300+ rebuild

[Freightrain]

1 hour ago, davehummell said:

Many years ago I worked at a trucking company that ran the 285's with the 5 speed in several cabovers to the coast and they sent a R model with a 237 with 5 speed on a weekly run to Canada. I knew a guy that I used to do work for that had a R model running to Texas and back

The difference is, the 237 and 285 were made for only 5 gears.  The 300+ isn't, so I bet it was slow to recover on a shift.

[cruiseliner64]

Im very interested in this build.please keep us up to date with it.A bit of a side question but how rare is a tip turbine nowadays?I have never seen one but Im interested in how they run.. ....

Paul

[Freightrain]

I was going to try to add one to my 237, but got a whole motor.  I hear they are quiet noisy at full song?  Guess I will find out.

 

Seeing they are 40+ yrs old, it is likely harder to find one?  Mine does work, as I had motor running and if I jabbed the throttle it would send a touch of wind into it and it would spin easily.

They were popular before CAC was mounted in front of radiator.

[Geoff Weeks]

2 hours ago, Freightrain said:

I was going to try to add one to my 237, but got a whole motor.  I hear they are quiet noisy at full song?  Guess I will find out.

 

Seeing they are 40+ yrs old, it is likely harder to find one?  Mine does work, as I had motor running and if I jabbed the throttle it would send a touch of wind into it and it would spin easily.

They were popular before CAC was mounted in front of radiator.

The tip turbine and Low Flow cooling were both attempts to better charge cooling without have to re design the front of the truck for enough room for an CAC cooling radiator (Air to air).

once trucks were being redesigned anyway, the reasons for the tip turbine and low flow systems went away. Having the charge cooler in front of the radiator give the best cooling, and what has become the std today. 

At the time, Mack tip turbine was revolutionary, both Cat and Cummins were still using water cooled aftercoolers, and low thermostat temps, to walk the fine line between good block temp and enough cooling for the charge air. 

 After Macks success, Cummins used the low flow system to run the "super cooled" multi-pass radiator coolant through the aftercooler, before sending it the engine. Cat never did and opted for the cooler in front of the radiator, which meant that their engines above 400 hp could not be fitted to many trucks. Cat engines below 400 hp still had the old water cooled aftercooler.

[Freightrain]

I got it up on legs and the pan dropped.  Looks like someone has been in it before.  Orange silicone on the back and the main bolts look like the paint is chipped off like it has been apart.  Rolled new brgs?  It has signs that things have been apart other places(orange silicone).  

When I looked at truck originally I tried to find the serial number on frame but severe mud and crap kept me from getting in too close.  I wonder if this is a transplant?  Truck had straight 5 spd, did it originally have a 285 and this was put in?  Never know now.

Has new air compressor and lots of other pieces that don't match paint.  It was definitely tinkered with.  No idea on mileage (or hours) either.

One bigass pan.

Noticable marks from previous fingers in the bottom end.

Will work on getting heads off next.

[Freightrain]

On 7/12/2025 at 1:34 PM, Geoff Weeks said:

The tip turbine and Low Flow cooling were both attempts to better charge cooling without have to re design the front of the truck for enough room for an CAC cooling radiator (Air to air).

once trucks were being redesigned anyway, the reasons for the tip turbine and low flow systems went away. Having the charge cooler in front of the radiator give the best cooling, and what has become the std today. 

At the time, Mack tip turbine was revolutionary, both Cat and Cummins were still using water cooled aftercoolers, and low thermostat temps, to walk the fine line between good block temp and enough cooling for the charge air. 

 After Macks success, Cummins used the low flow system to run the "super cooled" multi-pass radiator coolant through the aftercooler, before sending it the engine. Cat never did and opted for the cooler in front of the radiator, which meant that their engines above 400 hp could not be fitted to many trucks. Cat engines below 400 hp still had the old water cooled aftercooler.

I wondered what "low flow cooling" was.  Terms passed around and never knew what it was about.  Thanks for clarifying.

[mowerman]

Ha ha hey Larry, I was just thinking the same thing I never really knew what the turbine tip did. I never owned one but I think my 82  cruise liner had the air to air. I don’t remember I sold it a long time ago, but It  had a 350 Thermodyne, which was a really healthy engine, especially after getting out of a 237. And yes.Geoff thanks for the explanation.

[mowerman]

From here it looks like everything is relatively clean inside. Good luck Larry. It probably really doesn’t even need anything.

[Freightrain]

Got the heads off.  Yup, took a 5ft cheater to get them to SNAP loose.

Looks like I had a head gasket on its way out on #4?

Rest looks ok.  Cylinders ok, no damage.

Noticable wear on top of liner.  Not huge ridge, but very detectable.  Not a " fresh" rebuild.

[fjh]

33 minutes ago, Freightrain said:

Got the heads off.  Yup, took a 5ft cheater to get them to SNAP loose.

