3 GM 6.5's later now I have a Cummins

[computer-monkey]

I'll start off saying I don't think I have set up my engines any different than anyone else. I used Heath diesel injectors, pcm and water injections.

First engine was the original stock engine that came in the suburban. The number eight cylinder cracked which from my understanding was a know defect.

Engine (2005 GEP long block) two was went down from cracked main webs. Engine (2008 GEP long block) went down due to broken crank, main caps and cracked main webs.

The vehicle is used in vacations which are usually in the mountains.

Still have the original 4L80E transmission and 14 bolt semi float rear end.

So after 8 months going back and forth with GM I decided to do a engine conversion with a cummins.

14 weeks later I can not be more happier in doing this. With 21mpg plus and more power than a 6.5 would dream of in comparison I say I did the right thing.

Here are my thoughts.
The 12v is not as fast (but very close) acceleration. Maybe with a little more work on setting up the shift points on the tranny to match the low torque would help.
The 12v VE engine is more quiet than the 6.5. Starts way easier than the 6.5, in any temp(engine hot or cold)
Better fuel mileage towing or empty.
Here is my set up.
12v VE Cummins, Bosch 175hp injectors (15hp over stock) Stock VE pump, 98 Cummins inter-cooler, 02 Dodge Cummins radiator, Fass fuel system, Hy35w turbo 3" down pipe to 3.5" exhaust, straight through muffler

[Edahall]

14 weeks later I can not be more happier in doing this. With 21mpg plus and more power than a 6.5 would dream of in comparison I say I did the right thing.

Here are my thoughts.
The 12v is not as fast (but very close) acceleration. Maybe with a little more work on setting up the shift points on the tranny to match the low torque would help.
The 12v VE engine is more quiet than the 6.5. Starts way easier than the 6.5, in any temp(engine hot or cold)
Better fuel mileage towing or empty.
Here is my set up.
12v VE Cummins, Bosch 175hp injectors (15hp over stock) Stock VE pump, 98 Cummins inter-cooler, 02 Dodge Cummins radiator, Fass fuel system, Hy35w turbo 3" down pipe to 3.5" exhaust, straight through muffler

Welcome to the Cummins Club!! I would have to say the same about my conversion. I'm getting 26 mpg and that's with oversize 305 tires and a lift kit.

For better fuel economy and more power, advance the timing about 1/8". You might also consider installing a 3200 rpm spring. This is the best bang for the buck performance upgrade. Next thing is to install a Denny T Stage II Fuel Pin and turn up your injection pump. But before you do all of this, make sure you've got a pyrometer installed.

[computer-monkey]

Hi EdaHall

Sorry, I guess I should have listed all I have done.

I have all of the gauges from the 6.5 build (boost, EGT and trans temp). I have installed a 3200rpm spring. I haven't set the timing on the pump yet.

I have turned the pump up to compensate for the low idle instead of turning up the idle screw.

Just about everything is stock and original except the cummins engine, intercooler and radiator.
ie A/C, tranny, transfer case, axles.

[Edahall]

The Cummins does indeed make its power at a significantly lower rpm than the 6.2/6.5L. I'm using a manual transmission and my engine pulls very hard even from just above idle. I don't know for sure if such a thing is sold but you might check for a torque converter with a lower stall speed for your 4L80E. The converter that it has was probably matched for the 6.5L.

[Edahall]

I did some searching and it looks like the torque converter on your 4L80E has a stall speed of roughly 1700-1900 rpm's. Max torque on our Cummins engine comes in at roughly 1600 rpm's so even with the wheels locked up, you are already above the rpm's of max torque of your engine. I also found out that there are converters with different stall speeds for your transmission. Here is one with a stall speed of 1300-1600 that better matches our engine's torque curve.

http://www.racetransmissions.com/sto...roducts_id=281

Also check these guys out.

http://www.transmissioncenter.net/4l80e.htm

http://www.partshp.com/Converters.htm

[b1jetmech]

Computer monkey, does your Suburban still have the stock body and suspension lift?

Does the 5.9 clear your hood(especially up front)?

What did you use for an tranny adapter?

I'm contemplating on a 5.9 swap to my 99' Burb'.

Chase