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Author Topic: Coach Cooling System Modification  (Read 10201 times)
WorkingOnWise
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« on: April 15, 2007, 08:19:15 AM »

Hi All,
1) What would be the problem with changing the cooling system on a 1966 GMC TDH4519(Fishbowl) with a 6V71 and an automatic trans,  so there were no heater cores for parlor heat? Just the components needed for the engine, and small lines up to the dash and a small automotive heater core for defrost and driver heat? Except for the drivers heat and windshield defrost components, all cooling system components would be in the engine compartment. Parlor heat will come from an rv furnace.
I know that it will dramatically reduce the cooling system capacity, but modern day vehicles of the same weight, load, and horsepower get by just fine on 20qts.

2) What would be the problem with running a 12psi cap on a modified coolant tank, and allowing the engine to run at 195-205 operating temp? Much like a modern engine?

3) Can I loose the factory fan and run an electric fan instead? Or does that fan do more than draw air?

4) Why is the (I'm assuming it's a) fan clutch mechanism so long and heavy? It seems I could save a few hundred pounds by removing that and using the electric fan I mentioned in 2.

Thanks for any and all answers/ideas.

Keith
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tekebird
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« Reply #1 on: April 15, 2007, 09:10:18 AM »

I think you will find that stretching your bus will be a huge project, while doable, it won't be by most.  Keep in mind that everything on your bus is structural......start removing rivets at the rear and the engine will drop onto the ground.

as for your cooling system.  There is alot of arguement on both sides on the elctric fans......biggest is you loose that sensor and you overheat quickly.......

Removing your coach heat is no big deal other than loosing good free heat......while only saving a bit of coolant and gaining some small space.

your bus ins supposed to run at 180 degrees......205 is very hot.

You fan clutch is big....but what do you think saving 100 lbs will save you?


just my thoughts....but you ought to consider buying a bus that lends itself to a stretch or is already
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TomC
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« Reply #2 on: April 15, 2007, 09:29:00 AM »

PLEASE- leave well enough alone with the cooling system.  The 2 stroke engines are sensitive to overheat, 210 is the absolute highest they should go without cracking heads. 
Electric fans will NOT pull enough air through. Remember you are sucking all the air from the side rather than the nice frontal ram action trucks and cars have.  On my bus, the fan is a straight gear drive that is direct connected all the time.
On my transit, I ditched the under floor heater system (was a Portland Or bus, no A/C) and kept the big heater core.  Had it tested and mounted it going the length of the bus in the hallway beneath my closet/washer-dryer.  Then have 2-14" elec radiator fans with four vents just dumping into the hallway-no ducts.  It is so powerful, that when you turn it on, count to 10 and you can feel heat at the front of the bus.  Also kept the front defroster-that alone can heat nearly the whole bus.  You will be woefully disappointed trying to use RV heat while driving.  If it is propane, it will be blowing out constantly as you drive.  If you have hydronic heat (that takes alot of space) you could use that.
I hope you have at least a 3 speed V730 Allison transmission.  If you have only a 2 speed with the 6V-71, it will be actually unsafe to drive.  In my opinion the 6V-71 is not enough power. Luckily, you could change to the 6V-92TA without too much problems with the V730.  It will require a larger radiator, air cleaner and muffler (I know I just turboed my 8V-71), but since you're keeping it for the long run, it will be worth it.  What would really be the absolute best would be to have a Detroit series 50 (4 cylinder that can put out 350hp with 1100lb/ft of torque) used with a reverser gear (V drives run in reverse rotation) to
accommodate the V730.
Highly recommend that you look at systems that others are using and what is commonly used in the RV industry and keep with that.  Then your theory of simplicity with the fishbowl will be maintained throughout your conversion.  Good Luck, TomC
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Tom & Donna Christman. '77 AMGeneral 10240B; 8V-71TATAIC V730.
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« Reply #3 on: April 15, 2007, 09:30:51 AM »

with all these mod's you want to make to your bus ...I think you bought the wrong bus ... JMHO
Ron
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WorkingOnWise
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« Reply #4 on: April 15, 2007, 09:59:11 AM »

Paid $100 and drove it home...I way bought the right bus!
As for the powertrain, it is a 6V71 and a 2 speed.
I am perfectly happy tooling around at 55-60mph and 45 on the grades. I have no desire to go past 60 in anything I am in control of that weighs over 10k lbs! I'm kinda conservative that way. (My kids call it "chicken", but what do they know?!)
Seriously, I'm good with underpowered by todays standards.

