Somone school me on diesals real quick

Im still in the planning process of what i want to build, a 49 gmc pickup on a s10 body would be ideal if i can find them in my area. The part thats really up in the air is the engine. Its between a diesal or an LS, an ls i expect would be pretty straight forward even for me with my "learn as i go" style of mechanics. Diesals however i know nothing about.

Can prettymuch any old cummins engine be built in to somthing fast and powerful? When i read the stock power rankings on some of these old trucks on craigslist they only have like 180 or so hp. How much work is required to turn them in to the 350hp race engines you allways see in well built ratrods?

I expect it to be a bit more expensive than a LS engine but how much more expensive should i expect it to be?

Are there any engines that are better or worse or will prettymuch any be a decent starting place for a build?

I'll tell you what I know about big rig diesels from the best shops
it's tuning
On a diesel turning up the power a significant amount requires:
more compressor on the turbo
retarding the timing
increasing the fuel

adding a more efficient turbo. many after market turbos for big rigs use the stock exhaust side and change the compressor wheel and scroll. this is only necessary in the top tier hop ups.

Retarding the timing- it's something you need to do when adding a significant amount of cylinder pressure

Increasing the fuel- turning up the injection pump and adding larger injectors

You can hop up a diesel by advancing the timing but your playing with dynomite and you will run hotter exhaust temps

On most pickup diesels increasing the fuel just moves top end fuel capacity to the bottom end.
on top builds with pickup diesels for example the 7.3 powerstoke requires more capacity in the pump as max fuel has been reduced by increasing delivery on the bottom of the curve. these pumps only pump so much and they are spec'd for the stock engine.

On a big rig the fuel pump moves so much fuel that quite a bit is returned to the tank after the pump by the by-pass. This keeps the fuel in the tank warm in the winter.

if you build a passenger diesel to make big power you're going to spend alot more than you would on a gas engine and it will cost you more in fuel. hotrod passenger diesels don;t get good mileage.

I would only run a diesel in a passenger vehicle for the mileage

I had a gig once where I hauled a mostly empty 24' gooseneck from Omaha to Oklahoma city and back in a fairly new ford superduty with a 6.0 powerstroke
it got only 8 mpg @65 mph going easy.
I could have gotten the same with a 460 and it would have pulled just as well
They moved to diesels in the heavy light trucks mostly because of emissions.
EPA regs don't allow them to build big block trucks anymore and you just can't tow a big trailer with a 5.4 or a 4.6.
The newer diesels are tuned to run pretty clean and that's largely the only way the big 3 can legally put some real power under the hood these days. it's not because they are better at the job.

When they built diesels that got good mileage some people didn't like them because they thought hey it's a diesel it should pull 80,000# up a mountain at 70...

You have to consider that diesel costs more than gas and it has nearly $.40 a gallon in tax on it that gas does not have.

My freind hauls cars
he usually got around 10-13 with a 460
And 13-18 with a 7.3 powerstroke
even at that...the powerstroke cost him more to run than the 460.

If you dropped a 6.2 or 6.5 you could be getting 25-30 on the highway and they swap out with a small-block- no adapters.
it's not going to be a race truck
The new AM general engines are supposed to be putting out around 300 horses
I've got a couple of them old 5.7 diesels. they run about like a 305 or a 6 cylinder but get great mileage. I got 32 in a caddy.
arp rod bolts and the right head gaskets with stock tune on the injector pump and they are a fine engine

power comes from fuel
more power= more fuel

Everyone I've ever met who dynamited a 5.7 or 6.2 also got farmering round in the injector pump
Everyone I met who thought they were gutless had the misconception they were built for power just because you put diesel in the tank.
Alot of people think if they have a diesel it should run like a 454 or a 460. they don't. You won't be disappointed unless you want to win a race.
Have trouble pulling a hill? drop a gear like a professional and slow down.

