Found a complete set of Jake Brakes for our 8V71. They came from Central Truck in MN, and they should be here soon.
The guy said that the tall valve covers he had were aluminum and included breathers. Our current valve covers do not have breathers.
Question is this...
Any reason to do anything about the breathers? Assuming they don't bump into something, can I just leave them in place. Or, should I follow his suggestion and have the openings welded closed by someone that can handle the aluminum welding?
I know that I'll have to fabricate a bump-out in the engine cover, but I have no idea how the breathers will play into things.
They made covers for the breathers, but they usually come with the valve covers so you can switch the breather location. It wouldn't be hard to make one using the existing retainer ring and bolts.
Don't worry about the breathers the old 8v71 didn't have enough breather any ways,the only problem you will have is the location if the breather is on the top then it will interfere with the tail gate dog house and the upper bulk head.
You want the covers with the breathers on the side not the top those are not fun to cut a 4 inch hole in.
Like Geoff said you can try and find the relocation covers but I haven't seen any in years since the valves covers stopped coming with 2 holes.
Let me know if you need the side breather I have 8 sets of side covers with side mounted breathers and will trade you for the top mounted.
Keep the breathers on the valve covers then you don't need to worry about removing the breather on the back of the V71 to service it lol most people don't worry about it anyways I get those here no one has ever serviced caked solid because they never knew it was there
Quote from: luvrbus on February 19, 2018, 03:04:24 PM
Don't worry about the breathers the old 8v71 didn't have enough breather any ways,the only problem you will have is the location if the breather is on the top then it will interfere with the tail gate dog house and the upper bulk head.
You want the covers with the breathers on the side not the top those are not fun to cut a 4 inch hole in.
Like Geoff said you can try and find the relocation covers but I haven't seen any in years since the valves covers stopped coming with 2 holes.
Let me know if you need the side breather I have 8 sets of side covers with side mounted breathers and will trade you for the top mounted.
Keep the breathers on the valve covers then you don't need to worry about removing the breather on the back of the V71 to service it lol most people don't worry about it anyways I get those here no one has ever serviced caked solid because they never knew it was there
Thanks - I'll let you know when they get here if they are side mounted or top mounted when they get here. I also will probably need to swap the solenoids for 24v versions, since these are most likely 12v. Hopefully those are still available somewhere.
Otherwise, I think I've got a complete setup coming.
On my 4905 with Jakes the breather is on the top of the upper cover, not on side of upper cover. Lower cover has none. Upper cover also has a plugged approx 1 1/2 inch hole. The upper breather has a 1 inch hose attached to it that runs down on back side of engine. I can remove upper cover if I disconnect hose. Tight fit, but it'll come out.
Quote from: chessie4905 on February 19, 2018, 05:31:04 PM
On my 4905 with Jakes the breather is on the top of the upper cover, not on side of upper cover. Lower cover has none. Upper cover also has a plugged approx 1 1/2 inch hole. The upper breather has a 1 inch hose attached to it that runs down on back side of engine. I can remove upper cover if I disconnect hose. Tight fit, but it'll come out.
The 1-1/2 inch hole is a oil fill hole
Quote from: richard5933 on February 19, 2018, 03:38:57 PM
Thanks - I'll let you know when they get here if they are side mounted or top mounted when they get here. I also will probably need to swap the solenoids for 24v versions, since these are most likely 12v. Hopefully those are still available somewhere.
Otherwise, I think I've got a complete setup coming.
If those came from a 92 series you are going to need bridges for a 71 series the 92 series bridges will not work on a 71 series
Confirmed today that the covers have the breathers on the side, and the bridges are from a 71. Should be good to go on both of those counts.
I did get a NOS fast idle buffer switch for the setup, at cost, from another shop in MN. Lucked into that. I think that the only thing I'll be missing are the solenoids, as the ones being sent are thought to be 12v and not the 24v needed. My assumption is that they can be found, perhaps even new if needed.
Anyone have experience making the needed extension on the engine cover to allow the taller valve cover to protrude? Or, does it just fit into the slight bump already present where the license plate mounts?
The factory bulge won't even come close to fitting. Mine is rectangular shaped with no ends. Allows more engine heat to exit, I guess. Made out of aluminum.
Quote from: chessie4905 on February 20, 2018, 11:25:14 AM
The factory bulge won't even come close to fitting. Mine is rectangular shaped with no ends. Allows more engine heat to exit, I guess. Made out of aluminum.
How much further does the cover need to protrude? Am I correct in thinking that the opening from the factory bulge will be large enough to mount the new bulge, or will I need to open the rear of the engine cover further? If the taller valve cover will fit through the opening left after removing the factory bulge, it shouldn't be difficult to fabricate a new one that looks similar to the original but sticks out further.
I went out and measured it. It sticks out 3 inches, is 34 inches long and 12 inches high. The attachment screws are out of site on top and show on bottom. License plate is mounted on it. This gives 1 inch clearance to valve cover with tailgate closed.
