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Author Topic: Two question..  (Read 2213 times)
tucsontattoo
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« on: January 20, 2007, 07:49:57 AM »

First, does anyone know where or who would have parts for my Primus heater system. Can't find anything on the web Undecided
Second, My old 8v71 is loading up pretty badly when it sits and cools off. Blows a big cloud of white smoke when you start it.Had to use eather to get her going the last couple starts. Found my air cleaners to be way beyond used up so ordered some new ones.
 Also noticed a hint of black smoke even on flat ground at 65. the white clears up a few minutes after starting but she seems to be running real fat all the time now.  sooo, the question is, do i run the rack, dump in a half gallon of ATF and change the air cleaners or should I be thinking bad injector. Any ideas how to avoid wasting alot of time and money getting this cleared up. Don't want to pay for a tune-up then have to go back in and change an injector.
  Also wondering if I could read the book and do the rack myself. I'm a pretty fair mehanic but have no expereince with THE RACK..

                  Whatdayathink???                           T.T.
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Ray Powell
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« Reply #1 on: January 20, 2007, 06:47:39 PM »

I have a friend who is a retired mechanic. He told me I could read the book, but that doesn't get it. It's the feel you acquire after doing several.
C Ray
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tucsontattoo
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« Reply #2 on: January 21, 2007, 05:36:18 PM »

Thanks for the anwser Ray.  Judging by the reaction and prices I get from the service people around here I guess I'll be doing the job myself. Not much choice in the matter. Wish me luck. I'v pretty much done all my other work myself so far. Don't see why this should be any different.
 Besides, If it is something you have to do a couple times to get the feel of, thats pretty much the way I usually do things anyway. Cheesy

                               Later   T.T.
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Barn Owl
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« Reply #3 on: January 21, 2007, 05:50:18 PM »

T.T.,

Keep us posted on the rack. It would be incredibly empowering to know how to do it. It seems to be the “Holy Grail” of the DD. I would like to know how to “run the rack” myself.

L. Christley
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L. Christley - W3EYE Amateur Extra
Blue Ridge Mountains, S.W. Virginia
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Buffalo SpaceShip
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« Reply #4 on: January 21, 2007, 05:57:26 PM »

T.T., your air cleaners are paper, I take it? Yours it the real cool-lookin' 4106, right? If so, the paper elements were not stock... GMC used oil bath filters.

Anyways, what kind of temps. is blowing white smoke? Does it ever get cold in Tucson??  Grin

White smoke is usually unburnt fuel and and can happen pretty regularly in a cold engine (<40deg.). White smoke in warmer temps. usually indicates poor compression. It could also be coolant in the fuel system (head gasket, etc.) Smell the smoke and see if it smells like diesel (and waters your eyes). If it's sweet-smelling, it's probably coolant.

Black smoke is also unburnt fuel, but it's been compressed and over-fueled in an at-temp. engine (over 150deg. coolant temp). Hot-rod injectors (C or N65s and over in your 8v71) can blow black smoke, and/or aggressive throttle positions. Or your rack needing adjustment, like you say.

I have heard that rack adjustments can be pretty tricky and can lead to engine damage if done wrong. If you do take this on, please post your experiences here. I too would love to have the confidence to do something like this.

HTH,
Brian B.
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Brian Brown
4108-216 w/ V730
Longmont, CO
Barn Owl
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« Reply #5 on: January 21, 2007, 06:11:55 PM »

I was thinking about it, I do not know of a shop near me that has anyone who would know how to do much with the two stroke diesels. Most of the mechanics I see are too young to have even seen one. I work next to the DD service center here and they don’t even stock the filters for my engine. My point is that if I took my bus in for service I would have to pay someone to learn how to do it, being the guinea pig, with no guarantee that it would be right. I can learn just as well as anyone else, and once you know how to fish…………..
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L. Christley - W3EYE Amateur Extra
Blue Ridge Mountains, S.W. Virginia
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tucsontattoo
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« Reply #6 on: January 21, 2007, 06:58:19 PM »