I've never had a complaint about a pickup truck that got over 30 mpg.

if you have black smoke coming out of your tailpipe you're wasting money, your truck needs a tuneup, and your not driving it right. [ddd

Oh yeah..
And automatics are easier on things like head gaskets, head bolts, cranks, bearings etc than manual trannies.
In your truck you can run a stock 700r4 behind a 6.2 or 6.5 no problem
diesel torque converters- with Gm there is no diesel torque converter per se.
behind a diesel GM used the 6 lug low stall converters and had the fins furnace brazed to resist vibration.
You can also run a turbo 400 with highway gears.
I ran a th400 behind a 6.2 and 4.11's and 275 85 r 16's and the sweet spot was at 55
When I had a 700r4 in the truck i could do 65 max mileage.
so I put 3.22's in from a diesel van to work with the lack of an overdrive.

My 700r4 died because it had almost 200k miles on it, not because it was in a diesel
My 6.2... i killed it. My fault
When the head bolts get weak on a high mileage diesel antifreeze will seep out the head gasket.
In my case the engine drank it's own oil past the leaking gasket and I threw a rod running down the interstate 5 seconds after dropping oil pressure . things go boom really fast in a diesel.

If I was doing a 48 diesel I'd run one of my 70-81 firebird posi's with the 2:71 or 2:42 gears and a 6.2 with a th400.
I wouldn't mess with a 4bt unless I had one I needed to stick in something.
Frito lays runs alot of 6.2's in their trucks after taking out the 4bt's


A good aluminum radiator should be fine

STANS has headers for them

Ok what I meant by max mileage and sweet spot....
The fuel curve on a diesel is linear up to the sweet spot
when you step on the pedal it's the advance that speeds up the engine and the fuel just keeps up with the advance

once you are at max advance.... the fuel over runs the advance and gets richened up to gain more rpm's
for example
A 77 diesel I had... 18 town and 32 highway
around town your always into the fuel
Going down the road the advance is doing the work and in that truck max advance was somewhere between 60 and 65
So up to 60 I'd get 32mpg
And 65 and over it would drop to a flat 18
It never got worse than 18
18 at 65
18 at 85

with a gas engine you control the engine speed by throttling the air-fuel mixture
with a diesel you control the engine speed by modulating the advance, the fuel is fed in when the governor automatically does it's thing

basically with a diesel engine the foot pedal doesn't change the air or the fuel it changes the idle speed in the governor and the governor makes the timing and fuel adjustments to bring the engine to the new idle speed.

Goddamn man, thankyou so much. You went above and beyond with that post, i was just expecting a couple people warning me to stay away from such and such engines but you really took the time to teach me somthing.


Ford seems to be the more affordable way to go so i will probably go with an early 7.3 powerstroke assuming i can find one at my local pick-n-pull.

And when i say "racetruck" i just mean a rusty old daily driver/sleeper that can smoke some local ricers, my car now is a bmw pushing about 200hp and it gets up plenty quick, a 300hp small truck would be plenty.


This is more of a ford specific question than a diesel question but as far as compatibility goes, will a ford diesel v8 swap right out with a ford gas v8? I know powerstrokes were made by a different company up until recently but if could use parts from old mustangs and other trucks it would make my life a whole lot easier.

Unless someone tells me this plan sucks i think im gonna find myself a cheap gas ford with all the options i want (dually, 4x4, ect) find an old powerstroke at the junkyard and grab a bigger/newer turbo for it, grab some bigger injectors for it and probobley a boostcontroller, throw them all together and see where im sitting horsepower wise. In a barebones, small ass truck i imagine i will be more than happy with the power it has

Ok I didn't read all of what Torch wrote. I got to the part where he compared gas to diesels in pickups and I had to stop. I have to respectfully disagree. You can't compare all diesels in pickups after just being around a old ford power stroke. Older Power strokes are horrible on fuel. There's not a gas truc on the market that will compete with a cummins truck or any modern diesel. Not for fuel mileage, power, or torque. Or longevity for that matter.


