Who has done a 4BT swap?

[frenchsquared]

Im thinking about a 4BT swap but I am worried about top speed. I am looking for a truck that drives like a 2015 Silverado 1/2 Ton 4x4. I don't want some mud truck or 1 ton beast. I pull a 20' trailer with a Corvette on it. A new Silverado pulls it fine. Rather then buying a new Silverado I am doing a full restoration on a 76 Short Bed.

If you have driven a 4BT:
Tell me about the shake?
Whats it got for a top speed?
Is it faster then a 454?

IS there any real reason for a 4BT over a 454 other then kids think it is cool?

[DieselSJ]

I have driven a 4bt. They are not smooth, but they are not horrendous rattle-traps either. Liquid filled engine mounts are key.

Top speed is all about gearing. You want it to spin around 1600-1800 rpm on the highway. My diesel Jeep has 28" tires with 3.31 gears and 700R4 and it sits about where I want it on the highway and will do just over 100mph. What RPM is your current setup giving you on the highway?

Faster than a 454? Which 454? What mods to the 4bt? Faster as in top speed or faster as in can beat it in a stoplight to stoplight race?

4bt over a 454 - A 4bt will get you 20mpg plus with the right gearing. A 4bt can be built to generate a reliable 500ftlbs of torque and still retain nice manners. A 454 can also be built to do that, but it will drink probably twice as much as the 4bt.

IMHO a stock 4bt will be horribly disappointing, whereas one with pump mods, injector upgrade, valve spring upgrade, turbo upgrade would be a great engine for a 1/2 ton truck that occasionally pulls a 5k-lb trailer. Do not assume that you are going to drop in a stock 4bt and be happy - you won't be.

Why not find a 6.5 drivetrain from a late 90's truck and drop it in? I've got mine tuned to put out about 500ftlbs of torque and I get 24mpg on the freeway in a full-sized Jeep. That would literally bolt in to your truck.

Also, stop thinking about "speed" and "fast" with a diesel. You drive a diesel to pull things, not go fast. You want speed and fast and tow, do a mild 454. You want to tow and get 20mpg, then do the diesel.

[blakerj10]

I have one in my 78 k10 short box.

Runs very well after doing some tuning and turbo swap (hx30). Accelerates much harder than my stock tbi 350 /700r4 combo in my 90 k5.

It is a bit noisy at idle. On the highway not much difference in noise. Wind noise easily overcomes the objectionable diesel clatter.

Gets amazing fuel economy.

It does have liquid mounts. It does have a slight vibration/shake at idle. Not terrible but noticeable.

I acquired my 78 k10 for free. The body is falling apart. I didn't feel bad about hacking it up for the 4bt experiment. Turns out I like the 4bt so much, I bought a nice 90 k5 to use as a replacement vehicle for the 4bt.

[mongocanfly]

I would look into a duramax swap...that's the direction I was headed with my 81 1 ton when a lq9 fell in my lap for cheap..I don't regret the lq9 but I realize there's no comparison to a good diesel either..I regularly pull a 8-9000 lb loaded trailer..

[blakerj10]

Duramax would be amazing, but kind of a different animal. Way more power and towing ability. Way more complex and cost of components is certainly higher.

The 6.5 option is a good one. I had one in a 94 blazer. Great truck and engine. Easier to bolt in than a 4Bt. My 4bt seems to have more power. Certainly at lower rpms and lower speeds. Closer match on the interstate but I would still give the edge to the 4BT. 4Bt get better mileage than my 6.5 did. Not by much, but better.

[mongocanfly]

Yeah ..the l price of a donor duramax was another killer..

[andrewmp6]

Talk to member 1774btcrew he has one in his truck he can answer any question you have.

[frenchsquared]

Originally Posted by DieselSJ

What RPM is your current setup giving you on the highway?

Faster than a 454? Which 454? What mods to the 4bt? Faster as in top speed or faster as in can beat it in a stoplight to stoplight race?