exactly my thoughts fellas, I know my old engine is in good shape, she is a very strong 318 with hot rod injectors. probably only has about 20,000 on it sence it was overhauled. I'm thinking I might have one injector with bad seals. When the engine shuts down with that plunger down she sits and drips fuel on that hole until the line pressure bleeds off. When you go ti fire it up shes loaded up on that hole.
 Yes, I have the paper element conversion and they were in pretty bad shape. I will change the filters first and throw in a gallon or so of ATF. I find no sign of diesel in my oil and no loss of coolant.
  We were at a pretty high altitude (colorado Springs) for most of our last trip. That and the big injectors could be some of the smoke.
 Thank for the input guys, Will let you know how it goes with T.T. vs DA RACK.
  I will be hooking my propane injection system back up this year also. I think that might help keep some of the carbon build up (a pit fall of big injectors) from fouling my injectors.
 
 
 P.S.  I know allot of guys who run the 8v71s don't belive in running the big 65 and 70s . I've done allot of miles in an old GMC Astro with a 318 and 13 speed road ranger and I think my Dad said we had brown tag 70 injectors. use to come outa of the rock quarry weighin about 110,000 lbs and pull about 20 miles of 5 and 6 % grades gettin back to the big road. Dad had the governer set at 2250 and told me " keep her wound up. Downshift around 16 and keep her about 2100 in the big hole" I must have put 300,000 miles on that engine running it just like he said. Never had to change anything but the oil and filters. He swore if you lugged a detroit you would screw it up.
 I think the big problem with these GMC buses is not enough cooling and not enough gears to keep her where she needs to run. Never had the temp guage climb so fast in a pull with my truck as I do in my bus. If I could figure out how to shift it, I would have a 10 speed roadranger hanging back there.....   Just my take on the Detroits and big injectors!!
« Last Edit: January 21, 2007, 07:39:39 PM by tucsontattoo » Logged

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Buffalo SpaceShip
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« Reply #7 on: January 21, 2007, 09:46:21 PM »

If I could figure out how to shift it, I would have a 10 speed roadranger hanging back there.....   

Oh, you could learn to shift it in about 5 minutes. But v-drives coaches will never have any tranny options except the 4-speed Spicer, or a couple of Allison autos (VS2-8, V730). I'd love to have a 10-13 speed RR! But I couldn't go back to the Spicer... I couldn't get my bus backed up my driveway with it.

I also have C65's in my 4108. The problem with the "hot rod" injectors, esp. at altitude where I live, is that it's always over-fueled, blowing smoke and creating heat. Climbing up the big grades on I-70 is insane... huge, billowing clouds of black smoke and me babying it to keep it from overheating. Plus, the higher you get, the lower temp. that water boils. It's vicious.

Yes, I do like the extra power at <3000ft (it's always near the KS/CO or NE/CO border that it starts dogging down again). But nearer sea level, it's pretty handy, and almost never "blows black" unless I'm just being stupid with the throttle.  She even gets good mileage, up to 8.5mpg, when I keep it under 2000rpm (~68mph), which is pretty good for a V730 coach.

Take care,
Brian B.
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Brian Brown
4108-216 w/ V730
Longmont, CO
Stan
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« Reply #8 on: January 22, 2007, 06:27:29 AM »

A couple of comments on running the rack: If you have an inline DD it is relatively simple. If you know what injectors you have, and the timing, get the proper injector gauge from DD and just follow the book.

If you have a V engine it is a different situation. It is the same procedure to do the left half of the engine. Making the right half pull the same load as the left half is the problem, where it becomes more art than science. The left rack is operatated by a short curved rod out of the governor. The right bank is operated by a long curved rod out of the governor.  The temperature determines the ultimate length of these rods. A curved rod tends to straighten, and get longer, with heat. The long rod changes more than the short rod. A very small change in rod length changes the rack adjustment. If you have someway to hold the entire engine at operating temperature while you run the rack it would be fairly simple, otherwise it takes years of experience to get it right.
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Buffalo SpaceShip
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« Reply #9 on: January 22, 2007, 07:47:02 AM »

I've always heard about the "art of running the rack." And now I know why.

