673/Maxidyne Information Request

[SixSpeed]

Hello, I purchased a truck to use for a motor for my Mack and I am looking for clarification on what it is/specs.

The Engine # says its a T673C, but the tag says Maxidyne and it looks like a 675 (237) to me. The motor has been rebuilt at some point. The Turbo is an AiResearch unit "Remanufactured for Mack" and painted in the same coat. 

Few questions:

1.) Is is possible for this T673C to be rebuilt to Maxidyne specifications?

2.) Would there be any difference in this vs. a 675 then?

3.) How would i figure out what horsepower this engine is set at?

4.) Are exhaust/Intake manifolds interchangable between 673, 675 etc? I need to switch to a side/bottom mount turbo rether than top. 

Thanks! 

Edited July 9, 2022 by SixSpeed
Added #4

[theakerstwo]

The 673C is a 250 HP

Edited July 14, 2022 by theakerstwo
h

[doubleclutchinweasel]

IIRC, the 250 HP ENDT-673C Thermodyne did have the same head bolt pattern as the 237 HP ENDT-675 Maxidyne.  I believe it was the first (only?) Thermodyne to have that pattern.  I'm sure one of the guys on here will know for sure.  I HAVE heard of a 673 being "converted to Maxidyne".  But, as I recall, there were a LOT of things to change to do this...like crank, rods, cam, pump, etc.

That picture does look like it has 675 oil filters.  Maybe even the 675 oil cooler.  Again, there are guys on here who are a lot more familiar with the details than I am.  Maybe they can help.  A lot of them can identify manifolds and such on sight.

There IS a lot of commonality and interchangeability among the various 672" engines through those years.

Regarding that particular piece, is it possible that somebody put the gear case off a 673C on a 675 Maxi?  Or a 675 Maxi valve cover on a 673C?  Just throwing out ideas for somebody to hook into.  You say the "engine number" identifies it as a 673C.  Which/where number?  Might help somebody ID it for you.

Anyway, welcome to the Pound.

[SixSpeed]

16 hours ago, doubleclutchinweasel said:

IIRC, the 250 HP ENDT-673C Thermodyne did have the same head bolt pattern as the 237 HP ENDT-675 Maxidyne.  I believe it was the first (only?) Thermodyne to have that pattern.  I'm sure one of the guys on here will know for sure.  I HAVE heard of a 673 being "converted to Maxidyne".  But, as I recall, there were a LOT of things to change to do this...like crank, rods, cam, pump, etc.

That picture does look like it has 675 oil filters.  Maybe even the 675 oil cooler.  Again, there are guys on here who are a lot more familiar with the details than I am.  Maybe they can help.  A lot of them can identify manifolds and such on sight.

There IS a lot of commonality and interchangeability among the various 672" engines through those years.

Regarding that particular piece, is it possible that somebody put the gear case off a 673C on a 675 Maxi?  Or a 675 Maxi valve cover on a 673C?  Just throwing out ideas for somebody to hook into.  You say the "engine number" identifies it as a 673C.  Which/where number?  Might help somebody ID it for you.

Anyway, welcome to the Pound.

Interesting information and much appreciated! Here is a closeup shot of the gearcase. And a few more photos I hadn't uploaded. 

The motor I think has definitely been out of the truck. Rebuilt/Reman'd or straight out swapped I am not sure.

I tried to read through all the old threads I could find before I bought this truck for the Maxidyne. I thought it LOOKED like a Maxidyne and he said it had the Maxidyne tag so I was surprised when ai got home and the case said 673!  there is definitely a lot of knowledge around, hopefully I can track one of them down.

 Thanks again!

[Freightrain]

I'd go by 673C on front cover.  Valve covers are easy to swap.  Someone could have put oil filter and cooler on from a 237?

I put spin on filters on my 673 NA motor.  Bolts right on.

[fjh]

fuel pump numbers will reveal if its maxidyne or thermal!

[doubleclutchinweasel]

On 7/14/2022 at 11:37 AM, fjh said:

fuel pump numbers will reveal if its maxidyne or thermal!

Excellent point!

[SixSpeed]

On 7/14/2022 at 11:37 AM, fjh said:

fuel pump numbers will reveal if its maxidyne or thermal!

Do you know what the numbers should be? I am trying to find out. Here are a few more things I found on the engine. Most dates I could find on cast items were 80-82. There's a pile of numbers hand stamped on the passenger side of the block towards the rear on a flat machine surface. I'll have to clean it up and have a look at them

 

[doubleclutchinweasel]

I think that's a ENDT-673C fuel pump number.  Seems to match those other numbers.  I had this engine.  Drove another one years ago.  Was a good motor.