A project for Guidematic

[Gary]

http://cgi.ebay.com/ebaymotors/1950-Flxible-Custom-Coach-conversion-/190493585590?pt=Buses&hash=item2c5a4d70b6#ht_500wt_1182

Take lots of pics, Mike

Gary

[Denrep]

But man that V-6 Jimmy 
A garden hose couldn't keep up with its thirst for fuel. 

[DownUnderDeville]

A V6? Could that even move the thing? What's it out of I wonder?

[Denrep]

A V6? Could that even move the thing? What's it out of I wonder?

Oh Ueahg, it'd move it; they were strictly a truck engine, up to 478 cubes, GMC.

[Russ]

Misfits on the move. Bring the party to YOU 

[Carfreak]

Peekskill's got a 'Big GMC Inline 6", think its a 503 cid.

Don't know much about him, 640 series with 185" wheelbase and almost 9' tall - he's a biggun!

[Denrep]

That's the two-garden-hose model. 

[guidematic]

 That would be so cool. That would be a project for me if I ever won the lottery.

But at some point that bus was repowered. Originally, in 1950, Flxibles came with Buick engines, the big straight 8. But if it ran the big 478 V-6 then it would have plenty of power to move the rig. But these V-6's were also available in 305, 351and 401 inch versions. The Jimmy V-6 was released in 1960, and they were carried through at least the mid 70's.

I would repower it again with a big 500HP 8V92TA and an Allison auto. That would move that thing with extreme authority and likely get far better fuel economy than a 478 V-6 gas engine.

Mike

[Tailfin Joe]

Where do you park a bus at a car show or cruise in ? I met a guy who did a resto on a bus from this period really nice, but he even got tickets when he parked on the street be cause it was not city or state  owned.

[guidematic]

You have to take that into consideration when you have one. You can't just expect to show up at a cruise with a bus and be allowed to park it. Ditto for anywhere you take it.

You also need a good sized shop to keep it and maintain it. Granted these rigs were designed to spend much of their life outside, but the elements still take their toll. And they are fairly maintenance extensive if used regularly. An oil change with a Detroit will be 30+ litres of oil, 2 oil filters and 2 fuel filters. There are perhaps 25 or more grease points plus an inspection of several dozen items to keep them in top notch condition.

The air dryer should be serviced yearly as well. A brake reline is a huge job, but if used sparingly, should last many years.

There is also the yearly transmission service which are filters and up to 15 litres of oil.

Many of these conversion buses are not maintained properly, sit outside for months on end and then just driven occasionally when the mood hits. That's a recipe for disaster. So many systems deteriorate at a rapid rate and the bus becomes pretty much unuseable when one real problem hits. That's why you see so many that are just languishing beside barns. Like this one.

Mike

[ST Dog]

I would repower it again with a big 500HP 8V92TA and an Allison auto. That would move that thing with extreme authority and likely get far better fuel economy than a 478 V-6 gas engine.

Not to mention the difficulty finding parts for the big GMC engines.

But one of the GMC 12s would be quite the conversation starter.
http://www.6066gmcguy.org/TwinSix.htm

[guidematic]

 That's a fascinating engine. The reciprocating parts of 2 351 V-6's. Phenominal torque and power, but fuel consumption was on par with an ocean liner. my grandfather spoke of these engines with great admiration. They were easily the most powerful engines available, and could make any diesel of the day look like a child's toy.

There is an FWD wrecker locally that has one of these engines powereing it. To hear that thing is true music.

But it was a monster to run and maintain. A tune-up took an entire day, and feeding it, even in times when fuel consumption was not really important, was a major hurt. No wonder they tacked 2 more cylinders onto the 478 to make a V-8 with nearly the power, but much better fuel consumption and lower maintenance won out.

And diesels were coming on strong. The 60's was the hay day of the big gas engines, but diesels with their better fuel consumption and longevity were the way to go in big trucks. Once they started putting turbos on diesels, the gas engines were done.

Mike

[ST Dog]

No wonder they tacked 2 more cylinders onto the 478 to make a V-8 with nearly the power, but much better fuel consumption and lower maintenance won out.

Check the net numbers, http://www.6066gmcguy.org/EngineData.htm
250HP @ 2400 rpm  from the V12 vs 185HP @ 2800 rpm for the V8

I'd really like to see what they could do with higher compression (spec was 7.5:1) and modern camshaft designs.
I'm sure efficiency could be improved a lot. Bore it out to match the big 6 and 8 too.

That short stroke just hampers it a lot.

Granted it could never compete with a turbo diesel.

[Denrep]

You can't see it in the pitchur, but they had a strange distributor drive.
They used a drive which was about the diameter of an HEI unit, but flat, in the block.
Then, two separate six cylinder distributors fit into the drive unit, but each in a horizontal position. Does that explanation make sense? For some reason I'm thinking that the two distributors were Corvair based, but I'm not positive on that. They also had a jumbo balance tube between the carbs.

Good Luck

[guidematic]

 I always wondered why the power ratings were so low for truck engines, especially these big gas engines. I did read somewhere, and memory is a bit shadowy on this, that they were rated at 75% of their maximum duty cycle. In other words, that is what maximum power is rated continuously, but there is more in reserve if need be.

The big engines had lots of torque, and the more modern short stroke engines had benefits in less internal friction, less flame exposure to the cylinder wall and more compact dimensions. Certainly a longer stroke allows for greater torque at lower RPM, however, the benefits of a shorter stroke were seen as more desireable.

The 702 did have that bizarre distributor arrangement, and 2 carbs. It was not just replaceing 12 spark plugs and servicing 2 distributors, but setting, tuning and synchronising it all together to make it work well. I know 2 old mechanics that worked on these engines, and that is how it was put to me.

Mike