Rome Wasn't Built in a Day

WestBound · 03-08-2017, 10:52 PM

I don't get to share my love of my vehicle often enough so here it is.. I purchased a 1984 GMC Rally Wagon Custom G3500 4X4 school bus, with a professionally installed '01 5.7L Interceptor motor out of a police Tahoe, off Craigslist a few years ago for 4 grand from Phoenix, Arizona. It came with 19.5" military wagon wheels and I'm told it is difficult to get tires for those rims and I needed tires for the drive back to New York so I dropped $1,200 on off road rims and Rocky Mountain Falkens, which may I add have driven on the Rocky Mountains while we made a pit stop to Red Rocks Natural Amphitheater in Denver. I've put several parts into it including an emergency water pump in the Carolinas for $777.17 among others.
I've thought long and hard about it and I've decided I want a diesel. Specifically the 6.2L Detroit Diesel that was an option for the year model of my van and therefore lines up with the transmission and engine mounts.
At the moment I have been attempting to find a mechanic willing to do the project. I have a $1000 down payment for the work.
It has a 4" lift, professional wiring harness, and no computer.
Will post pictures as soon as I get them and can figure out how to use this.

cowlitzcoach · 03-09-2017, 02:14 AM

I am not sure exactly why you would consider swapping a Vortec5700 for a 6.2L diesel (and it is a GM diesel which is not the same as a Detroit Diesel).

The Vortec5700 will have considerably more HP and torque than the 6.2L. And a Vortec5700 will get as good or better fuel mileage than a 6.2L.

The very best we ever got out of our mini-buses with the 6.2L was in the 8-12 MPG range. Routinely the Vortec5700 buses got about the same on fuel that usually cost 10-20% less per gallon.

So I guess my question would be, what do you hope to achieve by doing the swap?

M1031A1 · 03-09-2017, 05:21 AM

Cowlitz, are you sure about that 6.2 getting such bad fuel economy? I ADORE my 6.2L in my M1031! The WORST I ever got from my 6.2 was 14 m.p.g. going to the grocery store 1.5 miles away from our home with 7 stop lights blocking us. I average 19 m.p.g. around town and 21 m.p.g. out on the highway with her (weighing 5.5 ton) without even trying to get good mileage. If I work for mileage, I get much better results. Yes she's slow to accelerate, 62 m.p.h. top end, but she's sooooooo reliable! I'd dump that gasser in a heartbeat for a 6.2L diesel!

EastCoastCB · 03-09-2017, 07:11 AM

https://www.youtube.com/watch?v=iV7y4jofIEc

cadillackid · 03-09-2017, 07:36 AM

if I were going to do a diesel swap.. the 6.2 would be a good candidate IF you already have a cheap source of the engine.. ie theres one on a stand in your garage, freshen it up and go... but parts are going to be scarce for those soon.. they have been out of service a long time...

if I was going to have to Build something up or buy an engine from scratch and wanted a diesel.. i'd probably go after a cummins 6BT...

then again if it was *ME* doing the job and an I-6 was too long to fit the engine bay i'd probably (Ok here comes the flames im sure) go after a Ford 7.3, a 444E can be had cheap harvested from a bus, but the ford version (7.3) has about every tuning and HP upgrade capability out there for the computers..

but really a good ole 350 is just awesome.. and with the right fuel injection system and tuning, and transmission, you can get pretty darn good fuel economy out of a 350.. not to mention that if cost is your reasoning, the fact in most states I travel, regular 87 Gasoline is 20-25% cheaper than diesel fuel on average.. so that should be considered into the equations.. not to mention parts for Vortec 5.7's are in every corner of the planet..

-Christopher

cowlitzcoach · 03-09-2017, 02:29 PM

Quote:

Originally Posted by M1031A1

Cowlitz, are you sure about that 6.2 getting such bad fuel economy? I ADORE my 6.2L in my M1031! The WORST I ever got from my 6.2 was 14 m.p.g. going to the grocery store 1.5 miles away from our home with 7 stop lights blocking us. I average 19 m.p.g. around town and 21 m.p.g. out on the highway with her (weighing 5.5 ton) without even trying to get good mileage. If I work for mileage, I get much better results. Yes she's slow to accelerate, 62 m.p.h. top end, but she's sooooooo reliable! I'd dump that gasser in a heartbeat for a 6.2L diesel!

I can only tell you what our experience has been with that engine in small buses.

The fuel mileage never ever got to 10 MPG on routes, even the routes that had several miles of highway to travel in order to get to the first stop in the morning.

The other issue with them was they didn't ever need a speedometer. A calendar probably would have sufficed for tracking speed.

WestBound · 03-09-2017, 06:31 PM

Quote:

Originally Posted by cowlitzcoach

I am not sure exactly why you would consider swapping a Vortec5700 for a 6.2L diesel (and it is a GM diesel which is not the same as a Detroit Diesel).

