Thermodyne And Maxidyne ?

[Ironman]

I hope this doesn't sound too much of a dumb question

What is Thermodyne and Maxidyne ?

and are they just a part of the B models?

[Lmackattack]

The thermodyne was a Diesel commonly used in the 50s. I dont recall what year production started but it could have been in the mid 40s. It was a engine model term used to discribe the engine series. they commonly came in 673,711 CID some turbocharged some Natural asperated. They needed to be kept in the high RPMS to pull good. The Maxidyne was the engine that came out in 66-67? High torqrise. In its day it was a power house and a blessing. you went from around 180HP,600TQ to 237HP/900TQ and only needed 5 gears to pull the same load a thermodyne with an 18 speed needed.

Maxidynes came out shortly after the R models were released. the first Rs had Thermodynes. Some have recently said the last few B models had Maxidyne test engines in them?

Econodyne was another version basicly a copy of the maxidyne but needed a few more gears to get the job done. they had a little more HP but had a little less overall TQ

HTH

Trent

[vanscottbuilders]

I'm surprised this question hasn't filled the page with replies!

So - I'll be careful since there will surely be criticism:

The Thermodyne diesel engines were the Mack engines through the 50's and into the 60's, following the early French Lenova diesels.

Thermodyne engines provided simple, dependable power for a new generation of post-war trucks in a rapidly growing country. The Mack truck reputation for toughness grew and grew with these steady, simple powerplants. Horsepower was not their long suit. (the range was from 170 to 250 horsepower depending on the series and the set-up) A relatively narrow power band necessitated transmissions with a lot of gear selections. (Quadraplex, Triplex and Duplex married box dual transmissions were the most common offered from Mack) Big rear end ratios (7:--/1, 5.--:1 etc.) were the norm. Remember that really good roads were just being built, interstates were brand new, and hgh cruising speeds were not necessary. Moving loads day after day was the mission, and a Mack could make you money with its' simplicity and dependability.

Anyway - without getting too wordy:

The Maxidyne engines were a new engineering study by Mack that would yield a "high-torque" rise engine with a much broader power band, much higher torque ratings and the same old dependability and toughness. The Maxidyne became available in 1966, with the introduction of the venerable R model Mack. The Maxidyne was not offered in the B models from the factory that I am aware of. Thermodynes continued in production, although in smaller and smaller numbers each year until somewhere around 1969.

A Maxidyne 237 horsepower engine required a simple five speed transmission for most applications. A huge difference from the old Thermodynes. The additional torque allowed higher rear end ratios for better road speeds on those roads that the old B models built!

Maxidynes have been built up to 400 horsepower from the factory, I believe, each with the broad torque band and easy operation that has made them so popular.

It is very popular to convert B model Macks to Maxidyne power. There is some justified concern with using the older transmissions with the more powerful engines, and the clutch set-ups can be very different. But - the best advice is from Doug Fetterly, who told me a few years ago: "Drive it like you own it, and you'll be fine". So if you're thinking about a conversion, I would offer you the same advice.

Hope this helps!

Paul Van Scott

[daveigou]

To expand a little bit on what Trent said, the Thermodyne designation came about around 1953, with the introduction of the "B" series, and when Mack re-designed the END 672 "Lanova" pre-combustion style engine to open chamber direct injection. The engine came to be called the Thermodyne END 673, and variations followed.

The Thermodyne name also followed the gas engines in the same period, going from "Magnadyne" to "Thermodyne"

I'm not sure, but I think the Thermodyne designation probably ended with the introduction of the "Maxidyne" engines, and the change over to chassis mounted charge air coolers and the "Econodyne" designation.

Trent is also correct in the original Maxidyne engine came to market in late 1966, with it's relatively constant horsepower over a much broader operating range.

The "Maxidyne" designation continues to this day. The three configurations of the MP engine family are "E" Econodyne, "C" for Maxi-Cruise and "M" Maxidyne.

Dave

[Ironman]

Thanks a bunch guys for the info