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Old 03-21-2005, 10:15 PM   #1
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Major engine problems

So I just took our bus in for a mechanical inspection. I thought it was in pretty good shape considering it ran, started, changed gears and stopped all without horrible noises or mysterious fluids leaking out. Oh, how wrong I was. The mechanic did a compression test and found that two cylinders were at 0, one at 65, another at 85, and the rest over 100 but still low. So it is currently running on 5 cylinders, which explains the lack of power (even for a bus) and poor milage. Their estimate was that the exhaust valves were pooched. The propane burns at a higher temperature and caused them to burn out (he figures ).
So we are looking at a minimum of $1500 for repairs up to $4000 for a rebuild. I contacted a shop in town that specializes in motors and they want to do there own diagnostic (understandibly) then go from there. That's the best estimate I can get. ARRGH!
I have invested too much time to dump this bus and get another that may have a similar problem. So I think we will bite the bullet and pay to have the shop fix the stupid thing. I thought of doing the job myself but I am a touch overwhelmed about the idea of tackling such a large job without a shop and much knowledge of propane converted engines.
I'll keep you all posted with the progess. -Richard
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Old 03-21-2005, 10:41 PM   #2
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OUCH! Sorry to here about your engine! As a small engine mechanic (I also do most of the work on my own vehicles), I woudl heartily suggest biting the bullet and go for the rebuild. The reason being: you could pay that $1500 to get the valves done and something else could go out on the way home. If your compression is that low on so many cylinders, it is highly likely that other engine parts are worn or damaged from the heat of the blow-by. Believe me, I know how painful major repairs can be, but it's cheaper to do it right once than piecemeal many times.
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Old 03-22-2005, 11:13 AM   #3
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To replace or not to replace the bus, that is the question.

Hello Everyone. Since my enging problems I am trying to decide if it's worth rebuilding the motor in the 85 gmc or to purchase another one that's already had a conversion done on it that is in relitively good shape.
The mechanic finished the inspection on the gmc and explained that the rest of the bus was in good shape, it's just the engine. So I don't know, mabye it's worth keeping. I was looking in the paper today at converted buses and found this one. I would attach a photo but I don't know how. It looks pretty sweet though. Mabye it would be simpler just to purchase somone elses bus that is proven and works. The guy who owns it has gotten a bit older and is not racing cars anymore. He converted it. here are the specs.
I need help making an educated decision. If I opt for this, then I still have to sell our bus. Which will be a pain I am sure.
HELP ME PLEASE!!!


1975 – Blue Bird (army bus)
30’ total
Flat nose
Air Brakes
Decent tires
Runs well (he said)
gas (5.somthing litre he could not remember)
Allison transmission auto
Signal light broken
Generator Honda 4.5 kw
carries 2 race cars, a/c, awning, stove, shower, bunks, roof rack,
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Old 03-22-2005, 11:45 AM   #4
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I don't know what an engine swap would cost or if you would want to do it yourself. It may be something to consider though. It is usually not hard to find a rust bucket with a good engine for cheap.
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Old 03-22-2005, 11:58 AM   #5
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Busone.

Well, I looked around at used engines. They range from $1000 and up. But I do not feel capable enough without an enclosed shop to even attempt it myself. The shop said it would cost almost the same to switch engines as it would to rebuild the current one. Also I do not want to buy someone elses headache and be in the same position in a few months. I am sure there are those that feel confidant about switching engines or opening this one up, unfortunatly I am not one of them (yet). Thanks - Richard
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Old 03-22-2005, 12:29 PM   #6
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Re: Busone.

Quote:
Originally Posted by captainkf
Also I do not want to buy someone elses headache and be in the same position in a few months.
I think this could still happen if you buy the Army bus. At least with your current one, you KNOW what's wrong / right with it (outside of the engine). I still think you'd be better served to have the rebuild & done by someone reputable that will give you more than a "Threshold" Warranty, and you'll have (essentially) a new engine. Just a thought.
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Old 03-23-2005, 09:59 PM   #7
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Made a decision.