Also, stop thinking about "speed" and "fast" with a diesel. You drive a diesel to pull things, not go fast. You want speed and fast and tow, do a mild 454. You want to tow and get 20mpg, then do the diesel.

No idea what RMP is on high way. No tack and no speedo. Just started the build.

I have a close friend who works for Cummins. He says he will build one for a red line of 4,000 with about 400hp and 700ft or torque. Wants me to use Dodge NV4500 and 3.54 gears.

No, I am not going to stop thinking about speed and fast. I am not building a truck to tow. I am building a daily driver. I like speed and fast. I have 2015 Z28 and 2000 Supercharged Corvette that is 622hp. I want to be doing 75 on the highway floor it and pass cars hitting 100 easily like I can in my old 2015 Silverado. My goal is more speed then a 2015 4x4 short bed regular cab with a 5.7 in it. about 400 flywheel hp. A stock 454 will pull anything I need.

Its very possible a fuel injected 502 will be a better engine for me. Duramax would be cool, but to much money. The hook up at Cummins makes there engines much better option for me.

[v30crewcab]

4bt's are neat, but I get better fuel mileage and tow better with my 6bt in my lifted 4x4 than my dad does in his 2wd with a 4bt. if you plan on towing, get a 6bt.

[DieselSJ]

Originally Posted by frenchsquared

No idea what RMP is on high way. No tack and no speedo. Just started the build.

I have a close friend who works for Cummins. He says he will build one for a red line of 4,000 with about 400hp and 700ft or torque. Wants me to use Dodge NV4500 and 3.54 gears.

No, I am not going to stop thinking about speed and fast. I am not building a truck to tow. I am building a daily driver. I like speed and fast. I have 2015 Z28 and 2000 Supercharged Corvette that is 622hp. I want to be doing 75 on the highway floor it and pass cars hitting 100 easily like I can in my old 2015 Silverado. My goal is more speed then a 2015 4x4 short bed regular cab with a 5.7 in it. about 400 flywheel hp. A stock 454 will pull anything I need.

Its very possible a fuel injected 502 will be a better engine for me. Duramax would be cool, but to much money. The hook up at Cummins makes there engines much better option for me.

Yeah, go build a gasser. When you say a stock 454 will pull anything, keep in mind that some 454's were only rated at like 230hp.

LOL at that 400/700 number. Anyone who knows the formula for torque and the power curves for BT series engines will laugh at those numbers being used together. Achieving either of those numbers in a 4bt is going to be a significant build. Drop in a Duramax and add a tuner and you will be much happier than with the 4bt modded to those specs.

[1774btcrew]

I will weigh in here. My dad and I did a 4BT in my 77 crew cab short bed. It has a 4l80e with compushift controller, 3.73 gears and 295 50 15 tires. I get 25-26 MPG highway and 19-20 in town. Neither is with towing anything. Top speed is around 85 with this set up. I really don't have any desire to go any faster but I am sure with a couple minor mods it would improve the top speed. As said above, it is noisy at idle but at freeway speeds it is hardly noticable and I haven't even done any sound deadener.
We have done 7 Cummins conversions in Chevy trucks in years ranging from my 77 all of the way up to 2002. Of those 2 were 12v 6BTs and the rest were 4BT conversions. They are great engines and super reliable with easy to get parts. The only thing I may have changed on my conversion is running a NV4500 instead.

[frenchsquared]

Originally Posted by DieselSJ

Yeah, go build a gasser. When you say a stock 454 will pull anything, keep in mind that some 454's were only rated at like 230hp.

LOL at that 400/700 number. Anyone who knows the formula for torque and the power curves for BT series engines will laugh at those numbers being used together. Achieving either of those numbers in a 4bt is going to be a significant build. Drop in a Duramax and add a tuner and you will be much happier than with the 4bt modded to those specs.

Not spending the money for a Duramax. If I go that route I will go back to the original plan and order a new truck from GMC. Wife talked me out of spending $60k on a new truck and building an old one.

Im just going with the numbers from Cummins. Thats what the said it would be.

