   #9
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Quote:
Originally Posted by docj View Post
I believe that the CAT 3406B was a great engine before the introduction of modern electronic engine control. It's my understanding that the operation of engine brakes was quite a bit different on engines of that era. As a result, I suspect your experiences with the Paccar and Jacobs brakes is not relevant to today's engines. My Jacobs engine brake works quite well with my C-12.
My current Cat C15 Acert (2007) does have a Pac Brake also a Retarder (Brake Saver).........
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Old 10-13-2014, 07:07 PM   #10
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Van,

To preface this comment, I am under the assumption that you need more engine braking than you now have.

My previous coach was a 38' 99 Dynasty and I had no problem descending 6% grade with a 5000 lb toad. If you are not getting braking from the PacBrake (non PRXB) something maybe amiss. Before throwing the baby out with the bath water, let's take a look at everything next week when I arrive.

An item you can check is the rear end ratio. My 99 Dynasty had a 4.78 ratio and my Camelot has a 4.30 ratio. Let me tell you that 10% difference is a big deal. Before I resolved my exhaust brake issues, I bought a 4.78 third member to swap out mine with. The reworked PacBrake helped slow me down on the 6% grades to an acceptable manner, but not as nice as the last coach. I added an MP-8 for going up the hill. Now that I can go up and down the local mountains better than when stock, I decided to accept what I have.

There is a tag, spot welded to the third member, with a lot of black paint on it. It will have the model number along with the ratio on it. Take a look.
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Old 10-13-2014, 07:41 PM   #11
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I'm sure it can be done, but I'm interested in how much your coach weighs... I just have an exhaust brake and as others have mentioned, I've never found myself lacking for braking -- if anything I sometimes find myself wishing that I could reduce the overall level of exhaust brake because on a 4-5% grade I end up cycling it on and off.

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Old 10-13-2014, 07:49 PM   #12
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Hmmm....wonder why Cummins engineers never offered it? My guess is that the ISC was never intended to be a class 8 truck engine hauling 72,000 lbs up and over the Rockies....
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Old 10-13-2014, 07:52 PM   #13
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Quote:
Originally Posted by DMTTRANSPORT View Post
Oh, so its called a Compression Brake, I was referring to a over head engine brake not an exhaust brake, what is it you are looking for sorry I muddied your water LOL! FYI, I happen to know the difference, it's not a COMPRESSION Brake it actually holds the exhaust valves open...............Releasing the COMPRESSION!
Even though it releases the compression they still call them compression brakes.
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Old 10-13-2014, 08:24 PM   #14
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I must apologize, I incorrectly said a "Jake brake" is a compression brake, which is NOT true according to Jacobsvehiclesystems.com A Jake brake is the registered and trademarked brand, not the type.

Quote:
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Hmmm....wonder why Cummins engineers never offered it? My guess is that the ISC was never intended to be a class 8 truck engine hauling 72,000 lbs up and over the Rockies....
You are right, it is a medium-duty truck engine according to Cummins.

DMTRANSPORT, you are correct in compression brake operation.
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