28 replies to this topic

[jmodge]

 I bought an 8600 gvw tbi in Detroit for a work vehicle once. It had 4.10's and a TBI, State of Mich fleet vehicle, I filled before leaving. 170 miles home and I forced 17 gallons into it. Ran AC and cruise part of the time. Great truck, when I replaced it I bought a 2 door '99 Tahoe and drove it home from Florida, also a State fleet vehicle. Still have it, 16mpg for mixed driving with it. The aerodynamics and engine controls are quite a bit advanced on those from the previous straight axle models.

 

 True on the power range of the 6.2, Way more torque off idle than the 350 though. I drove it about 7 miles to the property and it ran very strong. But I do remember delivering parts in the early '80's and there was a dually with a 6.2, The only two things I could pass were time and gas. There was no leaving the right lane. 1800 seems to be the sweet spot that is spoken about with a cruising range of 1700 to 2100. Too bad I can't drive that thing around for a while.

 

 You guys might have points about gear ratios though, I have boogied down the freeway faster than usual with the FWC and still managed over 12.

[Zoomad]

A 5.3 was what I had, it was free. Had I been able to go with the 6.0 I would have. But having more cubes is always better. Yeah it is still rev happy than a big block but it would do the job just fine.

As far as the swap goes, it's pretty close to a bolt in. You need swap brackets to adapt the LS engine mounts to the stock engine mounts. Next up is the harness and engine control module, Many places sell them ready to run, saving the hassle of pairing down the factory harness and getting the tune done. You do need to switch out the fuel pump with a higher pressure unit. Tilden sells complete packages, engine, harness, and Ecm.

Keeping your 700r4 is possible if you go with an earlier LS with the cable throttle. With the cable throttle you can use the LS tv cable kit from bow tie over drives. Or move to a 4L60 so it could be run by the LS engine module. Since the 4L60 is the electric version of the 700 it's the same length so no driveshaft mods are required.

It's not always the cheaper way to go, even less if you pay a shop to have it done. If you were closer I'd sell you my complete setup that would drop in pretty quickly.

[jmodge]

 When did the LS go to DBW? Friend of mine has one along with an ecu, don't know what year.  I think aerodynamics play the biggest role in mpg on our trucks though, not a whole lot to be done there. I did not pay attention to your engine swap, did you make your own control harness? 

 

 I made a couple hotfoot runs home from the U.P. where I had sustained speeds of 73 to 76mph and points where I buried the 85 mph speedo. I was surprised to matched my peak mpg, I attributed it to small sample error. But your theory on operating under the power curve has some merit.

 My rear diff could use a rebuild, howls on decel, and they make an 8.5" 3.90 gear. I am going to contemplate that one because I plan to do that anyway.

[jmodge]

 as a side note on GM 6liters, we had some in service trucks. Had the opportunity to see one with heads off. They have a long stroke and very tall runners in the heads, must be what gives them the wide power band. Is the 5.3 head constructed the same way?

[Zoomad]

When did the LS go to DBW? Friend of mine has one along with an ecu, don't know what year.  I think aerodynamics play the biggest role in mpg on our trucks though, not a whole lot to be done there. I did not pay attention to your engine swap, did you make your own control harness? 
 
 I made a couple hotfoot runs home from the U.P. where I had sustained speeds of 73 to 76mph and points where I buried the 85 mph speedo. I was surprised to matched my peak mpg, I attributed it to small sample error. But your theory on operating under the power curve has some merit.
 My rear diff could use a rebuild, howls on decel, and they make an 8.5" 3.90 gear. I am going to contemplate that one because I plan to do that anyway.

So I did something fairly unique for the harnes and ecm. I used a harness and mefi4 Eco from Howell. The mefi4 controller is the exact same unit used in the two gm ramjet crate engines. It works quite well, but support for it is nearly non existent. My buddy originally used it on his 8.1 swap to his K10. He ended up going back to Howell for another harness using a factory controller. I'm not sure it could even be bought anymore. So for the upcoming big block swap I'm going to Howell for the harness and controller. The money spent is well worth it.

Here's the link to my build. There's a lot in there.
https://ck5.com/foru...454-fun.322351/

As far as the gearing idea goes, I'd just make the jum to 4.10's if you are going to make a change. It's a more common ratio and a little more gear will help with the power and keeping the engine (either what you have or LS) in its torque curve.