No one said stock used, tired wore out 454. I will do a full build. It will be an easy 500hp. I know gas engines. I have no issues getting 500hp from a BBC.

[frenchsquared]

Originally Posted by 1774btcrew

My dad and I did a 4BT in my 77 crew cab short bed. It has a 4l80e with compushift controller, 3.73 gears and 295 50 15 tires. I get 25-26 MPG highway and 19-20 in town.

I wish there was a way to get a ride in one. Its a lot of money for something I might hate.

[DieselSJ]

Suggestion - go spend some time over at 4btswaps.com. Go through the dyno results thread and look at the power output and the mods they had to do to get there, and look at where they make peak power (higher power output = higher RPM = reduced economy = reduced driveability while waiting for the huge turbo to spool). 4bt's don't drive like a DMax or a 24v Cummins or a PSD. You can get those modern diesels to feel like a built big block gasser. That isn't saying that you can't get a 4bt to make great power with great street manners, because you absolutely can. It is all about setting expectations on how it will feel to drive it.

[DieselSJ]

Originally Posted by frenchsquared

A stock 454 will pull anything I need.

Originally Posted by frenchsquared

No one said stock used, tired wore out 454. I will do a full build. It will be an easy 500hp. I know gas engines. I have no issues getting 500hp from a BBC.

You didn't say stock 454? Sorry, I must have misread.

[andrewmp6]

The thing to me is the price of a 4bt vs a 12 valve here.The 4bt are not easy to come by here and last one i seen listed was 2k and it wasnt a running engine.But i could get a early 12 valve that runs for 1500 to 2k.

[frenchsquared]

Originally Posted by DieselSJ

You didn't say stock 454? Sorry, I must have misread.

Yes, a stock one will pull anything I need. Was just using that to point out I don't need pulling power. I only trailer a 2015 Z28 at 3800lbs. My 2004 2wheel drive, 5.3 pulls it fine.

I will throw some flat top pistons, aluminum heads, cam, intake and fuel injection on the base 454. Will most likely go with a 502. All for way less then a diesel swap. I know my gas milage will suck. Don't care. Im just trying to decide what will be the better driving truck for me.

[frenchsquared]

I am not doing the 4BT or the 6BT. The rmp range is to low for me. I am currently researching Duramax swaps but I am having a hard time finding a way to mate an Allison to an NP205. Heavily leaning towards a BBC build.

[wilkin250r]

I'm just trying to read between the lines, here. It does indeed sound like a BBC is more the style you're looking for.

[mongocanfly]

The high donor cost was a big deterant in my choice not to use a duramax

[andrewmp6]

You could go divorced t case and run a 2wd trans.

[v30crewcab]

the ve pumps can run a 3200 rpm gov spring, and the p-pumps can run either a 4000 or 5000 rpm gov setup. I run a 4000 in mine and its plenty. I ran over the pass in colorado with a big camper and it was no problem pulling it. held speed just fine.

[DieselSJ]

Originally Posted by frenchsquared

I am not doing the 4BT or the 6BT. The rmp range is to low for me. I am currently researching Duramax swaps but I am having a hard time finding a way to mate an Allison to an NP205. Heavily leaning towards a BBC build.

Stop equating engine RPM with speed. Diesels are not high revving. You do not need to spin them up like a gasser to get your HP and torque. You gear it for 1800rpm at 65mph and by the time you spin it up to 3000rpm you are going plenty fast. DMax's don't spin any faster than a Cummins or a P-stroke.

[Dieselwrencher]

I have a 12 Valve in my 68 Vette and it runs 11.30s at 130-132 mph in the 1/4, and I am not at 4k rpm going through the traps. It has a lot left in it. I haven't raced it since we fixed the trans. Diesels will go fast. You just have to gear them properly. I'd put my 24 valve in my 72 against any 454 on a tow test. I couldn't go back to a gas engine for any towing now. The duramax can and has been done but get ready to spend some coin.

[andrewmp6]

Dieselwrencher whats the mpg different between the cummins swaps and what it got before ?