What was old is new again

[chessie4905]

   Maybe you could find a 478m v6 and install a larger carburetor. They have pretty low comp. ratio in the 7's. Or instead of the 8.1 get a 502 block with stroker crank for maybe 565 cubes set up with small port heads and Quadrajet or Holly, torque cam and 8 to 1 comp ratio. Old school dist and coil, etc.

http://www.chevrolet.com/performance/crate-engines/big-block-zz-572-620.html

[tom120]

Ive seen that 572 engine Chessie. Its amazing. The 478 is nice but like the 401 the parts are drying up. The rebuilders have been breaking up their engine kits and offing them on Ebay for a couple years now. And there isn't much on there anymore. Would need a whole new Flywheel assembly and hub pilot built for the 8 bolt 478 crank bolt circle as well. Hanging the Allison on the back of the 401 was kind of working backwards but this bus needed to be out on the road this season and the 401 is in excellent mechanical condition. Used 2 qts of oil in 4000 miles. If we were put- putting around town I would just leave the existing engine in it. But we do trips that  are usually 4,000 miles or more. Would like to have new and have modern. Chevrolet was on the side of the bus this year as a sponsor. Going to see if they can offer any deal on an engine and components. Go on Youtube and type 1947 Clipper Allison Conversion into the search window. Its a quick video that we haven't really finished. Cant get the link to work for some reason.  The bus has a carb, points ign and a computerized overdrive auto trans. Its the junkyard trans bolted to the 50 year old motor in the almost 70 year old bus. Tom

[tom120]

Good question on the weight Digesterman. Never weighed it but plan to this summer. Factory spec engineless was 17,000. GVWR with the engine and passengers is prob 23,000. Tom

[tom120]

Also Chessie there are no Torque specs below 3k on the 572 but the  torque curve line is dropping down very steeply pre 3k. Tom

[chessie4905]

   Going to depend a lot on the camshaft and heads installed. Lingenfelter could build one with stumps pulling power at low rpms. Many other big engine builders could do also with bulletproof parts. Forget about turbocharging the factory 8.0. From what I've read on forums, the pistons and rods aren't up to it.             They build the 50 series for natural gas usage. We have some of our local transit buses with them.

https://en.wikipedia.org/wiki/Detroit_Diesel_Series_50

http://www.ebay.com/itm/2003-Detroit-Diesel-Series-50-CNG-Engine-04R0044363-/311344678318?hash=item487d96c5ae&vxp=mtr

[RoyJ]

Tom120, 500ft/lbs of torque is less than the diesel pickups. It is half as much as the 6V92TA in my bus, which goes down the road nicely, but will not pin me back into the seat with my foot to the floor. Most big rig engines now have torque approaching 2000ft/lbs. I think your Clipper will be pretty slow with the 500 ft/lbs 8 L GMC.

JC

Torque was an important figure back in the days of 3 speed non-lockup transmissions - it represented your average hp output, or the area under the hp/rpm curve.

These days, with 6 and soon to come 8 speed, fully locked transmissions, it's much less of an issue. A diesel making 300hp @ 2100 rpm will pull a coach up a hill at exactly the same speed as a gasoline making 300hp @ 5000 rpm, provided you have the gearing to keep the gasoline near 5000 rpm at any road speed.

Considering the short trips and low annual mileage of a school bus, a modern gas engine totally make sense. Think about the maintenance of a modern gas V8, running full synthetic at 10k mile interval. Except for oil and air filter changes, and plugs at 100k, NONE!

If Dodge ever put an HD 8 speed ZF behind their 6.4L Hemi, that would be a good candidate as well.

[HB of CJ]

Or ... consider putting a blower or turbo on you excellent condition existing 401 V6?  That was one tough engine.  Heavy iron block, heads, gear driven cam, low compression pistons ... valve rotators, etc..

Edit:  Forged steel crank and rods?  Heavy flywheel?  Mechanical governor?  Lots of room around and above the engine in a Flexxie engine compartment?

Could you turn you Flexxie into a real hauler?  Dunno.  Anyhow, just another idea that might work out for you.  A custom low pressure high volume low end tuned turbo with intercooler might work very well?

[oltrunt]

But I love my DD 8v92 and I don't care if it tends to overheat  a bit.  It'll pull my house off it's foundation with it's torque and kill all the mosquitoes on the way!

[tom120]

Mind can run wild with possibilities Chessie. You are right the 572 short block would make a good starting point. Heads cam,etc could be added. Problem is the cost though.  HB the turbo angle on the 401 is interesting but its still a 50 year old engine and has close to a half million miles on it. Would need to be freshened and balanced and parts availability is still getting leaner and leaner. It wouldn't be a cheap prospect either. Got a price last year of $26k for a fully dressed GMC 8.0L Pithon with the Powertrain Integration LPG intake, air brake compressor and accessories. Its expensive but when you start pricing out the long block and adding accessories it adds up very quickly. Ideal would be a salvage vehicle but a large salvage truck is still expensive and expensive to move. Probably not going to find one of those. Tom

[Hawkeyenfo]

Rebuilt the Intl 549 gas engine in my Supercruiser twice.  Since then, have replaced it with a CAT 1160.  It was actually 1in shorter than the 549!  Love the way it has changed the bus, plenty of torque, seems better than the gas engine in all areas.  That said, the 549 was one smooth running engine!  Still running my Spicer 5 spd.  It's definitely not fast but it's reliable 😏