The Vortec5700 will have considerably more HP and torque than the 6.2L. And a Vortec5700 will get as good or better fuel mileage than a 6.2L.

The very best we ever got out of our mini-buses with the 6.2L was in the 8-12 MPG range. Routinely the Vortec5700 buses got about the same on fuel that usually cost 10-20% less per gallon.

So I guess my question would be, what do you hope to achieve by doing the swap?

Is that what the motor is called? I'm not vehicle savvy like you guys. I'm here to learn. To be Frank, I live and travel in it. I always hear how much better diesels are in almost all aspects and seeing as this one mechanic said my motor is toast, I've been weighing my options. Although I don't even know my options. I don't know anybody down here and don't want to have to cart the van to several locations to see if this mechanic is right about the engine. Nobody talks about the engine trouble I have online, but then again I'm probably not describing it properly. Nobody told me anything about what I have in the dog house other than it came out of a police Tahoe. What does a rebuild cost? Is a diesel conversion a good idea or straight dumbassery? I was going for what I thought was more torque and better mileage and better for the environment. But if I have some badass engine or something maybe I should look into rebuilding it? From what I've read on Wikipedia the year model of my van will fit a 6.2L "Detroit Diesel," whatever that entails, it mates with the THM400 tranny I have now. I'm Not looking to do a tranny swap as well. I don't even want to think about how much more that would be. I need to keep the cost down, get it done, pay the man, and begone. It sounds like it would be a fun, not to difficult, interesting job, no? But to no avail. Y'all don't understand, this van is my livelihood. My home. I wish I knew everything there was to know about it. And I will. Right now it drives but the motor is making a horrendous screeching squeaking from possibly the right front cylinder area. I took the accessory belt off, it doesn't sound like a belt issue. I'll try to send a video of it.

WestBound · 03-09-2017, 07:16 PM

Quote:

Originally Posted by M1031A1

Cowlitz, are you sure about that 6.2 getting such bad fuel economy? I ADORE my 6.2L in my M1031! The WORST I ever got from my 6.2 was 14 m.p.g. going to the grocery store 1.5 miles away from our home with 7 stop lights blocking us. I average 19 m.p.g. around town and 21 m.p.g. out on the highway with her (weighing 5.5 ton) without even trying to get good mileage. If I work for mileage, I get much better results. Yes she's slow to accelerate, 62 m.p.h. top end, but she's sooooooo reliable! I'd dump that gasser in a heartbeat for a 6.2L diesel!

Although I'm not dumping it, I'm converting it.

M1031A1 · 03-09-2017, 07:27 PM

Quote:

Originally Posted by WestBound

Although I'm not dumping it, I'm converting it.

That's what I intended to say, dump the gasser engine and put in that beautiful 6.2L!

cowlitzcoach · 03-09-2017, 07:37 PM

Swapping engines is never an easy task.

Swapping from gas to diesel entails more than just swapping the engine in.

Depending upon what is wrong with the engine that you have in your bus currently it still might be a whole lot less expensive to fix what you have than to swap to a 6.2L.

The 6.2L spe'c's in standard form are in the 130-160 HP range and 245-285 ft/lbs torque range.

The 5.7L, the Vortec5700 in particular, had 260-305 HP range and 325-340 ft/lbs. torque range.

Granted we are talking the difference between diesel and gas engine spe'c's. But the feeling you get in the seat of your pants will tell you the 6.2L is a slug compared to the 5.7L.

EastCoastCB · 03-09-2017, 07:38 PM

I have to agree with Cowlitz. The 6.2 is *ok* but I'd never dream of going through a swap for one.

WestBound · 03-09-2017, 08:04 PM

Quote:

Originally Posted by cadillackid

if I were going to do a diesel swap.. the 6.2 would be a good candidate IF you already have a cheap source of the engine.. ie theres one on a stand in your garage, freshen it up and go... but parts are going to be scarce for those soon.. they have been out of service a long time...

if I was going to have to Build something up or buy an engine from scratch and wanted a diesel.. i'd probably go after a cummins 6BT...

then again if it was *ME* doing the job and an I-6 was too long to fit the engine bay i'd probably (Ok here comes the flames im sure) go after a Ford 7.3, a 444E can be had cheap harvested from a bus, but the ford version (7.3) has about every tuning and HP upgrade capability out there for the computers..

but really a good ole 350 is just awesome.. and with the right fuel injection system and tuning, and transmission, you can get pretty darn good fuel economy out of a 350.. not to mention that if cost is your reasoning, the fact in most states I travel, regular 87 Gasoline is 20-25% cheaper than diesel fuel on average.. so that should be considered into the equations.. not to mention parts for Vortec 5.7's are in every corner of the planet..