As for horsepower. You can do very little money wise to a first generation cummins and build the 300 plus horsepower you want. Adjust the timing a little, adjust or replace the fuel plate. (Fuel plates are about $35) and you can adjust the fuel pressure on the pump in about 15 minutes. You will enough torque that you won't even care about horsepower and will still get low to mud 20 mpg depending on the rest of your drivetrain.

Actually I wasn't comparing to a ford diesel. The 7.3 or T444 isn't really a pickup engine. it's a mid sized truck engine in a pickup.
The Gm diesel was designed for a light duty truck.
A 1991 6.5 turbo diesel in a HD3500 chevy and a 12' flatbed will beat a dodge 3/4 ton pickup with a 5.9.
Worked for a guy who had 2 of each brand new and we'd race them all the time.
6.5 was faster 5.9 got better mileage.
That 2010 ford superduty got worse mileage and was slower than the 460's I've had but my 460's were not stock. that diesel might make it through the mountains better than a 460 but a waste of money unless you have plenty to throw around. over engineered and underpowered showpiece.
God forbid I would ever have to try to work on one.
But then again I think nearly everything newer than 2000 is an abortion XDDDD

Doing an engine swap on a 2000 f150 4.6 and it has to be the most god awful miserable experience and I haven't gotten to putting it back together again.
the 7.3 power stroke blows the 6.0 away. I'd say it was probably the last good diesel engine your ever going to see in a pickup.

The 7.3 IDI is NOT a powerstroke
If I was going to choose a ford Indirect injected diesel I'd go with a 6.9 over a 7.3 for the little bit better mileage.
If I had to tow a trailer heavier than 10,000# I wouldn't be doing it with a pickup truck. no way.

Right Willy
I didn't lump everything together in one comparison like that.
I dumped a ton of info without much comparison but its largely geared to a 48 chevy half ton that's not likely to be pulling any 20,000# goosenecks
to be more specific:
Your not going to get the mileage out of a workhorse diesel that you will get out of a passenger car/light truck diesel. it's one or the other. power or mileage.
gas is cheaper than diesel gallon for gallon.

The point being for a driver that is not a commercial truck...
The 4bt cummins is going to be slower than a good gas engine
it MIGHT get better mileage just for something weird to putt around in. IDK all of the 4bt's Ive seen were too slow to get out of their own smoke.
That's that stereotypical optimism I was thinking of. Someone sees cummins in the name on the 4bt and has a daydream of a flat top Peterbuilt topping a hill at 80k lbs doing 70 mph...
Same misconception dudes had when they went out and bought a 5.7 diesel in the late 70's and had a big let down.

If it's mileage he is going for with some light to moderate towing and wanted a diesel I'd think he'd be better off sticking with a 6.2 or a 6.5 turbo or going to an am General hummer engine.
any of those will out-pull the 4bt
I wouldn't put a 5.9 in a 48 chevy either. too heavy and too slow. The 5.9 would be the best light truck choice for towing economically but The 6.5 turbo will outrun the 5.9

If he's just driving it no towing I'd also recommend using a turbo diesel from a Mercedes.
That actually would probably be the best choice for that truck.

I don't care what kind of diesel you put in a 48 Chevy Willy I can spend 1/4 the money or less on a gas engine and beat you in the quarter mile. [P

Expect to spend at least twice as much on buying a diesel.
the advantage of a diesel is
Doing a job too large for a gas engine
while getting a little better mileage than a gas engine

The diesel is a little more efficient at putting the fuel to the ground and the fuel itself has more btu than gas.

