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2V maxidyne, issue pulling heads off


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2 minutes ago, mechohaulic said:

pulling both as one unit  -no problem . except when only lifting device is two hands and strong back.  the reassembly done MANY times as one unit works. prefer reassembly as two separate  units myself. 

No way I could pull this assembly up by hand !!!

I had a service crane with 4 chains to keep it level. 

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1 minute ago, Lmackattack said:

Hope not. Liners were very smooth so she probably needs new rings and a cross hatch. At that point might as well inframe it. I'm not sure if it's ever been rebuilt.

Pistons looked very clean for it's age. No carbon build up on them or heads.

What is the 542c stamp on the piston telling us.?

 

 

 

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is that not a crack in liner ??? 542c  ??

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1 minute ago, mechohaulic said:

enlarged to max ;that's not a crack . 

I'll get a better picture of it tomorrow. I got done with work around 4. And spent the next hour, pulling the heads off before i had to head home. I didn't feel anything but I also don't have a lot of experience with engine internals. 

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3 minutes ago, Lmackattack said:

Yes sir. ITS A 283HP ENDT676

memory is correct the 675 becomes a 676 with the tip turbine. I  do recall a 300 /315 version talked of way back then when they were NEW products. wasn't a lot of rebuilding then being new  and the  slogan "built like a Mack truck meant something.

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4 minutes ago, mechohaulic said:

memory is correct the 675 becomes a 676 with the tip turbine. I  do recall a 300 /315 version talked of way back then when they were NEW products. wasn't a lot of rebuilding then being new  and the  slogan "built like a Mack truck meant something.

I think that is correct. What's odd is the 285 tipturbine is a maxidyne where the 315(300+) was still considered a thermodyne. These 2 valves were pretty bullet proof and easy to work on 

 

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thing about the "early mechanic days" ,  if you had half an interest in your job, you learned and studied. like high school what you put in is what you got out. thing is not much attention was paid to minor items as a thermo or maxi dyne. if it was gold it was a maxi  anything else was a mack. to see the start of the computer age in trucks wasn't easy to accept. how could an engine 250 hp become a 300hp with this little box plugged it. not a wrench involved. also 300 plus rings a bell.

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1 minute ago, mechohaulic said:

thing about the "early mechanic days" ,  if you had half an interest in your job, you learned and studied. like high school what you put in is what you got out. thing is not much attention was paid to minor items as a thermo or maxi dyne. if it was gold it was a maxi  anything else was a mack. to see the start of the computer age in trucks wasn't easy to accept. how could an engine 250 hp become a 300hp with this little box plugged it. not a wrench involved. also 300 plus rings a bell.

I think the concept of the 315 (300+) was a great option for those who did not like the maxidyne with only 5 speeds.

I the maxidyne made slightly more overall torque than the 315 but the 315s had more hp and their max torque more in the mid rpm range. The few 315s I drove seamed to pull better in the hills. 

 

And yes I was always surprised when a new diesel just needed a little reprogram to get +50hp.

It goes against everything we learned on mechanicals.

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9 minutes ago, JoeH said:

Pistons are usually done in balanced sets.  The C probably dictates what weight tolerance range the pistons are in.  

Thank you. That's what I figured. My book made no mention of that they were all stamped the same

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NOT SURE BUT  that does looked cracked my hopes are dashed! Liners come in standard 2 thou over 10 thou over ect!  on second glance with the pic blown up its a trickle of something!😅

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  • 3 weeks later...

Weather finally let up from the heat wave we have been dealing with. 67 degrees all morning so I jumped on getting the heads back on. Barely broke a sweat working outside until 2pm.

You can see the carbon build up on the 2 studs that was not allowing the heads to come off. I spend 2 hrs removing the stuck nuts from about 30 studs then wire brushed all the studs and threaded holes. Ran a tap thru them to clean them out and was able to put the studs in with just my fingers.

Scrubbed all the old gasket material off the mating surfaces, Pressure washed the heads  put New head gaskets on with new fire rings. 

Was able to set both heads on as an assembly just how i had removed them with absolutely no trouble.

 

One thing I noticed with this job is when I had removed the head studs/nuts all but a few came out with just a hand held 1' long 1/2" ratchet. They took no where near the effort of 175ft lbs to remove them.  Today I used a 3' long torque wrench and it was pretty obvious the old gaskets were not held down as tightly.

 

I suspect the old gasket was just soft with age or someone did not torque them properly. My book says to check them again after 1 hour of under load time. 

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