6.7 Cummins into 68 Dodge?

[GTX_Joel]

Hi, I am planning to set my 68 Dodge up for heavy hauling / towing. I was planning to use a p pump 12 valve with compound turbos to get the job done.
Recently I was talking to a guy who sounded pretty knowledgeable at a diesel shop and told him what I was planning to do. He suggested that I consider using a 6.7 Cummins instead of the 12 valve. He said that the 6.7 would make far more power for less money, be quieter, burn less fuel, and be cleaner. That all sounds great, but what would be the trade-off in reliability, repairability, and complexity?
I know very little about electronic stuff. But I do know that the 6.7 is electronic.
This truck Will be used exclusively for long distance road trips. It has to be very, very reliable.
So how feasible is a swap of a modern electronic engine like this into an old truck? What could I expect? What would I use for electronics and stuff? I did a little snooping around and I see that the 6.7's with an automatic transmission made more horsepower. Would I get some kind of aftermarket computer that would run the engine and transmission?
I would be very appreciative of any advice. Thanks, Joel

 

[petersonj]

He suggested that I consider using a 6.7 Cummins instead of the 12 valve. He said that the 6.7 would make far more power for less money, be quieter, burn less fuel, and be cleaner.

I would agree on quieter, burn less fuel (maybe), and be cleaner. "Far more power for less money"?...., I am not so sure. I would think the frame of the 1968 Dodge will be a limiting factor or horsepower / torque.

That all sounds great, but what would be the trade-off in reliability, repairability, and complexity?

I think the 12 valve wins here on all three accounts. I installed a Cummins 4BTA in a 1991 Ford F150 extended cab 4x4 immediately after purchasing the truck new. After a week of test driving to work and back, I left on a trip to Alaska from Colorado with a slide-in camper and pulling a small trailer. Even went north of the Arctic Circle to Prudhoe Bay. Put on 10,000 miles with zero problems. Sold the truck many years later at 300,000 miles. Engine / truck was very reliable and economical to operate.

Is your 1968 Dodge a 3/4 ton?, 1 ton?, 1 ton dually?. Two wheel or four wheel drive? Is it going to be an automatic or manual transmission?

The 6.7 liter engine will offer more braking power with an aftermarket exhaust brake, just because of the large engine displacement.
The 6.7 liter engine would be more attractive if it came with a six speed automatic transmission, versus a typical four speed transmission behind a twelve valve engine.

However, a manual six speed such as the G56 would be an excellent combination with either engine giving full exhaust braking in every gear.

It has to be very, very reliable.

Since you have stressed the importance of reliability, personally I would install a 12 valve engine with a manual six speed transmission and an exhaust brake. You would have excellent performance, both pulling and braking. Basic tools and a test light would allow you to diagnose any problem on a road trip, should one occur (which probably won't).

- John

 

[GTX_Joel]

Thanks for the reply John.
I have a 1991 2wd D350 cab and chassis dually diesel that is donating the frame and front suspension. It is 160-in wheelbase, same as the 1968 crew cab long bed. The Dana 80 and wider, longer, leaf springs out of a 1997 ram 3500 are going in with extra leaves.
I was planning to use the 12 valve out of the 97 ram, until this 6.7 idea was thrown at me.

 

[GTX_Joel]

This is my current rig. The 68 Crew cab will be replacing it. So you can see how it is loaded with the 6,000 lb camper, plus the race trailer.

 

[Ozymandias]

Why do you want to replace that wonderful first Gen? This is a rare vehicle by itself. Not many of these around any more.

 

[GTX_Joel]

I want to switch from a club cab to a full crew cab. And I like the styling of the 68 crew cab better than the 80s / 90s. Once the new truck is ready, the old truck will be for sale.

 

[SnoKing]

Hi, I am planning to set my 68 Dodge up for heavy hauling / towing. I was planning to use a p pump 12 valve with compound turbos to get the job done.
Recently I was talking to a guy who sounded pretty knowledgeable at a diesel shop and told him what I was planning to do. He suggested that I consider using a 6.7 Cummins instead of the 12 valve. He said that the 6.7 would make far more power for less money, be quieter, burn less fuel, and be cleaner. That all sounds great, but what would be the trade-off in reliability, repairability, and complexity?
I know very little about electronic stuff. But I do know that the 6.7 is electronic.
This truck Will be used exclusively for long distance road trips. It has to be very, very reliable.
So how feasible is a swap of a modern electronic engine like this into an old truck? What could I expect? What would I use for electronics and stuff? I did a little snooping around and I see that the 6.7's with an automatic transmission made more horsepower. Would I get some kind of aftermarket computer that would run the engine and transmission?
I would be very appreciative of any advice. Thanks, Joel

View attachment 133363

Now that's a B pillar!!!!!!!

 

[AnonEd]

I'll second the vote for the 5.9 based on simpler operation/repair, simpler installation, and on not knowing how much cooling you can pack in the front of the '68...making 350 hp and 800 lb-ft might be a cooling challenge with that aero profile. You'll have to keep us updated on the project now you got us interested.

 

[AH64ID]

VE pumped 6.7 with a HE351VE and a G56.

 

[GTX_Joel]

Have you tried that P-pumped 6.7? How feasible is that? What controles the VGT? Do you still need the electronics? Making a simple, non electronic motor out of it, but getting the extra displacement and the extra valve doesn't sound bad.

 

[AH64ID]

I have read about P pumped and VE pumped 6.7’s. If you’re looking for sub-450 rwhp I’d look at a VE pump, I prefer them due to the variable timing.

 

[Cummins12V98]

Delete a 6.7 with AISIN no issues with burning up #6.
Owned both and the 12v was great but I had to tow by the pyro. 6.7 put it to the floor it won’t hurt it’s self.

 

[RWherley]

I would be very careful about the word "delete" in the same sentence as 6.7, the EPA is actively looking for deleted trucks and they are throwing every book they can find at people the delete them. I know of a few shops that have been put out of business cause they deleted stuff, and while yes your chassis doesn't require emissions, your technically not supposed to remove emissions equipment from the engine it's self. I would stick with 5.9, even the common rail ones as they didn't have anything to delete so no worries