For the cooling system, 210f is the dangerzone? Cracked heads? I figured that as heavy as the DD engines are, and as big, anything short of a gallon of nitro poured into the intake would result in noisy protests at worst!

My desire isn't to modify for the sake of change, but to improve on what I have. Engineeres thought differantly and didn't know what we know today. The boost in temp is an attempted boost in efficiency. The boost in system pressure facilitates that.

The weight savings from dumping the clutch fan assembly is for handeling. Any weight removed from the engine compartment, or anywhere behind the rear wheels, will help with ride and handleing, if the shocks are adjusted to matck the new load.

As I said, I'm looking for improvements, bases on modern practices. I won't make a change that I think will increase complexity or reduce reliability. But I will brainstarm, and then throw it out here to see what comes back!

Thanks
Keith
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Paso One
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« Reply #5 on: April 15, 2007, 10:10:29 AM »

Hi Keith
 Is your bus a suburban Fishbowl??
 Where did it originate from??

 Have you crawled under the unit and read the differential Tag??

Have you had it on the highway???

I ask this as many of the "transit " Fishbowls have the 5:39 rear end which basically gives you 48-50 Mph with the VH 9 2 speed tranny.  That lets you see a lot of scenery on a trip.


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68 5303 Fishbowl 40' x 102"
6V71  V730 4:10
WorkingOnWise
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« Reply #6 on: April 15, 2007, 10:14:28 AM »

Paso Said "I ask this as many of the "transit " Fishbowls have the 5:39 rear end which basically gives you 48-50 Mph with the VH 9 2 speed tranny.  That lets you see a lot of scenery on a trip."
LOL!!! Yes it would!

Actually, the current rear gear doesn't matter because it will get a 2 speed diff, so I'll switch to the highway gear when I need it.
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tekebird
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« Reply #7 on: April 15, 2007, 10:24:29 AM »

Keith, Not knowing your qualifications and background I am going to have to say you have a huge project in front of you and alot of learning to do and alot of mistakes to make.

shaving a few hundred pounds is not going to affect your handling at all....keep in mind that your bus was designed to tote around 40 people at 160# each or so 6400# and that does not include standees.....this is not a japanese tuner car.......that you can goe by adjustable shocks etc for on the internet.


Screwing with the cooling will result in cracked heads......and at an op temp of 205 you are alomost to that point.

Also with that two spped tranny...with any grade your likely going to be closer to 20 mph

Just curious:  What do you intend your budget to be for the completed project?  And what ammount of time/labor do you think it is going to take?






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WorkingOnWise
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« Reply #8 on: April 15, 2007, 10:50:58 AM »

For qualifications, mechanical and electronic engineer, master auto mechanic, and more pig-headed that my wife can appreciate at times.

For the weight savings, no, a few hundred pounds wont matter unless they are in an area where it act like a lever, as does all the weight aft of the rear tires. 125lbs removed from the cl of the engine removes 400lbs of weight from the rear tires. I must remove 400 lbs just in front of the rear tires to have the same effect. I know it sounds wrong, but it's in the leverage and position of the weight. The vehicle weight will only change by 125lbs if I remove 125lbs, but the balance of the vehicle will change by 400lbs.


For things to learn and mistakes to make...yup! Thats why I'm here.


I will be using a 2 spd diff, so in theory I'll be ok on the grades.

