Enthusiast III
- 1,807
- First Name
- Brady
- Last Name
- Robinette
- Member #
-
16191
- Ham/GMRS Callsign
- KN4RRX
As putting pen to paper (or fingertips to keys) always seems to help clarify my thoughts, I decided to explore what my brain had to say about transplanted powerplants in vehicles.
What circumstances shape my opinion?...
First, I am a Reliability/Maintenance Engineer and Statistician by trade. This gives allows me two (sometimes conflicting) viewpoints on what "is" and what "might be" with regard to reliability and the effectiveness / efficiency of alternative solutions. Second, I'm winding down the--long--process of building what I fully intend will be the last truck I ever have to build/buy/procure.
I'll start by saying that my experience isn't a typical repower, in that I didn't start with vehicle A, remove engine A and install engine B in its place. Rather, I started with a new frame that was spec'ed for vehicle A (circa 1986 Jeep Scrambler), chose an engine that Jeep never intended under the hood (a newly-built Cummins 4BT) and relied on some top-notch fabricators to figure out how Slot A and Tab B went together and built everything else around it.
One would think--I did!--that this would be a simpler way of doing things than starting with an existing frame/body/suspension and figuring out how to make a different engine and transmission work. Maybe it was.
However, what I realized is that "simpl-ER" isn't the same thing as plain old "simple".
In no particular order, some of the larger issues we ran into:
Frame strength / thickness... stock dims and profile were ok for a 600 lb inline 258 gas mill... not even close for an 1100 lb diesel. Solved by spec'ing heavy wall boxed frame.
Frame width / front suspension location... CJ8 frame width not ideal for running heavier springs due to having to fabricate an outboard attachment system for them. Solved by spec'ing the width of the frame in the front to be slightly wider than stock.
Engine dimensions.. The 258 was about 34" long and 18" tall... the Cummins is not as long, at 30 or so inches, but is 37 inches TALL... since I consider a working hood to be in the "necessary" column, this required some consideration. Solved by mounting the Cummins very low (down between the frame rails) and as far back as possible.
These were items that had to be addressed anyway, since we were building this thing up from a bare floor... yet they were still hugely frustrating! Imaging how frustrating it would have been if we'd had to work around existing dimensions/frame/sheet metal, etc.
My view is, all other things being equal...
1) Sticking with a rebuilt / remanufactured stock application is best/least expensive/least frustrating/entirely acceptable for the vast majority of applications.
2) The second-best option is using a well documented, well-engineered, tried-and-true repower solution. The ubiquity of the Chevy LS makes this repower option very attractive and it can even be price-comparable to a fully-reman'ed original powerplant.
3) If (and only if) the above absolutely DISGUSTS you for some reason, proceed to a "unique" repower.
To cut to the chase, my choice to use a diesel impacted every single other part of the build.... from the transmission and transfer case used, their locations, overall length of the driveline, steering column and box locations, engine cooling solutions... blah, blah, blah. I knew this going into the build. My fab shop was also very up front about this.
Key Phrase?... "This is not a usual or typical equipment configuration."... translation, "This is going to be a real pain in the John Brown Hind Parts and cost many benjamens".
It's the "all other things being equal" that's the sticking point for some folks (me).
if you're considering Option 3, ask yourself "Why" about 20 times. Take the time to understand your motivations.
Ask yourself questions... This is a completely sane and socially-acceptable thing to do... you can even argue with yourself (silently, please).
Do you need more power (towing)? How much? Do you REALLLY need it?
Are you willing to pay 2/3/4 times as much to get something EXACTLY the way you want it? Look at that number again... are you SURE?
Do you have other specific criteria that make the repower attractive (solving a known engineering deficiency, enhancing reliability or usability in some way)? Is there really "worth" there?
If these answers tend toward yes, then by all means, proceed with your repower, document it and add it to the body of knowledge on this site!
Do I wish I'd went a different route? HECK NO! However, if I hadn't been really REALLY prepared for the time and cost associated with "non-standard, unique, custom, bring-benjamin-and-all-his-friends", I would have been setting myself up for some serious disappointment. I think this is why there are so many partially-completed projects available out there.
