JoeH

The real driving force behind whether or not you'll see them in another 10 years is a) they aren't building them any more b) they're so old that it's unrealistic to expect Mack to keep making parts for them and c) the repair industry is so much further down the road simply because of a) and b). There's no real reason you shouldn't expect one of these to perform admirably for you. Nothing's bulletproof, new or old. On these, if you're prepared to dig for spare parts and fix it in house then I'd say go for it. Just remember, Mack engineered their whole engine/drive line to work together "as engineered." Dont go ramping up the HP, Mack already built their engines to their limits.

If it happens again I've got 11 more good lifters in the spare engine, and I'll send the currently bum spare cam out to have a new lobe welded on while the good engine gets ready for cam swap.

*shrug* last time we lost a lifter the truck got the cam and a lifter out of our spare engine.

These motors will run until you break the carbide face on a valve lifter and wipe that lobe off the camshaft. Then you're borrowing the cam and a lifter from a spare engine. Could happen tomorrow, could happen in 20 years.

Yea, modern diesel is "bio" and grows stuff pretty quick. They make an algicide fuel treatment that will kill stuff, but won't break it down. Our front end loader sat for 6 months once while we pulled the motor to deal with oil leaks. When we got it back together it kept clogging the strainer in the electric primer pump.

What's with all that pitting around the machined part of the cast iron? Combined with the chipped teeth I'd wonder if something small went through there...

The truck my dad adjusted is a 1979 R686ST...

Glad someone chimed in with the "how to". I had no idea how. I only know that my dad adjusted the link in one of our trucks not too long ago so I threw it out to you as a possibility! Reasonable that a 20k axle is not adjustable. The one my dad adjusted is rated for something in the 10.5-11k range.

Humor me, change the fuel filters. If you already did, then do it again.

I've only heard one once here in PA, he pulled in next to me at the fuel island. There's no mistaking it's sound for an inline 6. He has it turned up to 600hp IIRC.

If you take the power to displacement ratio of the e7-460 at 12 liters and apply it to the Big Six at 14.5 liters then you wind up around 555hp. Decent, but unknown upward potential.

Fact is, Mack missed out on the Big Power market when they didn't move forward on their "Big Six" prototype sitting at the museum. Their E9 V8 is the only real Big Power option, but all I've heard is parts are hard to get and they suffer in the longevity department. Whether that's just scarcity and age or design flaws, I couldn't say. I have heard that V engines' main flaw is that they have to run 2 connecting rods on each crankshaft offset.

Pyro on my E7 says downshift at 1025 degrees. Pyro on my ENDT676 (1979 2 valve precursor to the E6, pretty much the same engine except for fueling/powerband) says downshift at 1125 degrees. You'll have 13 gears so that'll help you keep in the powerband. The E7 is only 12 liters, so at 11 on the E6 youre not far off.

11 liter, not 10. Don't be fooled by its size, Mack rated their HP at the wheels, not at the flywheel. So a 350 Mack should make more power than another brand 350. I haven't driven an E6-350, but it should pull well. Only turn it up if you're the only one that's going to drive it, and don't do much. They're incredible engines for their size, and Mack maxed them out at the perfect power vs durability ratio. If you tip more towards the power then you'll lose durability.

Our 2003 MR688 is an automatic. I love it. There's no going too fast in that truck, being a heavy spec cabover every bump in the road hurts.

The 2023 Ford Powerstroke High Output is an outrageous 500hp and 1200 ft lbs of torque, compared to the Cummins H.O. at 420/1075. Both of these are a measly 6.7 liters.

My 95 E7-350 is a bit of a dog; it's a great truck, but some more umph would be nice on some hills. At 25 tons or 36 doesn't really change how fast you are moving by the time you hit the top of the hill. Which is a bit sad, you'd think the truck would move noticeably better with 22,000 less lbs on board. But, it is a 12 liter engine, nearly 30 years old. 2023 Cummins 6.7 is boasting 370hp and 850 ft lbs. That's a lot of power from a little motor. Not far off of our old trucks. New trucks with a load on also drive like cars, which TBH is really kinda scary. I had an a$$hole hotrodding and tailgating another truck coming the opposite direction towards me the other week; he was halfway out in my lane chasing the truck in front of him coming around a bend; I didn't see him til the first truck got even with my front bumper. he got out of my way about 4 feet before he hit me. I put myself as far over as I could in my lane without wiping out the trees and ditch and locked up a couple tires to buy the inches that a$$hole needed to get back in line.

Looking at E7 tags found on used engines online I've seen 7-18.

All due respect and to keep things straight for reference, but the industry refers to those as Synchronized Transmissions, not Constant Mesh. The transmission in this DM is a Constant Mesh, and using that terminology to search for shifting advice will yield different shifting explanations than searching for Synchronized Transmission.

The oil fill tube on this does look like an E6 though. Doesnt match my e7's fill tube. More pictures would help.

Looks like an e7 to me. An E6 would have two removable plates on the side of the engine block next to the fuel pump. These plates provide access to where the pushrods set into the lifters.

If you go to your local Mack dealer they should be able to look up book # 5-672 and order it for you. It's an engine overhaul book for 1981. Pretty much identical engine to what you have, just 2 years newer should cover multiple HP ratings. Not sure what transmission you have, but that book will likely be available as well. Same on rears. Other than that you're largely on your own to figure things out by asking around here.

Not sure what book you're looking at. There's a whole slew of individual component books. Book for pretty much every engine, trans, chassis, suspension, fuel, etc. Usually each book is $40 or $50 at the dealer, but you gotta know which ones you want. They're numbered.

My 95 e7-350 mechanical had a bit of a stumble at one point. Almost sounded like the name brake was trying to come on under acceleration. I changed the fuel filters and it went away. Been 3 years now? Could be a lift pump at the borderline of spec, the truck does have 24,000 hours.

There's 2 brake light switches. One comes on when air pressure is sensed in the brake lines. The other is set to kick on below a certain pressure, when air in the parking brake circuit is dumped. If I recall, the service brake sensor should be attached to an airline on the interior firewall above the brake pedal. The parking brake one is probably on the parking brake knob in the dash. It might also run the low air pressure buzzer and light.