i am a new member with a reasonable amount of auto mechanical and modifacation expierience. i was wondering if it might be a reasonable idea to swap in one of the new GM 3.0 TURBO DIESEL engines . with 277 hp and 430 ft lbs of torque it seems like it might be a good fit and maybe get a little better mpg. what do you guys think?
engine swap ideas for more mpg
- Thread starter mldeolde
- Start date
Nope. For the cost and time to swap that you can buy enough fuel at 7mpg to travel anywhere you want for decades.
But dont let me stop you. Go for it so the rest of us can watch and learn.
My friend just sold his 45 mpg diesel bug. To drive a gas suv that I think might get 20mpg. He said he will be spending $40-50 more per month in gas. But he will be driving in comfort. And will not have to worry about expensive diesel repairs. Diesel fuel is much more money these days. Takes alot away from the gain in mpg.
Engine swaps in a gmc. Are like what the tiger king says. “You will not financially recover from that”. But more power up a mountain could be nice until the tranny gives up.
But dont let me stop you. Go for it so the rest of us can watch and learn.
My friend just sold his 45 mpg diesel bug. To drive a gas suv that I think might get 20mpg. He said he will be spending $40-50 more per month in gas. But he will be driving in comfort. And will not have to worry about expensive diesel repairs. Diesel fuel is much more money these days. Takes alot away from the gain in mpg.
Engine swaps in a gmc. Are like what the tiger king says. “You will not financially recover from that”. But more power up a mountain could be nice until the tranny gives up.
Even when it's easy due to the platform it's hard to justify the expense.
And without overdrive you probably wont get a huge increase in MPG anyways....
Here in Washington state Diesel is about 25% more expensive than regular, or about a dollar more per gallon.
I have wondered about a newer transverse turbodiesel motor with a 6speed transmision, that might be interesting. But youd have to drive 100k just to recover the expense before recognizing any benefit.
And without overdrive you probably wont get a huge increase in MPG anyways....
Here in Washington state Diesel is about 25% more expensive than regular, or about a dollar more per gallon.
I have wondered about a newer transverse turbodiesel motor with a 6speed transmision, that might be interesting. But youd have to drive 100k just to recover the expense before recognizing any benefit.
If you're swapping for "savings," you'll never get there. But there are other reasons to change to diesel (reliability, longevity, torque, long term fuel solutions (making diesel from plants), etc.).
The most success in the real world has come from the AM General 6.5 (easiest direct swap with least fabrication/modification). Manny was going to market a line of drop-in crate motors based on the AM General, but I think the plan fizzled. Here's an article: http://gmcws.org/blog/manny-trovao-...a-drop-in-diesel-engine-for-our-classic-gmcs/
The most success in the real world has come from the AM General 6.5 (easiest direct swap with least fabrication/modification). Manny was going to market a line of drop-in crate motors based on the AM General, but I think the plan fizzled. Here's an article: http://gmcws.org/blog/manny-trovao-...a-drop-in-diesel-engine-for-our-classic-gmcs/
I believe Manny gave up on the AM General swap kit because they drastically increased the price of the crate engine.
The only way something like this would be reasonable, cost wise, is to buy a write-off with a good motor from an insurance company.
In BC this is probably easier than elsewhere as our insurance corporation is the only vehicle insurer and it holds weekly auctions of damaged vehicles online, a la eBay.
Only drawback is one has to be a registered car dealer to bid or even view the auctions.
In BC this is probably easier than elsewhere as our insurance corporation is the only vehicle insurer and it holds weekly auctions of damaged vehicles online, a la eBay.
Only drawback is one has to be a registered car dealer to bid or even view the auctions.
If you own any computer, get a spreadsheet. There are a number available for download free. And then there is Google Office that you work online. Get one, learn to use it and you will quickly identify the issues. There are not many powerplants that can fit in a GMC/TZE frame with the requirement for the right side drive axle and the Rear Face of Block for a 425 is a Cadillac and Oldsmobile only. The RFB can be handle Dave Lenzi has done this with his 8.1 installations. But that man is a true wizard at these thing and yes, he does make an oil pan with a though port and reworks the RFB of the new engine. I do not know what he charges for this operation, but I have been told is is not inexpensive and the ROI is up towards 200K miles.
Matt
Matt
As others have inferred, diesel swaps don't really pencil out from a financial point of view. BUT, if you just like diesel for whatever reason (and there are quite a few) they can be made to work well.
If you have the skills to attempt the project it's really not 'rocket science'. but it can be quite an undertaking depending on how involved you get.
I used the 6.5TD with an overdrive transmission and have enjoyed it for 35,000+ plus miles averaging about 13 mpg, mostly towing. Most of the driving has been in the west with plenty of hills which aren't the best for economy, of course. It all depends on what you want to do.
Diesel on...
Hal
If you have the skills to attempt the project it's really not 'rocket science'. but it can be quite an undertaking depending on how involved you get.
I used the 6.5TD with an overdrive transmission and have enjoyed it for 35,000+ plus miles averaging about 13 mpg, mostly towing. Most of the driving has been in the west with plenty of hills which aren't the best for economy, of course. It all depends on what you want to do.
Diesel on...