-Christopher

That sounds groovy but I don't want to cut anything or weld, anything that would jack the price up. And I want something that will line up with my transmission so I figured the 6.2L is my best bet. So I'll just need new gas lines and... what else? It has a 4" lift and a pro harness and no computer. Doesn't that all make it just that much easier?.?

M1031A1 · 03-09-2017, 08:04 PM

Quote:

Originally Posted by WestBound

That sounds groovy but I don't want to cut anything or weld, anything that would jack the price up. And I want something that will line up with my transmission so I figured the 6.2L is my best bet. So I'll just need new gas lines and... what else? It has a 4" lift and a pro harness and no computer. Doesn't that all make it just that much easier?.?

Yep! It sure does! You'll need to clean the fuel tank too....

WestBound · 03-09-2017, 08:09 PM

Quote:

Originally Posted by cadillackid

if I were going to do a diesel swap.. the 6.2 would be a good candidate IF you already have a cheap source of the engine.. ie theres one on a stand in your garage, freshen it up and go... but parts are going to be scarce for those soon.. they have been out of service a long time...

if I was going to have to Build something up or buy an engine from scratch and wanted a diesel.. i'd probably go after a cummins 6BT...

then again if it was *ME* doing the job and an I-6 was too long to fit the engine bay i'd probably (Ok here comes the flames im sure) go after a Ford 7.3, a 444E can be had cheap harvested from a bus, but the ford version (7.3) has about every tuning and HP upgrade capability out there for the computers..

but really a good ole 350 is just awesome.. and with the right fuel injection system and tuning, and transmission, you can get pretty darn good fuel economy out of a 350.. not to mention that if cost is your reasoning, the fact in most states I travel, regular 87 Gasoline is 20-25% cheaper than diesel fuel on average.. so that should be considered into the equations.. not to mention parts for Vortec 5.7's are in every corner of the planet..

-Christopher

Is that Vortec you're referring to throttle body injection? What do you think a rebuild of that engine would run?

WestBound · 03-09-2017, 08:22 PM

Quote:

Originally Posted by M1031A1

Yep! It sure does! You'll need to clean the fuel tank too....

Right on. Is there anything else? I shouldn't need a what'sit? torque plate converter?.? Besides the gas lines and tank what else would I possibly need? The webs gave me companies that do specialized conversions. The only one that was even in my state does Hummer gas to diesel conversions. I emailed them twice, I figured it would be easy for them because the military Hummer HMMWV (as well as a lot of regular H1s) has that engine but again, to no avail.

WestBound · 03-09-2017, 08:29 PM

Quote:

Originally Posted by cowlitzcoach

Swapping engines is never an easy task.

Swapping from gas to diesel entails more than just swapping the engine in.

Depending upon what is wrong with the engine that you have in your bus currently it still might be a whole lot less expensive to fix what you have than to swap to a 6.2L.

The 6.2L spe'c's in standard form are in the 130-160 HP range and 245-285 ft/lbs torque range.

The 5.7L, the Vortec5700 in particular, had 260-305 HP range and 325-340 ft/lbs. torque range.

Granted we are talking the difference between diesel and gas engine spe'c's. But the feeling you get in the seat of your pants will tell you the 6.2L is a slug compared to the 5.7L.

I'm glad I'm hearing this. I can't be making a huge financial mistake. The 350 in it does pull pretty good, it has great acceleration. I did not know the Vortec's torque was that much greater than the 6.2. Then again I did not know it was a Vortec5700.

EastCoastCB · 03-09-2017, 09:05 PM

Quote:

Originally Posted by WestBound

I'm glad I'm hearing this. I can't be making a huge financial mistake. The 350 in it does pull pretty good, it has great acceleration. I did not know the Vortec's torque was that much greater than the 6.2. Then again I did not know it was a Vortec5700.

5.7 Vortech is a great engine. Pretty easy to work on.

Stewzer55 · 03-10-2017, 12:07 AM

I don't know about the rest of the people here, but I need some pictures of this animal.

WestBound · 03-10-2017, 12:22 AM

Quote:

Originally Posted by Stewzer55

I don't know about the rest of the people here, but I need some pictures of this animal.

I'm going probably tomorrow to the shop to see how much they would charge me for a rebuild. I'm thinking of doing it myself, it's a fairly easy engine, and no offense to mechanics anywhere but I have bad luck with shops. It'd be a fun and rewarding experience. I'll take pictures then. I tried to post a video of the noise it's making but I can't for some reason.

M1031A1 · 03-10-2017, 05:25 AM

Yeah, I forgot about the flex plate, you'll need one. Starter for the 6.2 if they forgot it, needed as well....... Scary thing is I have all these parts sitting in the back of my M1031 "just in case"........

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