As for the budget- 15k and 1 year to be able to use it for weekends. Thats shell completed, interior in, basic services in and outer shell done and sealed, and tires.
another 60k  and 3 to finish the interior, paint the shell, good windows, fixtures and appliences, another set of tires.

We shopped for the coach we wanted, and when we found it, the price tag was 270k. And it was so modern that I would need another 12k in tools to service it, and still need help from the dealer. I don't trust many mechanics, and theres no way I'm letting some jo-bob wrench on a 270k vehicle of mine! If I cant fix it, it's not worth fixin. I have made a lot of money off the modern technology in todays vehicles. Most of it is un-needed at best. I'm anti-complicated. My DD6v17 runs as well or better than one with a DDEC system on it, and burning veggie oil, as I do, it's cleaner...and after it's started you can remove the battery and take it for a drive. Try that with a modern coach...lol

Sorry ..... I'll put away the soapbox now...

Keith
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Sam 4106
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« Reply #9 on: April 15, 2007, 11:20:01 AM »

Hi Keith,
If you find a 2-speed diff. that will work in our older GM buses please post here where you found it because there will be a lot of us that will want one. Have you been under your bus to see how the pinion shaft enters the diff. at an angle? I think this is unique to a v-drive bus and unless you build your own 2-speed, I don't think you will find one. I hope you do because then I can put one in our 4106 and make it a lot more driveable with the 4-speed manual transmission.
My experience has been that no matter what you think it will cost to convert a bus, you will be way under estimating. One way we saved a lot on our conversion was buying a late model wrecked travel trailer and using its components. I was amazed at the amount of small things we used from the trailer that had never gotten onto the list of items needed to convert a bus.
You have come to a very good site to learn about your hobby. Please continue with your questions and you will learn a lot here. Not only that, but, you will be helping the rest of us to learn along with you.
Good luck with your project. Sam 4106
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1976 MCI-8TA with 8V92 DDEC II and Allison HT740
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« Reply #10 on: April 15, 2007, 11:47:25 AM »

Obviously the reality of what you want to do has not set in yet.

Messing with the cooling system, Stretching an already limited chassis another 10 feet.
changing structural systems and DOT approved systems.

Running with an orphan powertrain with few parts available. That 210 hp 6V71 will dust your cookies as will the 2-speed
tranny.

If you want to be more realistic, Buy an RTS with a 6V92TA and V-730, gear it up for highway.

Buy another RTS shell and cut a section and add it for your 45 foot size.

It will be much cheaper and nicer looking and parts will not be an issue for the next 20 years.

 Cool Cool Cool
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« Reply #11 on: April 15, 2007, 12:55:28 PM »



"The weight savings from dumping the clutch fan assembly is for handeling. Any weight removed from the engine compartment, or anywhere behind the rear wheels, will help with ride and handleing, if the shocks are adjusted to matck the new load"
                       
                                                If a skinny friend wants to go for a ride,Dont let it sit in the back of the bus.......OR you will be back to square  one.
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NJT 5573
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« Reply #12 on: April 15, 2007, 01:01:49 PM »

Keith, I hope that was a misprint on your grade speed. The real speed on a real hill is going to be around 4.5 mph, not 45 mph. If you try to pull a trailer with that 2 speed you should consider a push vehicle as that tranny and engine combo will not pull the hills in low lockup with your trailer and its going to build a lot of heat in low converter. Perhaps an air cooled Deutz in the trailer would help. (Less coolant)! and a true pusher. The day of the 6V71 and 2 speed Allison are gone. In my opinion if you cross the California border you could risk being towed out of the state as well as jail time. CARB is gonna freak! The 2 speed Allison was designed for stop and go city driving. If you run it down the highway you need to stop and start often to cycle fluid thru the tranny to avoid melting the seals in the converter. It was not designed to be driven more than a few miles in hi lock. Any attempt to increase coolant pressure will need to be followed up with engineering improvements in hose and clamping areas. The main reason we don't run a lot of pressure in bus cooling systems (pre DDEC) is when you loose the coolant, the coolant temperature reads cold, not hot and you usually loose the engine as well. If you run over normal pressure on the cooling system it has to be tight and strong enough to hold up at highway speeds. Also realize when you tear into a 7 mile pull up the mountain, so you can see the other side, that I wasn't joking about your road speed not being anywhere near your projections. Seven miles up at 7 MPH is realistic with your equiptment. Last time I sat on a 7 mile pull at 7 MPH it took me almost an hour to get over the top! That is why the old time engineer put a 125lb fan on your bus. Paso One said it best "your gonna get to see a lot of scenery".
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WorkingOnWise
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« Reply #13 on: April 15, 2007, 06:29:07 PM »