Hal
Thanks for the input Hal. What OD transmission did you use?
I was just about to ask if anyone knows what sort of mileage people had gotten with the 6.5TD, IIRC it only got about 17 in a 9000# pickup with OD. Thats about all my much newer Turbo Diesel Pickup gets, and it drops to about what you claim (13mpg) when I strap a cabover camper on it that puts me at about the same weight of a GMC (13k#). That is at 65-70mph, so it might be slightly better.
I know diesel varies across the country, but as I stated previously it's about 25% higher than regular here in Washington. 25% fuel mileage increase is hard to justify with a 25% cost increase.
Don't think I'm bashing on you, I have 5 diesels and 4 turbo diesels. I like them all.
I was just about to ask if anyone knows what sort of mileage people had gotten with the 6.5TD, IIRC it only got about 17 in a 9000# pickup with OD. Thats about all my much newer Turbo Diesel Pickup gets, and it drops to about what you claim (13mpg) when I strap a cabover camper on it that puts me at about the same weight of a GMC (13k#). That is at 65-70mph, so it might be slightly better.
I know diesel varies across the country, but as I stated previously it's about 25% higher than regular here in Washington. 25% fuel mileage increase is hard to justify with a 25% cost increase.
Don't think I'm bashing on you, I have 5 diesels and 4 turbo diesels. I like them all.
I used a 4L80E coupled to a transfer case built for Revcon after the TH425's were axed by GM. I run a drive shaft forward to a 9.25" differential sourced from the front of a 2012 up Chevy/GMC HD 2500/3500 truck.
I too have a few diesels, 45' Eagle bus with a 14ltr Series 60, 2015 Golf SW TDI(towd), 2007 GMC Duramax 4x4(sometimes towd). I have a FMC I'm doing a Duramax/Allison swap on now I hope to have running by late summer and a stalled Duramax/Allison pusher GMC project.
BTW, in OD I have an effective 2.82 final ratio which helps with the mpg's and noise. The inntercooler helps keep egt's low even at 12+ psi boost pressures.
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A friend has an FMC.
There's a revcon listed for sale near me, they have been unresponsive.
If I ever came across a 23' in rough shape I'd look into the transfer case/TD install, I'd even dream about a 4x4 project.
I have a 2004 vw golf tdi with a towbar. It's my grocery getter.
Oh God another engine swap thread!! 
I was hot to do a diesel swap for a long time. Now, with the cost differential between gas and diesel being what it is, the economic savings are not there anymore
I still am convinced, however, that the GMC motorhome should get much better fuel economy than 8-11 mpg. My huge class A holiday rambler with 454 doing 60mph got 7.4 mpg. The HR was shaped like a brick, the GMC supposedly has a low coef of drag. The GMC is ~75% of its frontal area, and ~75% its weight and I'm getting 8.8mpg . Something is wrong, this just does not compute.
New brick shaped RVs get 7mpg going 70-75 mph. And they are huge (frontal area) and heavy (rolling resistance). This also does not compute.
I'm wondering if the 455 is just not that efficient at converting fuel into work compared to even a chevy 454 let alone a more modern engine.
I was hot to do a diesel swap for a long time. Now, with the cost differential between gas and diesel being what it is, the economic savings are not there anymore
I still am convinced, however, that the GMC motorhome should get much better fuel economy than 8-11 mpg. My huge class A holiday rambler with 454 doing 60mph got 7.4 mpg. The HR was shaped like a brick, the GMC supposedly has a low coef of drag. The GMC is ~75% of its frontal area, and ~75% its weight and I'm getting 8.8mpg . Something is wrong, this just does not compute.
New brick shaped RVs get 7mpg going 70-75 mph. And they are huge (frontal area) and heavy (rolling resistance). This also does not compute.
I'm wondering if the 455 is just not that efficient at converting fuel into work compared to even a chevy 454 let alone a more modern engine.
There was a "Dealer Service Information Bulletin" issued back on 5/1/83 about a "Dieselization Package" that explains how to make a GMC sound and act like a diesel.
Can't really address the efficiency of the 455 vs 454 (although there were a lot more 454ish chevy record holders than 455's at the drags) but when the GMC's were produced real gas was being delivered to a carb which was designed to run efficiently with it's properties. Todays 'gas' is formulated to run with current fuel injected engines, not so much with the old school carbs. Just adding the corn squeezings to the fuel takes a good 10% off your mpg's by itself. I guess it's just progress....Oh God another engine swap thread!!
I was hot to do a diesel swap for a long time. Now, with the cost differential between gas and diesel being what it is, the economic savings are not there anymore
I still am convinced, however, that the GMC motorhome should get much better fuel economy than 8-11 mpg. My huge class A holiday rambler with 454 doing 60mph got 7.4 mpg. The HR was shaped like a brick, the GMC supposedly has a low coef of drag. The GMC is ~75% of its frontal area, and ~75% its weight and I'm getting 8.8mpg . Something is wrong, this just does not compute.
New brick shaped RVs get 7mpg going 70-75 mph. And they are huge (frontal area) and heavy (rolling resistance). This also does not compute.
I'm wondering if the 455 is just not that efficient at converting fuel into work compared to even a chevy 454 let alone a more modern engine.
Hal