We decided to have our buses engine completely rebuilt by a shop that specializes in such things. I looked at the other bus, and was very tempted. To the point of calling off the tow truck driver last minute. It was tempting becuase it had so many things (ac, generator, forced air furnace, water heater, loading ramp to carry jeep inside the bus, winch) I wanted. But I had such a bad gut reaction to it when I went to pick it up. It is very low with only 9" of clearance under the engine's exhaust system, which would inhibit boondocking. When I started it up to move it there was a mysterious red oil like liquid spraying out from under the engine and the air stunk like gasoline. I thought "great, another fixer upper". So I backed out and feel this was the smart decision. With a new motor I should be good to go for 200.000 plus kilometers without headache or concern. But, oh it was nice to have the 6'3" of clearance inside. Oh well. -Richard
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Old 03-23-2005, 10:17 PM   #8
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If it's a 366 Chevy, you may want to upgrade--a 427 or 454 should bolt right in, & give you a much-needed power boost for the hills.
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Old 03-24-2005, 02:28 AM   #9
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Re: Larger Engine?

I had considered that however I was concerned about how the mechanics of the rest of the engine would work. They are as follows:
-How would the propane conversion work? Would I need a new carburator or interface?
-Is the cooling system sufficient for a larger engine?
-Would the tranny bolt up?
-Can I use the same motor mounts?
-Would I need to replace any other components that make up the engine as a whole?
-How much power would I gain?
-How would this effect my fuel economy?
-If I go for the rebuild is it worth looking into some of the aftermarket components that are designed for "rotroding" such as camshafts, bored out pisons and different compression ratio's?

Thanks to any and all answers. -Richard
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Old 03-24-2005, 05:57 AM   #10
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Re: Larger Engine?

I don't know anything about propane conversions, so I won't touch that.
The folks you mention at the engine specialty shop should be able to answer the rest of your questions. Since this is their forte', they should be able to give you list of options from a straight rebuild to complete hotrod blue-printing, and what benefits / detriments any modifications would have.

Anyway, they may have to re-work the pistons & cylinders, so it may not cost much more to have it bored & stroked. Along with the extra power however, will be a suffering of fuel economy if this is done.
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Old 03-24-2005, 10:42 AM   #11
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Re: Larger Engine?

Quote:
Originally Posted by captainkf
I had considered that however I was concerned about how the mechanics of the rest of the engine would work. They are as follows:
-How would the propane conversion work? Would I need a new carburator or interface?
-Is the cooling system sufficient for a larger engine?
-Would the tranny bolt up?
-Can I use the same motor mounts?
-Would I need to replace any other components that make up the engine as a whole?
-How much power would I gain?
-How would this effect my fuel economy?
-If I go for the rebuild is it worth looking into some of the aftermarket components that are designed for "rotroding" such as camshafts, bored out pisons and different compression ratio's?

Thanks to any and all answers. -Richard
Propane carb & interface should work, though it may need to be adjusted (basic tune-up stuff).
Cooling SHOULD be enough...I've seen a 366 radiator cool a 335HP 502 in a box truck.
Since the 366, 427, & 454 are externally the same, the trans & motor mounts should bolt right up.
You MAY need a different flywheel/flexplate & harmonic damper for a 454...not sure.
A 427 would be worh an easy 50HP over a 366...a 454 75+HP increase.
Replacing a 366 with a 502 in a C-60 box truck actually INCREASED mileage ~1MPG, because the engine wasn't running WOT all the time anymore.
If you are keeping the engine propane-fueled, bump the compression (propane's octane rating is, IIRC, 106). DO NOT DO THIS IF THERE IS ANY CHANCE YOU WILL BURN GASOLINE IN THE BUS!
DEFINITELY get a better cam...call Crane or Comp Cams, tell them the vehicle details, & they'll tell you what you need.
Don't overbore more than ABSOLUTELY necessary....030" is good, .020" (if pistons are available) is better.

I would not even think about doing this without using:
Fortged pistons with chrome-moly or tool steel rings.
Stainless steel valves & hardened seats, intake & exhaust.
Maybe sodium-filled exhaust valves (not cheap)
ARP studs on the main bearings.
Double roller timing chain.
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Old 03-24-2005, 10:46 AM   #12
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Jarlaxle?

Could you please expain the last list? Why would you replace with those parts? How do you think this will affect the milage? Thanks. -Richard
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Old 03-24-2005, 11:12 AM   #13
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Re: Larger Engine?

Quote:
Originally Posted by Griff
Along with the extra power however, will be a suffering of fuel economy if this is done.
Thank you Jarlaxle, you are correct, I should have said "MAY be a suffering of fuel economy depending on the modifications".