Quote from: chessie4905 on February 20, 2018, 03:48:29 PM
I went out and measured it. It sticks out 3 inches, is 34 inches long and 12 inches high. The attachment screws are out of site on top and show on bottom. License plate is mounted on it. This gives 1 inch clearance to valve cover with tailgate closed.
Thanks. That sounds like it's in about the same place as the factory bump. Were you able to keep the oil dipstick access door?
The factory bump is removed and this cover, which is same length and almost same height, replaces it. The tailgate is not modified. Oil door and everything else unaffected.
That's great to hear. Thanks.
I've been slowly putting this project together, and I'm just about at the point where I've got everything in place. If the valve cover will fit through the opening left from the stock bump, then I should be able to remove the factory bump before having the Jakes installed so that I'll be able to close the engine cover on the way home.
My plan is to fabricate a new bump that mimics the factory one but sticks out far enough to house the new valve cover. I think if I do it right I can even maintain the license plate mounts and maybe even the lights, although the license plate lights may need to be aftermarket. I've worked with a really great fabrication shop in town and I'm sure that they can get this done with no problem. It's a smaller mom & pop type shop and they are pretty willing to work on oddball projects like this.
Just about to get this project install underway. Before I have a new bump out made for the engine cover, I thought I'd give one last effort in finding a factory bump out that will clear the taller valve cover.
I've seen photos online engine covers with the bigger bump out, so I'm assuming that they were available at one time for buses running Jakes.
Anyone know of any salvage yards that might have such a thing? Anyone have an engine cover for a 4108/4903/4905 with the bigger bump out that they don't need?
Have never seen one. Ask Luke. How would know if the ever made one.
I have a question what is the purpose of a fast idle/buffer switch using a manual transmission
Quote from: luvrbus on March 06, 2018, 05:37:31 PM
I have a question what is the purpose of a fast idle/buffer switch using a manual transmission
I'm not sure I understand the question.
I'm not an expert by any means on how Jake Brakes work, but wouldn't I still want to be able to have fast idle work and to have the Jakes turn off when I depress the accelerator pedal? If you have something behind your question that would help me, then I'd appreciate some more information. It was explained to me that this was necessary to still have the fast idle function and have the Jakes properly turn off when they should.
Perhaps I'm using the wrong terminology, perhaps I don't fully understand, but this was part of the set of parts I was told were necessary.
I was just asking because I don't see many GM,Eagle.Mci.or Prevost with manual transmissions with the high dollar combo buffer switch all they have is the 5 to 40 buck micro snap switch mounted on the throttle linkage at the engine to keep the fast idle.Some have foot pedal control,clutch control, toggle switches and cruise control you name it there are dozens of ways to control a jake
My MCI has what I presume is the factory setup, a fast idle buffer switch (air cylinder and a micro-switch combined screws into the buffer hole). Electrically it goes power to dash switch (I set it up for both sides on, not hi/low) to clutch switch (jake only on when clutch is up) to buffer switch to solenoids. The alternative arrangement is for hi/low, and its power from the rear bus to buffer switch to hi/low/off dash switch at the front, back to the solenoids. My wiring harness had all the wires to do it either way. I never considered the fast idle to have anything to do with the jake function, I thought is was so you could idle fast and run the air conditioner or heater when idling.
Bevan6 - We're planning to go with the type of setup you have. Sounds like you've got the same combined switch.
I have maybe a 1/2 dozen of the combo fast idle buffer switches ,I just do it the way the customer wants to pay for,some go with the King Cruise with fast idle option you can buy those cheaper than the combo unit then they have cruise and fast idle .
Me personally I don't care for the fast idle on those old engines even with a fast idle under no load they still build gunk in the air box.I have a 8v92TA in the shop now from a MCI C3 the engine has been fast idled to death,Fast idle is on there just to keep the oil pressure and volume up, a DD will not oil good at the rear at 500 to 600 rpm.All highway DD engines come with a fast idle the military and industrial engines don't you shut it off
I took the stock engine door bulge off (not big enough for the Jake brake valve covers) and just let the valve cover exposed. Paint it, and sometimes I draw a face on it. Good Luck, TomC
I saw a neat bump out on a GM it was polished Stainless wire mess the guy had polished valve covers too
Richard -
Don gave you the measurements of the bump out on his 4905's tailgate, the cutout area on your 4108 should be identical.
FWIW & HTH. . .
;)
Quote from: RJ on November 29, 2018, 11:07:24 AM
Richard -
Don gave you the measurements of the bump out on his 4905's tailgate, the cutout area on your 4108 should be identical.
FWIW & HTH. . .
;)
I think you are correct - the bump I got from Luke was off a 4905. Got it installed this fall just before the weather turned cold.
There is another thread about the same topic which I replied to with some photos of my install:
https://www.busconversionmagazine.com/forum/index.php?topic=33651.0
Might be some confusion because I linked to this thread in one of my replies.
Yours is identical to mine except your ends are sealed.