Quote:
Originally Posted by rdt9910
Hello -
I just recently picked up a 1990 Crown Super Coach and have some initial questions regarding the Detroit 6-71T.
First where would be the best place to pick up service manuals for this particular bus? Not finding a whole lot online.
Secondly, I was told this particular bus doesn't have a governor. Not sure if that's by design or failure but how could I verify/fix this issue. I am new to driving the 10 speed and I am afraid of over revving this thing if I haven't already.
Can anyone suggest a fair/honest Detroit mechanic in the Billings area?
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I've read the other posts but will reply to this one.
First, Take a deep breath, and lets approach things slowly and logically.
So many posts/replies without enough information to answer properly.
Please post as much info as you can on the specifics of your Crown. Like is it a mid-engine Crown Super Coach as you stated, or a rear-engined Crown Super II as I think a couple other posters thought it might be. How long is it? 35, 36, 38 or 40 Feet. Try posting a pic when you can, or wait and send it to me as an attachment in email. How many axles 2 or 3.
Couple of things I'll infer, with no real data yet, like the others, but I'm willing to take some wild ass guesses based on what you've said so far.
It sounds to me like a mid-engined Crown Super Coach, reinforced by that little comment of that driver foot rest by the clutch pedal, that was a cool feature used on the Crowns forever and not so much on the Crowns II's which mostly had automatic transmissions when new. Also the ten speed is a giveaway because as I said most Crown II's were Allison autos and no manual transmissions, except for a very rare few I've been informed were special ordered by that district.
First off, all Detroit 2-strokes have a governor which is required for it to even operate at all, period. In the mid-engined mounted pancake Crown installation the low idle speed should be adjusted to about 650rpm. If your tach isn't showing about this, then I'd suspect the tach is off, not the engine.
At the top engine governed speed the series 71's were governed at about 2150 by the book. They were easily bumped up to around 2300 or a little more to gain more road speed from the school bus 4:10 rear-end gearing which would give almost 67mph or so, instead of the usual 63.
Try it out by giving it full throttle, while sitting still in neutral, and see were it goes and note the speed setting on the tach. Be suspicious of the tach until you can verify it isn't lying to you. Get it calibrated and or get a separate laser style rpm reading tool and measure the engine rpm directly from the crankshaft pulley. This isn't hard to do and most shops should have something on hand if you don't want to buy one yourself. Available on ebay or amazon for $20-30 and will come in handy as you convert the bus. If the governor is working correctly, you can't hurt it by over-revving it, it simply won't let you. If it's adjusted correctly. You should verify that pretty soon though with a mechanic.
Again, there is NO such thing as a road speed governor. It's all done by the normal operation of the engine governor and rear-end ratios. And there are no computers involved anywhere in the engine or transmission. Purely a mechanical system which is the very best thing to have. It will run forever. If you don't understand just how special that is, you will soon enough, when you see how reliable and solid a Crown is and that it will always get you home.
I also suspect that as you learned to drive, and did all the stuff you aren't describing, but I know you did, as you learned the very hardest of ways to drive a 10spd stick shift. You missed gears and had the throttle maxed out, and were trying to recover and find any gear at all, you may have noticed the tach swinging monetarily way high and showing 2500rmp.....that wasn't accurate and a result of the tach itself internally overshooting.
The engine is set for whatever it's set at and it won't go higher than that.
I'd also forget whatever that seller told you about the bus, since he obviously was very misinformed, and start doing your own research and get your own facts. You'll find that an amazing and enjoyable journey.
The engine governed high speed no-load setting is the highest it will go and determines the max road speed along with the rear-end ratio. Most Crowns were sold with the school bus gearing of 4:10 where they would do a very max 63mph at about 2200rpm. Some bumped the engine to 2300 or a little more to gain some road speed. For a private owner looking for 70+ mph highway speeds you'll have to change the rear-end ratio, which is a simple thing to do. You may also look at changing that 10spd to an Overdrive transmission, but that means taking it out and having it opened up and the gears moved around internally. No big deal, once it's removed and on a bench, but that's a chore. The differential is probably easier.
It's good to want to find a local 2-stroke mechanic. I'd suggest that you look for city bus lines, charter companies that have been around for a while and had MCI, Prevosts, maybe even GMC coaches, all with 2-stroke engines. Also some truck companies may still be running them for logging and oil field service. The oil patch still uses a lot of Detroits so you may be able to find a service company that has experienced 2-stroke mechanics around. Even stationary backup generators in hospitals and other places like that had lots of Detroit 2-strokes as the engine of choice. You may find out whoever services those. The Detroits aren't gone but the Gov't Nazis are doing their best. Good luck.
There's a ton of stuff to go over and I can't do it all at once. The important thing is to find out exactly what you have and I'll help you with how to get info and lead you in the right direction.
You can get engine manuals, which I've been doing for years online and that's no problem. I do use Ebay quite successfully and get good bargains.
Also the transmission manuals. About that transmission. Can you describe how it shifts, exactly how it shifts. Do you do the first five gears in low range with no air valve operations? Then pull it into high range and do the five again? If so that's 99% an (Eaton)-Fuller Roadranger style of operation and what most 10spds were that got installed in Crowns. If, by chance, you have to flip a little (air valve) lever to "split" each gear while in that gear, then that's a Spicer transmission and certainly not a favorite of mine.
One other thing, if it's a Fuller, is the shift pattern, and where 4th and 5th gear are located.
Note this carefully. If 4th gear (and 9th) are up and to the right as in a standard pattern then you have a non-overdrive where 10th is a direct 1:1 output ratio. If 4th is DOWN and to the right and 5th (and 10th) is up and to the right then that is an Overdrive with an output of about 1:.87 for about 12mph higher road speed. If so it may do a little over 70. But check and verify your speedo and tach before you believe anything, or use a GPS to verify true road-speed.
Get under the bus and look for ID plates with manufacturer, models, and serial numbers.
The Crown itself didn't really have manuals as most people think of them for other vehicles. Crowns are essentially built as a Peterbilt or Kenworth tractor is built, as a totally customized vehicle to the customers specs. Their "Manuals" consisted of 3-Ring Binders with the information from the various manufacturers of the components used in that Crown build. This is the one reason why Crowns are still on the road and in commercial service after more than 30 years, at least, of the last ones built in 1991. Due to the commonly available and mostly still made parts used in the Crown. Fifty+ year old Crowns are still being run and they are easily kept in good condition and parts are available to do that today. You can research whats used on your Crown and duplicate those binders for yourself and be in good shape.
I should stop now, and I Strongly suggest that you contact me directly via email and we can talk on the phone too for a better ability to impart the needed information you're going to need to get comfortable with you're Crown.
I look forward to hearing from you and I can take away your apprehension as well as getting you together with other Crown owners for their inputs to your concerns. There's a guy in Montana with a Crown who could be of assistance.
Crown ownership is becoming a new sub-culture as more and more folks acquire them all over the country. I expect to see more dedicated support groups spring up to help with supporting the community. Welcome and you'll be amazed as you learn more about your Crown.
mikemcc2k@yahoo.com
He has an uncanny ability to sniff out everything Crown and I've learned a lot from those discussions. 
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