Captainkf: Jarlaxle is on target on his list of recommendations. I know what he's talking about, but don't know how to put it in layman's terms like he will be able to. The bottom line is: these parts are more durable & will stand the heat better.
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Old 03-24-2005, 01:14 PM   #14
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Griff

Thanks Griff. I contacted the engine shop this morning and talked with the head forman. He said don't do it. The 366 has more torque than those other engines. Beause of the shorter piston arms it is able to get more low end torque while being better on fuel than a larger displacement. Also it will cost less. The 366 is used in many moving vans, buses and other comercial vehicles where the low end torque is an asset while not needing the higher RPM's. Just thougth I'd put this out there as I had not read it anywhere else on this site. -Richard
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Old 03-24-2005, 01:40 PM   #15
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OK, so much for major bore & stroke, but Jarlaxle's list is still a first-rate suggestion on the parts & basic cylinder bore / honing!
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Old 03-24-2005, 11:17 PM   #16
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I have a 88 Chevy Wayne bus, it had a 366 with an auto tranny.
I have a steep hill to climb to get it in my backyard. With the 366 engine, it ran out of power and would stop at the top, not making it up.
I had to back down and get a run at it and jump the curb.
I replaced the 366 with a 454, and now it will spin the wheels going up, if need be. It has a WHOLE LOT more power and torque. It dropped in and bolted up fine. I can't tell any difference in gas mileage, it still drinks gas like there's no tomorrow. It now does 75+ MPH.
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Old 03-25-2005, 12:48 AM   #17
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Re: Griff

Quote:
Originally Posted by captainkf
Thanks Griff. I contacted the engine shop this morning and talked with the head forman. He said don't do it. The 366 has more torque than those other engines. Beause of the shorter piston arms it is able to get more low end torque while being better on fuel than a larger displacement. Also it will cost less. The 366 is used in many moving vans, buses and other comercial vehicles where the low end torque is an asset while not needing the higher RPM's. Just thougth I'd put this out there as I had not read it anywhere else on this site. -Richard
Run away from this shop as fast as you can. The head foreman has absolutely no clue. The 366 has LESS torque than a 427 or 454 (very simply, displacement is torque), & may well burn MORE fuel than the larger, less-stressed engines.

The 366 is used for 3 reasons: it's cheaper when ordered in a new truck/bus than the 427/454, around town (school bus, delivery truck), it MAY use a bit less fuel, and it keps incompetent drivers from tearing up transmissions as quickly.

Finally, since it's an oddball engine (compared to the very popular 454 & 427), 366 parts may actually cost MORE than 454 parts.

OK, now about my part list:
Forged (not fortged--I can't type worth anything) pistons are more durable than typical rebuilder-special castings, & less liklely to come apart if the engine detonates under load. However, detonation will kill any gas engine in a hurry.

Stainless valves are durable, & this engine will see tremendous heat when lugging a 12-ton bus. Sodium-filled valves are hollow, & the sodium melts from engine heat, & "sloshes" back and forth as the valve moves, transferring heat away more quickly...that's what I run on my 460.

Studs give a more precise clamping force than bolts...ARP is a brand, & a very good one. I won't build an engine without main bearing studs.

For a double-roller timing chain, picture a motorcycle drive chain, & you have the general idea.
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Old 03-25-2005, 06:34 AM   #18
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I've heard very good things about the 454 powerplant in buses when it comes to power and performance.

I"m a diesel man myself, but if i was to go with a gasser, i'd want a 454.
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Old 03-25-2005, 12:34 PM   #19
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Thanks for the feedback

hello Everyone. Well I apreciate your ideas and thoughts about my current situation. I priced out a number of different engine options and have decided to stick with the bus's current engine size. It does not seem feasible to spend twice as much on an engine for possible more power. I called a number of shops around town and a few mechanic friends I have and they all quoted high numbers to source another engine block and install. I look forward to an engine that works and will last! I am contacting the shop about the specific parts you mentioned and will be requesting them though. Thanks again. -Richard
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Old 03-25-2005, 03:20 PM   #20
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If you check junkyards yourself, you should be able to dig up a 454 without too much trouble. A good 60-70% of big (StepVan/ValuVan 30/35) delivery trucks had them.

Also, look in motorhomes, chassis-cab pickups, & MDT's.

As I said, reuild parts (pistons, etc) for the 454 are probably CHEAPER than for the 366.
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