Thanks for the info, Stan!

bb
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Brian Brown
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« Reply #10 on: January 22, 2007, 12:30:37 PM »

Any mechanically inclined person with the right tools can set the rack on a 2 stroke DD. If you follow the book, you will not cause a disaster. On the other hand, it may not be as good as it was before you started.  I did one of my 8V71 engines so many times (trying to get it right) that I could do it in the dark. I had a DD approved shop do it and they made it worse than what I had accomplished. I was then referred to a young (about 35) mechanic who had been doing them since he was 18. He  had his own shop doing nothing but 2 strokers..  I watched him do it and he spent about two hours, but he had the engine performing better than it ever had since I bought it. Most  of the two hours was spent on the right bank, going back and forth between banks and feeling things with his fingers (amount of movement, amount of freeplay, etc.) and then making another adjustment on the right bank..
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Utahclaimjumper
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« Reply #11 on: January 22, 2007, 04:31:50 PM »

I learned to "do the rackboogie" about 8 years ago and have done it several times since. But be real carefull the first and evan second time, the first and second time I made the adjustments the engine RPM went straight to the governed speed on start-up these things will really get your attention. After a few times I aquired the "feel" and got it right. >>>Dan
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Utahclaimjumper 
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tucsontattoo
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« Reply #12 on: January 22, 2007, 06:20:30 PM »

Thanks for the help guys, I will be trying this myself in a few weeks. As has been mentioned, most all of the service people I talked with here in Tucson are younger than some of the socks I own. Swore a while back I wouldn't let anyone who doesen't have the raido tuned to the oldies station work on anything I own.
 Use to watch my father run the rack on our old trucks, kinda know the drill but its that feel thing that I do worry about. Have heard a few D.D.s hit high C on start up. I worked as a deisel mechanic for the big GMC dealer back home when I was young but the rack stuff was always left to the old guys. The young guys got to do the transmission and suspension stuff
 But if anyone is going to learn how on my equipment it will be me!! I'll be doing alot of reading this week and If you guys don't mind some brain pickin. so I'll post more later.
 Thanks again for all the input and support, especially the long rod short rod thing. Stan, if its not to much trouble maybe you could elaborate a little on what you would be feeling for when you reach that point of balancing the right bank with the left.

                             Thanks again..............  T.T.
« Last Edit: January 22, 2007, 06:22:50 PM by tucsontattoo » Logged

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« Reply #13 on: January 23, 2007, 05:35:20 AM »

tucsontattoo: As I said in my previous post, I gave up trying to get it right and went looking for expert help (Iknow it is hard to find).  With your experience, I definitely would be giving it a try. Get the proper injector gauge (about $5.00 at a DD dealer)  IIRC, on a 8V71 with 60 injectors, it is a 1.460. BTW: A proper valve adjusting wrench makes doing ther valves a lot easier. Make sure you have new cotter pins for the rack clevis pin.

 One thing the mechanic did show me was to put one hand on a middle cylinder exhaust on one bank and your other hand on the oposite bank. From a cold start you should feel warm at the same time on both hands. You can do this on a MCI with the fan belt off and on engines with a side rad you have to stop the air flow that will cool one side more than the other.

I am quite sure that the mechanics who do a good job on the rack sent out a lot of less than perfect jobs as they learned all the secrets of doing it.  Also, there seems to be a wide range of being "just acceptable" and being 100%. With modern day electronics, it should be possible to measure all the parameters as you make the adjustments but by the time these electronics were developed the 2 stroke was a dying breed. 
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Barn Owl
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« Reply #14 on: January 23, 2007, 10:10:54 PM »

Quote
put one hand on a middle cylinder exhaust on one bank and your other hand on the oposite bank

Do you think an infrared thermometer would work as well if not better? Checking exhaust temps makes sense to me.
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L. Christley - W3EYE Amateur Extra
Blue Ridge Mountains, S.W. Virginia
It’s the education gained, and the ability to apply, and share, what we learn.
Have fun, be great, that way you have Great Fun!
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