Looks like I had a head gasket on its way out on #4?

Rest looks ok.  Cylinders ok, no damage.

Noticable wear on top of liner.  Not huge ridge, but very detectable.  Not a " fresh" rebuild.

Check the fire ring grooves on the heads  ! This will be important on re assembly!

[Freightrain]

11 minutes ago, fjh said:

Check the fire ring grooves on the heads  ! This will be important on re assembly!

They are there, #4 had some crud in the area where gasket was blown.  It was going to get worse had I try to just install and run it.

[fjh]

6 minutes ago, Freightrain said:

They are there, #4 had some crud in the area where gasket was blown.  It was going to get worse had I try to just install and run it.

The groove needs to be at least 5 thou or better! I prefer deeper! Just me!

[Freightrain]

They are at least that.

The deck has 020 hand stamped at each cylinder?

Protrusion is more then that?  Fire ring may be that by feel?

[Freightrain]

Was hesitant to pull injectors, but going to have heads cleaned up.  Should I zip the two bolts out of clamp and do they pop out easily?  Will there be a seal ring in hole?

[Mark T]

That head gasket looks more like it was rotted. Doesn't seem to be passing combustion there. If you decide to resurface the heads, be sure you're friends with someone who can recut the fire rings, and you may want check that person has a tool that'll hit the same circle. Old heads mightalready be done once or twice and not enough left to mill off and start over again. So if the cut on them now is a little out of round, it will have been ok as long as it was into the ring, new cut a little off of the existing circle....no good (F's right they're important) Why's that main cap painted ?  Pay attention what's going on there. Like make sure it's not cut already and requires a different bearing. ( they did stuff like that back then, like cut one journal a couple thousanths and nothing else is cut ) If I remember, it was a "P" number that went along with bearing size.  Engine looks like a good candidate for a rebuild.

[Freightrain]

Shop I use can cut rings.  No issue there.  Using fingernail, I'm guessing +.020 deep currently.  Pretty solid groove.

I did get #6 piston out.  Was able to wiggle past oiler. 

Rod bearing was 12-7 112

62GB33-P1

Crank and bearings look fine.

 

[Mark T]

That "P" part is what tells if it's standard or oversized. That piston and bearing looks good, like nothing out of the ordinary 👍

[mowerman]

I only rebuilt one maxidyne that was 40 years ago. Wasnt the fire rings attached to the head gasket? I cannot remember it was too long ago.

[Mark T]

5 minutes ago, mowerman said:

I only rebuilt one maxidyne that was 40 years ago. Wasnt the fire rings attached to the head gasket? I cannot remember it was too long ago.

The part that goes around the top of the liner is soft enough to get squished into the top of the liner and the grove cut in the head. 

[Joey Mack]

Was that engine built with 2 pc pistons originally? Just curious, and the year of the engine as well.  Lookin good sir

[Freightrain]

Not sure of year.  Only thing I have is serial on motor.

EtAZ673C 7S8762. If that means anything.

I looked on Agkits and they want truck serial number.  I hope we can work around that.

[fjh]

1 hour ago, Mark T said:

That head gasket looks more like it was rotted. Doesn't seem to be passing combustion there. If you decide to resurface the heads, be sure you're friends with someone who can recut the fire rings, and you may want check that person has a tool that'll hit the same circle. Old heads mightalready be done once or twice and not enough left to mill off and start over again. So if the cut on them now is a little out of round, it will have been ok as long as it was into the ring, new cut a little off of the existing circle....no good (F's right they're important) Why's that main cap painted ?  Pay attention what's going on there. Like make sure it's not cut already and requires a different bearing. ( they did stuff like that back then, like cut one journal a couple thousanths and nothing else is cut ) If I remember, it was a "P" number that went along with bearing size.  Engine looks like a good candidate for a rebuild.

Yup p number is important they can start as low as p2 up to p30 check em as up pull them look at the numbers! For sure good call Mark! Rods as well ! Eyes pealed for this  part number then p2/10/20 and so on!

[Freightrain]

Ford had similar coding for clearances so they could put correct parts together without having assembler measure anything.

[fjh]

18 minutes ago, Freightrain said:

Ford had similar coding for clearances so they could put correct parts together without having assembler measure anything.

Mack would sometimes do one journal I was taught to always look! Mains and rods ! On a v8 they sometimes they would mark the caps main or rod M 2.

[Joey Mack]

I was taught the same thing.  Mack would only cut the journal that needed cutting. To this day i look at all the counter weights, and bearing numbers.. i dont assume. And Mack bearing kits are not always packed in the correct order.  I was blessed to have a cranky old Man take me under his wing... Earl Harnden was his name.   Maine Mack, 299 Warren ave. ,Portland M.E.   

I had to post his name.. He went home a couple years ago..