The disadvantages:
slower and more expensive to buy and maintain


Around here 5.9 cores sell stripped for close to $2,000
I wouldn't want one unless I already had a dodge. Not saying they are a bad engine just can't justify spending that much money just to make my truck heavier and slower.

im getting about 20mpgs right now and i run premium which costs more than diesel where i am so anything close to 20 would be amazing.

i am not committed to either a powerstroke, cummins or anything else for that matter. a diesel longblock at my junkyard is $600 nomatter what truck it came from at my local junkyard so it just is a matter of what pops up. i would feel like im breaking some unwritten rule if i source all the parts for a powerstroke and end up putting it in a chevy body though.

i will probobley just end up grabbing whichever deal pops up first and going from there


compatibility wise, can any ford diesel v8 bolt right on to any ford transmission for the most part? i wouldnt try using a focus tranny ofcourse but any tranny that came from a gas v8 of a similar year?

You can use a 4BT Cummins that's from a delivery van. (bread truck) (Hostess Twinkie truck)
These aren't as smooth running as a 6BT but are great little engines.
A friend of mine put one in a 29 Chevy sedan and got 41 miles to the gallon with it.

On the 7.3 powerstroke or the 6.9/7.3 IDI they are both international motors

They require an adapter to bolt to a ford transmission but I've read they bolt directly in place of any international V8 So I Assum ou could use any IH tranny or bell on one directly

Here's where it gets weird
Ford uses an adapter on the IH diesel to get it to a ford bell housing pattern
Why they didn't choose an existing ford bellhousing pattern is beyond me
The ford bellhousing pattern for the IH diesel is unique
it LOOKS like a 460 bell housing
But it aint.
A 460 transmission won't bolt to the diesel.
I've heard some guys have drilled the holed bigger and ground them oblong or something to make it work but directly with no mods- no

If you want to run a 6.9/7.3 or 7.3 powerstroke your going to have to source a ford diesel transmission or bell.
The 6.9 used an aluminum bell with a conventional 4 speed
the 7.3 used a ZF 5 speed with intergral bell.
the 6.9 and early 7.3 HD used a solid flywheel that is interchangeable between the 6.9 and 7.3
Most 7.3 used the dual mass flywheel. the entire assembly bust be replaced at clutch time and it's around $1500
You can run a ZF behind a 6.9 or 7.3 using the 6.9 solid flywheel and the clutch disk for the first 2 years of the ZF that had the medium futy truck HD solid flywheel option
Or you can spend round $800 for the after market dual mass eliminator kit that comes with it's own solid flywheel.

The ZF clutch disk is a solid hub
Since the dampening comes from the dual mass flywheel there are no springs in the hub
The clutch disk for the solid flywheels has the dampener springs we are all familiar with.
The ZF has an input size and spline unique to only it. the clutch for a 4 speed will not work

You will not find that ZF clutch disk with the dampener springs in any online parts list
Only the places that use the book can find the part number but any old school clutch shop should have one or two on the shelf.

If you put the disk with the solid hub behind the solid flywheel the vibration and the humming will drive you insane and it will probably shake stuff loose.

the 6.9/7.3 IDI is an entirely different engine than the powerstrokes
The power-stroke didn't come until about 2000. You can identify one by the diamond shape to the ends of the vavle covers and the lack of any expternal injection pump or injector lines
Powerstrokes have an internal injection system where high pressure engine oil plunges individual injectors triggered electronically

Any ford diesel that has an external injector and injector lines like on a Chevy diesel is NOT a power stroke.

Flywheels and bellhousings are interchangeable between powerstroke and IDI
But somewhere along the way ford began having the blocks cast with their diesel tranny pattern without the IH adapter. don't remember when.



Common failures on the powerstroke are the High pressure oil pump goes bad or the orings in the injectors go bad and the thing won't run or runs horrible. easy fix if the engine is still otherwise good.

Ford also had a brazillian made straight six diesel which can be found in alot of ISUZus, ford cabovers and f600-f700. it had it's issues but for most people was a good engine similar to cummins.

Check this out

https://www.youtube.com/watch?v=-XfDdW5X4EQ