It is obvious, but I will say I have never driven this coach, or any coach with a 2 speed, past 42mph. The tires on it right now are really rough, so I have not pushed my luck. As it is a project right now, tires are not a priority.
With that said, my thinking is this, regarding highway capabilities. The 4519's all had 6v71's and either 4speeds or the 2 speed auto. They did highway service, even if it was not their intended purpose. That led me to presume that the limitations are purely gearing, and with the right gears, it will do whatever I need it to. The engine is not a limiting factor up to maybe 65mph.
Am I on track in this thinking? Even if it means a differant trans?

NJT 5573 said "If you run it down the highway you need to stop and start often to cycle fluid thru the tranny to avoid melting the seals in the converter. It was not designed to be driven more than a few miles in hi lock."
The fluid doesn't circulate enough in high lock to prevent damage? Is this trans really that bad for highway use? I know a 2 speed is not ideal for highway, but is it as bad as it sounds?

"The day of the 6V71 and 2 speed Allison are gone" While it may be true of the Allison (I have no idea and won't claim to know these tranmissions), IMHO, the day of the 6V71 is here now more that enev, compared some of the over-complicated hulks that are available today. The beauty of a diesel engine is in it's simplicity and reliability. Numbers don't tell it all. Yeah, sub 300hp engines can be tough to live with at times...but not near as tough as a 375hp engine that wont run because some $400 sensor that takes 5 hours to replace has failed! Yes, parts for a 6V71, and the rest of my coach, are sparse. So is money sometimes, and parts are easier for me to make that money is. Those government types are persnickity about printing money!

Sam 4106, I have a few ideas for the 2 speed diff that I have to develop more, but I am confident that it will work. The pinion angle looks to be the only major hurdle. I'll post more as I develop it.

DrDave-Reloaded said to get a RTS...better looking finished project...
Nothing looks as good as a Fishbowl silly!

Maybe this thread needs to fork? We have drifted away from cooling systems a bit?

So it sounds like the objections to the cooling system mods I asked about are centered around leaks introduced from the increased pressure, and not knowing it by the gauge? So what if I could be equally sure that I won't spring any leaks at 12psi and 195-205f as I am of the factory system? Is that the only concern? Does reliability drop at that temp range? Do I run a risk of engine damage? Cracking heads? I can build a systen that won't leak. I can't build one that won't crack the heads if 220f with no steam pockets is all it takes.
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tekebird
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« Reply #14 on: April 15, 2007, 07:06:32 PM »

you will not gain any appreciable efficeincy running at 195-205 even if you don't crack your heads.

Don't you think the big room full of engineers might have an edge on you as well as the rest of us in the engineering department.

I just  sold my 4104 with a 6-71 ( inline) that I have driven all over the country and had  been in the family for 30 years.......and the new Corporate owners plan on doing a three year all over the coutry promotional tour with it........so power is not the issue.

Your trans may not be that bad.......early Buffalos came with VS2-8's and ran fine...in fact the newest addition will be headed east from CA on Wen  with a VS2-8.  On it's test drive it got to 75mph.


your larger headach will be the gearing.......and I think your two speed rear will be a problem as well

I would thin that if your willing to spend 80k over whatever period you might like to have something worth more than junk value at the end.  Unfortunatley that is what most fishbowl Conversion are worth.....and thats why most of them are not done to a high standard as far as the conversion.....hole with 6 wheels





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