  

as a side note on GM 6liters, we had some in service trucks. Had the opportunity to see one with heads off. They have a long stroke and very tall runners in the heads, must be what gives them the wide power band. Is the 5.3 head constructed the same way?

5.3's and 6.0's actually look identical on he outside. Heads have the same setup.

[ntsqd]

The whole LS family's controls are a quantum leap beyond the TBI's controls. Though they work very good for what they are, TBI's were pretty stupid the day they were born.

Factor in that the LSx engines are all (?) under square (more stroke than bore) and you get a far more efficient engine. If you're not in the year range where (I'm told) GM had to late inject a little fuel to keep the cat hot for emissions reasons, with a subsequent mpg loss, then that these engines could pull down some mpg numbers a good bit beyond that of the best tuned SBC is not a surprise, it is expected.

[Zoomad]

Missed answering the question on when the LS went DBW. The real answer is it depends. Car LS engines (5.7) in he vette and camaros were always DBW. Truck LS engines had DBC when they came out in '99. The DBW trucks started transitioning in around '04 I think.

There are schools of thought for both systems. I won't go into the debate here, but there is a very solid reason why I use cable and my buddy with two 8.1L powered squares runs cable on his. That's purely the simplicity of it. If a cable breaks we can Jerry rig our way back to civilization and fix it pretty quickly. If you loose an electrical component on a DBW you are dead in the water where ever the truck is. That's on the street a block from home or 50-100 miles off pavement like we like to do. Bringing spares of the throttle pedal and throttle body would help, but a wiring issue could be a culprit too. It is not with its downsides though. Idle tuning is a little tougher to do as the IAC (idle air control motor) does not have as much ability to change idle speed as just cracking the whole throttle like they do with DBW. With an auto it's not as big of an issue, but a manual can do odd things when the clutch pedal is on the floor.

That's not to say DBW is bad at all though. The technology has been out since '97 in the vette and improvements made many times along the way for sure. Working at the dealer and at workhorse and gm as long as I have I don't see failures daily. Gm did have some issues on '07 and later truck engines where a sensor inside the throttle body failed and had had an extensive bulletin on replacing the sensor that we did on many trucks. We just don't see a lot of repairs on them otherwise. But even knowing that I'll run a cable on mine for the one less thing to fail idea. As far as LS swaps go I'm well in the minority on that idea too.

One other thing I stated before, if you intend on keeping the 700r4, you have to stay with cable. Otherwise you have no way to hookup the tv cable for the trans. If you do you'll get peppered by other swappers why not go with the 4L60e. I did. The reason was simple, I didn't have a 4L60e to use and buying one and possibly having to rebuild it was more cost than th bow tie tv cable kit.

[jmodge]

 Yeah, hard to beat technology when it comes to results of power and FE. But, I was raised in the age of simplicity and still cling to much of it. Familiar with the TV cable and the results of not having it tight enough, learned that lesson years ago. Had to fab a mount when I put the vortec heads on, as well as my cruise control which operates via the throttle lever as well.

 

 The truck is loaded with about every option available at the time and it all works, I am unlikely to deviate from that since it is quite dependable, and for me that is important. I do have other toys to romp on

 

 Will pay close attention to the rpms, power range, and any possible future tire size change to determine a gear change since I am going to dig in there anyway. Thanks.

[Zoomad]

The TBI system you have is stone simple and reliable.   I'd run it as is, with the possibility of bumping the gearing up.  If anything you can collect the parts needed to do the swap later.  

[jmodge]

 Geared down I believe you mean, but yeah, I like the TBI. very reliable. I saw someone rigged up something to stream data on one, about a 4 second delay, but it was there. I think it was an offshoot of a tunerpro system. That was the only downside to OBDI, not being able to read live data. I grew up with point systems and HEI so I have tuned and troubleshooted before computors came out. Well versed in the small block Chevy and it's habits as well as what tweaks do what.

 

 As far as swapping, not likely, but if I went through the expense and effort it would be the 6.2 diesel with a small amount of boost at 2100 rpm. But at 60 years old and other things to do, it would be a waste of my time I believe. This truck will take me where I want to go when I want to do it. I think I will save my money for gas. Always nice to hear someone else's opinions to bring things into perspective though, thanks. Happy Camping, who knows, maybe we will run across each other some day. My buddy with the hunting property has an ex neighbor out in Colorado that invited him up Elk hunting a year ago or so. Might be in my future. I think it is up by four mile park, something like that.