Anyway, marinate on that for a lil' bit...
~doc
What circumstances shape my opinion?...
First, I am a Reliability/Maintenance Engineer and Statistician by trade. This gives allows me two (sometimes conflicting) viewpoints on what "is" and what "might be" with regard to reliability and the effectiveness / efficiency of alternative solutions. Second, I'm winding down the--long--process of building what I fully intend will be the last truck I ever have to build/buy/procure.
I'll start by saying that my experience isn't a typical repower, in that I didn't start with vehicle A, remove engine A and install engine B in its place. Rather, I started with a new frame that was spec'ed for vehicle A (circa 1986 Jeep Scrambler), chose an engine that Jeep never intended under the hood (a newly-built Cummins 4BT) and relied on some top-notch fabricators to figure out how Slot A and Tab B went together and built everything else around it.
One would think--I did!--that this would be a simpler way of doing things than starting with an existing frame/body/suspension and figuring out how to make a different engine and transmission work. Maybe it was.
However, what I realized is that "simpl-ER" isn't the same thing as plain old "simple".
In no particular order, some of the larger issues we ran into:
Frame strength / thickness... stock dims and profile were ok for a 600 lb inline 258 gas mill... not even close for an 1100 lb diesel. Solved by spec'ing heavy wall boxed frame.
Frame width / front suspension location... CJ8 frame width not ideal for running heavier springs due to having to fabricate an outboard attachment system for them. Solved by spec'ing the width of the frame in the front to be slightly wider than stock.
Engine dimensions.. The 258 was about 34" long and 18" tall... the Cummins is not as long, at 30 or so inches, but is 37 inches TALL... since I consider a working hood to be in the "necessary" column, this required some consideration. Solved by mounting the Cummins very low (down between the frame rails) and as far back as possible.
These were items that had to be addressed anyway, since we were building this thing up from a bare floor... yet they were still hugely frustrating! Imaging how frustrating it would have been if we'd had to work around existing dimensions/frame/sheet metal, etc.
My view is, all other things being equal...
1) Sticking with a rebuilt / remanufactured stock application is best/least expensive/least frustrating/entirely acceptable for the vast majority of applications.
2) The second-best option is using a well documented, well-engineered, tried-and-true repower solution. The ubiquity of the Chevy LS makes this repower option very attractive and it can even be price-comparable to a fully-reman'ed original powerplant.
3) If (and only if) the above absolutely DISGUSTS you for some reason, proceed to a "unique" repower.
To cut to the chase, my choice to use a diesel impacted every single other part of the build.... from the transmission and transfer case used, their locations, overall length of the driveline, steering column and box locations, engine cooling solutions... blah, blah, blah. I knew this going into the build. My fab shop was also very up front about this.
Key Phrase?... "This is not a usual or typical equipment configuration."... translation, "This is going to be a real pain in the John Brown Hind Parts and cost many benjamens".
It's the "all other things being equal" that's the sticking point for some folks (me).
if you're considering Option 3, ask yourself "Why" about 20 times. Take the time to understand your motivations.
Ask yourself questions... This is a completely sane and socially-acceptable thing to do... you can even argue with yourself (silently, please).
Do you need more power (towing)? How much? Do you REALLLY need it?
Are you willing to pay 2/3/4 times as much to get something EXACTLY the way you want it? Look at that number again... are you SURE?
Do you have other specific criteria that make the repower attractive (solving a known engineering deficiency, enhancing reliability or usability in some way)? Is there really "worth" there?
If these answers tend toward yes, then by all means, proceed with your repower, document it and add it to the body of knowledge on this site!
Do I wish I'd went a different route? HECK NO! However, if I hadn't been really REALLY prepared for the time and cost associated with "non-standard, unique, custom, bring-benjamin-and-all-his-friends", I would have been setting myself up for some serious disappointment. I think this is why there are so many partially-completed projects available out there.
Anyway, marinate on that for a lil' bit...
~doc
