" The bus"

[cadillackid]

Lookin good! any reason why you would downgrade from 392 to 345?
-Christopher

[Ronnie]

I was wondering who might ask that. For me it is an upgrade. The 392 has been nothing but trouble. can not keep coolant in it, and the trans boils the coolant too when using the retarder. New radiator, added an auxiliary oil cooler, and running straight antifreeze all helped but in the end was not enough. Great on paper but real life just not worth it. The later improved cooling ones may well be a good choice though.

The 345 I have had before and are a great engine. I block filled the exhaust crossover in the intake to keep that heat out, enlarged the throttle bore to allow free and good flow from the throttle body injection, already have duel exhaust, 3inch, and will set it up with cold air intake. All of these should put power wise where the stock 392 was. At least I have done this before with very nice results on other 345's. So building a known quantity that has proven itself for me. Also going to a 5 speed manual and that will free up some power too.

Must say I do not expect many to understand my choice of bus or power. Perhaps just a bit loyal to old Internationals.

I am curious to see what happens with fuel mileage. Best average was 5.75mpg before. My old dump truck with this setup used to get 8mpg. I noticed your comment elsewhere about 392's getting better mileage then 345. So hoping it does not go down.

Bottom line I feel good about this combo.

[cadillackid]

oh i can totally understand switching out the transmission.. and the 345 is a great motor.. but the 392 does a much better job of low-end torque.. its intake naturally flows better than the 345.. id go ahead and rebuild that 392 and install it with the Manual transmission.. you'll have a powerhouse!

[cadillackid]

well one thing is for sure you will probably get better MPG than you did before as your 392 wasnt in good health.. an engine in bad health will get terrible mileage.. the 345 should be better than the poor 392.. I just dont believe in the 345 vs a good solid 392.. plus an AT540 will eat any engine alive. with heat.. thats a given
-Christopher

[Ronnie]

I have the MT-40 is that the same as the AT540? Mine does have a lock up torque converter, and is 6 speed. No overdrive.

If I stayed with a 392 I would want to get a newer improved cooling one. The coolant flows into the block instead of the heads, and the block itself is a different casting with different coolant passages between the heads and block. So rebuilding mine I do not feel would be smart. Maybe for a pickup that it not under so much load it would b fine. I did look around for a good used one and was not finding anything. The 345 was in a running dumptruck that I got real cheap truck and all.

[cadillackid]

I didn’t realize there were cooling issues .. mine is a 1978, I’ll have to look it up and see whether I have bad cooling passages or not.i know the thing is powerful even with an AT540 transmission .. of my bus was going to be more than a classic restoration I would swap to manual or a 643.
Christopher

[EastCoastCB]

Had a 345 in my 73 Scout II Terra. Was an amazing machine. I'd always thought of a 392 swap and most of the diehard scout guys I've met like the 392.

Nice to see others love old cornbinders too.

[Ronnie]

Because a 392 is a large bore 345 the coolant passages between the cylinders are narrow and tend to boil dry momentarily under heavy load. This gives hot spots and detonation. Hence my messed up pistons. A re design was done I believe in 73 or 74. The easy way to tell an improved cooling is look at your water pump the pipes should go into the front of the engine block if it is improved cooling. Otherwise they go into the heads.

[cadillackid]

Most of my childhood and until I moved out from my folks was around scouts!! Our first one was a 345 scout II with a 4 speed .. then dad ordered 2 new 1980 diesels when he heard scouts were going away.. we wheeled the heck out of those scouts.. Moab, Colorado Springs, Arizona , if it was out west we wheeled it..

I learned to drive in the 2 diesels.. both were stick and both had A/C.

I got to drive the 345 off road as a 10 year old .. we were in the desert in summer it was hot as hell.. I wanted to go slow but I had to keep the revs up or it would overheat and I’d have to shut off the AC..

Loved those scouts.. they rusted easily but ran forever.. I think dad still has one of the diesels ..
Christopher

[Ronnie]

My Dad had one of the "half" engine 4 cylinder ones he bought new. Dark green. Think it was a 67. I remember many a times stuck in thick goes mud. Our soil around here is mostly clay. It was rusted out and gone by the time I learned to drive. So learned on a Subaru .

[cadillackid]

rust + scout == extremely common.. we fought rust on thise darn things all the time.. esp the rockers, doors.. and tailgates
-Christopher

[EastCoastCB]

Yep. Mine was a one owner barn find with 80k on it. Rusted in the usual places.
But the box steel frames were solid.

[cadillackid]

the MT40 was a great transmission.. as long as you didnt blast it with diesel torque.. was one of the best for the old gassers.. i think GM used them on the wanderlodges and gasoline busses before the MT600s came out.. those things would lock up in first if i remember them right..

[Ronnie]

Yes it does lock up in every gear. Heavy beast for sure. If you know any who needs one send them my way, like to get something for it, and seems it might be of use.

[cadillackid]

I actually looked for one in good working order last summer for my DEV bus after it blew the AT545... I was going to install 4.10 gears and use an MT-40 6 speed as a means of essentially have a low RPM highway geared bus witrhout an electronic transmission.. couldnt find anything.. then I found smokin deals on reman MT643 so I went that route and figured at some pint ill go to a 4.44 gear..



the idea behind the MT40 and the 4.10 gears is I could run it in 4 or 5 when I needed more power.. then 5 or 6 when I wanted flat land cruising... 6 gears is more flexibility than 4..

-Christopher

[Ronnie]

Latest update, Have the new engine in place, just made up a new driveshaft front portion to match the new tranny. Went to the boneyard the other day to source a clutch pedal.

The motor mounts for the rear of the engine are on the bell housing and the Allison has very different mounts then the manual trans. The Allison has a really nice mounting system, so ended up machining and welding adapters to get everything to work.

Today I hope to get the clutch pedal and linkages in and make the hole in the floor to get the gearshift through, and get all that in. Might need to bend the gearshift lever to get it in a good place for comfortable shifting. I have some real work to do today, so will see how much time I have to work on the bus.That is my plan anyway.

[Tango]

Sounds like a lot of work and a lot of progress. Hope to see some pix soon. Keep after it!

[Yukon Cornelius]

Originally Posted by Tango

Sounds like a lot of work and a lot of progress. Hope to see some pix soon. Keep after it!

I'm with Tango, hope to see some pics sounds like a sweet fab job

[Ronnie]

A few pictures.

[cadillackid]

good deal.. coming along nicely.. the allisons have a really easy mounting system... nice enough that id put a lockup allison before a stick shift... nevertheless this is coming along nice and sounds like you got past the moiunting issues. just pay attention to your pinion and U joint angles...
-Christopher