Pacbrake question

[John Berger]

I recently purchased a used Pacbrake from a fellow TDR member. In the plate there is a quarter inch hole that bleeds off some of the back pressure; which was a must on 12 valve engines that do not have 60 lb. exhaust springs. Since I've got a 24 valve, I need that hole plugged. Any ideas on what would work that would maintain the integrity of the brake (welding is not a good idea), and that I also won't have to worry about breaking loose and flying out the tailpipe. I think a nut and bolt would do, but would like to know if there are any better tried and true methods. TIA

 

[bighammer]

If I remember right, there is also a smaller hole as well. The one you are talking about is countersunk on one side? There was a very short bolt with a nut that went in the larger one.

 

[jtisdale]

Originally posted by John Berger

I recently purchased a used Pacbrake from a fellow TDR member. In the plate there is a quarter inch hole that bleeds off some of the back pressure; which was a must on 12 valve engines that do not have 60 lb. exhaust springs. Since I've got a 24 valve, I need that hole plugged. Any ideas on what would work that would maintain the integrity of the brake (welding is not a good idea), and that I also won't have to worry about breaking loose and flying out the tailpipe. I think a nut and bolt would do, but would like to know if there are any better tried and true methods. TIA

What part number of brake did you get? I have the C14025, and mine only has the 1/4" hole. Are we sure it's a good idea to plug this? Without having a pressure gauge, how would I know if I am putting too much back pressure on the engine?

Thanks

 

[Wheaties]

Huh? I don't believe the hole is for the 12 valve, I believe the hole is to keep the back pressure below 60lb, and the 12er should replace the exhaust springs with something stronger to bring it up to tolerate the 60lb back pressure.



But don't take my word for it, call Pacbrake!



www.pacbrake.com



Matt

 

[CRWilliams]

I second that. CALL PACBRAKE. They can get you any of the small parts. When I installed mine I broke the diode on the pedal switch. They had a new diode in my hand in a couple of days.

 

[WDaniels]

That is exactly what the hole is for. If you order the heavy duty kit for the pac break all that comes is the bolt and nut. That is if it is for the 12v. Don't know about the 24v. It is up to you to order and install the 60lb springs. When I bought the kit I think I paid a buck 60 for it from Pac.

WD

 

[John Berger]

I was mistaken. I have two holes in the plate. It's the larger hole that I want to plug and the smaller hole stays as it is, correct?

 

[Wheaties]

Originally posted by WDaniels

That is exactly what the hole is for. If you order the heavy duty kit for the pac break all that comes is the bolt and nut. That is if it is for the 12v. Don't know about the 24v. It is up to you to order and install the 60lb springs. When I bought the kit I think I paid a buck 60 for it from Pac.

WD

Well I'll be danged! You seem to know what you're talking about, and I think I was wrong once before..... That's what the TDR is all about!



Matt

 

[FDziurda]

Which PacBrake

I just recently had my 24V PacBrake out for cleaning and it only has one hole in the butterfly. The older 12V PacBrakes, for use with 30# valve springs had 2 holes. You place a special bolt in one of the holes when you upgrade your 12V with 60# valve spings. Either version should work but the single hole version is for the 24V trucks.



Frank

 

[John Berger]

Frank, do you know the size of the hole on your brake? My brake is for a 24v engine according to the instruction book I got with it, but the guy I got it from had it on a 12v truck. I'm pretty sure the bigger hole is the one that needs to be plugged, but I want to make sure. I'm waiting on the adapter plate that I had to order from Pacbrake before I can do the install. One other question: Do most of you guys with 24v engines wire the brake manually or off of the ECM?

 

[jelag]

Guys



There are several models of PacBrake that will bolt to the early turbo housing... ... It's important that you identify the unit before installation..... the wrong housing with the incorrect back pressure can and will cause severe engine damage... ...



There is an ID tag on the unit with model and serial number... . with that we can tell you whats up... .



The early units were standard transmission and automatic transmission and each butterfly had 2 holes..... the sizes of the holes were different... ... .



One hole is tapered on one side for a special plug, when the HD exhaust valve springs are installed... . the plug comes with the springs... . do not plug this hole unless you the HD valve springs on a 12 valve engine... . if you plug this hole use the correct plug with lock nut... . if this plug and nut comes loose and it falls into the trubo damage will result..... the springs supplied by PacBrake are Cummins springs.....



Later as the kit was changed for only the 24 valve engine the tapered hole was left out of the butterfly and the housing was standardized for the stick and automatic transmissions... ...



If you have any additional questions give us or PacBrake a call...



Jim at 800. 445. 4696

 

[FDziurda]

PacBrake

John,

If you have one of the 2-hole butterflys and have a 24V ISB, you will need to plug the hole that is tapered on one side of the butterfly. I'd contact PacBrake and get the proper nut & bolt. I am running my PacBrake manually, with the microswitch that's under the throttle, not connected to the ECM. My understanding is the ECM connection provides a delay before activation, which I didn't want.



I just cleaned one of the older 2-hole butterfly units yesterday, so I am pretty sure I'm correct.



Hope this helps,



Frank

 

[jelag]

Frank



Your right... . however I talked to John a day or so ago and this is what we found..... He has an exhaust brake that has been modified by someone who drilled the hole out... so the taper that you refer to is not there... ...



This was an exhaust brake that had been modified to fit and early 12 V and now he wants to use it on a 24 V..... here is what I shared with him... ...



the standard restriction in the brake is 9/32" this is the factory setting for 60 psi back pressure... ... I cautioned him to check the following before installation.....



1 - make sure the butterfly is not loose... . to close the butterfly and hold the assembly up to a light..... the valve should be fully closed with some light showing around the complete circle of the valve... . this is not field adjustable as there is an allowance for the butterfly to expand as it heats up..... remember it could see as much as 1200 degrees... .



2 - since the one hole has been drilled it won't accept the factory tapered plug..... I suggested he cover the hole with a bolt... use a lock nut(one without a nylon insert) once that was done he check the other hole and make sure its to the 9/32 standard... .



3 - I suggested that before he puts this to a test with a trailer or load he install the brake and put a pressure gauge in the port designed for that purpose and actually test the back pressure... . I suggested he go to the home improvement store of his choice and get a 100 psi gauged for an air compressor and fit it to the brake and take the truck for a road test... .



4 - with the truck at 2200-2500 rpm he turn on the brake and see what the gauge goes to... . he should approach this with caution as he is working with an un tested unit... . he should never exceed 60 psi..... exceeding 60 psi can and will cause damage to the engine... ... it can float the exhaust valve and the piston can than strike it.....



5 - once he is satified that the brake works as designed he can remove the test gauge and replace it with his temp probe.



Have a great day... .



Jim / Pacific Clutch

 

[FDziurda]

Thanks Jim

Jim,

Good info. Sorry to hear someone modified the butterfly on John's PacBrake. Sounds like he is on the right path.

Frank

 

[John Berger]

Just to follow up on this, the brake is on the truck and is working very well. I have an air leak that I'm working on, but no ill effects, just annoying. I tested the brake at around 2650-2700 rpm and never exceeded 60 psi. The wife said it looked like it went over a little bit, but I tried a number of times and never saw it go past 60 psi. There were two holes in the butterfly. The big hole worked out to be 1/2 inch, which is just slightly bigger than the factory 31/64 inch that I've been told about. I installed a steel bolt that had to be cut and used red loc-tite on the threads. I had two threads showing once the bolt was good and snug. I took a punch and chisel (go slowly) to those threads to bugger them up in the event the bolt tries to work loose.